Colloidal synthesis of large near-bulk InAs quantum dots through seeded and seedless growth using cluster precursors

Domain: physics
Published: 2026-02-12
Editorial outcome: major_revision

Abstract
Quantum dots are high-potential materials for a wider range of applications, particularly in the infrared spectral range, including telecommunications, security, sensing, photovoltaics, and bioimaging. The size and chemical composition of semiconductor quantum dots determine their optoelectronic properties. While II-VI and IV-VI quantum dots are well-studied, the colloidal synthesis of infrared-active III-V quantum dots such as InAs, which are compliant with the European Union directive for restriction of hazardous substances, remains underdeveloped. In particular, the synthesis of larger InAs quantum dots is challenging due to the strong covalent character of In–As bonding, limited control over precursor reactivity, and complex growth pathways. Here we show the synthesis of large, near-bulk InAs quantum dots using atomic clusters as precursors. All nanostructures are synthesized from ‘green’ commercially available precursors. These results extend the accessible size regime of colloidal InAs nanoparticles to diameters approaching 40 nm and establish a platform for their use in infrared technologies.

Introduction
Colloidal quantum dots (QDs) form a class of nanomaterials with promising optoelectronic properties, which can cover a wide spectral range reaching from the visible (VIS) to the infrared (IR). The near-infrared (NIR) and the short-infrared (SWIR) regions have attracted growing interest due to a rapidly increasing number of applications in sensing, imaging, and spectroscopy1. These technologies are relevant for industrial and consumer sectors, including automotive systems, smartphones, environmental monitoring, material sorting, and enhanced night vision1–3.

Despite the availability of low-cost silicon-based detectors, their spectral sensitivity is limited to below ≈1100 nm4,5. To access longer IR wavelengths, current technologies commonly rely on epitaxially grown materials such as indium gallium arsenide (InGaAs), which are costly due to energy-intensive deposition processes5,6. In contrast, IR-active colloidal QDs could offer advantages due to their low-cost wet-chemical synthesis and deposition possibilities1,2,7.

For applications in consumer electronics and biomedicine, the use of the European Union directive for restriction of hazardous substances (RoHS) compliant QDs is essential8,9. A suitable candidate is indium arsenide (InAs), which combines a small bulk bandgap of 0.36 eV (≈3444 nm)10,11 with high electron mobility12 and a cubic zinc blende crystal structure, which facilitates epitaxial growth of colloidal core/shell heterostructures such as indium arsenide/indium phosphide/zinc selenide/zinc sulfide (InAs/InP/ZnSe/ZnS) QDs interesting for light-emitting technologies9,13–20. These properties make InAs QDs an attractive material for advanced optoelectronic applications.

While II-VI and IV-VI QD systems such as mercury telluride (HgTe) and lead selenide (PbSe) have been thoroughly investigated3,21,22, the colloidal synthesis of III-V QDs like InAs is less developed20,23–25. The reason is the higher covalent bonding character, which leads to challenges in precursor reactivity and in the growth control. Hence, harsher reaction conditions like higher temperatures are required, challenging size control and uniformity26–28 Although large InAs QDs grown epitaxially have been reported in 199929, the colloidal synthesis of QDs larger than 7 nm, with excitonic absorption peak above 1400 nm, remains a considerable challenge11,24,30. Larger sizes are essential for accessing deeper IR wavelengths and approaching bulk-like properties, but requires synthetic strategies that can overcome the limitations of precursor chemistry and growth dynamics.

Among III-V materials, InAs has the lowest covalent bonding character, making the synthesis more controllable28. However, the most developed synthesis routes for colloidal InAs QDs rely on pyrophoric, toxic, and not readily available arsenic precursors like tris(trimethylsilyl)arsine (TMSAs)10,11,20. In 2016, the commercially available and less toxic tris(dimethylamino)arsine (TDMAAs, or amino-As) was identified as a viable alternative10,31,32. Although its first use in the InAs QD synthesis was reported in 2000, the initial thermolysis method had several disadvantages compared to TMSAs-based methods, including long reaction times of up to 6 days and the production limited to amorphous nanoparticles (NPs) with sizes up to 2 nm10,33.

More recently, several synthesis approaches for InAs QDs using the 'greener' amino-As have been developed13,17,20,34,35. Commonly, these methods involve InCl3 in combination with an external reductant, such as diisobutylaluminium hydride (DIBAL-H) or dimethylethylamine aluminium hydride (DMEA-AlH3)13,17,20,34. For example, this was demonstrated when the largest non-elongated InAs QDs reported to date were produced by this method, achieving an absorption peak in the range up to ≈1850 nm and QD sizes up to ≈13 nm34. Also, the largest elongated colloidal InAs QDs reported so far (first absorption peak ≈1650 nm) were synthesized using InCl3, but in this case, with an alternative arsenic precursor30.

Another promising route for ‘green’ colloidal InAs QD synthesis is based on indium(I) chloride (InCl). This precursor serves as both an indium source and a mild reducing agent. In solution, it tends to disproportionate into indium(III) chloride (InCl3) and metallic indium (In)26. This eliminates the need for an additional reducing agent, as required in the case of InCl3 32. Furthermore, it prevents potential contamination of InAs QDs with metallic cations from the reducing agent. However, the indium side product may reduce the chemical yield, and its temperature-dependent equilibrium is not fully investigated. The synthesis protocol for InAs QDs based on this chemistry was published by Ginterseder et al., who reported a synthesis route for InAs QDs with a first absorption peak up to 1363 nm26. This method was later adapted for the synthesis of InSb and InP QDs36–38, but has not been further developed for InAs QDs.

A further synthesis strategy is the seeded growth approach, in which small, preformed nanocrystals serve as seeds. In this context, InAs clusters have emerged as promising precursors for controlled overgrowth13,39,40. The first demonstration by Tamang et al. in 2016 involved a combination of indium(III) oleate and TMSAs to form such clusters and seeds39. Two years later, Srivastava et al. reported a method that relied on InCl and amino-As13. In 2021, Kim et al. presented a process based on indium(III) acetate and TMSAs40. The largest InAs QDs obtained by the seeded growth method were ≈9 nm40.

In this work, rather than exploring alternative precursors to grow large InAs QDs, we present a strategy that combines the established InCl precursor chemistry26 with the use of clusters as readily available precursors. First, we synthesize InAs clusters from “green” InCl and amino-As precursors (Fig. 1a). We then use these clusters to produce small InAs QDs with a low dispersity in size via a heat-up method (Fig. 1b). To grow large QDs, we employ cluster precursors in either a seeded growth (Fig. 1c) or a seedless growth approach (Fig. 1d), and provide insights into the formation mechanism of the QDs from cluster precursors. Both seeded and seedless methods involve alternating cluster injection and annealing steps to drive the growth of non-elongated, non-agglomerated InAs NPs with tunable sizes up to 40 nm, exhibiting optical activity extending beyond ≈2600 nm. The resulting NPs show high crystallinity consistent with the bulk cubic structure of InAs and reach bulk values. Compared to non-elongated InAs QDs34, our NPs exhibit a further redshift in absorption of ≈1000 nm. The strategy also offers a potential for scalability and integration into continuous flow reactor systems, enabling the industrial production of RoHS-compliant, IR-active QDs. Our findings provide a basis for fundamental studies and applications in optoelectronic technologies, especially in the SWIR region.

Results
Synthesis of InAs cluster precursors
In the past, it has been shown that clusters have already served as precursors for the growth of different QD systems13,39,41–44. Also in our approach, the first stage of growing large InAs QDs involved the synthesis of small InAs clusters (Fig. 1a), which exhibited optical activity in the VIS range.

For cluster synthesis, amino-As solution in oleylamine (OAm) was hot-injected into a mixture of InCl in OAm and trioctylphosphine (TOP) at 130 °C, and the reaction was maintained for 76 min. A 3.1:1 ratio of In:As was used, as described in ref. 26 (for reaction yield, see “Methods”). Figure 2a shows absorption spectra of five InAs cluster precursors synthesized using this method, measured after removing insoluble byproducts. The spectra showed minimal variability, demonstrating the method’s reproducibility. In the high-resolution transmission electron microscopy (HR-TEM) images (Fig. 2b, c), small nanostructures can be seen. Some of the structures seem to form elongated aggregates (with short and long axes measuring ≈1 and ≈4 nm, respectively), possibly during the deposition process on the grids. Due to the low contrast, neither the crystallinity nor the shape of the clusters can be clearly determined from the HR-TEM images.

A representative selected area diffraction (SAED) pattern of InAs clusters (Supplementary Fig. 1) showed broad, diffuse diffraction pattern, suggesting either a short coherence length or disorder within the clusters’ crystal structure.

To investigate the nature of the insoluble byproducts formed during cluster growth, we performed X-ray diffraction (XRD) analysis (see Supplementary Fig. 2). The precipitate primarily contained metallic In, likely arising from the disproportionation of InCl, as reported in ref. 26. Traces of InAs and indium oxide (In2O3) were also detected. The formation of In2O3 could be attributed to side reactions with oxygen-containing impurities in OAm. No pure InCl was detected.

In subsequent experiments, clusters were also synthesized via hot injection at temperatures ranging from 110 to 180 °C. Supplementary Table 1 lists the spectral positions of the first absorption maxima for the clusters samples, measured after removal of insoluble byproducts. A higher reaction temperature and longer reaction time resulted in a redshift, indicating the formation of larger clusters.

To investigate cluster growth more thoroughly, a representative reaction was conducted at 110 °C and monitored by taking aliquots. Figure 3 shows photographs of aliquots taken before (Fig. 3a) and after (Fig. 3b) the sedimentation of insoluble byproducts. The color of the supernatant, ranging from yellow to dark red, indicated the formation of small InAs nanostructures over time. The absorption spectra (Fig. 3c) revealed an evolving absorption band in the VIS range (indicated by an arrow), which became more pronounced and redshifted as the reaction progressed, suggesting a reduction in quantum confinement during cluster growth. Additional absorption features were observed in the ultraviolet (UV) range at ≈315 and ≈350 nm. Prolonging the reaction time beyond 30 min led to a decrease in the prominence of the UV features.

We attribute the absorption features in the UV to molecular structures such as organometallic intermediates or small clusters of a few atoms. In a separate experiment (Supplementary Fig. 3), similar features were observed (Supplementary Fig. 4a). Comparing the corresponding absorption spectrum with those of early-stage aliquots taken during synthesis at 110 °C (see Fig. 3), we observed similar absorption maxima at ≈315 and ≈350 nm, with a higher intensity ratio (Supplementary Fig. 4b). This suggests that the absorption features correspond to the formation of specific small structures active in the VIS range.

While the formation process of the clusters including the origin of the structures absorbing in the UV is beyond the scope of this work, we demonstrated that the absorption features, and thus the cluster size, could be tuned via adjusting the growth temperature and reaction time. Furthermore, these clusters were found to be chemically stable and could be stored for years at room temperature (RT) within a nitrogen-filled glovebox, even after drying and redispersion in the solvent. For example, the absorption data of cluster samples after years of storage are shown in Supplementary Fig. 5.

Interestingly, a room-temperature reaction proved unsuitable for producing InAs clusters (see Supplementary Note 1 and Supplementary Fig. 6). The absorption spectra of the particles formed were consistent with metallic nanostructures as presented in Supplementary Figs. 7 and 8.

Nevertheless, the clusters synthesized at 130 °C for 76 min were used as precursors for the growth of larger InAs nanocrystals via seeded growth (Fig. 1c) and seedless growth (Fig. 1d), as will be described in the following.

Synthesis of InAs seeds
In the second stage of growing large InAs QDs via the seeded growth approach (Fig. 1c), we synthesized small InAs QDs to be used as seeds. These were prepared from clusters in a heat-up process (Fig. 1b). A similar heat-up method was employed by Srivastava et al.13, heating a so-called “amorphous prenucleation cluster solution”, obtained at RT, to a desired temperature between 180 and 290 °C to grow crystalline InAs NPs.

In our study, we explored various combinations of temperatures and reaction times. We first synthesized cluster precursors at either 130 or 180 °C, and then heated a cluster mixture to 300 °C, where the reaction was quenched either immediately or after a defined reaction time by cooling to RT (Fig. 4).

Clusters synthesized at 130 °C for 1 h are shown in Fig. 4a, with additional HR-TEM and high-angle annular dark-field scanning TEM (HAADF-STEM) images provided in Supplementary Fig. 9. Upon subsequent heating to 300 °C, small InAs QDs were formed, as seen in Fig. 4b. The absorption spectra of the particle solution exhibited a pronounced excitonic absorption peak (Fig. 4d, red line). However, a tendency to form ’necks’ between the QDs was observed in the TEM images. This is likely due to a small fraction of particles undergoing agglomeration, the deposition process during TEM sample preparation, or specific imaging conditions. Further annealing of the reaction mixture at 300 °C for 30 min led to additional growth of the QDs, but also to a broadening of the size distribution (Fig. 4c). The trend was consistent with the changes in the corresponding absorption spectra (Fig. 4d, blue and violet lines), which showed a redshift and broadening of the absorption onset during longer reaction times at 300 °C.

A significant increase in size and narrowing of size distribution were achieved by initially synthesizing clusters at a higher temperature of 180 °C for 15 min (Fig. 4e), followed by a temperature increase to 300 °C (Fig. 4f). This modification resulted in a redshift of the first absorption peak by ≈150 nm compared to the previous synthesis. The seeds showed lower size dispersity (12 % vs. 15%), and the corresponding XRD and HR-TEM data (Supplementary Figs. 10 and 11) confirmed the crystalline nature of these particles.

Further increasing the final reaction temperature to 320 °C produced larger QDs, but with a broader size distribution and a less pronounced absorption maximum (see Supplementary Fig. 12, double lines). Therefore, an initial reaction temperature of 180 °C, followed by a final reaction temperature of 300 °C (Fig. 4e, f), was adopted as the standard heat-up approach for seed production (for reaction yield, see “Methods”).

We analyzed the insoluble byproducts from the standard heat-up approach using TEM and XRD. From the TEM images (Supplementary Fig. 13), a mixture of size-disperse particles with undefined shapes, along with smaller spherical particles and darker particles, was observed. As in the case of the cluster synthesis, InAs, along with a small amount of In2O3 and metallic In, were identified from XRD (Supplementary Fig. 14).

Although the reaction mechanism of the heat-up synthesis was not investigated in detail, the method showed high reproducibility, as demonstrated by consistent absorption spectra of four seed solutions prepared via the standard heat-up method, and measured after separation of insoluble byproducts (Supplementary Fig. 15). Elemental analysis of the isolated QDs gave an In:As ratio of 1.78:1 (Supplementary Table 2). The In-rich QDs were in agreement with InAs QDs synthesized from amino-As13.

In all heat-up experiments described, insoluble byproducts from the initial cluster precursor synthesis were not removed prior to heating. In contrast, as a control, when insoluble byproducts of the cluster synthesis were removed by centrifugation prior to heating, smaller QDs with a broader size distribution and reduced concentration were formed (see Supplementary Fig. 12, dashed lines). TEM revealed the presence of larger, darker particles, likely metallic In (Supplementary Fig. 16), suggesting incomplete reaction in the initial cluster growth. These findings suggest that the byproducts may serve as a reservoir during the heat-up process, influencing the local chemical environment and promoting more uniform nucleation and growth of the QDs. However, prior to using the seeds for the growth of larger InAs QDs in the seeded growth approach, insoluble byproducts were consistently removed by centrifugation.

