Light-induced self-adaptive growth of photonic crystal structures in perfluorosulfonic acid ionomer films

Domain: physics
Published: 2025-12-10
Editorial outcome: major_revision

Abstract
Intricate interactions between light and matter form the foundation of photonics innovation. This study presents a light-induced self-adaptive growth strategy for engineering multiscale ordered photonic crystal structures in perfluorosulfonic acid ionomer films. By incorporating anthracene-functionalized quaternary ammonium salts into the polymer matrix, UV irradiation triggers anthracene photodimerization, initiating localized phase separation and directional aggregation of nanoparticles along the light propagation path. The resulting nanoparticle columns exhibit programmable vertical or tilted configurations controlled by the incident light angle, establishing a bidirectional feedback loop where evolving structures modulate light propagation to guide subsequent growth. Using patterned photomasks, angle-dependent structural colors are achieved through selective reflection governed by incomplete photonic band gaps. Furthermore, anisotropic PC architectures enable tunable light scattering and programmable grating devices, demonstrating potential applications in functional optical materials and LED displays. This fabrication strategy overcomes the static limitations of conventional photonic crystals, providing a versatile platform for creating programmable photonic architectures.

Introduction
The interaction between light and matter has long been a cornerstone of modern photonics1–5. Leveraging its spatiotemporal precision6,7, light excitation enables controlled material restructuring through phase transitions8–11, molecular rearrangements12–14, and nanoscale organization15–18. These light-induced structural adaptations correspondingly modify optical phenomena including reflective properties19–21, and emissive behaviors22–24, establishing a dynamic bidirectional relationship where light actively configures and is reconfigured by the evolving material architecture. This mutual interaction is pivotal for advanced technologies such as adaptive optics25–27, reconfigurable photonic devices28–30, and smart displays31,32. For instance, in PCs, the periodic arrangement of dielectric materials generates photonic band gaps that selectively reflect or transmit specific wavelengths of light33–35. The dual capacity to both initiates and continuously regulates structural order via photonic inputs opens avenues for designing optically addressable materials with real-time property tuning. Yet, achieving this dynamic light-structure-light feedback loop remains a significant challenge, as it demands precise spatiotemporal control over both light-driven structural evolution and the resulting optical response.

Natural and synthetic systems provide some examples of light-structure interactions. For example, plant phototropism relies on asymmetric auxin distribution under directional light36,37, causing stem curvature that optimizes light harvesting—establishing a continuous feedback loop where structure modifies light absorption, which further refines growth. Similarly, chameleon skin contains tunable guanine nanocrystals whose light-triggered reorganization alters both color and reflectance38,39, enabling real-time camouflage. In engineered materials, researchers have developed various platforms to harness light for structural control40–43. For instance, by designing topological PC structures using electron-beam lithography, robust topological resonant modes immune to structural perturbations have been achieved, enabling wavefront manipulation based on disorder44. Likewise, the integration of movable atoms with nanophotonics using optical tweezers has established a promising platform for developing quantum light nodes for large-scale atomic quantum processors45. These examples illustrate light’s versatility in guiding structural evolution and tailoring optical properties46,47. Nevertheless, despite these advancements, critical challenges remain in achieving spatiotemporal control over light-induced structural growth. Specifically: (1) Light-driven structural evolution often introduces scattering or defects that disrupt the optical functionality governed by photonic band gaps48,49. (2) Light serves merely as a structural initiator50, neglecting bidirectional interactions where structures dynamically modulate light propagation. This unidirectionality hinders the realization of adaptive, feedback-driven photonic materials. (3) Structural evolution and optical feedback face inherent limitations, including energy dissipation51, kinetic metastability52, and multifunctional integration within monolithic systems. Addressing these challenges requires innovative approaches that enable precise control over light-structure interactions.

Here, we propose a light-induced self-adaptive growth strategy for generating PC column structures via precise spatiotemporal control of reaction-induced phase separation in perfluorosulfonic acid (PFSA) ionomer films. By integrating An-Am into the polymer matrix enables UV-triggered photodimerization, inducing localized phase separation and directional nanoparticle growth along the light propagation path (Fig. 1). Crucially, the directionality of structural evolution is governed by the angle of incident light, enabling the programmable alignment of PC columns into vertical or tilted configurations. This directional growth is underpinned by supramolecular interactions, where ionic clusters act as nucleation sites for nanoparticle aggregation. In contrast to static systems, our approach establishes bidirectional feedback: the growing structures modulate light propagation, influencing subsequent growth patterns and optical effects. To demonstrate this, we fabricated patterned structures with angle-dependent structural colors using photomasks, wherein selective reflection is governed by PC column orientation. Our strategy, which combining light-guided fabrication with self-adaptive optical responses, paving the way for smart photonic materials capable of real-time environmental adaptation, where light and structure co-evolve in a feedback-driven loop.

Results
Light-induced adaptive growth strategy for multiscale ordered structure
Figure 1 illustrates the strategy for fabricating multiscale ordered structures in films based on light-induced adaptive growth of nanoparticles. PFSA is a polymer composed of hydrophobic backbone and hydrophilic side chains, which form distinctive ion clusters upon film formation53,54. Its low refractive index and excellent shape memory properties made it the ideal polymeric material. An-Am was chosen as a UV-responsive component critical for phase separation, which synthesis and characterization were provided in detail in Supplementary Fig. 1-4. After mixing An-Am containing anthracene group with PFSA (named as PFSA-An), ammonium ions and sulfonic acid ions formed ionic clusters through supramolecular interaction (Fig. 1b), accompanied by the anthracene group into the polymer side chain, while the remaining An-Am was homogeneously dispersed in the film. Upon irradiation of 365 nm UV light at 80 °C, the dimerization of anthracene, triggered the aggregation of ionic clusters, resulting in the formation of nanoparticles (Fig. 1c, Stage 1). This phenomenon was attributed to reaction-induced phase separation, driven by a reduction in entropy. Heating facilitates molecular migration within the PFSA-An film, thereby promoting the formation of microstructures. With prolonged exposure to light, the phase separation progressively developed into larger nanoparticles (Fig. 1c, Stage 2). The difference in refractive index between An-Am (1.45) and PFSA matrix (1.38) in the phase-separated region further creates an optical waveguide, and subsequent particles preferentially grow in the direction of irradiation, eventually forming PC particle column structures (Fig. 1c, Stage 3 and Fig. 1a). Further, the region where the particle column structures are generated is selectively controlled by using a photomask. For example, when the film was selectively irradiated with different angles of UV light through a strip-shaped micron-pitch photomask, we successfully fabricated vertically and tilt-spaced grating structures inside the film, each consisting of several particle columns (Fig. 1d). In addition, by expanding the exposure area using a macroscopic photomask, particle columns with different orientations were successfully fabricated in the same layer of film, allowing precise control of the viewing angle of the complementary structural color pattern (Fig. 1e). The quaternary ammonium salts An-Am required for this strategy were universal, octyl quaternary ammonium salt was used in our experiments unless otherwise specified.

Self-adaptive growth kinetics of nanoparticles
To elucidate the self-adaptive growth mechanism of PC particles, the growth kinetics of the particles were investigated in Fig. 2. Critically, supramolecular interactions between ammonium and sulfonic acid ions served as the foundation for this self-adaptive growth. FT-IR spectra of PFSA-An film demonstrated that an increase of An-Am content caused a shift of the sulfonate vibration peak to lower wavelengths, confirming the presence of these interactions (Supplementary Fig. 5). In the pure PFSA film, sulfonate grafted on the side chain was assembled into ionic clusters, exhibiting an island-like phase structure. In the PFSA-An film, part of An-Am molecules were bound to these ionic clusters to form nano-aggregation, while others were dispersed in the matrix. Upon irradiation of UV light for initial 2 min, the photodimerization of anthracene groups facilitated the formation of nanoparticles from ionic clusters (Supplementary Fig. 6). The enrichment of N and S elements in these particles stems from the presence of strong supramolecular interactions between ammonium and sulfonate ions, while the growth of free An-Am into the ion clusters lead to the aggregation of additional Cl elements. In contrast, no significant nanoparticle structures or elemental aggregation were observed before UV irradiation (Supplementary Fig. 7a, b). Extending irradiation to 10 min promoted nanoparticle aggregation and proliferation (Fig. 2a). No crystals were detected by XRD testing during this process (Supplementary Fig. 8), further confirming that the particle structure is an aggregation of An-Am rather than crystallization.

