bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Insights into Structural Evolution of Lithium Peroxides with Reduced Charge Overpotential in Li−O2 System
Authors: Lu Jun
Published: May 2020

Reducing charge-discharge overpotential is of great significance to enhance the efficiency and cyclability of Li−O2 batteries. Here we successfully achieve dramatically reduced charge overpotential (0.4 V) via a rational design of cathode architecture, which features highly uniform Pt and Pt3Co nanocrystals embedding within nitrogen-doped cobalt@graphene heterostructures. Because of the improvement on the catalytic efficiency for optimizing the electrical and dynamic properties, the cathode design enables promising electrochemical performance. More importantly, the results reveal different overpotential prompted by different structural evolution of bulk Li2O2, which depends on the Pt modification approach (surface-coating and bulk-doping). This dependence is found to be attributed to the influence of Pt nanocomponents and their dispersion on the formation and decomposition mechanism of Li2O2. Density functional theory calculations provide mechanistic insights into the promotional effect of Pt and Pt3Co on the reduction of the charge overpotential. Finally, an inner relationship between overpotential and electrochemical kinetics is proposed.
(Invited) Enabling High-Performance Sodium Batteries By Facile-Processed Nanocarbon
Authors: Li Weiyang
Published: May 2020

Sodium (Na)-based batteries are considered to be the next-generation cost-effective energy storage devices due to the low cost and high natural abundance of Na sources. Here we present the use of facile-processed nanocarbon to realize two types of high-energy Na-based battery systems: Na-sulfur (S) and Na-carbon dioxide (CO2) batteries. A highly stable room-temperature (RT) Na-S battery is achieved using a facile-processed nanocarbon promoted S cathode and polymer electrolyte (PE). The RT Na-S battery can deliver a reversible capacity of >700 mAh g−1 with near 100% Coulombic efficiency and an ultrahigh capacity retention of 98.2% at 0.2C after 200 cycles. Moreover, an all-solid-state Na-CO2 battery is constructed using a nanocarbon-based cathode and a liquid-free PE. The all-solid-state Na-CO2 batteries exhibit excellent performance with long cycle life (320 h with a fixed capacity of 1,000 mAh g−1), high discharge capacity (>10,000 mAh g−1), and high energy density (180 Wh kg−1 in pouch cell) at 50 oC.
Up- and Down-Converting Photons in Molecular Carbon Materials
Authors: Guldi Dirk M.
Published: May 2020

The Shockley-Queisser limit places an upper bound on solar conversion efficiency for a single p-n junction solar cell at slightly more than 30%. To surpass this limit, multi-exciton generation is being explored in inorganic semiconductors, while singlet fission (SF) is being investigated in arrays of conjugated organic molecules. In an optimal SF process, the lowest singlet excited state of one molecule (S1) that is positioned next to a second molecule in its ground state (S0) is down-converted into two triplet excited states (T1) each residing on one of the two adjacent molecules. The two triplet states initially form a correlated pair state 1(T1T1), which then evolves into two separated triplet states (T1 + T1). As such, the energetic requirement for SF is E(S1) ≥ 2 ´ E(T1).

We have set our focus in recent years on intramolecular SF in molecular carbon materials and their studies in solution rather than on intermolecular SF investigations in crystalline films.

Implicit in intramolecular SF is a resonant, direct excitation of the SF material. In dimers of molecular carbon materials linked by a myriad of molecular spacers, SF takes place with quantum yields of up to 200%. In addition, all key intermediates in the SF process, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons, have been identified. This approach is, however, limited to the part of the solar spectrum, where, for example, the dimers of carbon materials feature a significant absorption cross-section. To employ the remaining part of the solar spectrum necessitates non-resonant, indirect excitation of the SF materials via either up- or down-conversion. For example, the up-conversion approach is realized with singlet excited states , which are accessed by two-photon absorptions (TPA). TPA is then followed in the second step of the sequence by an intramolecular SF – similar to what is seen upon resonant, direct excitation. Quite different is the down-conversion approach, which is based on an intramolecular Förster resonance energy transfer (FRET) and thereby the (photo)activation of the SF material. FRET requires the use of a complementary absorbing chromophore and enables funneling its excited state energy unidirectionally to the SF performing pentacene dimer. Again, SF completes the reaction sequence.
(Invited) Nanostructured Carbon Composite Materials for Electrocatalytic Conversion Reactions
Authors: Shao Yuyan
Published: May 2020

Nanostructured carbon and carbon composite materials have been key component in almost all electrochemical energy devices, such as fuel cells, batteries, supercapacitors. In this talk, we will present our work on nanostructured carbon composite materials for electrocatalysis, including oxygen reduction reaction (ORR), electrocatalytic hydrogenation, with a focus on materials stability. We will introduce fundamental understanding on the degradation mechanisms of this kind of carbon-based materials, including electrochemical and chemical oxidation (by radicals) – for atomically dispersed M-N-C nonprecious metal catalysts, it also includes the stability of metals. Our strategy to improve the stability of carbon-based materials will also be presented, including incorporation of metal oxides to protect carbon defects and to scavenger radicals.
(Invited) Near Infrared Imaging of Chemical Signaling between Cells Using Fluorescent Nanosensors
Authors: Kruss Sebastian
Published: May 2020

Cells use small molecules to exchange information. A very prominent example is neurotransmitter signaling between neuronal cells or paracrine signaling between blood cells. However, it is up to date difficult to visualize signaling processes between cells with high spatial, temporal and chemical resolution. We are interested in developing fluorescent sensors/probes that overcome these limitations and answer novel biological questions.