Seeded growth synthesis of large InAs QDs
In the last stage of growing large InAs QDs via the seeded growth approach, we used InAs cluster precursors and seed solutions after removing insoluble byproducts. Cluster precursor solutions were continuously injected into a solution of InAs seeds at a constant reaction temperature of 300 °C using a syringe pump. Key parameters, such as cluster and seed size, concentration, and injection rate of clusters, were critical for obtaining non-agglomerated InAs QDs larger than 8 nm. Suboptimal conditions, like i.e., too slow (3.0 mL h−1) or too high (36 mL h−1) cluster injection rates, or improper cluster precursor concentration, led to secondary nucleation and interparticle ripening (Supplementary Fig. 17). The effects of the different reaction conditions are summarized in Supplementary Table 3.

By optimizing these parameters, as detailed in Supplementary Table 4 and Supplementary Fig. 18, and by introducing injection-annealing cycles (see Fig. 1c), we directed the growth of non-agglomerated, large InAs QDs. Specifically, an injection rate of 6 mL h-1 was used for adding of 4.5 mL of InAs cluster solution (1.1 mg mL−1) into 6.0 mL of InAs seed solution (1.3 mg mL−1), attributing to one injection step, followed by a 30-min annealing step at 300 °C. This process was repeated up to 16 times (8 injection and 8 annealing steps, or 8 growth cycles) and could be quenched after each step depending on the desired QD size. We refer to this as our standard seeded growth synthesis. The samples were purified post-synthetically using size-selective precipitation techniques (hereafter referred to as ‘precipitation techniques’, see Methods). As a result, each growth step contributed to the increase in QD size, as observed in the fraction containing the largest QDs, as summarized in Supplementary Table 5.

Figure 5 summarizes the data of the resulting InAs QDs after applying the precipitation techniques. From the absorption spectra (Fig. 5a), multiple absorption features corresponding to excitonic intraband transitions45 were observed. For samples with the first absorption peak below ≈2000 nm, well-resolved absorption features were noted, along with the expected redshift upon growth. However, the spectra of the larger QDs showed lower quality due to their poor solubility at RT. The absorption edge for the largest QDs (produced after 8 growth cycles) shifted deep into the SWIR region, reaching up to ≈2300 nm (≈0.54 eV).

In Fig. 5b, we compared the experimental QD sizes and corresponding first absorption maxima with values calculated using Eq. (1) provided by Kuno et al.46, which relates the size of InAs QDs to the energy Eg of their first excitonic transition. This correlation is a slightly modified version of the one proposed by Yu et al.47. Both experimental and calculated values are provided in Supplementary Table 5 and are plotted in Fig. 5b. The good agreement between the experimental and calculated plots indicated that the Eg-d relationship, originally derived for InAs QDs with sizes up to 6 nm48, is also applicable to larger InAs QDs with sizes at least up to 18 nm.

Eg = 0.29 eV + 4.96 eV nm / d + 2.24 eV nm^2 / d^2 (1)

TEM and HR-TEM images provided in Fig. 5c–f showed InAs QD samples with low size dispersity and up to 18 nm in size. Larger QDs exhibited a preferred octahedral and “fortunacookie” morphologies, while smaller ones exhibited a preferred spherical and tetrahedral shapes. Before size selection, QDs obtained, e.g., in a 16-step synthesis had an average size of 14 nm (Supplementary Fig. 19). XRD patterns (Supplementary Fig. 20) confirmed the cubic zinc blende crystal structure of InAs, showing that the seeded growth synthesis provided highly crystalline InAs QDs.

To access the role of annealing steps in our seeded growth method, we conducted a control experiment where cluster solution was continuously injected without any annealing steps in between (Supplementary Table 6). Also here, non-agglomerated large InAs QDs were produced, but the absorption edge reached only 1750 nm after injection of the same amount (22.5 mL) of cluster precursor solution, compared to ≈1940 nm for the standard seeded growth method. The smaller QD size in the control experiment suggests that the annealing steps were crucial for promoting further QD growth, likely due to the lower reactivity of the cluster precursors. However, continuous injection without annealing could be advantageous for adapting the process to continuous flow reactors, with spatially separated nucleation and growth.

Seeded growth synthesis utilizing diluted seeds
To target the growth of even larger InAs QDs, we diluted the seed solution by a factor of five and performed a synthesis procedure similar to our standard seeded growth method, involving injection-annealing cycles. According to classical nucleation and growth theory28, dilution of the seed solution, where all seeds compete for the same amount of precursors, should promote the growth of larger QDs. Details of the synthesis parameters are provided in Supplementary Fig. 21, Supplementary Table 7, and in the Methods.

Already after the first injection of 4.5 mL of cluster solution, we achieved InAs QDs showing an absorption edge extending up to ≈1600 nm, compared to ≈1150 nm produced by the standard method with a fivefold higher seed concentration. Following annealing, the QDs grew so large that they became colloidally unstable in tetrachloroethylene (TCE) or toluene at RT, making them unsuitable for absorption measurements in solution. After 5 injection-annealing cycles (10 synthesis steps), InAs QDs with average sizes up to 36 nm (post-precipitation) were obtained; representative TEM images are provided in Fig. 6a, b. Before size-selection, the QDs in the sample obtained after 10 synthesis steps had an average size of 24 nm (see Supplementary Fig. 22). Compared to the standard seeded growth approach (Supplementary Fig. 19), the size distribution became broader (46% vs. 34%), and a bimodal size distribution could be observed. Nevertheless, the experiment revealed alternative InAs QD morphologies, including icosahedrons and 8-edged polyhedrons. The representative XRD diffractogram of the largest InAs QDs (≈36 nm) in Fig. 6c confirmed the cubic zinc blende crystal structure and showed high crystallinity.

Seedless growth synthesis of large InAs quantum dots
To further investigate the effect of seeds on QD size, we reduced the seed concentration to zero, replacing the seed solution with an equivalent volume of 5.9 mL OAm and 0.1 mL TOP. We refer to this method as seedless growth (see Fig. 1c).

For the seedless growth, all other reaction parameters were kept identical to those of the standard seeded growth approach (see 'Methods'. Remarkably, by applying this technique, we were able to produce even larger InAs NPs (Fig. 7a–d). Supplementary Table 8 summarizes the NP sizes achieved after each synthesis step. After 5 injection-annealing cycles (10 synthesis steps), we achieved InAs NPs with average sizes up to 40 nm, with some individual particles reaching 55–65 nm (Supplementary Figs. 23 and 24). A representative HR-TEM image is shown in Supplementary Fig. 25. The as-received NPs (prior to size-selection) had an average size of 34 nm and a bimodal size distribution (see Supplementary Fig. 26). Notably, the size distribution decreased compared to the seeded growth method utilizing diluted seeds, both before size selection (35% vs. 46%). The QDs exhibited morphologies similar to those observed in seeded growth syntheses, including tetrahedral, octahedral, 8-edged polyhedral, and ‘fortunacookie’ shapes49,50. Notably, the average size of the InAs NPs produced in this seedless growth method (after precipitation techniques were applied) was more than three times larger than the largest colloidal, non-elongated InAs QDs reported in ref. 34.

SAED analysis (Fig. 7e) and XRD diffraction pattern (Supplementary Fig. 27) confirmed the crystalline nature of the reaction product, consistent with the cubic zinc blende crystal structure of bulk InAs. SEM (scanning electron microscope) images of 40 nm large NPs drop-casted and dried on silicon wafers showed favorable stacking behavior (Supplementary Fig. 28) and highlighted their potential for self-assembly into structures with long-range order in two or three dimensions. These characteristics are particularly promising for applications such as the development of absorber layers in optoelectronic devices.

Absorption spectra of large, colloidally unstable InAs NPs in TCE (Supplementary Fig. 29a) showed absorption in the range up to ≈2600 nm, but without distinct absorption maxima. Beyond ≈2600 nm, scattering from NPs and overlap with ligand absorption interfered with the measurements.

Absorption measurements using an integrating sphere were not feasible in the MIR range due to technical limitations. Therefore, additional measurements were conducted on a substrate (Supplementary Fig. 29b). However, scattering effects and ligand absorption features persisted above ≈2600 nm. Despite the absence of distinct absorption maxima, a redshift in the absorption edge was observed, suggesting quantum confinement effects. In general, QDs sized between the electron Bohr radius (28.5 nm for InAs)51 and the exciton Bohr radius (30–44 nm for InAs)10,51,52 are expected to fall into the weak confinement regime, where absorption maxima are typically absent51,53. This means, in our case, that probably, no distinct absorption maxima would be observed for large InAs NPs in this size regime.

Given the ongoing debates surrounding the exciton Bohr radius of InAs QDs (ranging from 30 to 44 nm, as mentioned above)10,51,52, it remains uncertain whether InAs NPs larger than 30 nm can be classified as QDs. Even if they do, they likely would not exhibit distinct absorption bands, as they would fall into the weak confinement regime. Instead, they would be better classified as near-bulk QDs51. Due to the addressed wavelength range, an extensive optical characterization of the large InAs particles’ properties requires further improvements. This characterization is within the scope of follow-up studies, where measurements on the near-bulk QDs could provide insights into the exciton Bohr radius of InAs QDs, a fundamental parameter in the study of QD systems.

We also performed initial experiments to investigate the mechanism behind the seedless growth process. As detailed in Supplementary Note 2, we observed a delay of several minutes after the start of cluster precursors supply, indicated by the color change of the reaction solution (Supplementary Fig. 30). We attribute this delay to the dissolution and monomer release process of the clusters, during which the concentration of free In3+ and As3− monomers increased as cluster precursors were introduced. Once the critical concentration was reached, nucleation of small InAs QDs (seeds) began. These QDs continued to grow, forming larger particles. Due to the relatively low number of these naturally formed seeds, the final particles were larger compared to those obtained using the same amount of cluster precursor in the seeded growth method. However, since these seeds could format different times during the reaction (continuous nucleation), the growth period for the final particles varied, leading to a broader distribution in particle size.

These findings are supported by absorption spectra taken during the cluster injection process (Supplementary Fig. 31, black and red lines). We observed an increase in concentration over time, accompanied by higher absorbance at longer wavelengths, indicating the growth of larger nanostructures. A sharp absorption maximum at ≈350 nm indicated the presence of ultra-small, naturally formed InAs seeds (Supplementary Fig. 31, black line). This peak slightly broadened with further cluster supply (Supplementary Fig. 31, red line). Comparing this to the spectra of early-stage structures from Fig. 3c (also shown in Supplementary Fig. 31, dashed green and violet lines), we observed a ≈320 nm minimum, where the early-stage structures exhibited a second-order maximum. This suggests that early-stage structures were not present in these aliquots. In addition, there was no overlap with the band offset (532 nm) of the initial cluster solution (Supplementary Fig. 31, blue double line), further emphasizing the dissolution and conversion process of the clusters.

To minimize size broadening, future studies should focus on developing strategies to better control the nucleation process. Possible approaches include reducing the initial volume of hot solvent, adjusting the cluster injection rate immediately after nucleation, and optimizing the cluster concentration.

In a control experiment, no annealing steps were conducted. Consistent with the control-seeded growth experiment, non-agglomerated, large InAs QDs were still produced. After injecting the same volume of cluster solution (22.5 mL) as in the standard seedless growth approach, the resulting QDs were 27 nm in size, compared to 40 nm when annealing steps were included (after precipitation techniques were applied). This suggests that alternating annealing steps play a crucial role in the growth process when using clusters as precursors.

In conclusion, our work demonstrates colloidal synthesis strategies for InAs NPs across a broad size regime, from clusters to near-bulk QDs, overcoming long-standing challenges in the growth of large III-V nanocrystals. Our ‘green’ synthesis approach introduces a versatile, scalable platform to deliver long-term stable InAs clusters as precursors, enabling both the seeded growth and the seedless growth pathways. This flexibility allows tuning of size and optical properties, with access to NPs reaching (and possibly exceeding) the exciton Bohr radius, depending on its 'true' value, which is still under discussion.

Beyond enabling access to large InAs QDs reaching near-bulk values, our method offers a more sustainable alternative to traditional organometallic routes10,26,32, combining the use of less hazardous and cheaper, commercially available chemicals26 with involving clusters as precursors13,39,40. The issue with metallic In formation26 was addressed by removing the byproducts of cluster and/or seeds synthesis prior to their use in subsequent seeded or seedless growth. The strategy is compatible with continuous flow reactors, enabling large-scale production of RoHS-compliant Pb- and Hg-free colloidal QDs for the NIR and SWIR regions. By extending the accessible size range and optimizing the synthetic toolbox for InAs NPs, this work provides a basis for studies and applications in IR optoelectronics, including biophotonics, telecommunications, and sensing.

Methods
Materials
Indium(I) chloride (InCl, anhydrous, PURATREM, 99.99%), tetrachloroethylene (TCE, anhydrous, Th. Geyer, ≥99%), tri-n-octylphosphine (TOP, Strem Chemicals, 97%), tris(dimethylamino)arsine (TDMAAs, amino-As, Strem Chemicals, 99%), liquid paraffin oil (Th. Geyer), toluene (anhydrous, Sigma-Aldrich, 99.8%), and ethanol (anhydrous, VWR, ≥99.8%) were used as received. Oleylamine (OAm, Merck, 98%) was dried at 80 °C under vacuum for 1.5 h. All chemicals were stored and handled in an inert nitrogen atmosphere within a glovebox, where OAm was kept refrigerated.
Caution: Although amino-As is considered as a 'greener' precursor, it is highly toxic and should only be handled inside a glovebox under an inert atmosphere.

Synthetic procedures
All synthesis, purification, and sample preparation procedures were conducted inside a nitrogen-filled glovebox equipped with a Schlenk line and a Minispin centrifuge. Larger volumes were centrifuged outside the glovebox in hermetically sealed tubes.

Arsenic precursor solution for cluster synthesis
The arsenic precursor was prepared in situ following a procedure from ref. 26 with modifications, using 150 µL of amino-As in 2.0 mL of OAm. The solution was heated to 50 °C and stirred for at least 15 min, until no bubble formation was observed.

Synthesis of InAs cluster precursors
For the synthesis of InAs cluster precursors, we used a procedure from ref. 26 with modifications. A mixture of InCl (0.300 g, 2.00 mmol, 3.1 eq.) and dry OAm (28.8 mL) was degassed at RT for 10 min. After switching to nitrogen, 1.2 mL of TOP was injected, and the mixture was heated to 110–180 °C. The arsenic precursor solution (1.6 mL, 0.64 mmol As, 1 eq.) was then added via hot injection. The reaction was maintained for 2 min to 3 h 20 min at a constant temperature, depending on the desired average cluster size (Supplementary Table 1). The synthesis was scaled down proportionally if smaller volumes of cluster precursor solution were sufficient. Insoluble byproducts were removed by sedimentation or centrifugation.
Clusters used as precursors in the seeded and/or seedless growth approaches were synthesized at 130 °C for 76 min. The reaction yield of these clusters was 49% based on As and 16% based on In, as determined by thermogravimetric analysis (TGA), with a concentration of 1.9 mg mL−1.
The reaction yield was estimated as follows. First, the reaction mixture was centrifuged to separate insoluble byproducts. Then, 3.0 mL of 36.1 mL original red supernatant containing InAs clusters (stock solution) was washed with ethanol. The resulting pellet was used for the TGA. With 20.26% of inorganic compounds, this resulted in 5.7 mg of InAs clusters. Since the original solution was 31.6 mL, this corresponded to 59.99 mg (0.316 mmol) of InAs clusters. For further details, see Supplementary Note 3 and Supplementary Table 9.

