Aligning silver nanowire films with cellulose nanocrystal nematics

Abstract

Anisotropic plasmonic films are a desirable material for many optoelectronic applications. Here, we propose a method to align silver nanowires (AgNWs) with the help of uniaxial nematic alignment of cellulose nanocrystal (CNC) liquid crystals (LCs) that can preserve their LC orientation in solid film. AgNWs are doped into uniaxial nematic CNC LCs, where AgNWs are oriented parallel to the director of shear- aligned CNCs without aggregation. The AgNWs orientations are determined by polarized optical and dark field microscopic images. The alignment of AgNWs is characterized by the scalar order parameter S, and the measured S around 0.59 for aligned AgNWs presents an improved anisotropy with the assistance of uniaxial nematic CNC LCs. The electrical property of aligned AgNWs is examined by the four-probe method and exhibits the maximum ratio of anisotropic sheet resistance around 5, consistent with the simulated percolation probability performance using the Monte Carlo computation. Our results show that the uniaxial nematic CNC LCs can act as an effective template in aligning AgNWs, which is compatible with 3D printing and microfluidics, and allows for the preparation of low-cost, innovative optical materials and devices.

Aqueous Coassembly of Small TiO2 Nanorods with Cellulose Nanocrystals into Transparent, Uniaxially Aligned Inorganic Thin Films for Waveplates

“…It has been previously reported that CNCs can aid in aligning high-aspect-ratio nanowires by preventing aggregation and enhancing orientational order. 34,35 In our case, CNCs facilitate the alignment of much smaller nanorods under shear. Our observation of uniaxial alignment of coassembled composite system is consistent with oriented, low-aspect-ratio gold nanorods mixed with CNCs as demonstrated by Liu et al 20 Although Liu's study was limited to low loading of gold nanorods, they did not calcine the material to remove organics.…”