Biomimetic Optical Cellulose Nanocrystal Films with Controllable

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Biomimetic Optical Cellulose Nanocrystal Films with Controllable Iridescent Color and Environmental Stimuli-Responsive Chromism Yao-dong He, Ze-Lian Zhang, Juan Xue, Xiao-hui Wang, Fei Song, Xiu-Li Wang, Li-li Zhu, and Yu-Zhong Wang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b18440 • Publication Date (Web): 23 Jan 2018 Downloaded from http://pubs.acs.org on January 25, 2018

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ACS Applied Materials & Interfaces

Biomimetic Optical Cellulose Nanocrystal Films with Controllable Iridescent Color and Environmental StimuliResponsive Chromism Yao-dong He†, Ze-lian Zhang†, Juan Xue†, Xiao-hui Wang†, Fei Song*†, Xiu-li Wang†, Li-li Zhu‡, Yu-zhong Wang† †Center for Degradable and Flame-Retardant Polymeric Materials (ERCPM-MoE), College of Chemistry, State Key Laboratory of Polymer Materials Engineering, National Engineering Laboratory of Eco-Friendly Polymeric Materials (Sichuan), Sichuan University, 29 Wangjiang Road, Chengdu 610064, China ‡The Affiliated Hospital of Guizhou Medical University, Guiyang 510000, China *Corresponding author. E-mail: [email protected] Tel & Fax: 86-28-85410755

Abstract As a wise and profound teacher, nature provides numerous creatures with rich colors to us. To biomimic structural colors in nature as well as color changes responsive to environmental stimuli, there is a long way to go for the development of free-standing photonic films from natural polymers. Herein, a highly flexible, controllably iridescent, and multi-stimuli-responsive cellulose nanocrystal (CNC) film is prepared by simply introducing a small molecule as both plasticizer and hygroscopic agent. The presence of the additive does not block the self assembly of CNC in aqueous solution but results in the enhancement of its mechanical toughness, making it possible to obtain free-standing iridescent CNC films with tunable structural colors. In response to environmental humidity and mechanical compression, such films can change structural colors smoothly by modulating their chiral nematic structures. Notably, the chromism is reversible by alternately changing relative humidity between 16% and 98%, mimicking a longhorn beetle Tmesisternus isabellae. This chromic effect enables various applications of the bio-films in colorimetric sensors, anti-counterfeiting technology, and decorative coatings.

Keyword: cellulose nanocrystal, chiral nematic structure, structural color, flexibility, environmental stimuli-responsive chromism

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Introduction In nature exist many photonic structures that generate brilliant colors, providing us inspirations for developing diverse artificial photonic materials with wide applications in optical devices, sensors, security indicators, etc1-5. Different from colorant-based pigmentation, structural colors arise from the light interference in periodically layered or lattice structures, which are discovered in many animals and plants, such as insect cuticles, fish scales, bird feathers, fruits and leaves6-8. Inspired by these interesting phenomena, artificial structural colors have been created in the past decades with the assistance of photonic crystals9-11, bragg stacks12, and chiral nematic liquid crystals1315

. In contrast to the photonic materials with fixed structural colors, the counterparts

