Spontaneous Co-Assembly of Cellulose Nanocrystals and TiO<sub>2</sub> Nanorods Followed by Calcination to Form Cholesteric Inorganic Nanostructures
Wenshi Zhang, Xinquan Cheng, Shaw H. Chen, Mitchell Anthamatten
Abstract
High Resolution Image Download MS PowerPoint Slide Chiral nanomaterials possess unique electronic, magnetic, and optical properties that are relevant to a wide range of applications including photocatalysis, chiral photonics, and biosensing. A simple, bottom-up method to create chiral, inorganic structures is introduced that involves the co-assembly of TiO 2 nanorods with cellulose nanocrystals (CNCs) in water. To guide experimental efforts, a phase diagram was constructed to describe how phase behavior depends on the CNCs/TiO 2 /H 2 O composition. A lyotropic cholesteric mesophase was observed to extend over a wide composition range as high as 50 wt % TiO 2 nanorods, far exceeding other examples of inorganic nanorods/CNCs co-assembly. Such a high loading enables the fabrication of inorganic, free-standing chiral films through removal of water and calcination. Distinct from the traditional templating method using CNCs, this new approach separates sol–gel synthesis from particle self-assembly using low-cost nanorods.