Modified top-down approach for synthesis of molybdenum oxide quantum dots: sonication induced chemical etching of thin films

Abstract

A simple and modified top-down approach to synthesize molybdenum oxide (MoO _<i>x</i> : <i>x</i> = 2, 3) quantum dots (QDs) is proposed in this study. This modified approach involves the conversion of a bulk powder material into thin films followed by a sonication induced chemical etching process for synthesising QDs. X-Ray Diffraction (XRD) is used for crystal structural characterization of MoO _<i>x</i> thin films. The crystal structure properties of the MoO _<i>x</i> QDs are analysed by High Resolution Transmission Electron Microscopy (HRTEM) images and corresponding Selected Area Electron Diffraction (SAED) patterns. The optical band gap is estimated by Tauc's plot from UV-Vis-NIR absorption spectra. The excitation dependent photoluminescence (PL) emission of MoO _<i>x</i> QDs as a function of acid concentration is investigated. The growth mechanism of QDs in different crystalline phases as a function of acid concentration is also exemplified in this work. The micro-Raman and Fourier Transform of Infrared (FTIR) spectra are recorded to analyse the vibrational spectrum of the molybdenum-oxygen (Mo-O) bonds in the MoO _<i>x</i> QDs.