with chromic effects, which refer to reversible color changes upon external stimuli, are more welcome regarding the demand on smart materials. Till now, impressive progress has already been made on colloidal photonic crystals that can mimic chameleon, tortoise beetle, hercules beetle, blue damselfish, and so on16-19. Compared with that, however, we still have a long way to go for developing environmental stimuli-responsive chromic photonic materials from natural polymers. Cellulose nanocrystal (CNC), generally prepared by acid-catalyzed hydrolysis of bulk cellulose, can well disperse in water due to the introduction of sulfate ester groups on its surface as well as the resultant electrostatic repulsion20, which enables the formation of chiral nematic liquid crystals. Even after evaporation of water to yield solid films, CNC can maintain the liquid crystal structure and present iridescent colors if its helical pitch locates in the visible wavelength region21, 22. To control its iridescence as a result of the tunable pitch, different approaches, including ultrasound treatment, desulfation, and the introduction of salts or water-soluble polymers, have been widely reported23-28. Nevertheless, how to make the resultant CNC materials sense environmental changes in terms of chromism is rarely illustrated. Zhang et al. 29 prepared thick CNC films in Petri dish by a conventional solution-cast method, which showed humidity-responsive chromism. Liu and co-workers30 employed a layer-bylayer approach to develop iridescent optical CNC coatings on silicon wafers that could sense different vapors. It should be noted, however, that these films are not free-standing because of the high fragility of CNC. To overcome the shortage, MacLachlan’s group22,

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introduced urea-formaldehyde and amino-formaldehyde

resins into the CNC matrix, respectively, constructing mesoporous photonic CNC 2


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films sensitive to humidity and pressure. The presence of these thermoset resins did not disturb the self-assembly of CNC, however, alongwith the heat curing, volume shrinkage of such thermosets is difficult to avoid, even worse, resulting in apparent wrinkling of CNC films. Very recently, Zhou et al. reported the fabrication of flexible and humidity-responsive CNC films by introducing poly(ethylene glycol) as an additive 32. Inspired by the changed coloration of longhorn beetles Tmesisternus isabellae from golden at dry state to red at wet state33, herein, a small molecule, glycerol, is used as a plasticizer as well as a hygroscopic agent for CNC to develop flexible and multiresponsive chiral nematic films. By controlling the length and diameter of CNC rods, blue-iridescent CNC film is fabricated. Additionally, glycerol is introduced to tune the iridescent colors as well as the mechanical toughness of the CNC films. Depending on the addition amount of glycerol, controllably red-shifted iridescence and enhanced tensile strain are realized. In response to environmental humidity and pressure, in particular, the films can reversibly change structural colors, indicating potential applications in colorimetric sensors, anti-counterfeiting technology, and decorative coatings. Experimental section Materials Cotton wool (Product NO.: YZB/Chuan 0177-2013) was provided by Kangda Health Materials Co. (Sichuan, China). Sulfuric acid (CAS NO.: 7664-93-9) was purchased from Kelong Co. (Sichuan, China.) Glycerol (CAS NO.: 56-81-5) was obtained from Ruijin Co. (Tianjin, China). Deionized water was obtained from a Milli-Q Plus water purification system (Millipore, USA) and was used the solvent in all experiments. Preparation of Cellulose Nanocrystal (CNC) Films CNC was prepared by treating dried cotton wool (34 g) with a sulfuric acid solution (64% w/w, 300 mL) at 55 °C for 1 h, followed by adding cold deionized water (3 L) to quench the reaction. Such solution was left overnight, and the suspension was centrifuged at 9000 rpm for 5 min, washed with deionized water for several times and dialyzed against deionized water with dialysis membrane tubes (3500 molecular weight cut-off) till the complete removal of sulfuric acid at 25 oC. Finally, the as3