DMA measurements traced the film’s glass transition temperature (Tg), revealing molecular chain dynamics during light-induced nanoparticle evolution (Fig. 2b). Two distinct phase transition temperatures were identified in the PFSA film: a high temperature of 135 °C corresponding to the main chain Tg, and a low temperature of 20 °C associated with the side chain Tg. The incorporation of anthracene groups into the side chain enhanced the chain rigidity, resulting in an increase of the side chain Tg to 34 °C. Conversely, free An-Am acted as the small molecular plasticizer, reducing the Tg of the main chain to 125 °C. The photodimerization-induced growth of nanoparticles increased in both the main chain and side chain Tg. As the irradiation time extended, the continuous aggregation of nanoparticles increased the Tg of the main chain and side chain to 153 °C and 81 °C, respectively. Fluorescence spectroscopy was used to further investigate the particle’s self-adaptive growth processes (Supplementary Fig. 9). As photodimerization progressed, the anthracene groups were continuously consumed, theoretically leading to a gradual decrease in fluorescence intensity55,56. However, an initial rapid increase was observed at the beginning of the irradiation and then decreased continuously (Fig. 2c). The possible reason for this anomaly was to show that, in the absence of UV irradiation, the anthracene groups were concentrated in ionic clusters. The π-π stacking induces an aggregation-caused quenching (ACQ) effect that suppresses the full manifestation of fluorescence57–59. Under UV irradiation, anthracene dimerization partially disrupts the ACQ effect, resulting in a temporary enhancement of fluorescence intensity within the initial few minutes. These experimental findings elucidate the particle generation mechanism across multiple dimensions: (1). Initial ionic clusters in film due to supramolecular interactions. (2). The growth of the particles primarily focused on the initial aggregated structures, wherein free Am-Am initially merged following light-induced anthracene dimerization, leading to the subsequent growth of ionic clusters (Supplementary Fig. 10).

The influence of adaptively grown particles on the optical effects of films was explored in a series of experiments. Observation of the vertical cross-section of the sample using a super depth 3D microscope revealed that the particulate region strongly scattered light, appearing whitish. Anthracene absorbed UV energy and produced a shielding effect. In the early stages of UV irradiation, the surface-layer anthracene first absorbed UV energy and underwent a dimerization reaction. After the upper-layer anthracene dimerized, the lower layer began to react, indicating a progressive process. This progression resulted in an increase in the depth of the particles from 41.8 μm to 80.5 μm with prolonged UV exposure (Fig. 2d). In contrast, non-irradiated film remained structurally uniform. The effect of these PC particles on the structural color was assessed by UV-vis reflection spectroscopy (Fig. 2e). The PFSA film exhibited a reflectance of 5.5% at 400 nm and showed no structural color (Supplementary Fig. 11). Similarly, the PFSA-An film also lacked structural color. However, due to absorption by anthracene around 400 nm, its reflectance decreased to 3.3%. After UV irradiation, the PFSA-An film showed a reflection peak at 520 nm and reached its maximum intensity at 15 min, indicating that the increased number of particles enhanced the structural color. The width broadening of the reflection peak suggested a wider particle size distribution during the growth process. A similar trend was observed in PFSA-An film with different An-Am contents under identical conditions. However, when the content increased to 12 wt.%, the reflectance decreased from 12.4% to 11.1%, accompanied by a red shift of 41 nm in the reflection peak. These changes arise from the increased phase separation scale and reduced structural order at higher An-Am concentrations (Supplementary Fig. 12). For the following investigations, PFSA-An with 10 wt.% An-Am content and 10 min of UV exposure were selected, with particle sizes ranging from predominantly 100 to 180 nm (Supplementary Fig. 13).

Bidirectional feedback of light and PC particle column structure
The light-induced growth of the PC structure initiated a bidirectional feedback loop where the evolving nanoparticle columns modulated light propagation to guide their subsequent growth. The reaction-induced phase separation occurred exclusively along the light path, demonstrating a strong dependence on the direction of illumination. Varying the incident light angle enabled precise programming of particle column configurations—producing either vertical or tilted architectures (Fig. 3a). After UV light is scattered by the particle structures, the energy of the UV light along the original optical path remains higher than the energy in scattered directions. As a result, subsequent particles preferentially grow and align along this direction, forming initial particle column structures. Although scattered light would theoretically cause structural disorder, the refractive index difference between the PFSA and An-Am enables the particle columns to function like optical fibers, confining the scattered light within the columns. This creates a bidirectional feedback loop of UV light-particle column, leading to aligned growth of the particle columns along the optical path. For the sake of illustration, we define the direction perpendicular to the film as Mode I and the direction inclined to the film as Mode II.

To further demonstrate the dependence of the particle columns on the direction of UV irradiation, the morphology of the PC columns structure in Mode I and Mode II were observed by microscope in three views, where the front view, side view, and top view represent the X-Z, Y-Z, and X-Y planes, respectively. For Mode I, both front and side views of the PC particle column structure showed a rectangular shape with a width of 1.5 μm, and the internal particles are arranged in a linear configuration. (Fig. 3b and Supplementary Fig. 15), and the top view exhibited a uniform circular distribution (Supplementary Fig. 14a), indicating the cylindrical structure. In continuous observation along the Z axis, circular particle distributions were detected at a depth of 5 μm from the surface, which disappeared beyond the length of the particle columns, confirming their vertical alignment (Supplementary Fig. 14c and Movie 1). Interestingly, the width of the circular particles remained consistent and the length (ΔL) grew to 27.5 μm under different UV irradiation times, suggesting that the growth of the PC columns occurred mainly in the length direction (Fig. 3d and Supplementary Fig. 14e). In contrast, Mode II assumed the dependence of the self-adaptive growth direction on the incidence angle of UV light, so tilting the UV exposure at 45° along the X axis was used to irradiate the film. The front view revealed that the orientation of the PC particle columns closely aligned with the incident angle, while the side view displayed uniformly distributed elliptical aggregates of similar width to those in Mode I (Fig. 3c). The top view showed that, rather than circular shapes, the inclined PC structures appeared as parallel short bars (Supplementary Fig. 14b), confirming the presence of tilted columns. The continuous observations along the Z axis also demonstrated that the construction and disappearance of the parallel short bars were similar to those in Mode I, with the key difference being their tilted arrangement (Supplementary Fig. 14d and Movie 2). The height (ΔH) increased to 26.2 μm with the increase of UV irradiation time (Fig. 3e). These results support our assumption that the growth of PC particle columns was light direction-dependent. Layer-by-layer scanning of particle columns under two modes, followed by 3D reconstruction, revealed a clear contrast in their orientation (Supplementary Fig. 16). Similarly, PC particle columns with different tilted states were produced by varying the angle of incident UV light at 30° and 60°, respectively (Supplementary Fig. 17).