Synthesis of InAs seeds
InAs seeds were synthesized using a heat-up method. In our standard procedure, InAs clusters were first synthesized at 180 °C for 15 min, as described above. The reaction mixture was then heated to 300 °C and immediately cooled to RT using a paraffin oil bath. Insoluble byproducts were removed by sedimentation or centrifugation. The reaction yield of the resulting InAs seeds was 90% based on As and 23% based on In, as determined by TGA. The concentration of seeds was 3.3 mg mL−1.
To estimate the reaction yield, the reaction mixture was first centrifuged to remove any insoluble byproducts. Then, 900 µL of the supernatant containing InAs seeds were washed with ethanol, and the resulting pellet was used for the TGA. The sample contained 54.65% inorganic residuals, which corresponded to 3.1 mg of inorganic InAs material. For a total volume of 23.7 mL of the stock seed solution, it resulted in 81.6 mg (0.430 mmol) of InAs. For further details, see Supplementary Note 4 and Supplementary Table 10.

Seeded growth synthesis of large InAs QDs
Large InAs QDs were synthesized via a seeded growth method using InAs seeds and InAs cluster precursors. Prior to use, the cluster precursor and seed mixtures were separated from insoluble byproducts by centrifugation.
To ensure reproducible reaction conditions, the sizes and concentrations of seeds and clusters were monitored by absorption spectroscopy using the position and magnitude (optical density, OD) of the excitonic absorbance maximum (see Supplementary Tables 4 and 7). Concentrations were equalized by dilution with dry OAm to obtain the target OD values. For the standard seeded growth approach, the seed concentration was adjusted to 1.3 mg mL−1 (OD 0.16 at the absorption maximum of 931 nm), whereas for the diluted seed approach, it was adjusted to 0.24 mg mL−1 (OD 0.034). In both cases, a total seed solution volume of 6.0 mL was used. The InAs cluster concentration was set to 1.1 mg mL−1 (OD 0.22 at the absorption maximum) for both approaches. Depending on the number of synthesis steps, 4.5–36.0 mL of InAs cluster solution was loaded into a syringe.
A 6.0 mL volume of InAs seed solution was transferred to a three-neck round-bottom flask and heated to 300 °C under nitrogen flow. Upon reaching 300 °C, 4.5 mL of InAs cluster solution (corresponding to 4.9 mg of InAs) was continuously injected into the seed solution using a syringe pump at a rate of 6 mL h−1. This was followed by an annealing step of 30 min at the same temperature. The injection-annealing cycle was repeated multiple times to achieve the desired QD size (see Supplementary Table 5). A control experiment was performed without the annealing steps (Supplementary Table 6).
During quenching of the reaction in a paraffin oil bath, the black reaction mixture turned brown and became unstable, which was attributed to the presence of large InAs QDs that are colloidally unstable in OAm at lower temperatures.
InAs QD fractions with a low polydispersity were isolated using size-selective precipitation with anhydrous toluene as the solvent and ethanol as the non-solvent. The reaction mixture was first shaken and centrifuged to separate QDs with sizes above ≈9 nm, which were colloidally unstable in OAm at RT but stable in toluene and TCE for sizes up to ≈19 nm. If a pellet formed, it was dispersed in toluene or TCE, and centrifuged again to separate QDs larger than ≈19 nm. In the final step, if a pellet formed, it was dispersed in TCE or toluene, and ethanol was added dropwise until turbidity was observed. The mixture was centrifuged, and the resulting pellet was dispersed in TCE for characterization. If no pellet formed, the supernatant containing QDs was subjected to size-selective precipitation using ethanol as the non-solvent. A rainbow-like shimmer observed in regions of thin pellet thickness was attributed to interference effects, indicating an narrow NP size distribution.
For determining the reaction yield of the 16-step standard seeded growth synthesis, 500 µL of the reaction mixture was washed with ethanol, and the resulting pellet was used for the TGA. With 11.52% of inorganic material, this resulted in 3.7 mg of InAs. For 42 mL of the original reaction mixture, this corresponded to 36 mg (0.19 mmol) of InAs. For calculations of the reaction yield, see Supplementary Note 5.

Seedless growth synthesis of large InAs QDs
The seedless growth method was conducted analogously to the standard seeded growth approach, with the only difference being that an OAm-TOP solution (5.9 mL OAm and 0.1 mL TOP) was used instead of the seed solution (6.0 mL), see Supplementary Table 8. In a control experiment, no annealing steps were included. Purification was performed as described for the seeded growth approach. After storage of the reaction product obtained from 10 synthesis steps at RT without agitation, the supernatant became completely clear and colorless, indicating that all synthesized NPs, likely larger than ≈9 nm, had sedimented.
For determining the reaction yield of the 10-step seedless growth synthesis, 1000 µL of the reaction mixture after shaking was washed with ethanol and dispersed in 100 µL of TCE, from which 25 µL was used for the TGA, resulting in 6.15% inorganic material (3.5 mg InAs). For 28.5 mL of the final reaction solution, this results in 24.5 mg (0.129 mmol) of InAs. For determining the reaction yield of the 6-step seedless growth synthesis, 45 µL of the reaction mixture was used for TGA without further purification, with 0.09% inorganic material (0.0392 mg) in 43.6 mg of a liquid sample containing non-evaporable OAm and TOP. In a total reaction volume of 19.5 mL, it corresponds to 17.0 mg (0.0896 mmol) of InAs. For calculations, see Supplementary Note 6.

Optical absorption spectroscopy
Absorption measurements were performed using a Cary 5000 UV-Vis-NIR spectrophotometer (Varian) in a dual-beam mode. Sample preparation was carried out inside a glovebox.
For absorption measurements in solution, the sample was placed in a 1.00-mm-thick quartz cuvette from Hellma and hermetically sealed. After measurements, the sample was returned to the glove box. For measurements up to ≈2300 nm, 110-QS High Performance cuvettes (200–2500 nm) were used, whereas for measurements in the MIR range, 110-QX Extended Range cuvettes (200–3500 nm) were utilized.
Sample preparation for absorption measurements on substrates was conducted inside a glovebox. Purified QDs were deposited as a thin film by drop-casting from TCE or toluene onto a 25 mm diameter water-free fused silica (SiO2) substrate (Andover Corporation). After solvent evaporation, measurements were performed under ambient conditions.

ATR-IR spectroscopy
ATR-IR measurements were conducted using a Golden Gate ATR System from Bruker Optik GmbH (6000 – 600 cm−1). Prior to measurement, the QD sample was repeatedly precipitated and redispersed in toluene inside a glovebox. The resulting dispersion was drop-cast onto the ATR crystal under ambient conditions, allowing the solvent to evaporate. This procedure was repeated until a sufficiently thick film had formed on the crystal surface. Before sample acquisition, the background spectrum was recorded and automatically subtracted from the sample spectrum.

TEM and SAED
TEM images and SAED patterns were acquired using a JEOL JEM 1011 transmission electron microscope equipped with a LaB6 cathode operating at an acceleration voltage of 100 kV, and a SIS CCD camera system (1376 × 1032 pixels). The purified and diluted sample was drop-cast onto a carbon-coated copper grid (Science Services) under normal conditions, allowing the solvent to evaporate.

HR-TEM and HAADF-STEM
HR-TEM and HAADF-STEM samples were prepared under a nitrogen atmosphere using the same procedure as for TEM sample preparation. Images were obtained using JEOL JEM-2200FS equipped with a field emission gun.

SEM
For SEM analysis, the purified and concentrated QD sample was drop-cast onto a silicon wafer under ambient conditions, followed by solvent evaporation. SEM was performed using an FEI Quanta 3D FEG instrument equipped with a field emission gun.

XRD
XRD sample preparation was carried out inside a glovebox. A purified dispersion in toluene was drop-cast onto a silicon wafer, and the solvent was allowed to evaporate. Then, the resulting film was optionally covered with an insulating Kapton® polyimide tape to prevent exposure to oxygen and moisture. Measurements were performed using either a Panalytical MPD X’Pert Pro diffractometer or a Philips X’Pert PRO MPD diffractometer, both equipped with a CuKα X-ray source, under continuous nitrogen flow. Backgrounds from empty wafers, or those covered with Kapton® polyimide tape, were subtracted from sample measurements.

Elemental analysis
The sample was prepared inside a glovebox by washing three times with ethanol and finally dissolving in toluene. Outside the glovebox, the sample was digested at 250 °C in a microwave using nitric acid (HNO3) and water, and subsequently diluted. The analysis was performed in triplicate to ensure reproducibility, using ICP-OES spectrometer ARCOS from Spectro.