prepared CNC dispersion was concentrated to the concentration of 8.5 wt% with a rotary evaporation apparatus. Prior to the film formation, different amounts of glycerol (0.2-1.0 g) were added in the aqueous CNC suspension (20 g) and mixed at 25 oC for 12 h, followed by casting such solution into PTFE molds (5 cm in diameter) and drying at 45 °C to give freestanding CNC films. The pure CNC film in the absence of glycerol was also prepared as a reference. Characterization FT-IR spectra were recorded on a Fourier transform infrared spectrometer (Nicolet 6700, USA) within a wavenumber range of 4000 to 700 cm-1. Molecular composition of sample (concentration: 0.5 mg/L) was determined in terms of element analysis by inductively coupled plasma-atomic emission spectrometry (ICP-AES, Iris Advantage 1000, USA). Zeta potential measurement was conducted on the CNC dispersion sample with the concentration of 0.01wt% by the Zetasizer (Zetasizer Nano ZS90) at room temperature to measure the zeta potential and understand the surface charge density. For each sample, six measurements were performed to give the average values. X-ray diffraction (XRD) patterns were collected by an X-ray diffractometer (XRD-6100, Shimadzu) between 5 and 80° with a Ni-filtered CuKα radiation (1.5418 Å). Texture of samples was observed using a polarized optical microscope (POM, ECLIPSE 50i POL). Prior to the measurement, a sample drop was deposited onto a glass slide. Scanning electron microscopy measurement was conducted on a scanning electron microscope (SEM, JSM-5900LV, JEOL Co. Japan). Samples were operated in high vacuum mode at 5 kV accelerating voltage and fractured to expose their crosssectional areas. Transmission electron microscopy (TEM) analysis was performed by a transmission electron microscope (ZEISS LIBRA 200FE) at a voltage of 75 kV. Samples were prepared by depositing a suspension drop onto a wax sheet, followed by immersing a copper grid in for a few minutes. Structural coloration of film samples was measured using UV-visible spectroscopy (Varian Cary 50 spectrophotometer), in terms of the extinction intensity within the wavelength range of 300-800 nm. For each sample, five scans were recorded to give an average spectrum. Mechanical property was investigated using a universal testing machine (Model 3366, Instron Crop, USA) equipped with a 100 N load cell. Sample size was of 4 mm in width and 25 mm in length, the tensile speed was set at 5 mm/min. 4


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Humidity- and Pressure-responsive property Humidity-responsive performance was evaluated by placing sample films in the containers with different relative humidities (RH), which were built as reported previously34, that is, saturated Anhydrous CaCl2, K2CO3, NaCl solutions and distilled water for 16% RH, 43% RH, 75% RH, and 98% RH, respectively. After being incubated for 1 h, the films were taken out, and their UV-vis extinction spectra were recorded. For the investigation on pressure-responsive property, different compressive stresses were applied by a small-scale powder press machine (HW-01, Jinwei) on samples under the load range of 0-10 MPa for 3 s, followed by recording the changes of their UV-vis extinction spectra. Results and Discussion Herein, CNC is prepared by an acid hydrolysis approach reported before35. As determined by TEM, the as-prepared CNC is of rod-like morphology with the average length and diameter of 222 nm and 7 nm, respectively (Figure 1a). Due to the presence of negatively charged sulfate surface groups, CNC can disperse in water homogeneously without precipitation. The zeta potential and sulfur content of the CNC prepared in this work are -15.8 mV (Figure 1b) and 0.0124 mol/g. According to a previous report 36, colloidal particles tend to flocculate in case of the zeta potential is lower than 25 mV. For CNC, however, its agglomeration starts once the zeta potential becomes lower than 15 mV28. As a result, the aqueous CNC dispersion prepared herein is stable. Additionally, surface charge density is thereafter calculated as 0.34 e/nm2 according to the following equation28: =

∗% ∗ :

(1),

where MSO3 is the molecular weight of sulfate half-ester, %S is the sulfur content, Na is the Avogadro’s number, SA:V refers to the surface to volume ratio and dcell represents the density of cellulose. As reported previously37, 38, the surface charge density of CNC is required to locate within the region of 0.16-0.66 e/nm2, in case of self-assembly in water. Therefore, it is reasonable to assume the CNC we prepare can be used to develop iridescent films. According to the equation proposed by Gray39, the critical concentration, where CNC dispersion starts to exhibit lyotropic chiral nematic behavior, is calculated as approximately 5.04 wt%. Consequently, the CNC concentration of the film-forming dispersion is set as 8.5 wt%. As shown in Figure 1c, 5



the characteristic birefringent and “fingerprint” textures are observed for the CNC dispersion by POM, from which the chiral nematic pitch (P) is measured as twice the distance between the fingerprint lines in the inserted enlarged photos. Accordingly, the P value of the neat CNC dispersion is 840 nm. The introduction of glycerol shows no obvious effect on the appearance of birefringent and “fingerprint” textures but on the P values, depending on the addition amount. For specific CNC/glycerol dispersions, which are named in accordance with the amount of glycerol, their P values as a function of the glycerol percentage are illustrated in Figure 1d, presenting a positive correlation.