For that purpose we use near infrared (nIR) fluorescent single-walled carbon nanotubes (SWCNTs). SWCNTs fluoresce in the nIR tissue transparency window (900 nm -1700 nm) and do not bleach. They are chemically modified to render them selective for neurotransmitters such as dopamine and serotonin. In this context, we developed different chemical strategies that include screening for artificial binding motifs, aptamers and nanobodies. Using these strategies we created sensors for the neurotransmitters dopamine and serotonin that increase their fluorescence in the presence of the target molecule and detect down to single molecules. Fast parallel imaging of many of those sensors provides a nIR image (>900 nm) of the neurotransmitter concentration around cells. This technique was used to image hot spots of dopamine release from primary dopaminergic neurons. It enabled us to observe localized release sites and correlate it with the exocytosis machinery of the cells. Neurotransmitters are not only relevant in the neuronal system but as well in the periphery e.g. in blood cells. In this context, we imaged for the first time how human blood platelets release serotonin after activation and resolved the heterogeneity in release patterns. These results illustrate that tailored SWCNTs are powerful tools for quantitative chemical imaging of biological processes.
(Invited) Near-Infrared Optical Probes for Imaging Neuromodulators with High Spatiotemporal Resolution
Authors: Beyene Abraham G , Delevich Kristen , Wilbrecht Linda , Landry Markita P
Published: May 2020

Dopamine neurotransmission plays critical roles in brain function in both health and disease and aberrations in dopamine neurotransmission are implicated in several psychiatric and neurological disorders, including schizophrenia, depression, anxiety, and Parkinson’s disease. Until recently, measuring the dynamics of dopamine and other neurotransmitters of this class could not be achieved at spatiotemporal resolutions necessary to understand how dopamine regulates the plasticity and function of neurons and neural circuits, and how dysfunctions in this regulation lead to disease. Probes that satisfy critical attributes in spatial and temporal resolution, and chemical selectivity are needed to facilitate investigations of brain neurochemistry.

To address this need, we developed an ultrasensitive near-infrared “turn-on” nanosensor (nIRCat) for the catecholamines dopamine and norepinephrine and implemented nIRCat to study endogenous dopamine dynamics in brain tissue. nIRCats are synthesized from photostable and near infrared emissive functionalized single wall carbon nanotubes (SWCNT) and exhibit maximal relative change in fluorescence intensity (ΔF/F0) of up to 35-fold, with a dynamic range that spans physiological concentrations of their target brain analytes. We demonstrate that nIRCat can detect electrically and optogenetically evoked release of dopamine in brain tissue, revealing putative hotspots of activity that exhibited a log-normal distribution in size, ranging from 2 – 10 µm for mice brain tissue in the dorsomedial striatum. Furthermore, the synthetic nature of the molecular recognition platform afforded compatibility with dopamine-receptor targeting antipsychotics and psychoactive drugs and permitted studies of how such receptor-targeting drugs modulate evoked dopamine release. This assay revealed presynaptic correlates of drug activity at the level of putative dopamine release sites, which had heretofore been inaccessible to probe with existing tools. Our results suggest that nIRCat technology may uniquely support similar explorations of processes that regulate dopamine neuromodulation at the level of individual synapses, and exploration of the effects of receptor agonists and antagonists that are commonly used as psychiatric drugs as well as drugs that lead to substance use disorder. We conclude that SWCNTs can serve as versatile synthetic optical scaffolds for monitoring interneuronal chemical signaling in the brain extracellular space at spatial and temporal scales pertinent with the encoded neurochemical information.
(Invited) In Vivo Analyte Detection Via Single-Walled Carbon Nanotube Near-Infrared Fluorescence
Authors: Williams Ryan M. , Harvey Jackson , Galassi Thomas , Heller Daniel A.
Published: May 2020

Implantable optical nanosensors hold the promise of rapid, minimally-invasive longitudal monitoring of analytes in a patient or animal. Such devices will allow for informed clinical intervention based on changes in drug, biomarker, or disease state profiles. We developed implantable nanosensors based on the optical properties of single-walled carbon nanotubes (SWCNT). SWCNT fluorescence is in the ‘tissue-transparent’ near-infrared spectrum, allowing for fluorescence measurements after implantation inside an animal. Further, SWCNT fluorescence is photostable, allowing for multiple measurements over time. We engineered separate SWCNT-based sensors such that their fluorescence emission responded to various analytes, including small molecule drugs as well as protein and nucleic acid biomarkers. Each sensor device was immobilized into a semi-permeable biocompatible membrane, allowing analyte penetration but retaining SWCNT inside. We implanted each sensor device into live mice, either in the peritoneal cavity or subcutaneously, and performed whole-mouse near-infrared fluorescence imaging to ensure the stability of the membrane and sensor brightness. We used a sensor implant specific for the chemotherapeutic doxorubicin to drug monitor transport within the animal. We used sensor implants specific for the ovarian cancer protein biomarker HE4 or for individual microRNA sequences to measure exogenous or cancer-generated quantities of each biomarker in mice. We expect these implantable sensors to have potential as research tools or clinical diagnostics to monitor pharmacokinetics or locally measure disease biomarkers in real-time.
(Invited) Modulating Neuronal Activity with out-of-Plane Grown Three Dimensional (3D) Fuzzy Graphene
Authors: Rastogi Sahil Kumar , Scopelliti Matteo , Pinto Bernardo I. , Hartung Jane , Garg Raghav , Kim Seokhyoung , Murphey Corban G.E. , Johnson Nicholas , San Roman Daniel , Bezanilla Francisco , Cahoon James F. , Gold Michael S. , Chamanzar Maysam , Cohen-Karni Tzahi
Published: May 2020