TGA
TGA was employed to determine the weight percentage of the inorganic component in the sample, which was then used to calculate the reaction yield. A measured volume of the liquid sample was placed into a TGA sample cup inside a glovebox, allowing the solvent to evaporate at 80 °C. The mass of the remaining residue was subsequently recorded. TGA measurements were performed using a NETZSCH TG 209 F1 220-10-039-K thermogravimetric analyzer.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The manuscript from Salikhova et al. describes a method to synthesize very large colloidal InAs QDs. Given the relevance of such QDs for SWIR applications and the increasing interest from the research community in this class of QDs, I believe the manuscript could be worth of publication in Nature Communication. Nonetheless, the manuscript cannot be accepted in its current state, given the lackluster and qualitative discussion and lack of experimental details (seriously hampering the possibility to reproduce such synthetic approach in other labs). An extensive revision of the manuscript is necessary before it can be accepted for publication.\nPlease, see my comments and questions here below:\n- In general, the authors should revise the manuscript to avoid qualitative words like “huge”, “increased monodispersity”. In addition, the text is sometimes hard to follow (especially the final parts); the authors should improve its clarity.\n- The authors wrote: “The as-taken aliquots were grey-brown due to the presence of metallic indium and insoluble organometallic intermediates. After sedimentation, the real color of the cluster solution could be observed.” The authors should show XRD or another analysis to confirm the nature of the sediment (an elemental analysis?).\n- How was the size of the clusters estimated in Figure 3a? It seems impossible from low resolution TEM. The authors should carry out HAADF-STEM to understand shape and size.\n- What is the reaction yield of the clusters (e.g., those shown in Figure 3a)?\n- The authors wrote: “For example, the clusters synthesized at a temperature of 135 °C for 1 h (Fig. 3a) and then heated up to 300 °C (Fig. 3b) led immediately to the formation of spherical particles, but with a tendency to form `necks` between the QDs”. How is it possible that the absorption spectrum is so well defined if necking and/or aggregation and precipitation are present? One would not expect to observe the exciton peak in these conditions.\n- The authors wrote: “The TEM images of those samples revealed the presence of larger, darker appearing nanostructures (see Supplementary Fig. 8), most likely metallic indium nanoparticles. This assumes that the cluster growth in the first reaction step was not stoichiometric, but that there was still unreacted In precursor present, bevor the QD growth started.” When heating the clusters up to 185°C and then increasing the temperature to 300°C what are the byproducts of the synthesis and what is the synthesis yield? What is the stoichiometry of the InAs QDs made with this route?\n- How can the authors calculate the amount of starting InAs QDs and clusters to be used in the seeded-growth approach, considering that in both cases they have to remove byproducts?\n- The authors wrote: “For the synthesis process, 4.5 mL of InAs cluster solution was slowly injected into a solution of InAs seeds, followed by 30-minute annealing steps. This process was repeated multiple times, while the reaction temperature was maintained at 300 °C.” Please, explain this procedure in more details as it is written now it is impossible to understand it.\n- The authors wrote: “By tuning the concentration and size of clusters and seeds, as well as the injection rate, we were able to control the growth process, i. e., we managed to avoid side reactions such as interparticle ripening or secondary nucleation.” Please, also here include the parameters used and add relevant experimental details (which concentrations and sizes were used? What are the results for non-optimized parameters, all the discussions are extremely lackluster and superficial).\n- What does it mean, “a 16-step seeded growth synthesis”? Are the authors injecting 16 times the precursors? In addition, the clusters the authors inject, at what temperature are they prepared (do the authors centrifuge each of these 16 additions to avoid injecting metallic or precipitating stuff)?\n- “Fig. 4a shows that we obtained InAs QDs with well-defined multiple absorption features” Please explain the absorption features, are these real electronic transitions?\n- The authors wrote: “The absorption spectra of the samples with larger sizes are of less quality, because these particles were hardly soluble at room temperature”, then in the next line:“These results show that the huge non-agglomerated InAs QDs are highly monodisperse and highly crystalline.” Which one is which? This makes no sense.\n- The authors wrote: “We compared our experimental results for QD sizes and first absorption maxima (Supplementary Table 3) with the values calculated using the formula provided by Kuno et al.[17], which is a slightly modified version of the formula from [18]. This formula is based on the relationship between the first exciton transition peak energy and QD size. The resulting plot (Supplementary Fig. 11) demonstrates that the formula, originally developed for InAs QDs with average sizes up to 6 nm[19], remains applicable to larger QDs with sizes at least up to ~ 18 nm.” Please, add a graph with all data points, like this is very hard to follow.\n- The authors wrote: ““In a control experiment, we also tested if the continuous injection of cluster solution without performing the annealing steps in between also leads to non-agglomerated huge InAs QDs. In fact, this procedure also worked, but the final absorption edge was only 1,750 nm after injecting 22.5 mL of cluster solution (see Supplementary Table 4). This shows that the annealing steps are highly beneficial for the QD growth from cluster precursors, most likely due to the low reactivity of the clusters.” Please explain what are these annealing steps.", "reviewer_2": "This paper describes a novel method for growing large InAs QDs up to around 40 nm with high crystallinity and good size control starting from non-pyrophoric precursors. It addresses the long-standing challenge of extending the absorption range of InAs QDs in SWIR from 1600 nm to much longer wavelengths, beyond 2600 nm. The main approach relies on the use of well-defined InAs clusters obtained at lower temperature (180°C), which are either grown to 4 nm nanocrystals used in a seeded-growth reaction, or directly applied in a heat-up approach. The samples were characterized using standard techniques, in particular absorption spectroscopy, X-ray diffraction and TEM, and the main reaction parameters were explored to optimize the synthesis methods. In the introdution and conclusion, a bigger accent could be put on the impact for SWIR applications, since it presents a core achievement of the work and there are not much other Pb- and Hg-free QDs that can reach this region.\nAll in all, this manuscript appears perfectly suitable for puclication in Nature Communications, due to the originality of the approach and quality of the results, which open up new horizons.\nNonetheless there is a list of points which should be addressed:\n1) The difference between seeds and clusters is a bit hard to follow, especially in the second part of the manuscript, I would suggest to elaborate in more details figure 1 with some key features of both. Fig. 1 could also be improved to make it visually more attractive.\n2) What are the reaction yields for the cluster synthesis and for the seeded-growth synthesis? insoluble side-products such as metallic indium (p. 3) were observed. In other words, how much, approximately, of the initially used InCl transforms into clusters and how much into In(0)? Does the yield change with bigger particles? Or between seedless and seeded growth?\n3) Did the authors also try the seedless growth without annealing steps?\n4) In Fig.2 the T0 spectrum could be added.\n5) The absorption spectra of the >20 nm nanocrystals could have been taken on solid samples by applying diffuse reflectance spectroscopy instead of liquid phase measurements in TCE. Given the unique size regime of the obtained samples, this information would have been quite interesting and would potentially allow to draw figure S11 (which I suggest to put into the main manuscript) up to 40 nm. Also, it would allow to give a more precise evaluation of the absorption range covered by the obtained samples, the value of 2600 nm seems to be a rough estimation.\n6) In SI, Fig 1, not sure if the evolution is related to the reaction proceeding over longer times (two years!), or particles being slowly oxidized by traces of oxygen that might be present in the inert atmosphere.\n7) Experimental findings should not be discussed in the Conclusions but in the Discussion section. In particular, Fig. S16 (the RT evolution of clusters) is intriguing: the authors ascribe the sharp absorption features to the formation of metallic nanoparticles - are there any data supporting this hypothesis?\n8) The last phrase of the conclusions says that the continuous injection approach could be easily adapted to continuous flow synthesis. How could this be practically achieved? It seems that the continuous injection of precursors to a given reaction volume is indeed one step difficult to implement in continuous flow (?)\n9) Given the size distribution, the specification of 40.5 nm looks like excessive precision, I would suggest throughout the manuscript to mention that the method gives access to QDs of up to 40 nm size.\n10) Fig. 2: the inscription on the vials should be removed and eventually be replaced by a real legend.\n11) A 1:1 In:As ratio has been applied for the cluster synthesis. In principle a 3:1 ratio would be required to reduce As from +3 to -3, it should be discussed why 1:1 is used.\n12) The use of the term \"highly monodisperse\" may not be appropriate for the clusters, as their absorption spectra are not that well defined showing a rather broad excitonic peak. For the TEM images a couple of size histograms would be helpful.\n13) The particles in Fig. 3a with an absorption maximum at 556 nm are estimated to have a size of 2.3 nm. Is this consistent with the sizing curve of InAs QDs? They could be likely smaller (cf Fig. S2)\n14) In the Introduction there is a lack of references and precision: use of vague phrases in the introduction (“extraordinary optoelectronic properties”, “crucial role”, “variety of materials”, “harsher reaction conditions”, “several disadvantages”). For example, while as stated no further developments of the In(I)Cl / aminopnictogen method have been reported for InAs QDs, this synthetic route has been used for InP and InSb, which could be mentioned in the introduction.\n15) On p. 5 it is stated that keeping the insoluble side-products from the cluster synthesis improves the quality of the final QDs leading to larger sizes and narrower size distributions. Do the authors have any hypothesis on the mechanisms behind this behavior?\n16) Fig. S6: the reference diffraction pattern of InAs should be added. Idem Fig. S10\n17) Fig. S7: why absorbance is given in arbitrary units?\n18) In the Manuscript and Supplementary Information \"heating up\" should be termed \"heat-up\" throughout the text.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_4": "The manuscript from Salikhova et al. describes a method to synthesize very large colloidal InAs QDs. Given the relevance of such QDs for SWIR applications and the increasing interest from the research community in this class of QDs, I believe the manuscript could be worth of publication in Nature Communication. Nonetheless, the manuscript cannot be accepted in its current state, given the lackluster and qualitative discussion and lack of experimental details (seriously hampering the possibility to reproduce such synthetic approach in other labs). An extensive revision of the manuscript is necessary before it can be accepted for publication. Please, see my comments and questions here below:\n- In general, the authors should revise the manuscript to avoid qualitative words like “huge”, “increased monodispersity”. In addition, the text is sometimes hard to follow (especially the final parts); the authors should improve its clarity.\n- The authors wrote: “The as-taken aliquots were grey-brown due to the presence of metallic indium and insoluble organometallic intermediates. After sedimentation, the real color of the cluster solution could be observed.” The authors should show XRD or another analysis to confirm the nature of the sediment (an elemental analysis?).\n- How was the size of the clusters estimated in Figure 3a? It seems impossible from low resolution TEM. The authors should carry out HAADF-STEM to understand shape and size.\n- What is the reaction yield of the clusters (e.g., those shown in Figure 3a)?\n- The authors wrote: “For example, the clusters synthesized at a temperature of 135 °C for 1 h (Fig. 3a) and then heated up to 300 °C (Fig. 3b) led immediately to the formation of spherical particles, but with a tendency to form `necks` between the QDs”. How is it possible that the absorption spectrum is so well defined if necking and/or aggregation and precipitation are present? One would not expect to observe the exciton peak in these conditions.\n- The authors wrote: “The TEM images of those samples revealed the presence of larger, darker appearing nanostructures (see Supplementary Fig. 8), most likely metallic indium nanoparticles. This assumes that the cluster growth in the first reaction step was not stoichiometric, but that there was still unreacted In precursor present, bevor the QD growth started.” When heating the clusters up to 185°C and then increasing the temperature to 300°C what are the byproducts of the synthesis and what is the synthesis yield? What is the stoichiometry of the InAs QDs made with this route?\n- How can the authors calculate the amount of starting InAs QDs and clusters to be used in the seeded-growth approach, considering that in both cases they have to remove byproducts?\n- The authors wrote: “For the synthesis process, 4.5 mL of InAs cluster solution was slowly injected into a solution of InAs seeds, followed by 30-minute annealing steps. This process was repeated multiple times, while the reaction temperature was maintained at 300 °C.” Please, explain this procedure in more details as it is written now it is impossible to understand it.\n- The authors wrote: “By tuning the concentration and size of clusters and seeds, as well as the injection rate, we were able to control the growth process, i. e., we managed to avoid side reactions such as interparticle ripening or secondary nucleation.” Please, also here include the parameters used and add relevant experimental details (which concentrations and sizes were used? What are the results for non-optimized parameters, all the discussions are extremely lackluster and superficial).\n- What does it mean, “a 16-step seeded growth synthesis”? Are the authors injecting 16 times the precursors? In addition, the clusters the authors inject, at what temperature are they prepared (do the authors centrifuge each of these 16 additions to avoid injecting metallic or precipitating stuff)?\n- “Fig. 4a shows that we obtained InAs QDs with well-defined multiple absorption features” Please explain the absorption features, are these real electronic transitions?\n- The authors wrote: “The absorption spectra of the samples with larger sizes are of less quality, because these particles were hardly soluble at room temperature”, then in the next line:“These results show that the huge non-agglomerated InAs QDs are highly monodisperse and highly crystalline.” Which one is which? This makes no sense.\n- The authors wrote: “We compared our experimental results for QD sizes and first absorption maxima (Supplementary Table 3) with the values calculated using the formula provided by Kuno et al.[17], which is a slightly modified version of the formula from [18]. This formula is based on the relationship between the first exciton transition peak energy and QD size. The resulting plot (Supplementary Fig. 11) demonstrates that the formula, originally developed for InAs QDs with average sizes up to 6 nm[19], remains applicable to larger QDs with sizes at least up to ~ 18 nm.” Please, add a graph with all data points, like this is very hard to follow.\n- The authors wrote: ““In a control experiment, we also tested if the continuous injection of cluster solution without performing the annealing steps in between also leads to non-agglomerated huge InAs QDs. In fact, this procedure also worked, but the final absorption edge was only 1,750 nm after injecting 22.5 mL of cluster solution (see Supplementary Table 4). This shows that the annealing steps are highly beneficial for the QD growth from cluster precursors, most likely due to the low reactivity of the clusters.” Please explain what are these annealing steps."}, "author_response": "Response to the Reviewer #1\nWe sincerely thank the Reviewer for their insightful suggestions and valuable feedback. We\nhave carefully addressed the points raised in the review and made the following revisions.\nThe manuscript from Salikhova et al. describes a method to synthesize very large colloidal InAs\nQDs. Given the relevance of such QDs for SWIR applications and the increasing interest from\nthe research community in this class of QDs, I believe the manuscript could be worth of\npublication in Nature Communication. Nonetheless, the manuscript cannot be accepted in its\ncurrent state, given the lackluster and qualitative discussion and lack of experimental details\n(seriously hampering the possibility to reproduce such synthetic approach in other labs). An\nextensive revision of the manuscript is necessary before it can be accepted for publication.\nPlease, see my comments and questions here below:\n- In general, the authors should revise the manuscript to avoid qualitative words like “huge”,\n“increased monodispersity”. In addition, the text is sometimes hard to follow (especially the\nfinal parts); the authors should improve its clarity.\nWe sincerely thank the reviewer for this constructive comment.\nIn response to the reviewer’s suggestion, we have carefully revised the manuscript to replace\nsubjective expressions and qualitative terms such as ‘huge’, ‘ultra-large’, and ‘increased\nmonodispersity’ with more precise, quantifiable descriptions. This revision enhances the\nclarity and accuracy of our work. We have also revised the manuscript title for greater\nspecificity.\nAdditionally, we have focused on improving the clarity and flow of the manuscript, especially\nin the final sections. We believe these revisions will address the concerns raised and hope that\nthe updated manuscript now meets the expected standards.\nWe appreciate the reviewer’s valuable feedback and hope that the revised manuscript now\nmeets the expected standards.