This bidirectional feedback of light and structure enabled continuous structural adaptation, with the growing columns dynamically influencing light scattering and further reflecting the growth process. We investigated the correlation between the height of PC particle columns and the scattering patterns during their self-adaptive growth under Mode I and Mode II over UV irradiation times ranging from 2 min to 15 min. Figure 3d illustrates that in Mode I, under continuous UV irradiation, the particle column significantly elongates, triggering a more pronounced Mie scattering effect, ultimately forming a clearly visible circular halo. In contrast, the spatially inhomogeneous scattering effect of the tilted particle columns structure in Mode II (45°) results in a curved arc with two symmetric scattering spots (Fig. 3e). In addition, we further investigated the correlation between the laser scattering pattern and the direction of the particle column by rotating the laser incidence angle. In Mode I, the laser was parallel to the PC column (θR = 0°), producing a uniform scattering circular pattern (red frame in Fig. 3f). As the angle of incidence increased, the transmitted laser intersected the PC column (θR > 0°), forming a curved arc with two symmetrical scattering spots. On the contrast, in Mode II (45°), a uniform scattering pattern was generated only when the laser was aligned with the direction of the prefabricated PC column (θR’ = 45°), otherwise two symmetrical scattering spots can be observed (red frame in Fig. 3g). Furthermore, much like optical fibers, the particle columns guide light preferentially toward the tilted direction. This behavior leads to the re-emergence of symmetric spots in the opposite direction when the incident angle exceeds 45°. The interconversion between the uniform circular scattering spots and the symmetrical two scattering spots during laser rotation indicates that the scattering patterns are directly correlated with the relative orientation between the laser direction and the particle columns. This relationship allows us to determine the specific orientation mode of the particle columns through laser scattering analysis, and further confirms that the direction of UV light incidence determines the structure of the PC columns.

Based on the aforementioned results, we could programmatically control the orientation of the PC column to achieve the desired tilt angle. These programmed structures demonstrated distinct scattering patterns for transmitted light and exhibited characteristic optical properties. In Mode I state, when the film was parallel to the background, it produced strong scattering that completely obscured background details. By tilting the film 30° relative to the background, the scattering effect was attenuated, rendering the font “1896” visible (Supplementary Fig. 18a and Movie 3). In Mode II (45°) state, with the film parallel to the background, scattering remained weak, making “1896” clearly discernible. Conversely, when tilted to 45° (matching the prefabricated PC column angle), the font became blurred (Supplementary Fig. 18b). Thus, we could customize the film’s scattering pattern at various angles relating to natural light, creating optical devices capable of on-demand light path adjustment.

Patterned PC structures
The periodic PC particle columns constructed through self-adaptive growth exhibited a significant refractive index contrast with the PFSA-An film, which considerably altered the path of light propagation. This PC-type structure formed the basis for the pattern demonstration. In Fig. 4a, employing mask-assisted UV control, we demonstrated that the PC structure based on Mode I displayed different optical patterns and clear boundaries. In addition, by using a digital greyscale mask (ink-dot modulated light entry), it is even possible to produce complex drawing with a 3D effect. The fluorescence variations of these PC patterns, induced by the dimerization of anthracene, further contributed to the recognition of different PC patterns. This self-adaptive growth mechanism made it more likely that the internal particle structures were ordered along the UV direction, generating an incomplete photonic band gap (PBG), allowing light reflection exclusively along the ordered axis, rendering structural color visible only from that specific direction. In contrast, the absence of a PBG in other directions resulted in no structural color formation, and a scattering whitening effect was exhibited (Fig. 4b). As illustrated in Supplementary Fig. 19, PFSA-An films irradiated at three different angles (0°, 30°, and 60°) displayed angle-dependent structure color under white light. Only the films viewed precisely at the incident angle revealed the vibrant structural colors, whereas other angles showed significantly weaker color patterns. We combined Mode I and Mode II to produce an integrated display pattern with dual PC structures oriented in distinct directions. The ‘SJTU’ pattern was generated during the first exposure, using a UV lamp tilted at 45° through a mask, followed by a second exposure at 0° to create a complementary pattern without a mask. This approach enabled structural color observation from two viewing angles within the same film (0° and 45° shown in Fig. 4c). The second exposure did not alter the growth direction of the first exposed PC structures. Supplementary Fig. 20 showed two different types of self-adaptive growth particle column structures in one film. Leveraging this characteristic, we customized multi-level optical patterns in the film through multiple exposures. As shown in Supplementary Fig. 21, consecutive exposures using a stripe mask were employed to create a grid-like PC pattern. It was even feasible to construct composite PC patterns on both sides of the film by sequentially applying photomasks and UV irradiation to each side. Figure 4d displayed the “SJTU” on the front and the “butterfly” on the back, observed at different angles. The construction strategy of PC structure introduced a foundation for multidimensional, multi-angle, and multi-level optical patterns, with promising applications in anti-counterfeiting, holographic imaging, augmented reality, and related fields.

Construction and application of PC-type grating structures
The diffraction grating is an optical element that disperses light through multi-slit diffraction and consist of a plane with numerous parallel, equally spaced, and uniformly wide slits60. Motivated by the simple and robust characteristics of this strategy, we attempted to use photomasks with a higher resolution to explore the possibility of a self-adaptive growth technique for fabricating grating structures inside the film. As shown in Fig. 5a and Supplementary Fig. 22, the arrays of PC particle columns with 5 μm spacing were consistently observed in the film cross-section as well as X-Y plane following either vertical or oblique irradiation (stripe photomask spacing: 5 μm). The laser scattering patterns were consistent with the results shown in Fig. 3f, g, demonstrating the stability of the PC-type grating structure. Additionally, by utilizing different masks and patterns, a variety of customized grating structures were successfully fabricated, including stripe, dot-matrix, and circular patterns, which demonstrated excellent consistency with the mask patterns (Fig. 5b and Supplementary Fig. 23). The resulting grating structures split transmitted light into dual virtual images, suggesting their potential for directional imaging applications (Supplementary Fig. 24). The above experimental results demonstrate that adaptive growth of PC structures combined with mask-assisted patterning constitutes an effective and stable strategy for fabricating grating devices. Further, complexed PC grating structures could even be constructed on both sides of the film by sequentially applying photomasks and UV irradiation to each side. The cross-sectional ‘sandwich’ structure confirmed that the PC gratings on opposite sides of the film do not interfere with each other (Supplementary Fig. 25). Notably, constructing this PC-type grating as a secondary structure, complementing the primary PC particle column arrangement, introduced a coloring mechanism to the film (Fig. 5c). When white light was obliquely incident on the film’s surface with vertically aligned PC particle columns, the regions containing these columns predominantly exhibited disordered scattering and reflection. Conversely, regions of the pattern without particle columns emitted diffracted light due to compliance with Bragg’s law, producing vivid rainbow-like colors. In Supplementary Fig. 26, the left region of the film subjected to direct UV irradiation retained the intact PC particle column structure. In contrast, the right region, shielded by a 5 μm stripe photomask, formed a PC-type grating structure. Under 60° oblique incident light and viewed vertically, the intact PC particle column region on the left exhibited no rainbow colors, whereas the right region displayed vibrant colors, underscoring the critical role of the secondary PC-type grating structure. By superimposing a photomask with a macro-patterned design over a grating mask (Fig. 5d), the exposure area of the sample can be selectively controlled to produce a wide range of predictable PC-type grating patterns such as “SJ,” “pentacle,” and other intricate designs with vibrant structural colors (Fig. 5e and Supplementary Movie 4), while at the same time increasing the utilization of the photomask without the need for a separate custom grating-type photomask. In addition, diffraction and interference of the incident light through the PC-type grating structure produce angle-dependent transmitted colors (Supplementary Movie 5). As shown in Fig. 5f, when the film was tilted at 15° (θS), the transmission peak appeared at 485 nm, corresponding to a blue-green hue. Increasing the tilt angle to 30° caused a redshift in the transmission peak to longer wavelengths, resulting in a red appearance.

Leveraging the vivid structural colors of the PC-based grating architecture, we engineered a synergistic integration with the material’s shape memory effect to unlock multifunctional applications. The PFSA exhibited excellent shape memory capabilities61, and was not affected by the PC structure generated after UV light exposure (Supplementary Fig. 27a, b). In addition, the fracture strength of the film increased slightly after exposure, which was attributed to the reinforcement of nanoparticles inside the film (Supplementary Fig. 27d). This dual functionality—shape memory and mechanical resilience—enabled controlled structural reconfiguration, as evidenced by the morphological transition of PC columns from circular to spindle-shape geometries under tensile stress without structural degradation (Supplementary Fig. 27e, f). As shown in Fig. 5g, the PC-type grating QR code written into the film was readable by a mobile phone. The shape memory effect was then employed to stretch and fix the film, disrupting its ability to display the information. However, after the shape was restored, the information became readable again without compromising the structural color. Furthermore, harnessing the dual shape memory effect allowed multilevel structural control synchronized with 3D shape morphing (Supplementary Fig. 27c, g). Overall, the combination of the self-adaptive growth mechanism and the shape memory effect gives grating structures design flexibility, simplicity, and controllability, and represents an alternative in grating fabrication technology.

