Plasmonic materials with large chiroptical activity at visible wavelength have attracted considerable attention due to their potential applications in metamaterials. Here we demonstrate a novel guest–host chiral nematic liquid crystal film composed of bulk self-co-assembly of the dispersed plasmonic silver nanowires (AgNWs) and cellulose nanocrystals (CNCs). The AgNWs-CNCs composite films show strong plasmonic optical activities, that are dependent on the chiral photonic properties of the CNCs host medium and orientation of the guest AgNWs. Tunable chiral distribution of the aligned anisotropic AgNWs with long-range order is obtained through the CNCs liquid crystal mediated realignment. The chiral plasmonic optical activity of the AgNWs-CNCs composite films can be tuned by changing the interparticle electrostatic repulsion between the CNCs nanorods and AgNWs. We also observe an electromagnetic energy transfer phenomena among the plasmonic bands of AgNWs, due to the modulation of the photonic band gap of the CNCs host matrix. This facile approach for fabricating chiral macrostructured plasmonic materials with optically tunable property is of interest for a variety of advanced optics applications.Keywords: Cellulose nanocrystals; Chiroptical activity; Metamaterial; Plasmonic silver nanowires; Self-assembly;

Hierarchically nanostructured TiO2 has been hydrothermally synthesized using cellulose as a biotemplate involving various types of acids. We show that the surface charges of nanocrystalline cellulose and reaction parameters including reaction temperature, acid to cellulose ratio and reaction time have a large effect on the morphology and nanostructures of TiO2 products. The photocatalytic activity of as-synthesized, calcined hierarchically nanostructured TiO2 and calcined hierarchically nanostructured TiO2 loaded Au nanoparticles is evaluated by photo-degradation of methyl orange under white light.

The coupling between an inorganic nanostructure and a chiral molecule can give rise to a strong chiroptical response in a range from the UV to visible spectrum. In this work, novel plasmonic Ag@Ag3PO4 core–shell hybrid nanorods (CSHNRs) have been prepared via a wet chemical method. The cysteine molecules can adsorb on the surface of the plasmonic hybrid nanorods, leading to the appearance of new circular dichroism (CD) signals in the UV region. The Ag@Ag3PO4–cysteine CSHNRs show a similar CD spectrum to the Ag3PO4–cysteine polyhedral nanocrystals (PNCs), although they have different morphology and structure. The Ag@Ag3PO4–cysteine CSHNRs and Ag3PO4–cysteine PNCs have a stronger chiroptical response than the Ag–cysteine nanorods (NRs) attributed to the effect of phosphate groups. This indicates that the Ag+ ions on the surface of nanostructures can promote the formation of S–S bonds of oxidized cysteine under acidic conditions, rendering the uniformity of molecular conformation on the surface of nanostrucures, thus giving rise to the strong chiroptical response. Furthermore, the Ag@Ag3PO4 CSHNRs can spontaneously form a chiral liquid crystalline phase upon dispersion in the ethylene glycol solution owing to their large aspect ratio and the optimum solvating effect of ethylene glycol.

Helical core–satellite nanoarchitectures of AgNR@Cys@AuNPs have been successfully fabricated by self-assembly of Ag nanorods and Au nanoparticles, using l- and d-cysteine as bridging molecules, respectively. The chirality of the nanoarchitectures is confirmed by circular dichroism spectroscopy, and the results suggest that the chirality of nanoarchitectures relicates the l- and d-conformation of cysteine. The absorption peak of AgNR@Cys@AuNPs nanoarchitectures on the circular dichroism spectra shows a gradual red-shift with increasing cysteine concentration. The helical arrangement of Au nanoparticles in the nanoarchitectures is strongly dependent on the shape of Ag backbones and the cysteine concentration.

A novel silver cholesteric liquid crystalline (CLC) colloidal suspension has been fabricated by a shape-dependent self-assembly process via van der Waals and electrostatic interactions. The circular dichroism (CD) spectra show that the cysteine molecules have a strong effect on the as-obtained silver CLC structure, albeit it is very stable in the presence of many other kinds of amino acid molecules. The original silver CLC structure can be completely dissociated as soon as the concentration of cysteine solution arrives at a critical value. Furthermore, the cysteine molecules can translate their chirality to the silver nanorods (NRs) and silver nanoplates (NPs) by strong S–Ag bonds to form two novel chiral silver–cysteine nanocrystals, respectively. The colloidal suspension of silver–cysteine hybrid nanorods shows a much stronger CD intensity than the colloidal suspension of silver–cysteine hybrid nanoplates do, which can be attributed to its unique anisotropy of geometry and superficial constitution.