\n1\n- The authors wrote: “The as-taken aliquots were grey-brown due to the presence of metallic\nindium and insoluble organometallic intermediates. After sedimentation, the real color of the\ncluster solution could be observed.” The authors should show XRD or another analysis to\nconfirm the nature of the sediment (an elemental analysis?).\nWe thank the reviewer for this insightful suggestion.\nTo provide stronger evidence for the nature of the sediment, we have performed XRD analysis.\nThe new data, now included in Supplementary Fig. 2, clearly indicate that the sediment\nconsists predominantly of metallic indium, with minor contributions from In O and InAs. The\n2 3\npresence of traces of In₂O₃ is likely due to side reactions between the indium precursor and\ntrace amounts of oxygen-containing impurities in oleylamine. No pure InCl was detected.\nTo clarify this in the manuscript, we have added the following discussion on p. 6 of the revised\nversion: 'To investigate the nature of the insoluble byproducts formed during cluster growth, we\nperformed X-ray diffraction (XRD) analysis (see Supplementary Fig. 2). The precipitate primarily\ncontained metallic In, likely arising from the disproportionation of InCl, as reported previously[26]. Traces\nof InAs and indium oxide (In O ) were also detected. The formation of In O could be attributed to side\n2 3 2 3\nreactions with oxygen-containing impurities in OAm. No pure InCl was detected.[42]’\n- How was the size of the clusters estimated in Figure 3a? It seems impossible from low\nresolution TEM. The authors should carry out HAADF-STEM to understand shape and size.\nWe thank the reviewer for this valuable comment.\nDue to small size of clusters, and the low contrast, we could only estimate the size in the first\nplace, and we had estimated the size based on the longer axis of these elongated structures.\nWe have now proceeded additional HR-TEM and also HAADF-STEM measurements (as\nsuggested) to understand the shape and the size more carefully, and added the images to\nSupplementary Fig. 9. Also, from those images it can be seen that the clusters seem to form\nelongated aggregates – possibly during deposition on the TEM grids. Hence, we estimated the\nsize based on the average width of these aggregates to be 1.4 nm, which has been added to\nFig. 4a of the revised manuscript (corresponding to Fig. 3a in the original version).\n- What is the reaction yield of the clusters (e.g., those shown in Figure 3a)?\nWe thank the reviewer for raising this point. We have now determined the reaction yield for\nthe clusters prepared at 130 °C for 76 min, which we use as cluster precursors in both the\nseeded and seedless growth approaches. The reaction yield of the clusters was ~49% (related\nto As). This information has been added to the revised manuscript in the Methods section and\nSupplementary Note 3.\n2\n- The authors wrote: “For example, the clusters synthesized at a temperature of 135 °C for 1 h\n(Fig. 3a) and then heated up to 300 °C (Fig. 3b) led immediately to the formation of spherical\nparticles, but with a tendency to form `necks` between the QDs”. How is it possible that the\nabsorption spectrum is so well defined if necking and/or aggregation and precipitation are\npresent? One would not expect to observe the exciton peak in these conditions.\nWe thank the reviewer for this important point.\nThis is likely due to a small fraction of particles undergoing agglomeration. Another possible\nexplanation is that necking occurred during the deposition of samples for TEM analysis, or as\na result of the TEM imaging conditions. We have added these points to the revised manuscript\n(p. 9): ‘The absorption spectra of the particle solution exhibited a pronounced excitonic absorption\npeak (Fig. 4d, red line). However, a tendency to form `necks` between the QDs was observed in the\nTEM images. This is likely due to a small fraction of particles undergoing agglomeration, the deposition\nprocess during TEM sample preparation, or specific imaging conditions.’\nAt this point we would like to address a discrepancy in the reported reaction temperature. The\nvalue of 135 °C was mistakenly recorded. After review, we confirmed that the actual reaction\ntemperature was maintained at 130 °C throughout the experiment. This correction has been\nmade in the revised manuscript (p. 9, Fig. 4).\n- The authors wrote: “The TEM images of those samples revealed the presence of larger, darker\nappearing nanostructures (see Supplementary Fig. 8), most likely metallic indium\nnanoparticles. This assumes that the cluster growth in the first reaction step was not\nstoichiometric, but that there was still unreacted In precursor present, bevor the QD growth\nstarted.” When heating the clusters up to 185°C and then increasing the temperature to 300°C\nwhat are the byproducts of the synthesis and what is the synthesis yield? What is the\nstoichiometry of the InAs QDs made with this route?\nWe thank the reviewer for the questions.\nRegarding the synthesis at 180 °C (not 185 °C, which appears to be a minor oversight in the\nreviewer’s comment), followed by heating to 300 °C, the synthesis yield of InAs QDs was ~90%\n(related to As). This value has been added to the revised manuscript (see Methods section and\nSupplementary Note 4), as requested.\nOn p. 11, we added a discussion regarding the nature of byproducts: ‘We analyzed the insoluble\nbyproducts from the standard heat-up approach using TEM and XRD. From the TEM images\n(Supplementary Fig. 13), a mixture of polydisperse particles with undefined shapes, along with smaller\nspherical particles and darker particles, was observed. As in the case of the cluster synthesis, InAs,\nalong with a small amount of In O and metallic In, were identified from XRD (Supplementary Fig.\n2 3\n14).[42]’\nInsoluble byproducts of this reaction were determined by XRD and TEM analysis and the\ncorresponding data have been added to the revised manuscript (Supplementary Fig. 13 and\nSupplementary Fig. 14). The byproducts consist of InAs aggregates with undefined shape,\nminor amounts of In₂O₃ (likely formed via side reactions involving oxygen-containing\n3\noleylamine impurities), and small amounts of metallic In, consistent with incomplete precursor\nconversion and possible temperature-dependent equilibrium shifts. No pure InCl was\nidentified.\nThe stoichiometry of the InAs seeds synthesized via the heat-up method was determined as\n1.78:1, and the information added to the revised manuscript (Supplementary Table 2 and\np. 11): ‘Elemental analysis of the isolated QDs gave an In:As ratio of 1.78:1 (Supplementary Table 2).\nThe In-rich QDs were in agreement with previous report on InAs QDs synthesized from amino-As.[13]’\n- How can the authors calculate the amount of starting InAs QDs and clusters to be used in the\nseeded-growth approach, considering that in both cases they have to remove byproducts?\nWe thank the reviewer for raising this important point.\nDespite the batch nature of our cluster and seed syntheses, the resulting reaction solutions\nafter removing insoluble byproducts showed high reproducibility in absorption spectra (see\nFig. 2a and Supplementary Fig. 15). In our study, we standardized the amount and size of\nclusters and seeds used for the seeded and seedless growth approaches based on the optical\ndensity (OD) and magnitude of the absorption maximum, according to the values reported in\nSupplementary Table 4 and Supplementary Tab. 7. Such OD‑based normalization offers a\npractical alternative to mass-based concentration determination (see e.g., Kim et al., (2021)\n12:3013 Nat. Commun.).\nWe also have determined the mass-based quantities of starting InAs clusters and seeds and\ntheir concentrations. These values are provided in response to the reviewer’s later question\nregarding cluster and seed concentration and size, and are also included in the revised\nMethods section, Supplementary Note 3, and Supplementary Note 4 for completeness.\nWe now added this more in-detail description to the Methods section: ‘Previously, the cluster\nand the seed mixtures were separated from insoluble byproducts via centrifugation.[41,42] To ensure\nreproducible reaction conditions, the sizes and concentrations of seeds and clusters were monitored\nvia absorption spectroscopy (position and magnitude (OD) of the excitonic absorbance maximum; see\nSupplementary Table 4 and Supplementary Table 7). To equal the concentrations, dry OAm was used\nas a buffer to dilute the clusters and/or seeds to obtain the target OD. The seed concentration was\nadjusted to 1.3 mg mL-1 (OD 0.16 at the absorption maximum of 931 nm) for the standard seeded\ngrowth approach and 0.24 mg mL-1 (OD 0.034 at the absorption maximum) for the diluted seed\napproach, with a volume of 6.0 mL in both cases. An InAs cluster concentration of 1.1 mg mL-1 (OD 0.22\nat the absorption maximum) was used for both approaches.’\nOD-based reaction parameters are listed in Supplementary Tables 4 and Supplementary Table\n7 for both the standard and the diluted seeds seeded growth approaches. Below we\nsummarize the mass-based reaction parameters presented in Supplementary Notes 3 and 4,\nand in the revised Methods section:\ninsoluble byproducts; Supplementary Note 4): 3.3 mg/mL, corresponding to an OD of 0.46 at\nabsorption maximum.\nAdjusted seed solution concentration for the standard seeded growth approach\n(Supplementary Note 4): 1.3 mg/mL, corresponding to an OD of 0.16 at absorption maximum\n(Supplementary Tabl 4).\nAdjusted seed solution concentration for seeded growth approach with diluted seeds\n(Supplementary Note 4): 0.24 mg/mL, corresponding to an OD of 0.034 at absorption\nmaximum (Supplementary Table 7).\nAverage sizes of InAs seeds used for the seeded growth approach are presented in Fig. 4f\n(4.0 nm).\nStock cluster solution concentration (as-synthesized at 130 °C for 76 min, after removing\ninsoluble byproducts; Supplementary Note 3): 1.9 mg/mL, corresponding to an OD of 0.39.\nAdjusted cluster concentration used for seeded growth approaches (Supplementary Note 3):\n1.1 mg/mL, corresponding to an OD of 0.22 (Supplementary Table 4).\nAverage size of InAs clusters used for the seeded growth approach are presented in Fig. 2 and\np. 6, with short and long axes measuring approximately 1 nm and 4 nm, respectively.\nThese additions clarify the experimental conditions under which our QDs could be reliably\nobtained, and we hope they adequately address the reviewer’s concerns.\n- The authors wrote: “For the synthesis process, 4.5 mL of InAs cluster solution was slowly\ninjected into a solution of InAs seeds, followed by 30-minute annealing steps. This process was\nrepeated multiple times, while the reaction temperature was maintained at 300 °C.” Please,\nexplain this procedure in more details as it is written now it is impossible to understand it.\nWe appreciate the reviewer’s suggestion for further clarification. To address this, we have\nrevised the manuscript to provide a more detailed explanation of the seeded growth process.\nWe also introduced the term ‘injection-annealing cycle’ (p. 12) to define a complete process\nstep.\nIn our revised version, we have clarified the procedure as follows: ‘In the last stage of growing\nlarge InAs QDs via the seeded growth approach, we used InAs cluster and seed solutions after removing\ninsoluble byproducts. Cluster solution was continuously injected into a solution of InAs seeds at a\nconstant reaction temperature of 300 °C using a syringe pump.[41,42] […] Specifically, an injection rate of\n6 mL h-1 was used for adding of 4.5 mL of InAs cluster solution (1.1 mg mL-1) into 6.0 mL of InAs seed\nsolution (1.3 mg mL-1), attributing to one injection step, followed by a 30-minute annealing step at\n300 °C. This process was repeated up to 16 times (8 injection and 8 annealing steps, or 8 growth cycles)\nand could be quenched after each step depending on the desired QD size. We refer to this as our\nstandard seeded growth synthesis.’\nIn the revised Methods section, we wrote: ‘The seed concentration was adjusted to 1.3 mg mL-1\n(OD 0.16 at the absorption maximum of 931 nm) for the standard seeded growth approach and 0.24 mg\nmL-1 (OD 0.034 at the absorption maximum) for the diluted seed approach, with a volume of 6.0 mL in\nboth cases. An InAs cluster concentration of 1.1 mg mL-1 (OD 0.22 at the absorption maximum) was\nused for both approaches. Depending on the number of synthesis steps, 4.5 to 36.0 mL of InAs cluster\nsolution was loaded into a syringe. A 6.0 mL volume of InAs seed solution was then transferred to a\nthree-neck round-bottom flask and heated to 300 °C under nitrogen flow.[41,42]\nAs soon as 300 °C were reached, 4.5 mL of InAs cluster solution (4.9 mg InAs) was continuously injected\ninto the seed solution using a syringe pump at an injection rate of 6 mL h-1. A 30-min annealing step at\nthe same temperature followed. The injection-annealing cycles could be repeated multiple times,\ndepending on desired QD size (see Supplementary Table 5). A control experiment was performed\nwithout the annealing steps (Supplementary Table 6).’\n- The authors wrote: “By tuning the concentration and size of clusters and seeds, as well as the\ninjection rate, we were able to control the growth process, i. e., we managed to avoid side\nreactions such as interparticle ripening or secondary nucleation.” Please, also here include the\nparameters used and add relevant experimental details (which concentrations and sizes were\nused? What are the results for non-optimized parameters, all the discussions are extremely\nlackluster and superficial).\nWe thank the reviewer for requesting a more quantitative description. To address this, we have\nexpanded the description to include the experimental conditions and results for non-\noptimized parameters.\nWe have added the description of non-optimized parameters to the main text (p. 12) and\nSupplementary Table 3. Non-optimized reaction conditions led to secondary nucleation and\ninterparticle ripening. In order to show the resulting QDs, we added TEM images\n(Supplementary Fig. 17). We revised the text as follows: ‘Key parameters, such as cluster and seed\nsize, concentration, and injection rate of clusters, were critical for obtaining non-agglomerated InAs\nQDs larger than 8 nm. Suboptimal conditions, like i.e., too slow (3.0 mL h-1) or too high (36 mL h-1)\ncluster injection rates, or improper cluster concentration, led to secondary nucleation and interparticle\nripening (Supplementary Fig. 17). The effects of the different reaction conditions are summarized in\nSupplementary Table 3.[42]’\n- What does it mean, “a 16-step seeded growth synthesis”? Are the authors injecting 16 times\nthe precursors? In addition, the clusters the authors inject, at what temperature are they\nprepared (do the authors centrifuge each of these 16 additions to avoid injecting metallic or\nprecipitating stuff)?\nWe thank the reviewer for these insightful questions.\nRegarding the term ‘16-step seeded growth synthesis’, it does not refer to injecting the\nprecursors 16 times. Rather, it describes a sequence of 16 alternating synthesis steps (or 8\ngrowth cycles), consisting of 8 cluster injections and 8 annealing steps. Specifically, each cycle\ninvolves injecting 4.5 mL of the InAs cluster solution (1.1 mg/mL), followed by a 30-minute\n6\nannealing step at 300°C. This process is repeated up to 16 times, with the injection and\nannealing steps alternating. No purification steps are performed between the steps.\nTo clarify, we have updated the manuscript (p. 12): ‘Specifically, an injection rate of 6 mL h-1 was\nused for adding of 4.5 mL of InAs cluster solution (1.1 mg mL-1) into 6.0 mL of InAs seed solution (1.3\nmg mL-1), attributing to one injection step, followed by a 30-minute annealing step at 300 °C. This\nprocess was repeated up to 16 times (8 injection and 8 annealing steps, or 8 growth cycles) and could\nbe quenched after each step depending on the desired QD size.’\nAs for the InAs clusters used in the injections, they are prepared by heating at 130°C for 76 min.\nWe have now updated the revised manuscript (p. 5-6): ‘For cluster synthesis, amino-As solution\nin oleylamine (OAm) was hot-injected into a mixture of InCl in OAm and trioctylphosphine (TOP) at\n130 °C, and the reaction was maintained for 76 min.’ In the revised Methods section, we also\nprovide this information: ‘Clusters used as precursors in the seeded and/or seedless growth\napproaches were synthesized at 130 °C for 76 min.’\nFollowing this, the cluster reaction mixture is centrifuged to remove any insoluble byproducts,\nsuch as metallic In, which could interfere with the seeded growth synthesis. We have also\nadded this clarification to the revised manuscript (p. 12): ‘In the last stage of growing large InAs\nQDs via the seeded growth approach, we used InAs cluster and seed solutions after removing insoluble\nbyproducts.’\n- “Fig. 4a shows that we obtained InAs QDs with well-defined multiple absorption features”\nPlease explain the absorption features, are these real electronic transitions?\nWe thank the reviewer for this insightful question.\nThe multiple absorption features observed in Fig. 4a (now Fig. 5a in the revised manuscript)\nare indeed real electronic transitions. These features correspond to quantized excitonic\ninterband transitions in the InAs QDs, arising from the size-dependent confinement of charge\ncarriers in the nanocrystals.\nSpecifically, we refer to the work of Fang et al. [47], who reported up to five clearly resolved\noptical absorptance steps in ultrathin InAs quantum membranes (3–19 nm thick). These\nfeatures were attributed to discrete interband transitions between subbands in the valence\nand conduction bands. Despite the difference in geometry (2D membranes vs. QDs), the\nphysical origin of these features — quantum confinement — is the same. The observed\nsimilarity in spectral structure further supports the interpretation of our absorption features\nas real electronic transitions.\nFor our InAs QDs, we have observed up to five absorption maxima in QDs up to 18 nm in size,\nwhich aligns well with previous findings in the literature.\nTo provide additional clarity, we have included a brief explanation and an additional reference\nin the revised manuscript (p. 12): ` From the absorption spectra (Fig. 5a), multiple absorption\nfeatures corresponding to excitonic intraband transitions[47] were observed.`\n7\n- The authors wrote: “The absorption spectra of the samples with larger sizes are of less\nquality, because these particles were hardly soluble at room temperature”, then in the next\nline:“These results show that the huge non-agglomerated InAs QDs are highly monodisperse\nand highly crystalline.” Which one is which? This makes no sense.\nWe thank the reviewer for pointing out this phrasing.\nWe have revised the text in the manuscript to more clearly distinguish between the quality of\nthe optical spectra (first cited sentence) and the properties of the QDs determined from TEM\nand XRD analysis (second cited sentence).\nThe absorption spectra of the larger QDs showed light scattering due to their poor solubility,\nwhich affects the quality of the absorption spectra. We revised the text as follows (p. 8): ‘For\nsamples with the first absorption peak below ~2,000 nm, well-resolved absorption features were\nnoted, along with the expected redshift upon growth. However, the spectra of the larger QDs showed\nlower quality due to their poor solubility at r. t.’