Methods
Materials
The PFSA polymers (Mn = 335000) were provided by Dongyue Shenzhou New Materials Co. Ltd. (Shandong, China). Trimethylamine (2 mol/L in THF), N,N-Dimethylaminobutane, N,N-Dimethyloctylamine and 9-Chloromethylanthracene were purchased by Adamas-Beta Co. Ltd. (Shanghai, China). Other chemicals mentioned in this paper were obtained from Shanghai Titan Scientific Co. Ltd. (Shanghai, China). All reagents were obtained from commercial sources and used as received without further purification.

Synthesis of anthracene-containing ammonium salts (An-Am-1)
The An-Am was synthesized using the one-step method outlined in Supplementary Fig. 1. 20 mmol Trimethylamine (10 mL of Trimethylamine-containing THF solution) and 10 mmol 9-chloromethylanthracene (2.27 g) were dissolved in acetone solvent (50 mL) in a round bottom flask. The solution was stirred and refluxed under nitrogen protection for 5 h. After the reaction was completed, the purified product was obtained by several filtration and washing processes using ether and dried in vacuum at 60 °C for 24 h. The structure of An-Am-1 were confirmed by 1H NMR spectrum as shown in Supplementary Fig. 2.

Synthesis of anthracene-containing ammonium salts (An-Am-2)
20 mmol N,N-Dimethylaminobutane (2.02 g) and 10 mmol 9-chloromethylanthracene (2.27 g) were dissolved in acetone solvent (50 mL) in a round bottom flask. The solution was stirred and refluxed under nitrogen protection for 5 h. After the reaction was completed, the purified product was obtained by several filtration and washing processes using ether and dried in vacuum at 60 °C for 24 h. The structure of An-Am-2 were confirmed by 1H NMR spectrum as shown in Supplementary Fig. 3.

Synthesis of anthracene-containing ammonium salts (An-Am-3)
20 mmol N,N-Dimethyloctylamine (3.15 g) and 10 mmol 9-chloromethylanthracene (2.27 g) were dissolved in acetone solvent (50 mL) in a round bottom flask. The solution was stirred and refluxed under nitrogen protection for 5 h. After the reaction was completed, the purified product was obtained by several filtration and washing processes using ether and dried in vacuum at 60 °C for 24 h. The structure of An-Am-3 were confirmed by 1H NMR spectrum as shown in Supplementary Fig. 4.

The preparation of self-adaptive growth PC film
0.5 g PFSA polymers were dispersed in a mixed solvent of 1 mL DMF and 1 mL anhydrous ethanol at room temperature. After dissolving the required An-Am, with another addition of 0.5 mL deionized water, the mixture was poured into a glass mold and dried thoroughly to obtain a yellowish transparent film named PFSA-An. The film was placed on a heating table at 80 °C and covered with the custom photomask. The programmed films were obtained by controlling their radiation angle and time of the UV lamp, which were cut into customized shapes for tests.

