Synthesis and Characterisation of ZnO and ZnO /Ag Nanocomposite for application in Optoelectronics

Abstract

ZnO nanoparticles are of significant interest as they provide many practical applications worldwide. Its wide energy bandgap makes it a good photocatalyst material for optoelectronic devices. However, one drawback of using ZnO is that it has some structural defects, such as Zn/oxygen vacancies and therefore have many mid-gap trap states, which through recombination reduces its photocatalyst performance. In this study, ZnO nanoparticles (NPs) was synthesised using hydrothermal method. The synthesised ZnO was doped with Ag plasmonic nanoparticles by the reduction of AgNO3 via a simple chemical reduction method in order to enhance its light absorbance. XRD and UV visible spectroscopic analysis were used to investigate the structural and optical properties of the synthesised ZnO and Ag doped ZnO. Structural analysis revealed that ZnO NPs had a wurtzite hexagonal structure evidenced by the three major wurtzite peaks. Two other additional peaks reveals the presence of Ag in the ZnO oxide lattice. The spectra exhibit the absorption band which is a characteristics of wurtzite crystal ZnO. The pure ZnO had its absorption peak at at 263 nm while for ZnO/Ag1 (0.1 mmol of AgNO3), ZnO/Ag2 (0.2mmol of AgNO3) and ZnO/Ag3 (0.1mmol of AgNO3) the peaks are at 264, 270 and 286 nm respectively. These shows that there was a shift in absorption peak to higher wavelength. ZnO/Ag composite had the highest absorption in both UV and visible spectrum. Bandgap reduction as obtained from Tauc’s plot revealed energy below the conduction band making the Ag doped ZnO a good material for application in optoelectronics.