\nDespite the lower quality of absorption spectra due to poor solubility, the larger QDs were\nnon-agglomerated, monodisperse (after size-selection), and crystalline (as originally stated),\nas observed from the TEM images (as originally stated). We avoided using the qualitative term\n`highly monodisperse` to maintain objectivity in our description, and underlined the\napplication of size-selective precipitation to obtain monodisperse fractions. We revised the\ntext for clarity as follows (p. 13): ‘The samples were purified post-synthetically using size-selective\nprecipitation techniques (hereafter referred to as ‘precipitation techniques’), as described in the\nMethods section. […] XRD patterns (Supplementary Fig. 20) confirmed the cubic zinc blende crystal\nstructure of InAs, showing that the seeded growth synthesis provided highly crystalline InAs QDs.[41,42]’\nAnd later on (p. 13): ‘TEM and HR-TEM images provided in Fig. 5c-f showed monodisperse InAs QD\nsamples up to 18 nm in size.’\nWe hope these changes address the reviewer`s concerns.\n- The authors wrote: “We compared our experimental results for QD sizes and first absorption\nmaxima (Supplementary Table 3) with the values calculated using the formula provided by\nKuno et al.[17], which is a slightly modified version of the formula from [18]. This formula is\nbased on the relationship between the first exciton transition peak energy and QD size. The\nresulting plot (Supplementary Fig. 11) demonstrates that the formula, originally developed for\nInAs QDs with average sizes up to 6 nm[19], remains applicable to larger QDs with sizes at least\nup to ~ 18 nm.” Please, add a graph with all data points, like this is very hard to follow.\nWe thank the reviewer for the valuable suggestion.\nWe would like to point out that the requested graph with all data points was already included\nas Supplementary Fig. 11 (Fig. 5b in the revised version). However, we acknowledge that the\noriginal wording in the manuscript may not have clearly communicated that this plot contains\nboth the calculated values (in red) based on the empirical formula from Kuno et al. [48] and\n8\nthe experimentally measured data points (in black) derived from Supplementary Table 3\n(Supplementary Table 5 in the revised manuscript).\nTo address this, we have clarified the manuscript text and moved the plot to the main text for\nbetter visibility (p. 14). The updated text (p. 13) reads: ‘In Fig. 5b, we compared the experimental\nQD sizes and corresponding first absorption maxima with values calculated using the formula provided\nby Kuno et al,[48] which relates the size of InAs QDs to the energy of their first excitonic transition. This\nequation is a slightly modified version of one proposed by Yu et al.[49] Both experimental and calculated\nvalues are provided in Supplementary Table 5 and are plotted in Fig. 5b. The good agreement between\nthe experimental and calculated plots indicated that the formula, originally developed for InAs QDs\nwith sizes up to 6 nm[50], is also applicable to larger InAs QDs with sizes at least up to 18 nm.[41,42]’\n- The authors wrote: ““In a control experiment, we also tested if the continuous injection of\ncluster solution without performing the annealing steps in between also leads to non-\nagglomerated huge InAs QDs. In fact, this procedure also worked, but the final absorption edge\nwas only 1,750 nm after injecting 22.5 mL of cluster solution (see Supplementary Table 4). This\nshows that the annealing steps are highly beneficial for the QD growth from cluster precursors,\nmost likely due to the low reactivity of the clusters.” Please explain what are these annealing\nsteps.\nWe thank the reviewer for this important question.\nThe ‘annealing step’ refers to a 30-minute holding period at 300°C that follows the injection of\n4.5 mL of InAs cluster solution. During this time, the newly added clusters are allowed to fully\nintegrate into the growing InAs QDs, promoting further growth.\nIn the control experiment, continuous cluster injection was applied without the annealing\nsteps. As a result, the QDs grew less effectively, as indicated by the lower final absorption edge\n(1,750 nm) compared the standard procedure (~1,940 nm). This demonstrates the importance\nof the annealing steps for optimal QD growth, likely due to the low reactivity of the clusters.\nWe have revised the manuscript to clarify the term ‘annealing step’ and provide more context\nfor the reader. Specifically, we have updated the text on p. 12 to read: ‘Specifically, an injection\nrate of 6 mL h-1 was used for adding of 4.5 mL of InAs cluster solution (1.1 mg mL-1) into 6.0 mL of InAs\nseed solution (1.3 mg mL-1), attributing to one injection step, followed by a 30-minute annealing step\nat 300 °C. This process was repeated up to 16 times (8 injection and 8 annealing steps, or 8 growth\ncycles) and could be quenched after each step depending on the desired QD size.’\nWe also have revised the mentioned text passage as follows (p. 14): ‘To access the role of\nannealing steps in our seeded growth method, we conducted a control experiment where cluster\nsolution was continuously injected without any annealing steps in between (Supplementary Table 6).\nAlso here, non-agglomerated large InAs QDs were produced, but the absorption edge reached only\n1,750 nm after injection of the same amount (22.5 mL) of cluster precursor solution, compared to\n~1,940 nm for the standard seeded growth method. The smaller QD size in the control experiment\nsuggests that the annealing steps were crucial for promoting further QD growth, likely due to the lower\nreactivity of the cluster precursors.’\nFinally, we’ve also updated the Methods section to clarify the annealing procedure: ‘As soon as\n300 °C were reached, 4.5 mL of InAs cluster solution was continuously injected into the seed solution\n9\nusing a syringe pump at an injection rate of 6 mL h-1. A 30-min annealing step at the same temperature\nfollowed. The injection-annealing cycles could be repeated multiple times, depending on desired QD\nsize (see Supplementary Table 5). A control experiment was performed without the annealing steps\n(Supplementary Table 6).’\nOnce again, we sincerely thank the Reviewer for their valuable feedback and careful review of\nour manuscript.\nWe sincerely thank the Reviewer for their insightful suggestions and valuable feedback. We\nhave carefully addressed the points raised in the review and made the following revisions.\nThis paper describes a novel method for growing large InAs QDs up to around 40 nm with\nhigh crystallinity and good size control starting from non-pyrophoric precursors. It addresses\nthe long-standing challenge of extending the absorption range of InAs QDs in SWIR from\n1600 nm to much longer wavelengths, beyond 2600 nm. The main approach relies on the use\nof well-defined InAs clusters obtained at lower temperature (180°C), which are either grown\nto 4 nm nanocrystals used in a seeded-growth reaction, or directly applied in a heat-up\napproach. The samples were characterized using standard techniques, in particular\nabsorption spectroscopy, X-ray diffraction and TEM, and the main reaction parameters were\nexplored to optimize the synthesis methods.\nIn the introdution and conclusion, a bigger accent could be put on the impact for SWIR\napplications, since it presents a core achievement of the work and there are not much other\nPb- and Hg-free QDs that can reach this region.\nWe thank the reviewer for this insightful suggestion. We agree that emphasizing the\npotential of our InAs QDs for SWIR applications is crucial, especially in light of the limited\navailability of Pb- and Hg-free alternatives in this spectral range. We have accordingly revised\nboth the introduction and the conclusion to better underscore the significance of these\nfindings.\nIn the introduction, we added the following sections to highlight the relevance of SWIR\napplications:\n• ‘Despite the availability of low-cost silicon-based detectors, their spectral sensitivity is limited to\nbelow ~1,100 nm.[4,5] To access longer IR wavelengths, current technologies commonly rely on\nepitaxially grown materials such as indium gallium arsenide (InGaAs), which are costly due to energy-\nintensive deposition processes.[5,6]’\n• ‘Achieving larger sizes is essential for accessing deeper IR wavelengths and approaching bulk-like\nproperties, but requires […].’\n• ‘The strategy also offers […], paving the way for industrial production of RoHS-compliant, IR-active\nQDs. Our findings offer a new platform for fundamental studies and next-generation IR optoelectronic\ntechnologies, especially in the SWIR region.[41,42]’\nIn the conclusion, we highlighted the potential for large-scale applications with the following\naddition: ‘The strategy has the potential for adaptation to continuous flow reactors, moving the field\ncloser to large-scale production of RoHS-compliant Pb- and Hg-free NIR and SWIR CQDs. By unlocking\n1\na new size regime and simplifying the synthetic toolbox for InAs NPs, this work lays a foundation for\nadvances in IR optoelectronics, including biophotonics, telecommunications, and sensing\ntechnologies.’\nAll in all, this manuscript appears perfectly suitable for puclication in Nature\nCommunications, due to the originality of the approach and quality of the results, which\nopen up new horizons.\nWe sincerely thank the reviewer for the positive evaluation and encouraging remarks\nregarding the originality and significance of our work.\nNonetheless there is a list of points which should be addressed:\n1) The difference between seeds and clusters is a bit hard to follow, especially in the second\npart of the manuscript, I would suggest to elaborate in more details figure 1 with some key\nfeatures of both. Fig. 1 could also be improved to make it visually more attractive.\nWe thank the reviewer for this valuable suggestion.\nTo improve clarity regarding the distinction between clusters and seeds, we have revised\nboth the main text and Fig. 1. To avoid overcrowding the figure, we chose not to include\ndetailed feature lists directly in Fig. 1, but instead clarified these points in the main text.\nIn the ‘Synthesis of InAs clusters’ section, we expanded our description of the cluster\nprecursors (p. 4) and incorporated additional data into Fig. 2:\n• ‘For cluster synthesis, amino-As solution in oleylamine (OAm) was hot-injected into a mixture of InCl\nin OAm and trioctylphosphine (TOP) at 130 °C, and the reaction was maintained for 76 min. […] In the\nhigh-resolution transmission electron microscopy (HR-TEM) images (Fig. 2b-d), small nanostructures\ncan be seen. Some of the structures seem to form elongated aggregates, possibly during deposition\nprocess on the grids. Due to the low contrast, neither the crystallinity nor the shape of the clusters can\nbe directly determined from the HR-TEM images.[41,42]’\n• ‘[…] synthesis of small InAs clusters (Fig. 1a), which exhibited optical activity in the VIS range’.\nIn the ‘Synthesis of InAs seeds’ section, we added (p. 6): ‘The seeds showed lower size dispersity\n[…], and the corresponding XRD and HR-TEM data (Supplementary Fig. 10 and Supplementary Fig. 11)\nconfirmed the crystalline nature of these particles.’\nWe believe that the updated Fig. 1 provides a clearer overview of our synthetic strategy,\nwhile the revised text more explicitly outlines the distinguishing features of clusters and\nseeds.\n2\n2) What are the reaction yields for the cluster synthesis and for the seeded-growth\nsynthesis? insoluble side-products such as metallic indium (p. 3) were observed. In other\nwords, how much, approximately, of the initially used InCl transforms into clusters and how\nmuch into In(0)? Does the yield change with bigger particles? Or between seedless and\nseeded growth?\nWe thank the reviewer for requesting a more quantitative description of the reaction yields.\nIn response, we have added information about the reaction yield and corresponding\ncalculations to the revised manuscript: the cluster synthesis (Supplementary Note 3), the\nheat-up seed synthesis (Supplementary Note 4), the seeded growth approach\n(Supplementary Note 5), and the seedless growth of different sized QDs (Supplementary\nNote 6).\nWe also clarify that, prior to using clusters or seeds for either the seeded or seedless growth\nprocedures, insoluble byproducts were always removed by centrifugation. Importantly, no\ninsoluble byproducts were observed in either the seeded or seedless growth approaches, as\nconfirmed by XRD and TEM analyses (Fig. 5–7 and Supplementary Fig. 27). To make this point\nclearer, we revised the main text (p. 7) as follows:\n• ‘In the last stage of growing large InAs QDs via the seeded growth approach, we used InAs cluster\nand seed solutions after removing insoluble byproducts’.\nBelow we summarize the reaction yields presented in Supplementary Notes 4–6 and in the\nMethods section:\nCluster synthesis (relative to As): 49%\nCluster synthesis (relative to In): 16%\n- InCl was used as a 3.1-fold excess, following Bawendi et al. (2020)\n- Insoluble byproducts are therefore approx. 84% relative to InCl. explaining the pronounced\nbrown-grey coloration before purification\n- XRD (Supplementary Fig. 2) indicates these byproducts consist primarily of metallic In, with\nminor amounts of In₂O₃ and InAs\nSeed synthesis (relative to As): 90%\nSeed synthesis (relative to In): 23%\nSeeded growth synthesis (16 steps): 76%\nSeedless growth (10 steps): 98%\nSeedless growth (6 steps): 114%\n- Value slightly above 100% probably originated from the very small amount of inorganic\nmaterial used for analysis (0.09%), which increased weighing uncertainty\nbetween different particle sizes (Supplementary Note 6):\n• ‘By comparing the mass of the resulting InAs QD samples obtained at different synthesis stages of the\nseedless growth synthesis (15 mg after 6 steps, 25 mg after 10 steps), it is evident that continued QD\ngrowth takes place, which is consistent with observations from TEM analysis and absorption\nmeasurements. Since the seedless growth synthesis begins without any InAs material in the flask, the\noverall reaction yield after the same number of steps is lower than that observed in the seeded growth\nprocess.’\nWe hope these additions fully address the reviewer’s request for quantitative insight into\nreaction yields and byproduct formation.\n3) Did the authors also try the seedless growth without annealing steps?\nWe thank the reviewer for this important question. Yes, we performed a control seedless\ngrowth experiment in which all annealing steps were omitted. This experiment is described on\np. 13 of the revised manuscript (p. 9 in the original version):\n• ‘In a control experiment, no annealing steps were conducted. Consistent with the control seeded\ngrowth experiment, non-aggregated, large InAs QDs were still produced. After injecting the same\nvolume of cluster solution (22.5 mL) as in the standard seedless growth approach, the resulting QDs\nwere 27 nm in size, compared to 40 nm when annealing steps were included (after precipitation\ntechniques were applied). This suggests that alternating annealing steps play a crucial role in the\ngrowth process when using clusters as precursors.[41,42]’\nFor completeness, we have now also added a brief description of this control experiment to\nthe revised Methods section: ‘In a control experiment, no annealing steps were involved.’\n4) In Fig.2 the T0 spectrum could be added.\nWe thank the reviewer for this helpful suggestion. As requested, the T spectrum has now\n0\nbeen added to Fig. 2 (Fig. 3c in the revised version).\n4\n5) The absorption spectra of the >20 nm nanocrystals could have been taken on solid\nsamples by applying diffuse reflectance spectroscopy instead of liquid phase measurements\nin TCE. Given the unique size regime of the obtained samples, this information would have\nbeen quite interesting and would potentially allow to draw figure S11 (which I suggest to put\ninto the main manuscript) up to 40 nm. Also, it would allow to give a more precise evaluation\nof the absorption range covered by the obtained samples, the value of 2600 nm seems to be\na rough estimation.\nWe thank the reviewer for this constructive suggestion and agree that solid-state\nspectroscopy data for the very large InAs QDs (< 20 nm) would significantly enhance the\nanalysis. As recommended, we have now moved the plot from Fig. S11 to the main\nmanuscript (Fig. 5b).\nWhile diffuse reflectance spectroscopy (DRS) would be ideal for such measurements, we\nfaced limitations due to unavailable instrumentation. Instead, we explored several\nalternative approaches for measuring solid samples.\nUsing a Cary 5000 spectrometer equipped with an integrating sphere, which is well-suited for\nscattering samples, we encountered limits above ~2,600 nm. Despite optimizing parameters\nsuch as integration time and slit width, no suitable baseline could be collected. We have\nmentioned this issue on p. 11 of the revised manuscript: ‘Absorption measurements using an\nintegrating sphere were not feasible in the MIR range due to technical limitations.’\nAs an alternative, we performed solid-state measurements on the Cary 5000 without an\nintegrating sphere (same setup as for in-solution measurements). We observed a red-shifting\nabsorption edge with increasing NP size. This setup allowed detection of absorption edges\nextending up to at least ~3,000 nm for the largest QDs. However, scattering effects persisted,\nreducing the quantitative reliability of the measurements and potentially obscuring the\nabsorption features. For QDs larger than 28.5 nm (approaching the electron Bohr radius of\nInAs), absorption maxima are typically absent due to the weak confinement regime. These\npoints are now discussed in the manuscript (p. 11):\n• ‘Therefore, additional measurements were conducted on a substrate (Supplementary Fig. 29b).\nHowever, scattering effects and ligand absorption features persisted above ~2,600 nm. Despite the\nabsence of distinct absorption maxima, a redshift in the absorption edge was observed, suggesting\nquantum confinement effects.[42]’\n• ‘In general, QDs sized between the electron Bohr radius (28.5 nm for InAs)[51] and the exciton Bohr\nradius (30 – 44 nm for InAs)[10,51,52] are expected to fall into the weak confinement regime, where\nabsorption maxima are typically absent.[51,53] This means in our case, that probably, no distinct\nabsorption maxima would be observed for large InAs NPs in this size regime.[42]’\nTo complement the solid-state measurements, we performed additional ATR-FTIR\nspectroscopy, which revealed size-dependent mid-IR absorption features (1,600 - 920 cm⁻¹),\nlikely due to oleylamine (OAm) ligands. These results are shown in new Supplementary Fig.