Optical and Structural Properties of Solvent Free Synthesized Starch/Chitosan-ZnO Nanocomposites

Anandhavelu Sanmugam,Dhanasekaran Vikraman,Hui Joon Park,Sethuraman Venkatesan

doi:10.1155/2017/7536364

Abstract

The objective of this work is to develop an environmentally friendly method for preparation of ZnO nanocomposites. ZnO nanocomposites were prepared by three natural fibers such as coir, sawdust, and chitosan using aqueous solution of zinc chloride and sodium hydroxide. The functional groups of ZnO, C=O for polysaccharide, and N-H bending vibration of amine were confirmed by FTIR spectroscopy. A new high intensity absorption band has been observed at 424 cm−1 which corresponds to the E2 mode of hexagonal ZnO. The crystallinity and phase formation of coir, chitosan, and sawdust combined ZnO nanocomposites were confirmed by X-ray diffraction patterns. XRD patterns revealed the polycrystalline nature of ZnO composites belonging to the hexagonal phase with (101) preferential lattice orientation. The microstructural parameters were calculated for coir, chitosan, and saw wood combined ZnO composites. Also texture coefficients were estimated for all the diffraction lines of ZnO based nanocomposites. SEM and TEM analyses confirmed evenly distributed nanosized grains in the ZnO composites. The UV-Vis absorption spectra were observed where the blue shift absorption peak was at 334 nm. The optical band gap values were estimated in the range of 3.18–3.26 eV. The emission peak was observed at ~388 nm and ~463 nm by photoluminescence spectroscopy.

Highlights

The ecofriendly chemical route preparation is a modern research trend for global warming prevention
The C-H stretching vibration peak is exhibited at 2926 cm−1 and this peak is slightly shifting towards higher wavenumber for sawdust-zinc oxide nanoparticles (ZnO) and chitosan-ZnO composites
The observed functional peaks at 1636 and 1562 cm−1 wavenumber are attributed to deformation vibrations of N-H bonds in primary amines as shown in Figure 2 shows the Xray diffraction (XRD) patterns of coir-ZnO, sawdustZnO, and chitosan-ZnO composites

Summary

Introduction

The ecofriendly chemical route preparation is a modern research trend for global warming prevention. The various types of metal oxide nanoparticles, such as zinc oxide nanoparticles (ZnO), have accomplished tremendous attention and have been widely utilized in a variety of applications including optical materials, cosmetics, functional devices, catalysts, and UV-absorbers. ZnO is a wide band gap (3.37 eV) semiconductor, which has been extensively investigated for various applications such as transparent conductive coatings [1], electrodes for dyesensitized solar cells [2], and gas sensors [3]. The wide band gap makes ZnO a good candidate for blue optoelectronic applications and their large exciton energy makes it possible to employ excitonic recombination process as lasing mechanism. Synthesis of ZnO nanoparticles in aqueous solution has advantages like simplicity, low cost, lower reaction temperature, and soluble materials whose surface functionalization can be investigated. Template-free solvothermal approach was employed for fabrication of large-scale olivelike ZnO nanoparticles which exhibit a very strong ultraviolet emission centered at 383 nm and a weak green luminescence emission at around 522 nm [4]

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