Unidirectional Alignment of Surface-Grafted ZnO Nanorods in Micrometer-Thick Cells Using Low-Molecular-Weight Liquid Crystals.

Kaho Ogata,Kohsuke Matsumoto,Yoshiaki Kobayashi,Atsushi Shishido,Shoichi Kubo

doi:10.3390/molecules27030689

Kaho Ogata, Kohsuke Matsumoto + Show 3 more

Open Access

https://doi.org/10.3390/molecules27030689

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Abstract

Inorganic nanomaterials such as nanotubes and nanorods have attracted great attention due to their anisotropic properties. Although the alignment control of inorganic nanomaterials is key to the development of functional devices utilizing their fascinating properties, there is still difficulty in achieving uniform alignment over a large area with a micrometer thickness. To overcome this problem, we focused on liquid crystals (LCs) to promote the alignment of anisotropic nanomaterials, taking advantage of the cooperative motion of LCs. We present the uniform, one-dimensional alignment of ZnO nanorods along the direction of LCs in micrometer-thick cells by grafting nematic LC polymers from the nanorod surfaces to provide miscibility with the host LCs. Polarized optical microscopy and polarized UV–visible absorption spectroscopy revealed the unidirectional alignment of nematic LC polymer-grafted ZnO nanorods parallel to the nematic host LCs.

Highlights

Inorganic anisotropic nanomaterials such as nanotubes and nanorods have attracted great attention due to their remarkable properties derived from their size effects and anisotropic shapes, such as electrical conductivity [1,2], optical properties of polarized emission and absorption [3,4], and thermal conductivity [5,6]
Liquid Crystalline Behavior of the Nematic liquid crystals (LCs) Host Dispersed with LC Polymer-Grafted Nanorods
We anticipated the alignment of nanorods by the cooperative interaction of host LCs and nematic LC polymer grafted from nanorod surfaces

Summary

Introduction

Inorganic anisotropic nanomaterials such as nanotubes and nanorods have attracted great attention due to their remarkable properties derived from their size effects and anisotropic shapes, such as electrical conductivity [1,2], optical properties of polarized emission and absorption [3,4], and thermal conductivity [5,6]. Vertically aligned nanorods on substrates have been fabricated by metal organic chemical vapor deposition [13,14], pulsed laser deposition [15], hydrothermal growth [16], chemical bath deposition [17], surfactant-assisted sol–gel processes [18], and dopant mediated assembly [19] All these methods are applicable to substrates satisfying the condition of the controlled growth of materials. The formation of lyotropic LCs from nanorods modified with block copolymers has been shown to utilize LC properties [31,32,33] These studies suggest that the control of interactions between nanorods and LCs is key to their alignment. We investigate the optical properties of the surface-modified nanorods in the host LCs in 5 μm-thick cells and demonstrate their unidirectional alignment in homogeneous and homeotropic manners

Results and Discussion

Homogeneous Alignment of ZnO Nanorods in Host LC

Materials

Sample Preparation