Figure 1. (a) TEM image of as-prepared CNC; (b) zeta potential of CNC suspension; (c) POM images of neat CNC and CNC/glycerol suspensions (inserted photos are the high-magnification images taken at the locations marked with red ellipses); (d) chiral nematic pitch as a function of glycerol percentage for CNC/glycerol suspensions.

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Figure 2. (a) Photographs of solid CNC films containing different amounts of glycerol; (b) UVVis extinction spectra of neat CNC and CNC/glycerol films; (c) maximum extinction wavelength and chiral nematic pitch of CNC and CNC/glycerol films as a function of glycerol percentage.

To prepare iridescent CNC films, water is evaporated by a conventional solutioncast method. The photos of such CNC/glycerol films taken at the vertical direction are shown in Figure 2a, where different iridescent colors can be seen, that is, the color of such films changes from blue to red gradually with the increased amount of glycerol. The different “colorations” on the films are attributed to that the light with certain wavelength is extinct when passing through the films. A further quantitative analysis conducted by UV-vis extinction spectroscopy indicates that a gradual red-shift of the maximum extinction wavelength occurs from 347 nm to 610 nm with the incorporation of glycerol (Figure 2b). Generally, the iridescent colors are regarded as a result of Bragg reflection. Therefore, the P values of the solid CNC/glycerol films can be calculated by the following equation40: = sin

(2),

where nav is the average refractive index of the CNC-G film, P is the pitch and θ the incident angle of light. The effect of glycerol amount of the calculated P value is shown in Figure 2c. Concretely, P of such films increases from 227 nm to 402 nm with the increased glycerol amount. The results clearly explain why different 7



iridescent colors are presented on the CNC films, suggesting that the iridescent property can be controlled by simply changing the addition amount of glycerol.

Figure 3. (a) FT-IR spectra of neat CNC and CNC/glycerol films; (b) typical SEM images of neat CNC and CNC-G0.6 films showing regular layered structure; (c) a proposed molecular mechanism for the regulation of red-shifted structural color of CNC in the presence of glycerol.

To clarify the mechanism for the controllable iridescence, FTIR measurement is performed on the neat CNC and CNC/glycerol films. As shown in Figure 3a, the absorption band of neat CNC within 3300-3500 cm-1 attributing to O-H stretching suggests the existence of hydrogen bonding. Once introducing glycerol as the plasticizer, the band is obviously narrowed and shifts to low-wavenumber. Additionally, from the cross-section image of the representative blend film, CNC-G0.6, the parallel layered structure is still well remained, compared with the neat CNC film (Figure 3b). Nevertheless, the height of individual layer of the blend film is much greater than that of neat one. Figure S1 presents the XRD patterns of neat CNC and CNC/glycerol blends, where the characteristic crystalline peaks belonging to the (101), (10ī), (002), and (040) lattices of cellulose are observed for all samples. This suggests that the crystal structure of cellulose is not destroyed after the addition of glycerol. Based on the FTIR and XRD results, it is reasonable to believe that glycerol molecules diffuse into the CNC scaffold, locating at the amorphous region as well as the mesopores among the rods, and form hydrogen bonding with CNC at the hydroxyl groups of glucose ring. As a result, the presence of glycerol occupies some free volumes of CNC, resulting in the increase in the periodic arrays (in terms of P) as 8