The ability to modulate cellular electrophysiology is a fundamental aspect for investigation of tissue development, maturation and function. Currently, there is a need for remote, non-genetic, light-induced control of cellular activity in native-like state, three-dimensional (3D) tissues such as spheroids and organoids. Here, we report a breakthrough hybrid-nanomaterial for remote, non-genetic photostimulation of both two-dimensional (2D) and 3D neural cellular systems. We combine one-dimensional (1D) nanowires (NWs) and 2D graphene flakes grown out-of-plane for highly controlled photostimulation at subcellular precision with laser energies lower than hundred nanojoules, 1-2 orders of magnitude lower than Au-, C- and Si-based photostimulation. Photostimulation using NW-templated 3D fuzzy graphene (NT-3DFG) is flexible due to its broadband absorption and does not generate cellular stress. Therefore, it serves a novel powerful toolset for studies of cell signaling within and between tissues and can enable new therapeutic interventions.
(Invited) Development of Single Walled Carbon Nanohorn Systems for Biological Applications
Authors: Quinn Susan Jane
Published: May 2020

The combination of biocompatibility and unique surface properties has led to the extensive study of the biological applications of carbon nanomaterials. We are interested in the application of single walled carbon nanohorns (CNH) for the development of tools for cellular imaging, diagnostics and therapeutics. CNHs are made up of sp2 conical shaped postulates, with diameters of 2–5 nm and lengths of 40–50 nm, assembled into robust bud-like spherical aggregates of between 80 and 100 nm. The key advantage of these materials is their low toxicity, high surface area, and ease of functionalisation.1,2 In this presentation results from our recent work on the use of CNHs for enhanced biosensing of glutamate,3 to study of the cellular interactions of fluorescently labelled CNH systems and their use of CNHs to delivery photodynamic therapy agents to cells will be presented.

The poor cellular uptake of many porphyrins is a barrier to their application in phototherapeutic applications,4 biocompatible CNH carriers offer a means to overcome this. A spectroscopic study of the binding interactions of the PtTMPyP4 cationic porphyrin with oxidised carbon nanohorns through non-covalent, electrostatic interactions revealed a high a loading of 200 wgt%. Brightfield microscopy demonstrated the efficacy of sparsely loaded Porphyrin-CNH constructs to be internalised within HeLa cells, which were found to undergo rapid cell death upon visible light excitation.5

The ability to image processes in cells and track the interaction and efficacy of nanomaterial cellular uptake is of great interest. The use of an ON/OFF fluorophore whose emission is triggered upon cellular uptake will be described as a means to monitor time dependent uptake by live-imaging and also to report on the influence of functionalisation on the extent of cellular aggregation.6 Finally, some more recent results on tracking the destination of carbon nanohorns in cells will be reported.

1. Iijima, M. Yudasaka, R. Yamada, S. Bandow, K. Suenaga, F. Kokai, K. Takahashi, Chem. Phys. Lett. 1999, 309, 165−170.S.

2. Zhuab, G. Xu, Nanoscale, 2010, 2, 2538–2549.

3. R. Ford, S. J. Devereux, S. J. Quinn, R. D. O'Neill, Analyst, 2019, 144, 5299-5307

4. A. Rajora, J.W.H. Lou and G. Zheng, Chem. Soc. Rev., 2017, 46, 6433 – 6469.

5. J. Devereux, M. Massaro, A. Barker, D. T. Hinds, B. Hifni, J. C. Simpson and S. J. Quinn, J. Mater. Chem. B, 2019, 7, 3670–3678.

6. S. J. Devereux, S. Cheung, H. C. Daly, D. F. O'Shea and S J. Quinn, Chem. Eur. J., 2018, 24, 14162–14170.
Controlled, Stepwise Assembly of Highly Potent Drugs on Single-Wall Carbon Nanotubes
Authors: Jin Sumin , Dahl Kris Noel , Islam Mohammad F.
Published: May 2020

To utilize single-wall carbon nanotubes (SWCNTs) for biomedical applications, individual dispersion and coating of SWCNTs with biocompatible molecules are important to avoid triggering cytotoxicity and increase their stability in serum-containing media. One of the common methods for producing SWCNT-based drug delivery is to individually disperse SWCNTs in aqueous solutions with various biocompatible molecules such as DNA, biopolymers, and proteins, followed by attachment of drugs and targeting moieties to the biologically dispersed nanotubes. Another approach that is less frequently used involves attaching drugs to biocompatible molecules prior to dispersing SWCNTs in a solution. Unfortunately, both approaches suffer from low SWCNT dispersion yield and lack adequate control of drug loading process, especially if the drugs are highly hydrophobic. In this talk, we present an extremely facile schema to generate SWCNT-based drug delivery systems via a controlled, stepwise assembly of drugs and biocompatible molecules on preformed SWCNT networks. We first created a three-dimensional freestanding network of SWCNTs in either aqueous or non-aqueous solvents to facilitate loading of drugs; many potent drugs are only soluble in non-aqueous solvents. SWCNTs in freestanding networks were then coated with drugs such as doxorubicin, which is a common model drug used for characterization of drug loading and release processes owing to its optical properties, and paclitaxel, which is a model drug representing highly lipophilic drugs. Drug-coated SWCNT networks were coated with proteins, such as albumins, followed by dispersing in water via gentle sonication with almost no loss of SWCNT dispersion yield. Optical characterization and imaging have shown that SWCNTs/drug/protein complexes are highly individualized in solution and readily internalized by cells upon exposure. The loaded drugs were efficiently released upon internalization and displayed larger reduction in cell viability compared to free drugs. Further, to demonstrate robustness of our approach and to assist with drug release, we coated SWCNTs with biocompatible polymers prior to decorating with drugs to serve as a sacrificial yet assistive layer. The polymer coating did not alter SWCNT dispersion and drug loading significantly and allowed for faster release of drugs upon internalization in the cells. Overall, the proposed method allows for precisely controlled, stepwise assembly of SWCNTs with any drug and biomolecule combinations and could be further developed for multifunctional drug delivery platform utilizing SWCNTs.
Large Area, High-Density SWCNT Forests with Remarkably Invariant Structural Properties over a Wide Range of Synthesis Conditions
Authors: Park Sei Jin , Meshot Eric R. , Buchsbaum Steven F. , Jue Melinda L. , Wu Kuang Jen , Fornasiero Francesco
Published: May 2020