Characterizations
1H NMR spectra were acquired using a 500 MHz ADVANCE NMR spectrometer (Bruker, Germany) with tetramethylsilane (TMS) as the internal standard, and Dimethyl Sulfoxide (DMSO-d6) as the solvent at room temperature. FT-IR spectra were obtained using a Perkin Elmer Spectrum 100 FT-IR spectrometer (U.K.) with a diamond ATR probe. Phase separation of ~1 μm thick films spin-coated on silicon wafers were observed using tapping-mode atomic force microscope (AFM) (Multimode 8, Bruker, Germany). UV absorption spectra were measured using a UV-vis spectrophotometer (TU-1901, Perkin-Elmer, China). The elemental composition of the particles was examined using transmission electron microscopy (Talos F200X G2, Thermo-Fisher, USA). UV-vis reflectance spectra were obtained using a UV-vis-NIR spectrophotometer (Lamda 950, China). XRD analysis was performed using a multifunctional X-ray diffractometer (D8 ADVANCE Da Vinci, Bruker, Germany). SAXS data was recorded using small-angle X-ray scattering (Xeuss 2.0, Xenocs, France). SEM images were captured using field emission scanning electron microscopy (Apreo 2S, FEI, USA) with gold-coated films. Optical micrographs were taken using a super depth 3D microscope (VHX-7000, Keyence, Japan). The 3D images were acquired using a high-resolution laser scanning confocal microscope (Leica STELLARIS 5, Germany) with an excitation wavelength of 405 nm, by performing layer-by-layer scanning and subsequent reconstruction of the internal structure of the film. Refractive index data were acquired using an ellipsometer (V-VASE, J.A. Woollam, USA) with the film thickness of 10 μm. Fluorescence intensity was measured using an advanced fluorescence steady-state transient measurement system (QM/TM/IM, PTI, USA). To ensure consistency in the experimental procedure, the films were irradiated with UV light under heating conditions at 80 °C before fluorescence testing. Shape memory curves were recorded using a dynamic thermo-mechanical analyzer (DMA 850, TA, USA). The mechanical properties were evaluated using an electronic material testing machine (Instron 3365, Instron, USA). The wavelength of the UV light is 365 nm, and their radiation intensity is 60 mW·cm-2. The collimation characteristics of the UV light source allow for controlled irradiation at a tilt angle simply by tilting the lamp head.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript reports on an impressive body of work from Zhou et al, which I believe may be suitable for publication in\nNature Communications, subject to number of points being addressed.\nThere is a comprehensive demonstration of a light-directed control over phase-separation and patterning of polymeric\nmaterials to generate a widespread range of photonic crystals and structurally coloured films. There are some clear\nbreakthroughs here in terms of facilitating orientationally dependent designs, and associated applications in optoelectronics\nand photonics. My questions/feedback to the authors are as follows-\n1. My impression is that the \"light-induced self-adaptive growth\" (c.f. Title) relates to the light/photochemical feedback\ninteractions in the formation of structures. The end materials are not, in themselves, light adaptive as with the natural\nexamples mentioned, such as with plant phototropism? As the extension of the feedback to respond to external stimuli is not\nshown, I would like the authors to consider whether the final sentence of the abstract (\"This strategy overcomes the static\nlimitations of conventional PCs, offering a versatile platform for adaptive photonic materials with dynamic light-matter\ninteractions\") gives an accurate appraisal of the scope of the work?\n2. Analogies are drawn to holographic methods, both implicitly, and statedly at around line 329. I can see the point here, as\nthe optical properties can be made very strongly dependent on the light propagation direction and the re-illumination/viewing\nconditions. Would the other important visual cues of holograms, such as image stereopsis, be achievable with these\nmethods and structures?\n3. Figs 3d-3g, I would like to see more explanation of the scattering patterns reported;\n- which diffractive orders are spots are attributed to?\n- why there is a spatial \"curvature\" in the patterns, and whether this relates to structural properties or merely the projection\ngeometry?\n- does the halo emerging in Fig 3d at longer exposures have any significance regarding structural order/disorder?\n4. Fig 3b requires some extra work in making the reported SEM images clearer, and the structures more visible. To a lesser\nextent, I also find the fluorescence maps in Fig 1d/e quite difficult to make out.", "reviewer_2": "This manuscript proposes a method for fabricating self-adaptive optical materials for photonic engineering by incorporating\nanthracene into a polymer matrix to create films whose optical properties change upon photodimerization. In particular, the\ncreation of the PC particle column structures is interesting in that it involves an ingenious light irradiation method. I believe\nthat this work would be interesting to the readers of Nature Communications, and I can recommend it to consider for possible\npublication in the journal after addressing the following comments.\n1. It would be helpful to include information about the wavelength and intensity of the UV light being used for irradiation. Do\nyou have pictures of the photomasks that were actually used? I also recommend discussing the consistency of the size\nbetween the irradiated pattern and the formed structure. How is the light irradiated in the tilted state, as shown in Fig. 3?\n2. In Fig. 2c, is there a reason why the emission increases in the initial few minutes? If the emission decreases due to\nanthracene dimerization, it would be possible to examine whether it increases again after thermal cleavage.\n3. Among other things, have you compared the results in Figure 2e with the system without An-Am? If so, does it vary from\nthe original data?\n4. The present study was constrained to an experimental system in which 10 wt% An-Am was amalgamated with PFSA-An.\nHowever, the inquiry remains as to whether variations emerge based on the An-Am content.\n5. In Figures 3f and 3g, the diffracted light changes vertically according to the angle of incidence. Could you discuss the\nstructure formed based on the direction of the diffracted light in the vertical direction?", "reviewer_3": "In this article, Jiang and Xu et al. reported a light-induced self-adaptive growth strategy aiming to in-situ fabricate the\nphotonic crystal structures in an ionomer film and further proposed a bidirectional feedback loop between the incident UV\nlight and the nanoparticles generated. Based on these new construction methods, some angle-specific structural colors and\nfunctional PC-based gratings were prepared to demonstrate their promising potential in the future. This in-situ fabrication of\nstructural color by light-stimulus phase separation is very attractive. However, due to the lack of key evidence for the ordered\narrangement of the particle array, I am unable to recognize this cylindrical structure as a photonic crystal. Thus, I think that a\nmajor revision is necessary before accepting this manuscript in Nat. Commun, by clarifying the above concern and solving\nthe following comments:\n1. The heating treatment normally induced the decomposition of anthracene dimer. Why did the authors designed to treat the\nPFSA-An film upon irradiation of 365 nm UV light at 80 °C?\n2. How to measure or prove the refractive index of An-Am and PFSA?\n3. The element mapping of the PFSA-An film before upon irradiation of 365 nm is necessary to be supplied and compared\nwith the Supplementary Fig. 7.\n4. Why did the authors supply the fluorescence spectra of the film upon UV irradiation without heating (Supplementary Fig.\n9)? Please provide some comments to clarify this difference.\n5. Before attributing the increase in fluorescence to the alleviating of ACQ, the authors should provide more direct evidence\nto prove the existence of the ACQ effect in the initial film.\n6. Why did shielding result in deeper penetration of ultraviolet light? \"Shielding\" sounds more like something that would\nprevent the propagation of light.\n7. What did the inherent yellow color of the film depend on?\n8. Is there a method to control the particle size or interparticle distance? According to my speculation, when the content of An\nis low, the density of the initial clusters is low, and the spacing between the subsequent spherical-like phases will be\ndifferent, thereby affecting the position of the reflection peak. However, the concentration change shown in Supplementary\nFig. 11 only resulted in the variation of reflection peak intensity.\n9. Usually, scattering would reduce the ultraviolet transmission rate. Why, in this study, did it still maintain the highest level in\nthe direction of irradiation? Please provide more comments about the bidirectional feedback loop. The light beam is\ninherently directional, and this did not prove the function of the \"growing column\".\n10. The contrast of the images in Figure 3b and 3c is very low, making it difficult to discern the structure.\n11. The wavelength of the green laser is different from that of the actual UV light. Could this demonstrate the propagation\ncharacteristics of ultraviolet light within it?"}, "author_response": "Point to point responses to comments\nWe feel great thanks for the reviewers’ professional review work on our manuscript.\nBased on the insightful comments and suggestions, we have addressed all the issues\nraised in the manuscript and have done extensive corrections to our previous manuscript.\nThe detailed explanations are listed below.\nReviewer 1\nThis manuscript reports on an impressive body of work from Zhou et al, which I believe\nmay be suitable for publication in Nature Communications, subject to number of points\nbeing addressed.\nThere is a comprehensive demonstration of a light-directed control over phase-\nseparation and patterning of polymeric materials to generate a widespread range of\nphotonic crystals and structurally coloured films. There are some clear breakthroughs\nhere in terms of facilitating orientationally dependent designs, and associated\napplications in optoelectronics and photonics. My questions/feedback to the authors\nare as follows-\nResponse: Thank you very much for your positive evaluation and encouraging\ncomments. We are truly grateful for your recognition of the comprehensive\ndemonstration and the clear breakthroughs in light-directed phase-separation control\nand structurally colored film patterning. We sincerely appreciate your time and\ninsightful feedback.