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well as the red-shift of structural colors; a proposed mechanism is presented in Figure 3c. As well known, mechanical property is of great importance to practical applications. For the neat CNC film, however, it is impossible to perform the tensile test because of the high intrinsic brittleness. In contrast, the addition of glycerol induces the obviously increased tensile toughness of the CNC films. Particularly, the elongation at break exceeds 2% for CNC-G0.6 (Figure 4a), which is larger than many previous reports. 22, 32, 41, 42 The detailed tensile strength and elongation at break as a function of glycerol amount are provided in Figure S2. As shown in the inserted photo, moreover, the CNC-G0.8 film can be easily bended, presenting good flexibility that can be hardly realized for the neat CNC film. Owing to the high hygroscopicity of glycerol, the resulting films are readily able to capture water in a humid environment. Accordingly, their responses to relative humidity (RH) are investigated in detail. Taking CNC-G0.8 as the representative, it is stored at different RH levels. As shown in Figure 4b, the extinction wavelength of the CNC-G0.8 film shifts from 586 nm to 704 nm when the RH increases from 16% to 98%, indicating the red-shifted structural coloration. To understand whether the water molecules have such power to trigger the color variation, SEM images of the film are recorded after the treatment at different RH levels. From Figure 4c, we can see that the film thickness increases with the RH level, that is, from 91 ± 2 µm in the case of 16% RH to 155 ± 5 µm in the case of 98% RH. As a result, it can be reasonably deduced that the increased film thickness accounts for the increase of P value as well as the red-shift of structural color. In addition, all other films except the neat CNC one have humidity-responsive chromism performance; the detailed maximum extinction wavelengths are presented in Figure S3. This indicates that the presence of glycerol contributes to realize the humidity-responsive chromism function of CNC film. Besides that, the chromism is reversible in case of the changed environmental humidity. As shown in Figure 4d, when the CNC-G0.8 film is placed at 16% RH and 98% RH alternately, its structural color changes reversibly between “green” and “red”. Within 10-run alternations, the reversibility keeps well in terms of the nearly unchanged maximum extinction wavelength. Accordingly, the proposed mechanism is provided in Figure 4e.

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Figure 4. (a) Tensile property of neat CNC and CNC/glycerol films (inserted digital photograph is to show the bending flexibility of CNC-G0.8 film); (b) humidity-responsive effect and (c) corresponding cross-section structure of CNC-G0.8 film at different relative humidities; (d) reversible humidity response over 10 consecutive cycles between the relative humidities of 16% and 98%; (e) a proposed mechanism for the reversible humidity-responsive structural color change of CNC films; (f) pressure-responsive effect and (g) the corresponding chromism mechanism of the CNC-G0.8 film.

More importantly, the trigger signal to induce the chromism is not just limited as humidity. Giving the film a pressure can also cause the similar consequence. In particular, a monotonic dependence of the wavelength-shift on the applied pressure is found, that is, the higher pressure, the greater blue-shift of the maximum extinction wavelength (Figure 4f). As a clearer illustration, a “S”-shaped stamp is employed to press on the CNC-G0.8 film, leaving a blue mark after uplifting (Figure 4g), which can be attributed to the shortened P distance. Interestingly, the blue coloration is able to turn red once placing the film in high-RH condition; this phenomenon can be well explained by the close maximum extinction wavelengths of such film before and after

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the successive press-moisture absorption treatment. Owing to the poor elasticity, however, the “S” mark remains still in spite of the color recovery.