Driven by the exceptional thermal, electrical, optical, mechanical and fluidic properties of single-walled carbon nanotubes (SWCNT), commercial use of vertically aligned “forests” are on the horizon for applications1 ranging from optical absorbers and thermal interfaces to selective membranes and advanced fabrics.2,3 Large-area SWCNT forests with high densities and small diameters are especially important for many applications, yet they are conspicuously absent from the literature due to synthesis challenges.

Here, we demonstrate synthesis of high-density (> 1012 CNTs/cm2), small-diameter (~ 2 nm) SWCNT forests with structural characteristics that remain uniform over large areas (up to 6-in. diameter)4 and, surprisingly, largely unchanged over a wide range of synthesis conditions. We find also that our growth regime enables a record-high carbon conversion efficiency and a stable mass kinetics, both of which are invariant with catalyst type (Fe vs Fe/Mo mixes). To identify the limiting steps in the SWCNT growth kinetics and the factors contributing to the process robustness, we determine the dependence of the reaction rate and carbon conversion efficiency on broad ranges of synthesis parameters. Effects of catalyst area (from 1 × 1 cm2 to 6-in wafers), growth pressure (10-750 mbar), gas composition (30-fold acetylene partial pressure variation), and flowrates are presented.

Our demonstration of such exceptionally robust and reproducible synthesis of high-density forests over large areas provides valuable insights for future scale-up efforts of SWCNT forest production that are necessary for widespread adoption of advanced CNT technologies.

1. R. Rao et al., ACS Nano., 12 (2018) 11756.

2. N. Bui, E. R. Meshot, S. Kim, J. Peña, P. W. Gibson, K. J. Wu, F. Fornasiero, Adv. Mater., 28 (2016) 5871.

3. Y. Li, C. Chen, E. R. Meshot, S. F. Buchsbaum, M. Herbert, R. Zhu, O. Kulikov, B McDonald, N. Bui, M. L. Jue, S. Park, C. Valdez, S. Hok, C. J. Doona, K. J. Wu, T. M. Swager, F. Fornasiero, submitted (2019)

4. E. R. Meshot, S. Park, S. F. Buchsbaum, M. L. Jue, T. R. Kuykendall, E. Schaible, L. B. Bayu Aji, S. Kucheyev, K. J. Wu, F. Fornasiero, submitted (2019).

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-797268
Raman Imaging Study of Alpha-Sexithiophene Encapsulation in Single-Walled Carbon Nanotubes
Authors: Allard Charlotte , Gaufres Etienne , Desjardins Patrick , Martel Richard
Published: May 2020

Single-Walled Carbon Nanotubes (SWNTs) are nanosystems with a large aspect ratio that have potential in a wide range of optical applications. Notably, the hollowness of SWNTs interior allows endohedral filling, in which the SWNTs act as a template for the creation of new hybrid nanostructures. It was shown recently that dyes encapsulated inside carbon nanotubes (CNTs) are protected from degradation and present a strong Raman signature with narrow emission peaks, free of background fluorescence [1]. Further, confinement inside SWNTs was found to largely impact molecular organisation, tuning the physical and chemical properties of the encapsulated molecules. In this study, we explore the encapsulation mechanism of dye molecules in SWNTs. α-sexithiophene molecules were chosen due to their well-conjugated, rod-like structure and giant Raman signal upon encapsulation, at an excitation of 532 nm.

A model system composed of long (>10 um) and aligned SWNTs was used, in which CVD-grown SWNTs are patterned by electron-beam lithography (EBL) and opened by oxygen plasma reactive ion etching (O2 RIE). The encapsulation is carried-out using a liquid-phase protocol, which allows the study of different encapsulation processes, such as dye entryways, aggregation formation and dynamics, as well as the relationship between encapsulation parameters (concentration, temperature, solvent) and yield. Due to their length, these SWNTs are well resolved by Raman imaging (RIMA, Raman Imaging system, Photon etc.) and provide a direct visual of the encapsulation process in this 1D system.

[1] Gaufrès, E., et al. Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging. Nature Photonics 8(1), 72 (2014).
(Invited) Novel Designs for Single Photon Detection
Authors: Léonard François
Published: May 2020

Photodetection plays a key role in basic science and technology, with exquisite performance having been achieved down to the single photon level. Further improvements in photodetectors would open new possibilities across a broad range of scientific disciplines, and enable new types of applications. However, it is still unclear what is possible in terms of ultimate performance, and what properties are needed for a photodetector to achieve such performance. In this presentation, I will discuss recent theoretical and experimental work to address this question. On the theoretical front, we present a new general framework to establish the fundamental properties of photodetectors from a fully quantum perspective, and show what basic features are needed to achieve high performance. Novel photodetector designs emerge from these considerations, and we present initial experimentswith carbon nanotube devices to test these new designs.
(Invited) Growth and Characterization of Various Van Der Waals Hetero-Nanotubes Based on Single-Walled Carbon Nanotubes
Authors: Maruyama Shigeo
Published: May 2020

