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Glitter is a type of microplastic, and thus there is a need to assess its potential impacts on the environment and to assess the potential for non-plastic cellulose nanocrystal structurally colored glitters as safe and sustainable replacements. The ecotoxicity of glitter has been mostly ignored in the research literature, with only a few published studies focusing on aquatic organisms. Therefore, an exposure experiment was conducted to examine the impact of conventional polyethylene terephthalate (PET) glitter as well as untreated and heat-treated cellulose nanocrystal (CNC) based glitter on the survival, reproduction, and length of Folsomia candida (springtail). Folsomia candida reproduction was reduced by 61% (P = 0.013) after exposure to PET glitter at 1000 mg/kg, while no significant effects were observed on F. candida survival and length. In contrast, there were no significant impacts on F. candida survival, length, or reproduction when exposed to untreated or heat-treated CNC glitter. These results indicate that exposure to PET glitter may impact soil invertebrates at the population level, and that CNC glitter has potential as a biodegradable non-plastic alternative to PET glitter to decrease detrimental effects on soil ecosystems., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Benjamin Droguet reports financial support was provided by UK Research and Innovation - Engineering and Physical Sciences Research Council. Silvia Vignolini reports financial support was provided by UK Research and Innovation - Engineering and Physical Sciences Research Council. Benjamin Droguet reports a relationship with Sparxell UK Limited that includes: employment and equity or stocks. Silvia Vignolini reports a relationship with Sparxell UK Limited that includes: equity or stocks and funding grants. Benjamin Droguet has patent #WO2023025863A1/GB2610186B pending to Sparxell UK Limited. Silvia Vignolini has patent #WO2023025863A1/GB2610186B pending to Sparxell UK Limited. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

To manipulate the light-matter interaction effectively, we often rely on high refractive index inorganic nanoparticles. Such materials are contained essentially in everything that looks colorful or white: from paints to coatings but also in processed food, toothpaste, and cosmetic products. As these nanoparticles can accumulate in the human body and environment, there is a strong need to replace them with more biocompatible counterparts. In this work, we introduce various types of cellulose-based microparticles (CMPs) of four sizes with optimized dimensions for efficient light scattering that can replace traditional inorganic particles. We demonstrate that the produced materials can be exploited as highly efficient scattering enhancers, with designed optical performance. Finally, exploiting these cellulose colloids, we fabricated scattering materials and high transmittance/haze films with record performances with respect to the state-of-the-art values. The renewable and biocompatible nature of our systems, combined with their excellent optical properties, allows for the use of our cellulose-based particles in paints, LEDs, and solar cell devices and especially in applications where the biocompatibility of the component is essential, such as in food and pharmaceutical coatings.

Cellulose nanocrystals are renewable plant-based colloidal particles capable of forming photonic films by solvent-evaporation-driven self-assembly. So far, the cellulose nanocrystal self-assembly process has been studied only at a small scale, neglecting the limitations and challenges posed by the continuous deposition processes that are required to exploit this sustainable material in an industrial context. Here, we addressed these limitations by using roll-to-roll deposition to produce large-area photonic films, which required optimization of the formulation of the cellulose nanocrystal suspension and the deposition and drying conditions. Furthermore, we showed how metre-long structurally coloured films can be processed into effect pigments and glitters that are dispersible, even in water-based formulations. These promising effect pigments are an industrially relevant cellulose-based alternative to current products that are either micro-polluting (for example, non-biodegradable microplastic glitters) or based on carcinogenic, unsustainable or unethically sourced compounds (for example, titania or mica)., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

The ability to manipulate the optical appearance of materials is essential in virtually all products and areas of technology. Structurally coloured chiral nematic cellulose nanocrystal (CNC) films proved to be an excellent platform to design optical appearance, as their response can be moulded by organising them in hierarchical architectures. Here, we study how thermal treatments influence the optical appearance of structurally coloured CNC films. We demonstrate that the CNCs helicoidal architecture and the chiral optical response can be maintained up to 250 °C after base treatment and cross-linking with glutaraldehyde, while, alternatively, an exposure to vacuum allows for the helicoidal arrangement to be further preserved up to 900 °C, thus producing aromatic chiral carbon. The ability to retain the helicoidal arrangement, and thus the visual appearance, in CNC films up to 250 °C is highly desirable for high temperature colour-based industrial applications and for passive colorimetric heat sensors. Similarly, the production of chiral carbon provides a new type of conductive carbon for electrochemical applications., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Hydroxypropyl cellulose (HPC) is an edible, cost-effective and widely used derivative of cellulose. Under lyotropic conditions in water, HPC forms a photonic, liquid crystalline mesophase with an exceptional mechanochromic response. However, due to insufficient physical cross-linking photonic HPC can flow freely as a viscous liquid, preventing the exploitation of this mechanochromic material in the absence of any external encapsulation or structural confinement. Here this challenge is addressed by mixing HPC and gelatin in water to form a self-supporting, viscoelastic, and edible supramolecular photonic hydrogel. It is demonstrated that the structural coloration, mechanochromism and non-Newtonian shear-thinning behavior of the lyotropic HPC solutions can all be retained into the gel state. Moreover, the rigidity of the HPC-gel provides a 69% shorter mechanochromic relaxation time back to its initial color when compared to the liquid HPC-water only system, broadening the dynamic color range of HPC by approximately 2.5× in response to a compressive pressure. Finally, the ability to formulate the HPC-gels in a scalable fashion from only water and "food-grade" constituents unlocks a wide range of potential applications, from response-tunable mechanochromic materials and colorant-free food decoration, to short-term sensors in, for example, biodegradable "smart labels" for food packaging., (© 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

As with many other biosourced colloids, chitin nanocrystals (ChNCs) can form liquid crystalline phases with chiral nematic ordering. In this work, we demonstrate that it is possible to finely tune the liquid crystalline behavior of aqueous ChNC suspensions finely. Such control was made possible by carefully studying how the hydrolysis conditions and suspension treatments affect the colloidal and self-assembly properties of ChNCs. Specifically, we systematically investigated the effects of duration and acidity of chitin hydrolysis required to extract ChNCs, as well as the effects of the tip sonication energy input, degree of acetylation, pH and ionic strength. Finally, we show that by controlled water evaporation, it is possible to retain and control the helicoidal ordering in dry films, leading to a hierarchical architecture analogous to that found in nature, e.g. in crab shells. We believe that this work serves as a comprehensive insight into ChNC preparation and handling which is required to unlock the full potential of this material in both a scientific and industrial context.

Cellulose nanocrystals (CNCs) form chiral nematic phases in aqueous suspensions that can be preserved upon evaporation of water. The resulting films show an intense directional coloration determined by their microstructure. Here, microreflection experiments correlated with analysis of the helicoidal nanostructure of the films reveal that the iridescent colors and the ordering of the individual nematic layers are strongly dependent on the polydispersity of the size distribution of the CNCs. We show how this affects the self-assembly process, and hence multidomain color formation in such bioinspired structural films.