Conclusion In summary, highly flexible and iridescent CNC films with humidity- and pressureresponsive chromism effects are successfully prepared by introducing glycerol as the plasticizer as well as the hygroscopic agent. The iridescent color of such films is easily modulated from blue to red by controlling the addition amount of the small molecule. The presence of glycerol endows high flexibility to the CNC films, which can be bended and stretched with an elongation at break higher than 2%. When being exposed to different relative humidities, the films demonstrate reversible color changes. Furthermore, the films can quantificationally sense the compression pressure by presenting iridescent color changes. Based on the above properties and functions, the CNC films are expected to show applications in colorimetric sensors, anti-counterfeiting, and decorative coatings. For instance, the films can be designed in forms of security signs, labels and optical components, which can perceive external environmental changes by chromism. This behavior, conversely, can help to judge the true or fake. Besides that, the film can be also used as a functional coating displaying optional colors what we want, which is desirable for decoration. Nevertheless, it should be mentioned that, as well known, the surface migration of small molecules from polymeric films is generally difficult to avoid, especially in high humidity-environments, which might result in the loss of structural colors and relevant properties. Consequently, functional additives with higher stability in CNC will be explored in our future work for the long-term service of such environmental stimuli-responsive chromic photonic bio-based materials.

Associated Content Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: XXXXX/acsami.XXXXX, including XRD patterns, mechanical property and humiditydependent maximum extinction wavelength of neat CNC and CNC/glycerol films.

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Acknowledgments This work was supported financially by the National Natural Science Foundation of China (51773133 and 51421061), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (IRT1026).

References 1. Vukusic, P.; Sambles, J. R., Vukusic P, Sambles JR. Photonic structures in biology. Nature. Nature 2003, 424, (6950), 852-855. 2. Wiederhecker, G. S.; Chen, L.; Gondarenko, A.; Lipson, M., Controlling photonic structures using optical forces. Nature 2009, 462, (7273), 633-6. 3. Galisteo-López, J. F.; Ibisate, M.; Sapienza, R.; Froufe-Pérez, L. S.; Blanco, A.; López, C., Self-assembled photonic structures. Advanced Materials 2011, 23, (1), 30-69. 4. Qiao, W.; Huang, W.; Liu, Y.; Li, X.; Chen, L. S.; Tang, J. X., Toward Scalable Flexible Nanomanufacturing for Photonic Structures and Devices. Advanced Materials 2016, 28, (47), 10353. 5. Yu, K.; Fan, T.; Shuai, L.; Zhang, D., Biomimetic optical materials: Integration of nature’s design for manipulation of light. Progress in Materials Science 2013, 58, (6), 825-873. 6. Kinoshita, S.; Yoshioka, S., Structural colors in nature: the role of regularity and irregularity in the structure. Chemphyschem A European Journal of Chemical Physics & Physical Chemistry 2005, 6, (8), 1442. 7. Parker, A. R.; Townley, H. E., Biomimetics of photonic nanostructures. Nature Nanotechnology 2007, 2, (6), 347-53. 8. Vignolini, S.; Rudall, P. J.; Rowland, A. V.; Reed, A.; Moyroud, E.; Faden, R. B.; Baumberg, J. J.; Glover, B. J.; Steiner, U., Pointillist structural color in Pollia fruit.

Proceedings of the National Academy of Sciences of the United States of America 2012, 109, (39), 15712. 9. Yablonovitch, E., Inhibited spontaneous emission in solid-state physics and electronics. Physical Review Letters 1987, 58, (20), 2059. 10. John, S., Strong localization of photons in certain disordered dielectric superlattices. Physical Review Letters 1987, 58, (23), 2486. 11. Míguez, H.; Yang, S. M.; Tétreault, N.; Ozin, G. A., Oriented Free‐Standing Three‐Dimensional Silicon Inverted Colloidal Photonic Crystal Microfibers. Advanced Materials 2002, 14, (24), 1805-1808. 12. ‖, S. Y. C., †,; Marc Mamak, ⊥; ‡, G. V. F.; Naveen Chopra, A.; †, G. A. O., Mesoporous Bragg Stack Color Tunable Sensors. Nano Letters 2006, 6, (11), 24562461. 13. Shopsowitz, K. E.; Qi, H.; Hamad, W. Y.; Maclachlan, M. J., Free-standing mesoporous silica films with tunable chiral nematic structures. Nature 2010, 468, (7322), 422. 14. Khan, M. K.; Giese, M.; Yu, M.; Kelly, J. A.; Hamad, W. Y.; Maclachlan, M. J., Flexible mesoporous photonic resins with tunable chiral nematic structures. Angewandte Chemie 2013, 52, (34), 8921-4.