We have synthesized a new coaxial nanotube structure, in which mono- or few-layer hexagonal boron nitride nanotube (BNNT) seamlessly wrap around a single-walled carbon nanotube (SWCNT); SWCNT@BNNT [1]. We named these as one-dimensional van der Waals hetero-nanotubes, because we found no correlation between chiral angle of inner SWCNT and outer BNNT for ‘double-walled’ SWCNT@BNNT. We have further developed the 1D coating CVD of transition metal dichalcogenide nanotubes (TMD-NT), such as MoS2 nanotubes and WSe2 nanotubes. We can grow MoS2 nanotubes around relatively large diameter SWCNT or SWCNT@BNNT. These nanotubes can be labelled as SWCNT@TMD-NT or SWCNT@BNNT@TMD-NT as shown in Fig. 1. Because BNNT is thermally more stable than SWCNT, we can remove SWCNT from SWCNT@BNNT by the gentle oxidation process. Hence, we can produce BNNT with inner diameter determined by the original SWCNT. Then, the MoS2 CVD can result BNNT@TMD-NT or TMD-NT@BNNT as shown in Fig. 1. Recently, CVD growth of carbon nanotubes over SWCNT@BNNT is realized, resulting SWCNT@BNNT@SWCNT. These hetero-nanotubes are characterized by HR-TEM, STEM-EELS, optical absorption, FT-IR, Raman scattering, Photoluminescence spectroscopy.

Part of this work was supported by JSPS KAKENHI Grant Numbers JP15H05760, JP18H05329.

Reference:

[1] R. Xiang, T. Inoue, Y. Zheng, A. Kumamoto, Y. Qian, Y. Sato, M. Liu, D. Gokhale, J. Guo, K. Hisama, S. Yotsumoto, T. Ogamoto, H. Arai, Y. Kobayashi, H. Zhang, B. Hou, A. Anisimov, Y. Miyata, S. Okada, S. Chiashi, Y. Li, E. I. Kauppinen, Y. Ikuhara, K. Suenaga, S. Maruyama, arXiv:1807.06154 (2019).

Figure 1
(Invited) Combining Absorption, Wavelength-Dependent Raman and Fluorescence-Excitation Spectroscopy with High-Resolution Transmission Electron Microscopy for Determining the Chiral Purity of Sorted SWCNT Samples
Authors: Cambré Sofie , Forel Salomé , Castan Alice , Defillet Joeri , Levshov Dmitry , Fossard Frederic , Wenseleers Wim , Loiseau Annick
Published: May 2020

Single-wall carbon nanotubes (SWCNTs) possess unique electronic and optical properties that depend strongly on their exact chiral structure. Recent progress in the structure sorting of specific SWCNT chiralities, with increasing chiral purity[1], demands an effective characterization methodology to be developed to accurately determine the chiral composition of any SWCNT sample. Very often, optical spectroscopy is used to assess the chiral composition of a sample, but absorption cross-sections, PL quantum efficiencies and Raman cross-sections are all depending on the exact chiral structure,[2] and can be strongly influenced by other factors such as the specific internal and external environment of the SWCNTs.[3] In this work, we systematically compare the chirality distribution obtained from 3 different optical spectroscopic techniques, i.e. absorption, wavelength-dependent Raman and fluorescence-excitation spectroscopy with the chirality distribution obtained from high-resolution transmission electron microscopy for both chirality-sorted and unsorted SWCNT samples. This combined approach demonstrates the importance of using a multi-technique characterization strategy for a reliable determination of SWCNT chirality distribution.

[1] J.A. Fagan, Nanoscale Adv. 1, 3307 (2019) and references therein

[2] V.N. Popov, Nano Lett. 4, 1795 (2004)

[3] S. Cambré et al, Angew. Chem. – Int Ed. 50, 2764 (2011); ACS nano 6, 2649 (2012)
(Invited) Perfecting Defects
Authors: Wang YuHuang
Published: May 2020

Organic color-center quantum defects have emerged as a new class of quantum materials that are opening exciting possibilities for imaging, sensing, and quantum information. This talk will discuss progress from ongoing research in our lab on the synthesis and characterization of these synthetic chemical defects.
(Invited) Controlling Defect-State Emission in Covalently Functionalized Single-Walled Carbon Nanotubes: A Theoretical Perspective
Authors: Tretiak Sergei
Published: May 2020

Unique electronic and optical properties of chemically semiconducting carbon nanotubes have inspired a wide range of optoelectronic, sensing, imaging and quantum communication applications. As such, a great deal of recent research focuses on strategies toward rigid control of their photoluminescence characteristics. Such strategies include controlling the functionalization species, localized defect geometry, and defect concentration. Our quantum-chemical modeling have shown how chemical surface adducts locally alter the pi-conjugated network of the nanotube surface that leads to a spatial confinement of the electronically excited wavefunctions. Experimental photoluminescence studies reveal a complex structure of electronic states and their dynamics induced by surface modifications. Our simulations suggest an association of these spectroscopic features with deep trap states tied to different specific chemical species, nanotube chiralities and their mod index. Engineering of interfacial surface structures of single-chirality nanotube materials with dopant-induced defects then allowed us for accurate control over energy transfer and luminescence properties. Overall, these results suggest that covalent doping chemistry is a powerful route toward harnessing dynamics of excitons and charges in carbon nanotubes leading to new enhanced optical behaviors.
(Invited) Development of Single-Walled Carbon Nanotube-Based Optical Sensors Via Data Analytics
Authors: Yaari Zvi A , Kim Mijin , Yang Yoona , Chen Chen , Antman-Passig Merav , Jagota Anand , Wang Peng , Luo Hongbin , Wang YuHuang , Zheng Ming , Heller Daniel A.
Published: May 2020