\n29d-e. To aid in interpretation, we have included arrows indicating the estimated absorption\nmaxima, calculated using the formula provided by Kuno et al. These data show a redshift\n5\ntrend with increasing QD size, consistent with quantum confinement effects, and are\ndiscussed on p. 12:\n• ‘Further ATR-IR analysis of InAs NP samples with average sizes ranging from 12 to 36 nm\n(Supplementary Fig. 29d-e) revealed, in addition to the ligand features, a size-dependent, broad\nabsorption band in the mid-infrared (MIR) range (1,600 – 920 cm-1), likely associated with the\nvibrational modes of OAm.[42,56] As the QD size increased, this band shifted further into the red. Such\na size-dependent effect is particularly interesting and likely arises from the significant size variation\nwithin the same material, which amplifies this effect.[42]’\nWhile ATR-IR measurements revealed a qualitative redshift with increasing QD size, no distinct\nabsorption features were observed in the expected region. This is discussed on p. 12 and in\nSupplementary Fig. 29d-e:\n• ‘The measurements revealed a qualitative redshift in absorption as the NP size increased. However,\nno distinct absorption features were observed, as expected, since ATR-IR characterizes the NP\nsurface.[42]’\nWe also address the ongoing debate surrounding the exciton Bohr radius of InAs (ranging from\n30 – 44 nm). As noted on p. 12, based on our measurements, it remains unclear whether NPs\nlarger than 30 nm can be classified as QDs. This is a fundamental question that warrants\nfurther study.\n• ‘Given the ongoing debate surrounding the exciton Bohr radius of InAs QDs (ranging from 30 to\n44 nm, as mentioned above)[10,51,52], it remains uncertain whether InAs NPs larger than 30 nm can be\nclassified as QDs. Even if they do, they likely would not exhibit distinct absorption bands, as they would\nfall into the weak confinement regime. Instead, they would be better classified as near-bulk QDs.[51]\nDue to the addressed wavelength range, an extensive optical characterization of the large InAs\nparticles’ properties requires further improvements. This characterization is within the scope of follow-\nup studies, where measurements on the near-bulk QDs could provide insights into the exciton Bohr\nradius of InAs QDs, a fundamental parameter in the study of QD systems. For the first time, such large\ncolloidal InAs NPs are now experimentally accessible.[42]‘\n6) In SI, Fig 1, not sure if the evolution is related to the reaction proceeding over longer times\n(two years!), or particles being slowly oxidized by traces of oxygen that might be present in\nthe inert atmosphere.\nWe thank the reviewer for this insightful comment.\nTo clarify the nature of the spectral evolution, we compared the peaks from the 2-year\nsample with the absorption features of early-time aliquots from the cluster synthesis, as\npresented in Fig. 2 (now Fig. 3c). This comparison has been added to a new Supplementary\nFig. 4.\nThe characteristic peaks at ~315 and ~350 nm are consistent and even more pronounced in\nthe 2-year sample, indicating that the observed spectral changes are not due to slow oxidation.\nobserved during the early stages of cluster formation. This comparison supports the\nconclusion that the spectral evolution reflects chemical transformations linked to cluster\nformation rather than slow oxidation. We have included this discussion in the revised\nmanuscript (p. 5):\n• ‘We attribute the absorption features in the UV to molecular structures such as organometallic\nintermediates or ultra-small clusters. In a separate experiment (Supplementary Fig. 3), similar features\nwere observed (Supplementary Fig. 4a). Comparing the corresponding absorption spectrum with those\nof early-stage aliquots taken during synthesis at 110 °C (see Fig. 3), we observed similar absorption\nmaxima at ~315 and ~350 nm, with a higher intensity ratio (Supplementary Fig. 4b). This suggests that\nthe absorption features correspond to the formation of specific small structures active in the VIS\nrange.[41,42]’\n7) Experimental findings should not be discussed in the Conclusions but in the Discussion\nsection. In particular, Fig. S16 (the RT evolution of clusters) is intriguing: the authors ascribe\nthe sharp absorption features to the formation of metallic nanoparticles - are there any data\nsupporting this hypothesis?\nWe thank the reviewer for this important suggestion. In response, we have revised the\nmanuscript to move experimental findings into the Discussion section, as recommended.\nSpecifically, Fig. S16 (now Supplementary Fig. 7) and the corresponding discussion have been\nrelocated to the main manuscript (p. 5):\n‘Interestingly, a room-temperature reaction proved unsuitable for producing InAs clusters (see\nSupplementary Note 1 and Supplementary Fig. 6). The absorption spectra of the particles formed were\nconsistent with metallic nanostructures as presented in the in Supplementary Fig. 7 and Supplementary\nFig. 8.[41,42]’\nRegarding the hypothesis about presence of metallic NPs, we conducted an experiment\nwhere we measured the absorption of NPs in ethanol (non-solvent) and compared it to their\nbehavior in OAm (Supplementary Fig. 8). Upon redispersion in ethanol, the pink-purple NPs\naggregated, which caused broadening of their absorption maxima and increased scattering.\nThis spectral broadening upon aggregation is typical of metallic NPs due to localized surface\nplasmon resonance (LSPR), as reported previously for gold NPs by Raghavendra et al., 2013\n[3]. These results support the hypothesis that the observed nanostructures are metallic NPs,\nnot InAs clusters, and their characteristic pink-purple color arises from plasmonic resonance.\nWe discuss these findings in Supplementary Note 1:\n‘The absorption spectrum of the pink-red sample showed sharp peaks (Supplementary Fig. 7),\nsuggesting the formation of metallic NPs. The plasmonic nature of these structures was further\ninvestigated in a separate experiment (Supplementary Fig. 8), where they exhibited aggregation,\nscattering, and broadening of absorption maxima in the non-solvent ethanol. This behavior is typical\nfor metallic nanoparticles due to localized surface plasmon resonance (LSPR).[2,3]’\n7\n8) The last phrase of the conclusions says that the continuous injection approach could be\neasily adapted to continuous flow synthesis. How could this be practically achieved? It seems\nthat the continuous injection of precursors to a given reaction volume is indeed one step\ndifficult to implement in continuous flow (?)\nWe thank the reviewer for this thoughtful question. It is correct that directly translating the\ncontinuous injection strategy into a continuous flow setup is challenging, as continuous\ninjection into a fixed reaction volume does not directly apply to flow systems.\nHowever, we believe that utilizing liquid In and As precursors, which are already present in\nthe InAs cluster solution, represents a promising step toward their application in flow\nreactors. This approach also offers a safer and less toxic alternative to organometallic As\nprecursors. One potential solution could involve introducing the cluster precursors at\ndifferent points along the flow path or employing segmented reactors to better control the\nreaction process.\n9) Given the size distribution, the specification of 40.5 nm looks like excessive precision, I\nwould suggest throughout the manuscript to mention that the method gives access to QDs\nof up to 40 nm size.\nWe thank the reviewer for this helpful comment. In response, we have revised the\nmanuscript to more generally refer to NPs of up to 40 nm in size.\n10) Fig. 2: the inscription on the vials should be removed and eventually be replaced by a real\nlegend.\nWe thank the reviewer for this suggestion. The handwritten inscriptions on the vials in Fig. 2\n(now Fig. 3) have been removed and replaced by a legend.\n11) A 1:1 In:As ratio has been applied for the cluster synthesis. In principle a 3:1 ratio would\nbe required to reduce As from +3 to -3, it should be discussed why 1:1 is used.\nWe appreciate the reviewer’s attention to stoichiometry. Upon careful review, we confirm\nthat a 3:1 In:As ratio, consistent with the reduction of As³⁺ to As³⁻, was indeed used in the\ncluster synthesis (as described in the Methods section).\nWe have now clarified this point also in the main text (p. 4): ‘A 3.1:1 ratio of In:As as described\nin [26] was used.’\n8\n12) The use of the term \"highly monodisperse\" may not be appropriate for the clusters, as\ntheir absorption spectra are not that well defined showing a rather broad excitonic peak. For\nthe TEM images a couple of size histograms would be helpful.\nWe thank the reviewer for this helpful comment. We agree that the term ‘highly\nmonodisperse’ is not appropriate to clusters, given the broad absorption maximum (Fig. 2a)\nand the TEM images. To provide a more quantitative assessment, we have added a size\nhistogram of the clusters used as precursors in Fig. 2b, along with HR-TEM images.\nFurthermore, we have removed the term \"highly monodisperse\" from the revised\nmanuscript, as suggested.\n13) The particles in Fig. 3a with an absorption maximum at 556 nm are estimated to have a\nsize of 2.3 nm. Is this consistent with the sizing curve of InAs QDs? They could be likely\nsmaller (cf Fig. S2)\nWe thank the reviewer for this valuable observation.\nIn the original version, the size was estimated on the long axis, which explains the larger\nvalue. However, after considering the short axis, which is more relevant for quantum\nconfinement, we estimated the size to be 1.4 nm. This updated size has been reflected in Fig.\n4a and Supplementary Fig. 9.\nThis value corresponds to a calculated excitonic peak at 461 nm. The discrepancy between\nthe experimental absorption maximum (556 nm) and the calculated value (461 nm), which is\napproximately 100 nm, may arise from limitations in the formula used for size estimation.\nThe formula was initially developed for QDs in the size range of 3.4 – 6 nm and may not fully\naccount for the properties of smaller clusters. Additionally, determining the exact size and\nshape of the clusters from the microscopy images (Fig. 4a, Supplementary Fig. 9) remains\nchallenging.\nWe appreciate the reviewer’s observation, which has allowed us to update the cluster size\nestimate based on the short axis.\n9\n14) In the Introduction there is a lack of references and precision: use of vague phrases in the\nintroduction (“extraordinary optoelectronic properties”, “crucial role”, “variety of materials”,\n“harsher reaction conditions”, “several disadvantages”). For example, while as stated no\nfurther developments of the In(I)Cl / aminopnictogen method have been reported for InAs\nQDs, this synthetic route has been used for InP and InSb, which could be mentioned in the\nintroduction.\nWe thank the reviewer for this helpful comment.\nThe Introduction has been revised to use more precise language. Where such terms remain,\nthey are now supported by specific examples and appropriate references:\n• ‘Hence, harsher reaction conditions like higher temperatures are required, challenging the precise\ncontrol of the size and the size distribution.[26-28]’ ‘\n• […], the initial thermolysis method had several disadvantages compared to TMSAs-based methods,\nincluding long reaction times of up to 6 days and the production of small, amorphous NPs with sizes\nup to 2 nm.[10,33]’\nAdditionally, we have now cited relevant works in the introduction regarding the\nInCl/aminopnictogen approach applied to the synthesis of InP and InSb quantum dots:\n• ‘This method was later adapted for the synthesis of InSb and InP QDs,[36-38] but has not been\nfurther developed for InAs QDs.’\n15) On p. 5 it is stated that keeping the insoluble side-products from the cluster synthesis\nimproves the quality of the final QDs leading to larger sizes and narrower size distributions.\nDo the authors have any hypothesis on the mechanisms behind this behavior?\nWe thank the reviewer for this insightful question.\nWhile the precise mechanism is not fully established, we hypothesize that the insoluble side-\nproducts from the cluster synthesis (primarily metallic indium) may act as a reservoir of\nindium species during the subsequent heat-up. This reservoir could provide a more\ncontrolled and steady supply of In precursors, promoting uniform growth of the QDs.\nAdditionally, these byproducts might influence the local chemical environment, affecting\nnucleation and growth kinetics, which can lead to larger particle sizes and narrower size\ndistributions.\nWe have added this discussion to the revised manuscript (p. 7): ‘TEM revealed the presence of\nlarger, darker particles, likely metallic In (Supplementary Fig. 16), suggesting incomplete reaction in\nthe initial cluster growth. These findings suggest that the byproducts may serve as a reservoir during\nthe heat-up process, influencing the local chemical environment and promoting more uniform\nnucleation and growth of the QDs.’\n10\n16) Fig. S6: the reference diffraction pattern of InAs should be added. Idem Fig. S10\nWe thank the reviewer for the suggestion. Reference diffraction patterns of InAs have been\nadded to both Fig. S6 (now Supplementary Fig. 10) and Fig. S10 (now Supplementary Fig. 20),\nas well as to all other XRD diffractograms presented in our work.\n17) Fig. S7: why absorbance is given in arbitrary units?\nWe thank the reviewer for pointing this out. This was an oversight on our part — the\nabsorbance in Fig. S7 (now Supplementary Fig. 12), as well as in other absorption spectra,\nshould not have been labeled in arbitrary units. The data have now been updated with the\ncorrect absorbance scale in the revised version.\n18) In the Manuscript and Supplementary Information \"heating up\" should be termed \"heat-\nup\" throughout the text.\nWe thank the reviewer for pointing out this terminology issue. All instances of ‘heating up’\nhave been revised to ‘heat-up’ throughout the manuscript and Supplementary Information.\nOnce again, we sincerely thank the Reviewer for their valuable feedback and careful review of\nour manuscript.\nWe sincerely thank the Reviewer for their insightful suggestions and valuable feedback. We\nhave carefully addressed the points raised in the review and made the following revisions.\nThe authors reported the synthesis of free-standing InAs quantum dots by wet-chemistry.\nTheir main goal was to synthesize ultra-large InAs quantum dots. In order to reach their goal,\nthe chosen synthesis protocol is a wet-chemical synthesis one that involves three steps. The\nauthors mainly used UV-visible-NIR spectroscopy, Transmission Electron Microscopy and X-ray\ndiffraction to characterize their samples.\nHere are my comments:\n• Remarks on the text.\n1. The authors claimed that they have InAs quantum dots but nowhere they experimentally\nproved that they had quantum dots and not just InAs nanoparticles. Authors could use\nARPES, Raman spectroscopy or EELS spectroscopy to confirm that indeed they have\nquantum confinement on their InAs quantum dots.\nWe thank the reviewer for raising this important point. We fully agree that direct\ndemonstration of quantum confinement is essential to distinguish true quantum dots from\nlarger, bulk-like nanoparticles.\nIn our study, we observed a clear size-dependence in the optical absorption spectra of particles\nup to ~18 nm in diameter (Fig. 4a, corresponding to Fig. 5a in the revised manuscript). These\nspectra showed well-defined first excitonic transitions that redshifted with increasing NP size,\nin agreement with quantum confinement. Additionally, a comparison with the analytical\nexpression for the first exciton transition peak energy for InAs QDs revealed good\ncorrespondence in this size range (Supplementary Fig. 11, now Fig. 5b in the revised version).\nParticles larger than ~19 nm were colloidally unstable, and measurements in solution\n(including those after shaking the sample) resulted in scattering effects and overlap with ligand\nabsorption beyond ~2,600 nm. We pointed this out in the revised manuscript as well (p. 11):\n‘Absorption spectra of large, colloidally unstable InAs NPs in TCE (Supplementary Fig. 29a) showed\n1\nabsorption in the range up to ~2,600 nm, but without distinct absorption maxima. Beyond ~2,600 nm,\nscattering from NPs and overlap with ligand absorption interfered with the measurements.[41,42]’\nWe truly appreciate the suggested techniques and have carefully reviewed the possibility of\ncharacterizing our colloidal nanoparticles larger than 18-19 nm. While ARPES, Raman\nspectroscopy, and EELS are useful for epitaxial QDs, they are not standard characterization\nmethods for colloidal InAs quantum dots. Their applicability to our system is limited due to\nthe following reasons. Our particles are non-emissive, ruling out photoluminescence-based\nconfirmation. ARPES requires single-crystal epitaxial thin films and ultra-high vacuum, which\nare incompatible with our colloidal systems. EELS, while potentially offering insights into the\nelectronic structure, is not typically used to demonstrate quantum confinement in colloidal\nQDs capped with organic ligands. Raman spectroscopy is limited by weak signal intensity and\noverlapping modes, especially for colloidal QDs. Therefore, we have focused on well-\nestablished optical characterization techniques. Absorption measurements (including\nmeasurements on substrates) and ATR-IR spectroscopy were used to assess quantum\nconfinement in our NPs.\nTo minimize scattering effects during absorption measurements, we attempted to use an\nintegrating sphere; however, this approach was not feasible due to technical limitations (p.\n11): ‘Absorption measurements using an integrating sphere were not feasible in the MIR range due to\ntechnical limitations.’\nSubstrate measurements, while still showing scattering effects, revealed a redshift trend in\nabsorption, suggesting quantum confinement (p. 11): ‘Therefore, additional measurements were\nconducted on a substrate (Supplementary Fig. 29b). However, scattering effects and ligand absorption\nfeatures persisted above ~2,600 nm. Despite the absence of distinct absorption maxima, a redshift in\nthe absorption edge was observed, suggesting quantum confinement effects.[42]’\nRegarding larger NPs, we discussed the weak confinement regime as a possible explanation\nfor the absence of distinct absorption maxima. For larger NPs, the quantum dots are likely to\nbehave as near-bulk particles, leading to broader absorption features (p. 11): ‘In general, QDs\nsized between the electron Bohr radius (28.5 nm for InAs)[51] and the exciton Bohr radius (30 – 44 nm\nfor InAs)[10,51,52] are expected to fall into the weak confinement regime, where absorption maxima are\ntypically absent.[51,53] This means in our case, that probably, no distinct absorption maxima would be\nobserved for large InAs NPs in this size regime.[42]’\nAdditionally, ATR-IR measurements revealed a qualitative redshift in absorption with\nincreasing NP size, but no distinct absorption features were observed, as expected for this\nmethod (p. 12 and Supplementary Fig. 29d-e): ‘The measurements revealed a qualitative redshift\nin absorption as the NP size increased. However, no distinct absorption features were observed, as\nexpected, since ATR-IR characterizes the NP surface.