\nComment 1: My impression is that the \"light-induced self-adaptive growth\" (c.f. Title)\nrelates to the light/photochemical feedback interactions in the formation of structures.\nThe end materials are not, in themselves, light adaptive as with the natural examples\nmentioned, such as with plant phototropism? As the extension of the feedback to\nrespond to external stimuli is not shown, I would like the authors to consider whether\nthe final sentence of the abstract (\"This strategy overcomes the static limitations of\nconventional PCs, offering a versatile platform for adaptive photonic materials with\ndynamic light-matter interactions\") gives an accurate appraisal of the scope of the\nwork?\nResponse to comment 1: Thank you very much for your perceptive comments and\nprofessional feedback. We have revised the final sentence of the abstract to “This\nfabrication strategy overcomes the static limitations of conventional photonic crystals,\nproviding a versatile platform for creating programmable photonic architectures.” to\nmore accurately reflect that the adaptive behavior occurs during the light-guided growth\nprocess rather than implying inherent phototropic activity in the final material. The\nrevised version was marked as red color on line 25 of the revised manuscript.\nComment 2: Analogies are drawn to holographic methods, both implicitly, and statedly\nat around line 329. I can see the point here, as the optical properties can be made very\nstrongly dependent on the light propagation direction and the re-illumination/viewing\nconditions. Would the other important visual cues of holograms, such as image\nstereopsis, be achievable with these methods and structures?\nResponse to comment 2: Thank you for this thoughtful comment. We think that the\noptical directionality and viewing-angle dependence of our structures share similarities\nwith holographic principles. In our experiments, we indeed observed that light passing\nthrough the grating structures can split into dual virtual images (Fig. R1), suggesting\npotential in directional imaging. However, achieving full stereoscopic image\nperception—such as depth-aware stereopsis—remains beyond the scope of the current\nwork. We appreciate your highlighting this promising direction, and we plan to explore\nadvanced structural control for stereoscopic optical effects in future studies.\nFig. R1. (a) Photograph of the white light source. (b) Image of the white light source transmitted\nthrough a 3 μm stripe grating, showing virtual images of the source shape on both sides.\nComment 3: Figs 3d-3g, I would like to see more explanation of the scattering patterns\nreported;\nResponse to comment 3: Thank you very much for your comment, we appreciate the\nopportunity to provide further clarification regarding the scattering patterns in Figs. 3d–\n3g. We have expanded the corresponding explanations in the revised manuscript\n(around lines 280, 289, and 293) to more thoroughly address the origin and structural\nimplications of these features. Below, we provide detailed responses to each specific\nquestion:\n- which diffractive orders are spots are attributed to?\nResponse to comment: We appreciate the opportunity to clarify that the symmetric\nfeatures in the laser scattering pattern are actually interconnected rather than isolated,\nmanifesting as a curved arc with two symmetric spots. These features originate from\ninhomogeneous scattering caused by the tilted particle column structure, rather than\nfrom diffraction. Consequently, they cannot be attributed to specific diffractive orders.\nThis refined interpretation has been added to line 289 of the revised manuscript to\nprovide a more accurate and detailed description.\n- why there is a spatial \"curvature\" in the patterns, and whether this relates to\nstructural properties or merely the projection geometry?\nResponse to comment: We appreciate the opportunity to clarify that the curved arc in\nthe laser scattering pattern is primarily attributed to the structural characteristics of the\nparticle columns. Vertically aligned particle columns produce uniform scattering\npatterns, whereas tilted columns introduce directional inhomogeneity in the light path.\nIn this case, the particle columns act similarly to optical fibers, guiding more light\ntoward the direction of tilt, which results in the observed curvature. This mechanism\nhas been added in the revised manuscript (around line 293) to more clearly elucidate\nthe origin of this feature.\n- does the halo emerging in Fig 3d at longer exposures have any significance\nregarding structural order/disorder?\nResponse to comment: The observed change in the scattering pattern is primarily\nattributed to the increased length of the particle columns rather than to changes in\nstructural order/disorder. Shorter particle columns produce weaker Mie scattering,\nresulting in a faint and less distinct circular spot. Under prolonged UV exposure, the\nparticle columns grow significantly longer, leading to much stronger and more\npronounced Mie scattering that manifests as the clearly observable circular halo. This\ninterpretation has been added to the discussion section (line 280) to emphasize the size-\ndependent origin of this scattering feature.\nComment 4: Fig 3b requires some extra work in making the reported SEM images\nclearer, and the structures more visible. To a lesser extent, I also find the fluorescence\nmaps in Fig 1d/e quite difficult to make out.\nResponse to comment 4: We sincerely thank the reviewer for this valuable feedback\nregarding the image clarity. In response to your comments, we have taken several steps\nto improve the visualization. Since nanoparticle structures were challenging to resolve\nclearly in larger fields of view, a high-magnification image has been supplemented to\nillustrate the linear aggregation of particles within the columns (see Fig.R2), which has\nbeen added as Fig. S15 in the Supporting Information. To better illustrate the orientation\nof the particle columns, we have incorporated 3D structural imaging (Fig. R3),\nproviding a clear contrast between the two distinct alignment modes. These results are\npresented as Fig. S16 in the Supporting Information. Additionally, we have reacquired\nthe 3D fluorescence images with enhanced resolution and contrast (Fig. R4) and have\nreplaced the previous versions in Fig. 1d/e of the manuscript accordingly.\nFig. R2. SEM image of the particle columns terminal region within the PFSA-An film (Mode\nⅠ). Scale bar: 2 μm.\nFig. R3. 3D representation of particle columns distributions in (a) Mode I and (b) Mode II (45°)\nwithin the film, reconstructed from layer-by-layer scanning via high-resolution confocal laser\nscanning microscopy. All scale bars: 10 μm.\nFig. R4. 3D fluorescence images of particle columns distribution in (a) Mode Ⅰ and (b) Mode\nⅡ (45°). All scale bars: 5 μm.\nReviewer 2\nThis manuscript proposes a method for fabricating self-adaptive optical materials for\nphotonic engineering by incorporating anthracene into a polymer matrix to create films\nwhose optical properties change upon photodimerization. In particular, the creation of\nthe PC particle column structures is interesting in that it involves an ingenious light\nirradiation method. I believe that this work would be interesting to the readers of Nature\nCommunications, and I can recommend it to consider for possible publication in the\njournal after addressing the following comments.\nResponse: We sincerely appreciate your positive evaluation of our manuscript and are\ngreatly encouraged by your comments regarding the novelty and interest of our\napproach for creating self-adaptive optical materials. We thank you for your\nconstructive feedback and will address all your comments point-by-point in the revised\nmanuscript.\nComment 5: It would be helpful to include information about the wavelength and\nintensity of the UV light being used for irradiation. Do you have pictures of the\nphotomasks that were actually used? I also recommend discussing the consistency of\nthe size between the irradiated pattern and the formed structure. How is the light\nirradiated in the tilted state, as shown in Fig. 3?\nResponse to comment 5: Thank you for these insightful suggestions. The UV light\nused for irradiation had a wavelength of 365 nm and an intensity of 60 mW·cm⁻².\nThis information has been added to the Experimental Section of the Supporting\nInformation. As shown in Fig. R5, a quartz-based chromium photomask was used to create the\ngrating patterns. An optical micrograph of the photomask employed for the structure in\nFig. 5b (manuscript) is provided in Fig. S23, confirming good consistency between the\nmask features and the resulting structures, which has been noted in the manuscript on\nline 385. Furthermore, the directional nature of the UV source allowed controlled tilted-\nangle irradiation by simply tilting the lamp head, and this explanation has also been\nincluded in the Experimental Section.\nFig. R5. (a) Macrograph of the photomask used for fabricating the grating microstructure. Scale\nbar: 1 cm. (b) Micrograph of the corresponding photomask employed in the fabrication of the\ngrating microstructure. Scale bar: 10 μm.\nComment 6: In Fig. 2c, is there a reason why the emission increases in the initial few\nminutes? If the emission decreases due to anthracene dimerization, it would be possible\nto examine whether it increases again after thermal cleavage.\nResponse to comment 6: We sincerely thank the reviewer for this insightful question.\nThe observed increase in fluorescence intensity can be attributed to the following\nmechanism: In the absence of UV irradiation, anthracene aggregation induces π-π\nstacking, leading to an aggregation-caused quenching (ACQ) effect that suppresses the\nfull manifestation of fluorescence. Under UV irradiation, anthracene dimerization\npartially disrupts the ACQ effect, resulting in a temporary enhancement of fluorescence\nintensity within the initial few minutes. Corresponding explanations have been\nsupplemented in line 180 of the revised manuscript. The subsequent decline in\nfluorescence intensity due to anthracene dimerization is a well-documented\nphenomenon. For instance, Nat. Commun. 