The photoluminescence of single-walled carbon nanotubes (SWCNTs) offers unique advantages for the development of biological sensors, including the potential to sensitize emission to many classes of analytes. Methods to selectively transduce the local concentration of an analyte via an optical signal often involves the attachment of existing molecular recognition elements to the nanotube surface, or the development of selectivities by high-throughput screening or selection techniques. Due to the existence of several mechanisms of optical modulation of SWCNTs, as well as multiple carbon nanotube species with differing bandgaps, and the increasing number of excipients and polymers that can be used for colloidal suspension and non-covalent functionalization, new methods in data analytics, sometimes dubbed ‘molecular perceptron’, can be used to facilitate selective recognition of bioanalytes to detect and process multi-parametric spectroscopic fingerprints. These methods will be discussed for the detection of single and multiplexed analytes.
(Invited) Intertube Coupling in Double-Walled Carbon Nanotubes Beyond Mechanical Interaction
Authors: Gordeev Georgy , Wasserroth Soeren , Li Han , Flavel Benjamin S. , Reich Stephanie
Published: May 2020

Double walled carbon nanotubes (DWCNTs) are an intriguing example of a one-dimensional Moiré system, because they differ in diameter and chirality of the inner and outer tubes. For many years, DWCNTs have been described as two weakly coupled single walled carbon nanotubes (SWCNTs) without much electronic interaction. Advances in theoretical modeling, however, predicted diverse coupling possibilities when considering the electronic interactions between twisted layers of low dimensional materials. This coupling can induce the formation flat bands and strongly perturb the electronic states. Experimentally, this should manifest in a reduced bandgap in DWCNTs and a red-shift of the optical transition energies. Chasing this coupling effect, we used resonant Raman spectroscopy to measure the transition energies of semiconducting inner tubes in DWCNTs. The transition energies are indeed reduced, with varying red-shifts for the same inner wall chirality (50 and 150 meV). The shift depends on the electronic type of the host tube that we assign from based on the Radial breathing mode frequencies. The coupling increases from weak to strong by tightening intratube spacing in agreement with theoretical predictions. We discuss our observations in light of joint and localized vibrational and optical excitations in the two tubes making up the DWCNT.
(Invited) Different Fluorescent Modifications of Carbon Nanotubes with Aromatic Reactants
Authors: Bachilo Sergei M. , Zheng Yu , Weisman R. Bruce
Published: May 2020

Covalent functionalization of single-wall carbon nanotubes (SWCNTs) can produce a stable material with electronic and optical properties enhanced purposely as compare to original species. In the present report we describe a new category of reactions between photoexcited aromatic compounds and SWCNTs, creating different fluorescent trapping states in SWCNTs. The reactions take place in aqueous suspensions of SWCNTs with small addition of soluble or even very-slightly soluble organic aromatic compounds excited by UV light. The reaction rate depends on the aromatic compound structure and proportional to its concentration, and in some cases, as with aniline or iodoaniline, these strong spectral sidebands appear within one minute. Total SWCNT photoluminescence intensity can be increased by a factor as large as 5. Shifted emission bands and the trapping nature of them may be interesting for a variety of optical and electronic applications.

Most notably, in most cases of these photochemical reactions, the emission spectra of altered SWCNTs become different, never observed previously, upon removal of molecular oxygen from the solution, thus indicating different chemical products of the reactions. For instance, for (6,5) SWCNTs, treatment in oxygen presence gives a new emission band red-shifted by 160 meV from the pristine position, which is similar to many previously studied reactions starting with oxygen doping. However, same UV treatments after dissolved molecular oxygen removal will lead to two new emission bands red-shifted by 140 and 270 meV, growing with different rate under UV illumination. Variance spectroscopy shows the presence of individual “multicolor” nanotubes with three distinct emission bands, original plus two shifted. The reaction demonstrates new possibilities for creation different trapping states on individual nanotubes, and opens new options for tuning electronic and optical properties of nanotubes for possible applications.
(Invited) Thermal Exciton Radiation of Macroscopic Semiconducting Carbon Nanotube Membranes
Authors: Miyauchi Yuhei
Published: May 2020

Individual semiconducting carbon nanotubes at high temperature more than ~1000 K show narrowband near infrared thermal radiation owing to exciton resonances [1], which may be useful in thermophotovoltaic energy harvesting. However, it still remains to be clarified whether macroscopic membranes consisting of semiconducting carbon nanotubes can also show narrowband thermal exciton radiation. Our recent progress on the study of thermal radiation properties of macroscopic membranes of chirality-separated [2] semiconducting carbon nanotubes will be discussed. [1] T. Nishihara, A. Takakura, Y. Miyauchi, and K. Itami, Nat. Commun. 9, 3144 (2018). [2] H. Liu, D. Nishide, T. Tanaka, and H. Kataura, Nat. Commun. 2, 309 (2011).
Click Chemistry on Defects to Create Multifunctional Fluorescent Carbon Nanotubes
Authors: Kruss Sebastian
Published: May 2020

Single-walled carbon nanotubes (SWCNT) are versatile materials for imaging and sensing in the near infrared (nIR) range. Non-covalent adsorption with (bio)polymers such as DNA is a powerful approach to functionalize SWCNTs. This approach lead to a broad range of biosensors. However, covalent approaches would be beneficial for many applications because of higher stability and photophysical signal transduction. One route to covalent functionalization is reactions with diazonium salts that create covalent defects and a red-shifted peak in the nIR fluorescence spectrum attributed to a formerly dark exciton.