[42]’\nIn addition, a size-dependent, broad absorption band in the MIR range between\n1600-920 cm-1 (6,250 – 10,870 nm) was observed in the ATR-IR measurements, likely\nassociated with oleylamine vibrational modes (p. 12 and Supplementary Fig. 29d-e): ‘Further\n29d-e) revealed, in addition to the ligand features, a size-dependent, broad absorption band in the mid-\ninfrared (MIR) range (1,600 – 920 cm-1), likely associated with the vibrational modes of OAm.[42,56] As\nthe QD size increased, this band shifted further into the red. Such a size-dependent effect is particularly\ninteresting and likely arises from the significant size variation within the same material, which amplifies\nthis effect.[42]’\nLastly, we also addressed the ongoing debate regarding the exciton Bohr radius of InAs QDs\n(30 – 44 nm). As noted on p. 12, we cannot definitively classify NPs larger than 30 nm as QDs\nbased on our current measurements. Whether these particles can be considered QDs remains\nan open question, and further studies are needed to explore this fundamental question: ‘Given\nthe ongoing debate surrounding the exciton Bohr radius of InAs QDs (ranging from 30 to 44 nm, as\nmentioned above)[10,51,52], it remains uncertain whether InAs NPs larger than 30 nm can be classified as\nQDs. Even if they do, they likely would not exhibit distinct absorption bands, as they would fall into the\nweak confinement regime. Instead, they would be better classified as near-bulk QDs.[51]\nDue to the addressed wavelength range, an extensive optical characterization of the large InAs\nparticles’ properties requires further improvements. This characterization is within the scope of follow-up\nstudies, where measurements on the near-bulk QDs could provide insights into the exciton Bohr radius\nof InAs QDs, a fundamental parameter in the study of QD systems.’\nAs a result of these findings, we have revised the manuscript to describe InAs particles larger\nthan 30 nm as nanoparticles, rather than quantum dots. We also updated the manuscript title\nto reflect this distinction.\nWe hope the revised version clarifies the concerns regarding the classification of larger InAs\nparticles and provides a more accurate representation of our findings.\n2. What is the energy bandgap of your InAs quantum dots?\nWe thank the reviewer for this question.\nThe energy bandgap of the InAs QDs in our study depends on their size, as a result of quantum\nconfinement effects, and varies systematically with particle diameter. The energy bandgap\nwas determined from the first excitonic absorption maxima observed in the UV–vis–NIR\nspectra.\nFor InAs QDs in the size range of ~6 – 18 nm, the excitonic peaks correspond to bandgaps\nranging from ~1.1 eV to 0.54 eV (Fig. 5a-b in the revised manuscript). For larger NPs beyond\n18 nm, we were unable to identify distinct absorption maxima, due to factors such as\nincreased scattering, reduced colloidal stability, overlap with ligand absorption features in the\nSWIR, and detector limitations. As discussed in a previous response, we cannot definitively\nclassify the 40 nm particles as QDs. Based on the absorption edge observed around 3,000 nm\nin Supplementary Fig. 29b, we roughly estimate the corresponding bandgap to be 0.4 eV.\n3\n3. How polydisperse is your population of InAs quantum dots? Could you perform Dynamic\nLight Scattering (DLS) measurements on your colloids?\nWe thank the reviewer for this important question.\nWhile DLS is a common technique for analysis of colloids, it is not well suited for our system\nfor several reasons. DLS measures the hydrodynamic diameter, which includes contributions\nfrom the organic ligands and solvation layers, not just the inorganic core. For larger QDs (above\n~19 nm), colloidal stability is significantly reduced, leading to aggregation and strong\nscattering, which can compromise the reliability of DLS results. Furthermore, while DLS works\nwell for larger colloids (>100 nm), its reliability decreases for particles <100 nm, especially in\nthe presence of ligands and solvent shells, all of which strongly affect the measured\nhydrodynamic diameter.\nTo address this important question, we have provided TEM images and size distribution\nhistograms of the samples without size selection in the revised manuscript (Supplementary\nFig. 19, Supplementary Fig. 22, and Supplementary Fig. 23). As mentioned in the original\nmanuscript, the growth of large NPs was not monodisperse, and precipitation techniques were\nrequired for NPs obtained from both seeded and seedless growth methods. To clarify the use\nof size-selective precipitation, we revised the manuscript text (p. 8): ‘The samples were purified\npost-synthetically using size-selective precipitation techniques (hereafter referred to as ‘precipitation\ntechniques’), as described in the Methods section.’ Additionally, we updated the description later\nin the manuscript (p. 8): ‘Fig. 5 summarizes the data of the resulting InAs QDs after applying the\nprecipitation techniques.’\nWe also provided a more detailed description of precipitation process in the Methods section:\n‘For the isolation of monodisperse InAs QD fractions, size-selective precipitation techniques were\napplied using anhydrous toluene and ethanol as the solvent and non-solvent, respectively. First, the\nreaction mixture was shaken and centrifuged to separate QDs with sizes above ~9 nm, which were\ncolloidally unstable in OAm at r. t., but stable in toluene and TCE for sizes up to ~19 nm. If a pellet\nformed, it was dispersed in toluene or TCE, and centrifuged to separate QDs with sizes above ~19 nm.\nIn the last step, if a pellet formed, it was dispersed in TCE or toluene, and ethanol was added dropwise\nuntil the mixture became turbid. The mixture was then centrifuged, and the pellet dispersed in TCE for\ncharacterization. If no pellet formed, the supernatant containing QDs was size-selective precipitated\nusing ethanol as non-solvent, as described above. A rainbow-like shimmer in areas of thin pellet\nthickness indicated interference effects, suggesting a narrow size distribution of the NPs.[42]’\n4\n4. The authors claim that they synthesize very large InAs quantum dots. So, what is the\ncurrent state of the Art? What is the largest InAs quantum dot as of today? The problem\nis that I found a paper published by Saito et al. in Applied Physics Letters (APL) that already\nclaimed in 1999 their ability of synthesizing very large InAs quantum dots with sizes larger\nthan the ones you are currently reporting (~40 nm). Look specifically at the Figure 2\npublished in APL (1999), vol. 74, pages 1224-1226.\nWe thank the reviewer for pointing out the work by Saito et al. (1999). We are aware of this\nimportant contribution and would like to clarify a key distinction: the InAs quantum dots\nreported in that paper were grown epitaxially on GaAs substrates using molecular beam\nepitaxy (MBE). These are not colloidal quantum dots, and their growth mechanism differs\nfundamentally from the colloidal synthesis methods reported in our study.\nThe key difference is that MBE-grown InAs quantum dots form via an entirely different\nmechanism, typically resulting in island-like structures that are confined within the substrate,\nwhereas our work deals with solution-processed, colloidal InAs quantum dots that are free-\nstanding and synthesized in a liquid phase. The synthesis methods, structural characteristics,\nand the resulting properties of these two types of quantum dots are fundamentally different.\nThe largest colloidal InAs QDs reported to date are ~13 nm (p. 3): For example, this was\ndemonstrated when the largest non-elongated InAs QDs reported to date were produced by this\nmethod, achieving an absorption peak in the range up to ~1,850 nm and QD sizes up to ~13 nm.[34]\nTo clarify this distinction, we have added a reference to the work of Saito et al. in the revised\nmanuscript (Introduction, p. 2): ‘Although large InAs QDs grown epitaxially have been reported\n1999,[29] the colloidal synthesis of QDs larger than 7 nm, with excitonic absorption peak above\n1,400 nm, remains a significant challenge.[11,24,30]’\nThis addition should help make the distinction between epitaxially grown and colloidally\nsynthesized InAs quantum dots clearer to the reader.\n5\n5. The bibliography contains only 22 references which is very low for a topic like this one. A\nlot of work has been published on quantum dots and specifically on InAs quantum dots.\nAccording to the author guidelines of Nature Communications, you are allowed to\nreference 70 articles. So, you have a lot of room to improve the bibliography and context\nof your article.\nWe thank the reviewer for the valuable suggestion regarding the expansion of the bibliography.\nIn response, we have significantly extended the list of references to 56 in the revised\nmanuscript to better reflect the broad context of research.\n6. The acronym RoHS is used in the abstract (line 9). For clarity, acronyms should be avoided\nin abstract and RoHS should be spelled out completely.\nWe thank the reviewer for this helpful comment. We have now replaced ‘RoHS’ with\n‘Restriction of Hazardous Substances’ in the abstract for clarity.\nRemarks on the figures.\n1. The sketch used to describe the three steps synthesis protocol in Figure 1 could be\nimproved to be more visual than just using rectangles.\nWe thank the reviewer for the helpful suggestion. The schematic in Fig. 1 has been updated\nwith more visual graphics. We believe this will improve clarity and reader understanding.\n2. On the y-axis of Figure 2, absorbance does not have any units; not even arbitrary units\nbecause absorbance is by definition a logarithm and as you probably know a logarithm\ndoes not have any units.\nWe thank the reviewer for this helpful comment. Absorbance is indeed a logarithmic quantity and,\nas such, has no units. In the revised manuscript and supplementary materials, we have\nupdated the y-axis label accordingly, including for Fig. 2 (now Fig. 3c in the revised version).\n6\n3. The previous remark also applies to Figure 3 d, Figure 3e and Figure 4a.\nWe thank the reviewer for the additional note. The y-axis labels in Figures 3d (now Fig. 4d), 3e\n(now Fig. 4g), and 4a (now Fig. 5a) have been updated accordingly.\n4. On Figure 3f, the error bar and the announced value should have the same rank! If you\nhave an error of 1.2 nm than the announced value should be 3.5 nm.\nWe thank the reviewer for this valuable observation. The reported values in Fig. 3f (now Fig.\n4e), as well as in Figs. 4a-c and 4f, have been corrected to align with the precision of the error\nbars.\n5. The error bars on Figures 4b to 4e are wrong.\nWe thank the reviewer for the additional note. The error bars in Figures 4b-e (now Fig. 5c-f)\nhave been corrected accordingly.\n6. The error bars on Figures 5a and 5b are wrong.\nWe thank the reviewer for this observation. The error bars in Figures 5a and 5b (now Fig. 6a-\nb) have been updated accordingly.\n7. On Figures 5a and 5b, could you rotate the figures or just the scale bar in order to have\nthe scale bar horizontal? It will be easier for the readers to have all scale bars horizontal.\nWe thank the reviewer for this helpful suggestion. We have rotated the images in Figures 5a\nand 5b (now Fig. 6a-b) so that the scale bars are now horizontal, enhancing readability.\n7\n8. On Figure 5c, if you normalize the intensity, then the values on the y-axis go from 0 to 1\nand should be displayed. If you want you could display your y-axis from 0% to 100%.\nWe thank the reviewer for the suggestion. We have updated Fig. 5c (now Fig. 6c) to include\nthe reference for cubic InAs for better clarity. We chose not to display the y-axis values from 0\nto 1 in order to maintain consistency with the style used across all figures in the manuscript.\n9. The error bars on Figures 6a to 6d are wrong.\nWe thank the reviewer for the additional note. We have updated the error bars in Fig. 6a-d\n(now Fig. 7a-d) accordingly.\n10. On Figures 6a, 6b, 6c and 6d, could you rotate the figures or just the scale bar in order to\nhave the scale bar horizontal? It will be easier for the readers to have all scale bars\nhorizontal.\nWe thank the reviewer for this helpful suggestion. We have rotated Figures 6ad (now Fig. 7a-\nd) so that all scale bars are now displayed horizontally, ensuring consistency across the figures\nand improving readability for the reader.\nOnce again, we sincerely thank the Reviewer for their valuable feedback and careful review of\nour manuscript.\nI thanks the authors for addressing all the reviewer's comments/concerns regarding this manuscript,\nit has greatly improved.\nI believe the manuscript will be of great interest to readership of Nature Communication and the\ncommunity working on colloidal InAs Quantum dots.\nIn my view, the revised manuscript can be accepted for publication.\nWe sincerely thank the Reviewer for their positive feedback.\nWe also thank them once again for their insightful suggestions that helped improve our\nmanuscript.\nResponse to the Reviewer #2\nThe authors have carefully addressed all points I raised, and I recommend the publication of\nthis article in its present form. Once again I would like to point out the high importance of the\npresented results for this field.\nWe sincerely thank the Reviewer for their positive feedback.\nWe also thank them once again for their insightful suggestions that helped improve our\nmanuscript.\nMaybe one small final comment concerning the reaction yield calculations:\nthe molar quantity given (0.316 mmol, cf. Suppl. note 3) is not that of InAs clusters but that\nof InAs units and it does not appear to indicate the reaction yield according to In: due to the\nreaction mechanism, In has to be used with a 3:1 excess compared to As. Therefore, just\ngiving the reaction yield according to As will be good enough.\nWe sincerely thank the reviewer for this helpful comment. We have chosen to report the\nreaction yield according to In as well, to highlight the high amount of unreacted In precursor.\nA similar calculation is also shown in the case of InAs seed synthesis (Suppl. Note 4).\nResponse to the Reviewer #4\nThe authors have carefully addressed the comments from all reviewers. The clarity of the text has\nbeen improved.\nWe sincerely thank the Reviewer for their positive feedback.\nWe also thank them once again for their insightful suggestions that helped improve our\nmanuscript.\nReviewer #4\n(Remarks to the Author)\nManuscript #: NCOMMS-25-25803-T\nManuscript Title: Colloidal Synthesis of Ultra-Large InAs Quantum Dots 1\nAuthors: Ekaterina Salikhova, Alf Mews, Jan Steffen Niehaus\nThe authors reported the synthesis of free-standing InAs quantum dots by wet-chemistry.\nTheir main goal was to synthesize ultra-large InAs quantum dots. In order to reach their goal,\nthe chosen synthesis protocol is a wet-chemical synthesis one that involves three steps. The\nauthors mainly used UV-visible-NIR spectroscopy, Transmission Electron Microscopy and X-ray\ndiffraction to characterize their samples.\nHere are my comments:\n• Remarks on the text.\n1. The authors claimed that they have InAs quantum dots but nowhere they experimentally\nproved that they had quantum dots and not just InAs nanoparticles. Authors could use\nARPES, Raman spectroscopy or EELS spectroscopy to confirm that indeed they have\nquantum confinement on their InAs quantum dots.\n2. What is the energy bandgap of your InAs quantum dots?\n3. How polydisperse is your population of InAs quantum dots? Could you perform Dynamic\nLight Scattering (DLS) measurements on your colloids?\n4. The authors claim that they synthesize very large InAs quantum dots. So, what is the\ncurrent state of the Art? What is the largest InAs quantum dot as of today? The problem\nis that I found a paper published by Saito et al. in Applied Physics Letters (APL) that already\nclaimed in 1999 their ability of synthesizing very large InAs quantum dots with sizes larger\nthan the ones you are currently reporting (~40 nm). Look specifically at the Figure 2\npublished in APL (1999), vol. 74, pages 1224-1226.\n5. The bibliography contains only 22 references which is very low for a topic like this one. A\nlot of work has been published on quantum dots and specifically on InAs quantum dots.\nAccording to the author guidelines of Nature Communications, you are allowed to\nreference 70 articles. So, you have a lot of room to improve the bibliography and context\nof your article.\n6. The acronym RoHS is used in the abstract (line 9). For clarity, acronyms should be avoided\nin abstract and RoHS should be spelled out completely.\n• Remarks on the figures.\n(Remarks to the Author)\n1. The sketch used to describe the three steps synthesis protocol in Figure 1 could be\nimproved to be more visual than just using rectangles.\n2. On the y-axis of Figure 2, absorbance does not have any units; not even arbitrary units\nbecause absorbance is by definition a logarithm and as you probably know a logarithm\ndoes not have any units.\n3. The previous remark also applies to Figure 3 d, Figure 3e and Figure 4a.\n4. On Figure 3f, the error bar and the announced value should have the same rank! If you\nhave an error of 1.2 nm than the announced value should be 3.5 nm.\n5. The error bars on Figures 4b to 4e are wrong.\n6. The error bars on Figures 5a and 5b are wrong.\n7. On Figures 5a and 5b, could you rotate the figures or just the scale bar in order to have\nthe scale bar horizontal? It will be easier for the readers to have all scale bars horizontal.\n8. On Figure 5c, if you normalize the intensity, then the values on the y-axis go from 0 to 1\nand should be displayed. If you want you could display your y-axis from 0% to 100%.\n9. The error bars on Figures 6a to 6d are wrong.\n10. On Figures 6a, 6b, 6c and 6d, could you rotate the figures or just the scale bar in order to\nhave the scale bar horizontal? It will be easier for the readers to have all scale bars\nhorizontal.\n_____________________\n2"}, {"round": 2, "reviewer_comments": {"reviewer_1": "I thanks the authors for addressing all the reviewer's comments/concerns regarding this manuscript, it has greatly improved.\nI believe the manuscript will be of great interest to readership of Nature Communication and the community working on colloidal InAs Quantum dots.\nIn my view, the revised manuscript can be accepted for publication.", "reviewer_2": "The authors have carefully addressed all points I raised, and I recommend the publication of this article in its present form.\nOnce again I would like to point out the high importance of the presented results for this field.\nMaybe one small final comment concerning the reaction yield calculations:\nthe molar quantity given (0.316 mmol, cf. Suppl. note 3) is not that of InAs clusters but that of InAs units and it does not appear to indicate the reaction yield according to In: due to the reaction mechanism, In has to be used with a 3:1 excess compared to As. Therefore, just giving the reaction yield according to As will be good enough.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_4": "The authors have carefully addressed the comments from all reviewers. The clarity of the text has been improved."}, "author_response": ""}]

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