2023, 14, 7131 states: \"Upon extended\nirradiation with 365 nm UV light, the photodimerization of anthracene groups leads to\na sharp decrease in fluorescence intensity recorded in the spectra.\" Similarly, Adv.\nOptical Mater. 2022, 10, 2200608 notes: \"Primal anthracene groups (in monomeric\nform) exhibit blue fluorescence under 365 nm UV irradiation but transition to a non-\nfluorescent state (dimeric form).\" These references are cited in line 175 of the\nmanuscript.\nComment 7: Among other things, have you compared the results in Figure 2e with the\nsystem without An-Am? If so, does it vary from the original data?\nResponse to comment 7: We appreciate the reviewer's valuable suggestion regarding\nthe comparison with the system without An-Am. As shown in Fig.R6, we compared the\nreflectance spectrum of pristine PFSA film and PFSA-An film. The PFSA film exhibits\na reflectance of 5.5% at 400 nm and does not show structural color. Similarly, the PFSA-\nAn film also lacks structural color. However, due to the absorption of anthracene around\n400 nm, its reflectance decreases to 3.3%. We have included these additional data in\nthe Supporting Information (Fig. S11) and added a corresponding explanation in line\n198 of the revised manuscript.\nFig. R6. UV-vis reflectance spectra of PFSA film and PFSA-An film without UV irradiation.\nComment 8: The present study was constrained to an experimental system in which 10\nwt% An-Am was amalgamated with PFSA-An. However, the inquiry remains as to\nwhether variations emerge based on the An-Am content.\nResponse to comment 8: We appreciate the reviewer's insightful question regarding\nthe effect of An-Am content variation. As shown in Fig. R7, we have indeed\ninvestigated PFSA films with different An-Am contents and found that the 10 wt.%\nAn-Am exhibits the highest reflectance under identical irradiation conditions. When the\ncontent was further increased to 12 wt.%, the reflectance decreased from 12.4% to\n11.1%, accompanied by a 41 nm red-shift in the reflection peak. We attribute these\nchanges to increased phase separation scale and reduced structural ordering at higher\nAn-Am concentrations. These observations and interpretations have been added to line\n206 of the revised manuscript and Fig. S12 of the Supporting Information.\nFig. R7. Reflectance spectrum of PFSA-An films with different An-Am contents at 15 min of\nUV exposure.\nComment 9: In Figures 3f and 3g, the diffracted light changes vertically according to\nthe angle of incidence. Could you discuss the structure formed based on the direction\nof the diffracted light in the vertical direction?\nResponse to comment 9: We appreciate the reviewer's insightful observation\nregarding the vertical variation of diffracted light with incident angle in Figs. 3f and 3g.\nAs demonstrated in Figs. 3d and 3e, Mode Ⅰ and Mode Ⅱ exhibit fundamentally different\nscattering patterns under identical laser incidence conditions due to distinct orientations\nof the particle columns, producing uniform circular spots and symmetric arc patterns,\nrespectively. These results confirm that laser scattering can effectively verify the\npresence of particle columns within film. Furthermore, the transition between these\nscattering patterns observed in Figs. 3f and 3g through controlled adjustment of the\nlaser incidence angle demonstrates that the scattering patterns are directly correlated\nwith the relative orientation between the laser direction and the particle columns.\nThis relationship enables us to determine the specific orientation mode of the particle\ncolumns through laser scattering analysis. We have added further clarification regarding\nthis interpretation in line 297 of the revised manuscript.\nReviewer 3\nIn this article, Jiang and Xu et al. reported a light-induced self-adaptive growth strategy\naiming to in-situ fabricate the photonic crystal structures in an ionomer film and further\nproposed a bidirectional feedback loop between the incident UV light and the\nnanoparticles generated. Based on these new construction methods, some angle-\nspecific structural colors and functional PC-based gratings were prepared to\ndemonstrate their promising potential in the future. This in-situ fabrication of structural\ncolor by light-stimulus phase separation is very attractive. However, due to the lack of\nkey evidence for the ordered arrangement of the particle array, I am unable to recognize\nthis cylindrical structure as a photonic crystal. Thus, I think that a major revision is\nnecessary before accepting this manuscript in Nat. Commun, by clarifying the above\nconcern and solving the following comments:\nResponse: Thank you very much for your positive assessment of our work and we truly\nappreciate your insightful comments. In this study, the nanoparticle structures grow\nalong the incident light path, forming linearly aligned and locally ordered arrangements\n(Fig. R8). This specific organization gives rise to the observed structural color, though\nits intensity remains relatively weak. Furthermore, the linearly arranged nanoparticles\nfurther assemble into particle columns. Due to the local ordered arrangement of\nnanoparticles, we define these columnar structures as photonic crystal (PC) particle\ncolumns. We have visualized this oriented morphology through layer-by-layer scanning\nand 3D reconstruction of the columnar structures, supported by 3D fluorescence\nmapping (Fig. R9 and Fig. R10). We will make every effort to address your valuable\ncomments through additional experiments, further characterization, and detailed\nclarifications in the revised manuscript. We hope that these revisions will fully resolve\nyour concerns.\nFig. R8. SEM image of the particle columns terminal region within the PFSA-An film (Mode\nⅠ). Scale bar: 2 μm.\nFig. R9. 3D representation of particle columns distributions in (a) Mode I and (b) Mode II (45°)\nwithin the film, reconstructed from layer-by-layer scanning via high-resolution confocal laser\nscanning microscopy. All scale bars: 10 μm.\nFig. R10. 3D fluorescence images of particle columns distribution in (a) Mode Ⅰ and (b) Mode\nⅡ (45°). All scale bars: 5 μm.\nComment 10: The heating treatment normally induced the decomposition of\nanthracene dimer. Why did the authors designed to treat the PFSA-An film upon\nirradiation of 365 nm UV light at 80 °C?\nResponse to comment 10: We appreciate this important question regarding our\nexperimental design. We have investigated the depolymerization behavior of\nanthracene dimers under the 80 °C heating. UV-vis absorption spectroscopy confirmed\nthat only a minimal amount of anthracene dimers underwent depolymerization even\nafter 3 hours (Fig. R11). In our experiment, the PFSA-An film was exposed to 365 nm\nUV irradiation at 80 °C for only 10 min, ensuring that the dominant process during this\nshort period remains anthracene dimerization. The primary purpose of heating was to\nenhance molecular mobility of An-Am, thereby promoting efficient phase separation.\nWe have added an explanation of this rationale in line 113 of the revised manuscript.\nFig. R11. UV-vis absorption spectral changes during anthracene dimerization and\ndepolymerization in the PFSA-An film.\nComment 11: How to measure or prove the refractive index of An-Am and PFSA?\nResponse to comment 11: Thank you for raising this important methodological\nquestion. The refractive indices of both An-Am and PFSA were measured using a\nspectroscopic ellipsometer, and the experimental procedure has been provided in the\nExperimental Section of the Supporting Information.\nComment 12: The element mapping of the PFSA-An film before upon irradiation of\n365 nm is necessary to be supplied and compared with the Supplementary Fig. 7.\nResponse to comment 12: Thank you for this valuable suggestion regarding the\nelemental analysis. The elemental mapping of the PFSA-An film before UV irradiation\nis shown in Fig. R12. No nanoparticle structures or elemental agglomerations were\nobserved. This result confirms that the microstructural evolution is indeed triggered by\nanthracene dimerization under UV exposure. We have added this discussion to line 156\nof the revised manuscript, and these images have been added to the Fig. S7 of\nSupporting Information.\nFig. R12. TEM image and elemental distribution of the PFSA-An film before UV irradiation.\nScale bar: 200 nm.\nComment 13: Why did the authors supply the fluorescence spectra of the film upon UV\nirradiation without heating (Supplementary Fig. 9)? Please provide some comments to\nclarify this difference.\nResponse to comment 13: We appreciate the reviewer's attention to this detail\nregarding the fluorescence spectra. To clarify, the film was indeed UV-irradiated under\nheating at 80 °C before the fluorescence measurement, rather than at room temperature.\nThis condition was maintained to ensure consistency with the main experimental\nprocess. We have added a note in the Experimental Section of the Supporting\nInformation to prevent any potential misunderstanding regarding the measurement\nconditions.\nComment 14: Before attributing the increase in fluorescence to the alleviating of ACQ,\nthe authors should provide more direct evidence to prove the existence of the ACQ effect\nin the initial film.\nResponse to comment 14: We thank the reviewer for raising this important point\nregarding the evidence for ACQ in the initial film. The π–π stacking of anthracene\nyielding an ACQ effect is a typical phenomenon. For instance, the literature\n(Biomacromolecules 2014, 15, 9, 3383–3389) mentions that “a positively charged\nanthracene derivative (An-N+) is a typical ACQ molecule”, while another publication\n(Chem. Rev. 2015, 115, 21, 11718–11940) similarly states that “anthracene exhibits\naggregation-induced quenching (ACQ) behavior due to its planar π-conjugated\nskeleton”. These references have been added to line 180 of the revised manuscript to\nfurther substantiate the presence of ACQ in the as-prepared film.\nComment 15: Why did shielding result in deeper penetration of ultraviolet light?\n\"Shielding\" sounds more like something that would prevent the propagation of light.\nResponse to comment 15: We appreciate the reviewer's insightful comment on the use\nof the term \"shielding.