Here, we used novel synthesized diazonium salts to create defects that can be easily further functionalized with click chemistry reactions (Thiol-en and azid-alkine). The modified SWCNTs were additionally non-covalently wrapped in biopolymers for solubilization and characterized via nIR spectroscopy and atomic force microscopy (AFM). Using this approach we covalently conjugated diverse molecules including small aliphatic molecules, peptides, DNA and nanobodies to the SWCNT backbone. Successful functionalization was verified by conjugation of organic visible fluorophores and single SWCNT colocalization. Additionally, these multifunctional SWCNTs were used as building block for biosensors that detect disease markers.

In summary, we present a general approach to conjugate a broad range of molecules to SWCNTs using defect chemistry and demonstrate applications in biosensing.
(Invited) Environmental Impact of Carbon Nanotubes & Graphene and Related Materials (GRMs)
Authors: Flahaut Emmanuel , Evariste Lauris , Liné Clarisse , Mottier Antoine , Mouchet Florence , Barret Maialen , Pinelli Eric , Galibert Anne Marie , Soula Brigitte , Larue Camille , Gauthier Laury
Published: May 2020

Carbon nanomaterials (and especially carbon nanotubes) are often cited first when people are asked about "nanoparticles" in general. For some people, they represent a huge potential of applications due to their extraordinary properties (or more realistically because of their unique combination of different properties), while some others will mention first the (potential) related toxicity issues.

We will quickly review different aspects related to the potential environmental toxicity of carbon nanomaterials and will summarize our main results in this field. In particular, we have identified that the impact of carbon nanomaterials with very different morphologies ranging from zero-D (nanodiamonds) to 2D (few-layer graphene, graphene oxide) can be generalized when the metric used for the comparison of the data is the surface (m²/L) instead of the weight (g/L) [1]. We will illustrate in the specific case of graphene oxide how the modification of surface chemistry (reduction) can be used to significantly decrease the risk during handling and use, in the framework of a "safer(r) by design" strategy [2].

Finally, we will give a brief overview of our recent work on the impact of carbon nanotubes on plants grown in contaminated soils.

REFERENCES:

[1] A. Mottier, F. Mouchet, C. Laplanche, S. Cadarsi, L. Lagier, J-C. Arnault, H. Girard, V. Léon, E. Vazquez, C. Sarrieu, E. Pinelli, L. Gauthier, E. Flahaut, Nano Letters, 16 (6), (2016), 3514-3518, "Surface area of carbon nanoparticle: a dose-metric for a more realistic ecotoxicological assessment"

[2] L. Evariste, L. Lagier, P. Gonzalez, A. Mottier, F. Mouchet, S. Cadarsi, P. Lonchambon, G. Daffe, G. Chimowa, C. Sarrieu, A-M. Galibert, C. Matei Ghimbeu, E. Pinelli, E. Flahaut, L. Gauthier, Nanomaterials, 9, (2019), 584:1-16, "Thermal reduction of Graphene Oxide mitigates its in vivo genotoxicity toward Xenopus laevis tadpoles"
(Invited) Synthesis and Optical Properties of Graphene Quantum Dots
Authors: Lavie Julien , Zhao Shen , Orcin-Chaix Lucile , Liu Thomas , Rondin Loïc , Lauret Jean-Sébastien , Campidelli Stephane
Published: May 2020

The outstanding electronic, optical and mechanical properties of graphene strongly inspire the scientific community at both the fundamental and applicative levels. However, the key issue that needs to be addressed is the control and the modification of the electronic properties of graphene, and notably the opening of a sizable bandgap. For the last decade, a great attention has been paid to the size reduction of graphene using conventional top-down approaches (lithography and etching, thermal treatments and oxidation of bulk materials) to fabricate graphene quantum dots (GQDs)1 or graphene nanoribbons (GNRs).2 However, top-down approaches do not permit to manipulate the structure of the material at the atomic scale. In particular, they do not allow a sufficient control of the morphology and oxidation state of the edges, which drastically impact the properties. In order to truly control, with the required level of precision, the morphology and the composition of the materials and of its edges, the bottom-up approach is the relevant way to proceed.3,4

Recently, we reported on the synthesis and single photon emission properties of triangular-shaped GQDs.5 While, this initial report focused on functionalized nanoparticles, we now turn to non-functionalized graphene quantum dots that are in terms of structure closer to real graphene. Here, we described the synthesis, the dispersion and optical properties of a series of rod-shaped particles and we studied the structure-properties relationship in these graphene quantum dots. To this end, we designed a series of GQDs with a given edge type and by changing only one parameter (one dimension, namely the length or the width – Figure 1), we expect to follow simply the evolution of the optical properties.

References.

1. Haque, E.; Kim, J.; Malgras, V.; Reddy, K. R.; Ward, A. C.; You, J.; Bando, Y.; Hossain, M. S. A.; Yamauchi, Y. Recent Advances in Graphene Quantum Dots: Synthesis, Properties, and Applications. Small Methods
2018,
2, 1800050.

2. Xu, W.; Lee, T.-W. Recent progress in fabrication techniques ofgraphene nanoribbons. Mater. Horiz.
2016,
3, 186-207.

3. Narita, A.; Wang, X. Y.; Feng, X.; Müllen, K. New advances in nanographene chemistry. Chem. Soc. Rev.
2015,
44, 6616-6643.

