Structure Color Tuners of Cholesteric Cellulose Nanocrystal

Abstract

The broad utility of cellulose nanocrystals (CNCs) as green, vivid, and long-term photonic films is restricted by their coloration instability and limited gamut. Herein, four polyols, two monosaccharides, two organic acids, and four amino acids were doped into a CNC for a detailed structure and color hue investigation. The results show that polyols and saccharides bearing neural multihydroxyl groups promoted a doping-amount-dependent red-shift reflection. Polyols were also found to improve the flexibility of CNCs as effective plasticizers. Organic tartaric or malic acid showed effects on the overall blue shift although a switch from blue shift to red shift happened at a doping amount of 8 wt %. Nevertheless, amphoteric amino acids with multifunctional groups show limited regulating effects due to their poor compatibility and complicated interactions with CNCs. Therefore, acidic or alkaline functional groups, the isoelectric point, a compatible saccharide ring, the molecular weight, and crystallization of dopants are crucial factors for tuning the structure and properties of CNCs.

Design of experiments to investigate multi-additive cellulose nanocrystal films

“…Since the glucose and glycerol coefficients are negative, the effects of glucuronic acid are interpreted as dominant. This is very unlike the behavior of organic acids of similar size used in another work, where even films with a high concentration retained their chiral nematic organization (Li et al, 2021). The reason for this discrepancy could be that the CNCs used by Li et al (2021).…”

“…This is very unlike the behavior of organic acids of similar size used in another work, where even films with a high concentration retained their chiral nematic organization (Li et al, 2021). The reason for this discrepancy could be that the CNCs used by Li et al (2021). were in acidic form, resulting in a higher association of protons to the organic acids as the suspension is concentrated.…”

“…Xu et al, (2018) observed redshifts to wavelengths up to 834 nm and a significant plasticizing effect with glycerol contents of 10-40 wt%, attributing the result to glycerol acting as a spacer. Although not directly addressed in the literature, we hypothesize that LBG adsorption may screen the chiral interactions between twisted CNC, whereas glucuronic acid is hypothesized to influence CNC self-assembly in a concentration-dependent manner, like other organic acids (Li et al, 2021) or blue dextran (Beck-Candanedo et al, 2006).…”

Cellulose Nanocrystals for Environment-Friendly Self-Assembled Stimuli Doped Multisensing Photonics

“…Li et al 78 investigated the effect on structural coloration variation when four polyols, two monosaccharides, two organic acids, and four amino acids were used as dopants into the photonic CNC films. Tuning parameters such as the shift in maximum wavelength, brightness, reflectivity, and bandwidth depended on doping amount and the extent of H-bonding, attraction, or repulsive forces.…”

A Surface Diffusion Barrier Strategy toward Water-Resistant Photonic Materials for Accurate Detection of Ethanol

“…Structural colors widely found in a variety of organisms in nature, including fishes, insect shells, bird feathers, and other objects, arise from interactions of visible light with periodic structures of solid surfaces. − Unlike pigmentary colors, structural colors have advantages of long-term stability, environment-friendliness, and high controllability, showing broad application prospects in displays, decoration, anti-counterfeiting, , and sensing. , As a natural polymer, cellulose nanocrystals (CNCs) obtained by acidolysis of cellulose can form a left-handed helical structure via evaporation-induced self-assembly (EISA), thus becoming one of the most important candidates to prepare optical materials with brilliant structural colors. , Currently, the structural colors of CNCs have been regulated by some physical and chemical approaches, including suspension concentrations, evaporation rates, magnetic fields, electric fields, etc. Colloidal stability of CNC suspension is fundamental for developing structural color films, so for the blending approach, only hydrophilic compounds can be selected to incorporate into the CNC suspension, such as PEG, PVA, water-soluble polysaccharides, − and polyols. − The resulting blend films have tunable structural colors. However, due to the high sensitivity of CNC-based films for water, structural colors are easily affected by the environmental humidity.…”