12


Page 12 of 15

Page 13 of 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


15. Shopsowitz, K. E.; Hamad, W. Y.; Maclachlan, M. J., Flexible and Iridescent Chiral Nematic Mesoporous Organosilica Films. Journal of the American Chemical Society 2012, 134, (2), 867. 16. Lee, G. H.; Choi, T. M.; Kim, B.; Han, S. H.; Lee, J. M.; Kim, S. H., Chameleon-Inspired Mechanochromic Photonic Films Composed of Nonclose-Packed Colloidal Arrays. Acs Nano 2017. 17. Vigneron, J. P.; Pasteels, J. M.; Windsor, D. M.; Vértesy, Z.; Rassart, M.; Seldrum, T.; Dumont, J.; Deparis, O.; Lousse, V.; Biró, L. P., Switchable reflector in the Panamanian tortoise beetle Charidotella egregia (Chrysomelidae: Cassidinae). Physical Review E Statistical Nonlinear & Soft Matter Physics 2007, 76, (1), 031907. 18. Rassart, M.; Colomer, J. F.; Tabarrant, T.; Vigneron, J. P., Diffractive hygrochromic effect in the cuticle of the hercules beetle Dynastes hercules. New Journal of Physics 2008, 10, (3), 033014. 19. Kasukawa, H.; Oshima, N.; Fujii, R., Mechanism of light reflection in blue damselfish motile iridophore. Zoological Science 1987, 4, (2), p243-257. 20. Rånby, B. G., III. Fibrous macromolecular systems. Cellulose and muscle. The colloidal properties of cellulose micelles. Discuss:faraday Soc 1951, 11, 158-164. 21. Fernandes, S. N.; Almeida, P. L.; Monge, N.; Aguirre, L. E.; Reis, D.; de Oliveira, C. L.; Neto, A. M.; Pieranski, P.; Godinho, M. H., Mind the Microgap in Iridescent Cellulose Nanocrystal Films. Advanced Materials 2017, 29. 22. Giese, M.; Khan, M. K.; Hamad, W. Y.; Maclachlan, M. J., Imprinting of Photonic Patterns with Thermosetting Amino-Formaldehyde-Cellulose Composites. Acs Macro Letters 2013, 2, (9), 818-821. 23. Dongxue, M.; Gray, D. G., Induced Circular Dichroism of Isotropic and Magnetically-Oriented Chiral Nematic Suspensions of Cellulose Crystallites. Langmuir 1997, 13, (11), 3029-3034. 24. Beck, S.; Bouchard, J.; Berry, R., Controlling the reflection wavelength of iridescent solid films of nanocrystalline cellulose. Biomacromolecules 2011, 12, (1), 167-72. 25. Liu, D.; Wang, S.; Ma, Z.; Tian, D.; Gu, M.; Lin, F., Structure–color mechanism of iridescent cellulose nanocrystal films. Rsc Advances 2014, 4, (74), 39322-39331. 26. Revol, J. F. C. O.; Godbout, D. L.; Gray, D. G., Solidified liquid crystals of cellulose with optically variable properties. In EP: 1997. 27. Espinha, A.; Guidetti, G.; Serrano, M. C.; Frka-Petesic, B.; Dumanli, A. G.; Hamad, W. Y.; Blanco, Á.; López, C.; Vignolini, S., Shape Memory Cellulose-Based Photonic Reflectors. Acs Applied Materials & Interfaces 2016, 8, (46), 31935. 28. Bardet, R.; Belgacem, N.; Bras, J., Flexibility and color monitoring of cellulose nanocrystal iridescent solid films using anionic or neutral polymers. Acs Appl Mater Interfaces 2014, 7, (7), 4010-8. 29. Zhang, Y. P.; Chodavarapu, V. P.; Kirk, A. G.; Andrews, M. P., Structured color humidity indicator from reversible pitch tuning in self-assembled nanocrystalline cellulose films. Sensors & Actuators B Chemical 2013, 176, (6), 692-697. 30. Zhao, Y.; Gao, G.; Liu, D.; Tian, D.; Zhu, Y.; Chang, Y., Vapor sensing with color-tunable multilayered coatings of cellulose nanocrystals. Carbohydr. Polym. 2017, 174, 39-47. 31. Michael, G.; Blusch, L. K.; Khan, M. K.; Hamad, W. Y.; Maclachlan, M. J., Responsive mesoporous photonic cellulose films by supramolecular cotemplating. Angewandte Chemie 2014, 53, (34), 8880-8884. 32. Yao, K.; Meng, Q.; Bulone, V.; Zhou, Q., Flexible and Responsive Chiral Nematic Cellulose Nanocrystal/Poly(ethylene glycol) Composite Films with Uniform and Tunable Structural Color. Advanced Materials 2017, 29, (28). 13