4. Narita, A.; Chen, Z.; Chen, Q.; Müllen, K. Solution and on-surface synthesis of structurally defined graphene nanoribbons as a new family of semiconductors. Chem. Sci.
2019,
10, 964-975.

5. Zhao, S.; Lavie, J.; Rondin, L.; Orcin-Chaix, L.; Diederichs, C.; Roussignol, P.; Chassagneux, Y.; Voisin, C.; Müllen, K.; Narita, A.; Campidelli, S.; Lauret, J.-S. Single photon emission from graphene quantum dots at room temperature. Nat. Commun.
2018,
9, 3470.

Figure 1
Flexible Semiconducting Nanofibers Functionalized with ZnO for Enhanced and Sustainable Water Decontamination
Authors: Capilli Gabriele , Calza Paola , Minero Claudio , Cerruti Marta
Published: May 2020

We present here a photoactive system for water decontamination consisting of ZnO nanocrystals supported on a flexible mat of electrospun semiconducting nanofibers. The nanofibers have a core-sheath structure with a polyacrylonitrile (PAN) core and a sheath made of polypyrrole (PPY), a low band gap p-type semiconductor. Under UVA irradiation, the heterojunction formed between PPY and ZnO, an n-type semiconductor, promotes the separation of the charge carriers photogenerated at the interface. This decreases the charge recombination rate and increases the photocatalytic efficiency compared to a system where the same ZnO particles are supported on insulating bare PAN nanofibers.
The
photocatalytic tests and photoelectrochemical characterization
show
that the photoexcited electrons are preferentially collected on the PPY sheath and react with the dissolved oxygen
,
while the holes in excess on the ZnO surface degrade the persistent pollutants. The nanofiber production is scalable and sustainable. While previous works immobilized photoactive metal oxide nanoparticles on insulating mats to help their collection after use, this is the first report showing that a flexible semiconducting supporting material can play an active role in the photocatalytic process and significantly enhance its efficiency. This approach paves the way for the design of new supported hybrid materials for photocatalytic applications.

Figure 1
(Invited) Custom Low-Dimensional Material Systems Explored at the Atomic Scale
Authors: Luican-Mayer Adina
Published: May 2020

Innovative technologies have a history of capitalizing on the discovery of new physical phenomena, often at the confluence of advances in material characterization techniques and innovations in design and controlled synthesis of high-quality materials. Pioneered by the discovery of graphene, atomically thin materials (2D materials) hold the promise for realizing physical systems with distinct properties, previously inaccessible. In this talk I will describe experiments that seek to uncover the novel physical phenomena in 2D materials by using scanning tunneling microscopy and spectroscopy (STM/STS) and supporting spectroscopic techniques. Firstly, I will discuss the 1T polymorph of TaS2, which has one of the richest phase diagrams among the layered transition metal dichalcogenides and address the question of crossover from bulk to few layers. Secondly, I will describe atomic-scale characterization of the in-plane anisotropic semiconductor ReS2. We demonstrate that rhenium atoms form diamond-shaped clusters, organized in disjointed chains, and characterize the semiconducting electronic band gap by STS. By spatially mapping the local density of states around defects in ReS2, we explore their origin and electrostatic nature.
(Invited) Modulation of the Fermi Level in Single-Walled Carbon Nanotubes By Chromophore Encapsulation
Authors: Chambard Romain , Izard Nicolas , Aznar Raymond , Jousselme Bruno , Campidelli Stephane , Sato Yuta , Suenaga Kazu , Lauret Jean-Sébastien , Bantignies Jean-Louis , Alvarez Laurent
Published: May 2020

The one-dimensional structure of single-walled carbon nanotubes renders these materials ideal for optoelectronic applications as they can transport electrons or holes with quasi-ballistic features and as they display optical absorption and near-infrared emission (thanks to van Hove singularities). Nevertheless, functionalities can to be added to nanotube to both improve and control the physical properties. To this aim, chromophore encapsulation into host single-walled carbon nanotubes allows to create hybrid nano-systems with tunable opto-electronic properties. Up to now, we have been confining different kinds of molecules,1-4 either absorbing in the blue/green range, being electron donor (quaterthiophene derivatives (4T) and tetramethyl-paraphenylenediamine (TMPD)) or electron acceptor (tetracyanoquinodimethane (TCNQ)), or absorbing in the red visible range (phthalocyanine (MPc)).

In this study, we investigate, at both the macroscopic and the individual scales, the electronic and the optical properties of our hybrid systems by means of Raman and photoluminescence spectroscopies.

From Raman measurements, a significant charge transfer from the confined dye to the nanotube is evidenced. Experiments also suggest a photo-activated electron transfer for small diameter (~9 Å) semiconducting and metallic tubes. The main relevant parameters that govern the charge transfer are the nanotube diameter and the electronic properties of both the nanotube (metallic or semiconducting) and the chromophores (electron donor or acceptor).

Photoluminescence experiments clearly demonstrate changes on the emission properties after encapsulation. The intensities can be increased or reduced depending on the nature of the confined chromophores (electron donor or acceptor). These behaviors are consistent with a charge transfer.

Therefore, Raman and photoluminescence experiments strongly suggest charge transfer between the confined molecules and the nanotubes, leading to a Fermi level shift which governs the radiative de-excitation efficiency and the electron-phonon coupling.

References

[1] L. Alvarez et al, J. Phys. Chem. C, 119, (2015), pp. 5203−5210

[2] Y. Almadori et al, J. Phys. Chem. C; 118, (2014), pp. 19462−19468

[3] A. Belhboub et al, J. Phys. Chem. C; 120, (2016), pp. 28802−28807

[4] Y. Almadori et al, Carbon 149, (2019), pp. 772-780