\" Anthracene absorbs ultraviolet light and exhibits a shielding\neffect. At the beginning of UV irradiation, the upper layer of anthracene first absorbs\nUV energy and undergoes anthracene dimerization. After the upper anthracene is\ndimerized, the lower layer begins to react, making this a gradual process. Shielding\nblocks the propagation of ultraviolet light and does not directly lead to deeper\npenetration. The eventual deeper penetration is actually achieved under longer UV\nexposure, as the dimerized anthracene loses its shielding effect. We have added a more\ndetailed description of this stepwise reaction caused by the shielding effect on line 191\nof the manuscript.\nComment 16: What did the inherent yellow color of the film depend on?\nResponse to comment 16: We appreciate the reviewer's question regarding the origin\nof the film's inherent yellow color. The PFSA film itself is colorless and transparent.\nAs shown in Fig. R13 the yellow color of the PFSA-An film is primarily attributed to the\nintrinsic yellow appearance of the An-Am component. Regarding the yellowish-green\nstructural color observed in the film, it is mainly related to the size of the grown\nnanoparticles.\nFig. R13. Optical photograph of the An-Am, exhibiting a yellow powder morphology. Scale\nbar: 1 cm.\nComment 17: Is there a method to control the particle size or interparticle distance?\nAccording to my speculation, when the content of An is low, the density of the initial\nclusters is low, and the spacing between the subsequent spherical-like phases will be\ndifferent, thereby affecting the position of the reflection peak. However, the\nconcentration change shown in Supplementary Fig. 11 only resulted in the variation of\nreflection peak intensity?\nResponse to comment 17: We thank the reviewer for raising this important question.\nIn our current experiments, there are two methods to adjust the position of the reflection\npeak: UV irradiation time and An-Am content. As shown in Fig. R14a, during the 0–\n15 min irradiation period, the reflection peak remains at 520 nm while its intensity\ncontinues to increase. Further extending the UV irradiation to 30 min leads to a redshift\nof the reflection peak to 565 nm, accompanied by a continuous decrease in intensity,\nwhich is related to the continuous growth of nanoparticle size and increased disorder.\nIncreasing the An-Am content shows a similar trend: as indicated in Fig. R14b, when\nthe An-Am content is raised to 12 wt.%, the reflection peak shifts from 520 nm to 561\nnm under the same irradiation time. Fig. R14b has been added to the Supplementary\nInformation as Fig. S12. Considering that the 10 min of UV exposure was established\nas the standard condition in our experiments, and prolonged UV irradiation may\nadversely affect the ordered structure, further investigation into extended exposure\ntimes was not pursued.\nFig. R14. (a) Changes in UV-vis reflectance spectrum of PFSA-An film under UV irradiation.\n(b) Reflectance spectrum of PFSA-An films with different An-Am contents at 15 min of UV\nexposure.\nComment 18: Usually, scattering would reduce the ultraviolet transmission rate. Why,\nin this study, did it still maintain the highest level in the direction of irradiation? Please\nprovide more comments about the bidirectional feedback loop. The light beam is\ninherently directional, and this did not prove the function of the \"growing column\".\nResponse to comment 18: We appreciate the reviewer's insightful questions regarding\nthe ultraviolet transmission and the bidirectional feedback mechanism. The observation\nthat \"the highest level is maintained along the irradiation direction\" means that after\nUV light is scattered by the particle structures, the energy of the UV light along the\noriginal optical path remains higher than the energy in scattered directions. As a result,\nsubsequent particles preferentially grow and align along this direction, forming initial\nparticle column structures. Although scattered light would theoretically cause structural\ndisorder, the refractive index difference between the PFSA and An-Am enables the\nparticle columns to function like optical fibers, confining the scattered light within the\ncolumns. This creates a bidirectional feedback loop of UV light - particle column,\nleading to aligned growth of the particle columns along the optical path. Without this\nbidirectional feedback mechanism, UV light would diffract during the preparation of\ngrating structures, resulting in irregular patterns rather than well-defined structures. We\nhave further discussed this bidirectional feedback mechanism on line 233 of the\nmanuscript to provide a clearer explanation.\nComment 19: The contrast of the images in Figure 3b and 3c is very low, making it\ndifficult to discern the structure.\nResponse to comment 19: We appreciate the reviewer's feedback regarding the low\ncontrast in Figures 3b and 3c. To address this issue, we have taken additional measures\nto improve structural visualization. While nanoparticle structures remain challenging to\nresolve clearly in larger fields of view, we have now included higher-magnification\nimages showing detailed particles linear aggregation within the columns (as shown in\nFig. R15), which have been added as Fig. S15 in the Supporting Information. The\nprimary purpose of Fig. 3b, c was to demonstrate the orientation of particle columns.\nTo enhance this visualization, we have performed additional 3D imaging of the particle\ncolumns using high-resolution confocal microscopy. As shown in Fig. R16, the two\ndistinct alignment modes show clear contrast, and these results have been included as\nFig. S16 in the Supporting Information, with the imaging methodology provided in the\nExperimental Section.\nFig. R15. SEM image of the particle columns terminal region within the PFSA-An film\n(Mode Ⅰ). Scale bar: 2 μm.\nFig. R16. 3D representation of particle columns distributions in (a) Mode I and (b) Mode II\n(45°) within the film, reconstructed from layer-by-layer scanning via high-resolution confocal\nlaser scanning microscopy. All scale bars: 10 μm.\nComment 20: The wavelength of the green laser is different from that of the actual UV\nlight. Could this demonstrate the propagation characteristics of ultraviolet light within\nit?\nResponse to comment 20: We are grateful for the reviewer's insightful question\nregarding the use of green laser. The primary purpose of employing the green laser was\nto characterize the preformed structures rather than to directly illustrate UV propagation\nproperties. Since 365 nm UV light is not visible, we utilized visible lasers (635 nm,\n532 nm, and 405 nm) to infer the light behavior within the structured film, as demonstrated\nin Fig. R17. All tested wavelengths exhibited identical scattering patterns when the\nlaser was rotated by 45°. Additionally, the nanoparticles in the film range in size from\n100 nm to 180 nm, while the particle columns have a diameter of approximately 1.5\nμm. The wavelengths of 365 nm, 405 nm, 532 nm, and 635 nm all fall within this range.\nTherefore, without considering the energy absorption of anthracene by UV light, we\ninfer that 365 nm UV light and the green laser share similar propagation characteristics.\nFig. R17. Optical scattering patterns generated by laser irradiation at wavelengths of (a) 635\nnm, (b) 532 nm, and (c) 405 nm incident on vertical particle columns, along with corresponding\npatterns after 45° deflection."}, {"round": 2, "reviewer_comments": {"reviewer_1": "I am pleased to read the response of the authors to my original review, and note their strong engagement with the points raised (as with the other reviewers also). I thought the \"Fig R1\" image in the rebuttal document is a really nice illustration of the pseudo-holographic effects reported; I hope a place can be found somewhere in the manuscript for this.\nOverall, very good work on a prescient topic, which I recommend for publication in Nature Comms.", "reviewer_2": "The author has addressed the reviewer's recommendations, including the provision of supplementary data. The reviewer\nfinds the scientific soundness of this study to be sufficient and agrees to proceed with publication as is.", "reviewer_3": "My concerns have been addressed in the revisions. I have no other questions and I think it is publishable now."}, "author_response": "Point to point responses to comments\nReviewer 1\nI am pleased to read the response of the authors to my original review, and note their\nstrong engagement with the points raised (as with the other reviewers also). I thought\nthe \"Fig R1\" image in the rebuttal document is a really nice illustration of the pseudo-\nholographic effects reported; I hope a place can be found somewhere in the manuscript\nfor this.\nOverall, very good work on a prescient topic, which I recommend for publication in\nNature Comms.\nResponse: Thank you very much for your positive and encouraging comments on our\nrevised manuscript. We are delighted that you appreciated the \"Fig R1\" illustration. We\nhave now incorporated this figure into the Supplementary Information as\nSupplementary Fig. 24. Additionally, we have added a corresponding description of\nthese results in the main text (Line 335) to more clearly demonstrate the application\npotential of grating structures in the field of directional imaging.\nFig. R1. (a) Photograph of the white light source. (b) Image of the white light source transmitted\nthrough a 3 μm stripe grating, showing virtual images of the source shape on both sides.\nReviewer 2\nThe author has addressed the reviewer's recommendations, including the provision of\nsupplementary data. The reviewer finds the scientific soundness of this study to be\nsufficient and agrees to proceed with publication as is.\nResponse: Thank you for your final assessment of our manuscript and for your\nconfirmation that all points have been adequately addressed. We appreciate your time\nand insightful comments throughout the review process.\nReviewer 3\nMy concerns have been addressed in the revisions. I have no other questions and I think\nit is publishable now.\nResponse: Thank you for your final positive feedback on our revised manuscript. We\nappreciate your valuable time and insightful comments, which have significantly\nhelped to improve our paper."}]

Decision letter