33. Dong, B. Q.; Liu, F.; Zi, J.; Liu, X. H.; Zheng, Y. M., Structural color change in longhorn beetles Tmesisternus isabellae. Optics Express 2009, 17, (18), 16183-91. 34. Xie, D. Y.; Song, F.; Zhang, M.; Wang, X. L.; Wang, Y. Z., Soy protein isolate films with improved property via a facile surface coating. Industrial Crops & Products 2014, 54, (2), 102-108. 35. Xue, J.; Song, F.; Yin, X. W.; Zhang, Z. L.; Liu, Y.; Wang, X. L.; Wang, Y. Z., Cellulose Nanocrystal-Templated Synthesis of Mesoporous TiO2 with Dominantly Exposed (001) Facets for Efficient Catalysis. Acs Sustainable Chemistry & Engineering 2017, 5, (5). 36. Herlant, M., Effect of Arabic gum, xanthan gum and orange oil contents on ζpotential, conductivity, stability, size index and pH of orange beverage emulsion. Colloids & Surfaces A Physicochemical & Engineering Aspects 2008, 315, (1–3), 4756. 37. Stephanie Beckcandanedo; Maren Roman, A.; †, D. G. G., Effect of Reaction Conditions on the Properties and Behavior of Wood Cellulose Nanocrystal Suspensions. Biomacromolecules 2005, 6, (2), 1048-1054. 38. Xue, M. D.; Revol, J. F.; Gray, D. G., Effect of microcrystallite preparation conditions on the formation of colloid crystals of cellulose. Cellulose 1998, 5, (1), 19-32. 39. Dong, X. M.; Kimura, T.; Revol, J. F.; Gray, D. G., Effects of Ionic Strength on the Isotropic−Chiral Nematic Phase Transition of Suspensions of Cellulose Crystallites. Langmuir 1996, 12, (8), 2076-2082. 40. Vries, H. D., Rotatory Power and Other Optical Properties of Certain Liquid Crystals. Acta Crystallographica 1951, 4, (3), 219–226. 41. Vollick, B.; Kuo, P.-Y.; Thérien-Aubin, H.; Yan, N.; Kumacheva, E., Composite Cholesteric Nanocellulose Films with Enhanced Mechanical Properties. Chemistry of Materials 2017, 29, (2), 789-795. 42. Liu, P.; Guo, X.; Nan, F.; Duan, Y.; Zhang, J., Modifying Mechanical, Optical Properties and Thermal Processability of Iridescent Cellulose Nanocrystal Films Using Ionic Liquid. Acs Appl Mater Interfaces 2016, 9, (3).

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Biomimetic Optical Cellulose Nanocrystal Films with Controllable

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