Utilisation of Cellulose Nanocrystals for the Fabrication of Photonic Materials
Colour in our world is everywhere, and it is a fundamental aspect of communication. In nature some colourations are particularly mesmerising, such as the shimmering patterns on the peacock feather and the metallic blue wings of the Morpho butterfly. These natural objects have vibrant colours and a metallic appearance due to light interference, in contrast to the colour obtained by dyes and pigments which rely on absorption. Such colours are referred to as ‘structural’ as they are the result of the interaction of light with periodic nanostructures. The same striking optical response can be obtained artificially by structuring materials on the same length scale. As an example, naturally derived cellulose nanocrystals (CNCs) can be self-assembled to form a helicoidal nanostructured film that displays vivid structural colours, similar to the those observed in nature. While in recent years, enormous effort in the field has increased our understanding of the fundamental interactions regulating the self-assembly of cellulose nanocrystals, many challenges still remain unsolved especially in the context of exploiting such building blocks for the fabrication of optical materials. This thesis investigates the self-assembly pathway of CNCs to gather a deeper understanding on their driving forces. This knowledge is then applied to devise new scalable fabrication methods, such as inkjet printing and electrodeposition, which allow for the successful production of photonic materials with a designed optical response. Finally, CNCs are successfully demonstrated to be an alternative stabiliser for aqueous dispersions of graphene, producing highly stable inks without the use of surfactants that can negatively impact the desired properties. These graphene inks are then implemented into CNC films to provide a high contrast absorbers emphasising their colour.
Cellulose nanocrystals, colloids, graphene, optics, structural colour, enviromental science, materials science, inkjet printing
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