Abstract

Copper oxide and cobalt oxide (CuO, Co3O4) nanocrystals (NCs) have been successfully prepared in a short time using microwave irradiation without any postannealing treatment. Both kinds of nanocrystals (NCs) have been prepared using copper nitrate and cobalt nitrate as the starting materials and distilled water as the solvent. The resulted powders of nanocrystals (NCs) were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements. The obtained results confirm the presence of the both of oxides nanopowders produced during chemical precipitation using microwave irradiation. A strong emission under UV excitation is obtained from the prepared CuO and Co3O4 nanoparticles. The results show that the nanoparticles have high dispersion and narrow size distribution. The line scans of atomic force microscopy (AFM) images of the nanocrystals (NCs) sprayed on GaAs substrates confirm the results of both X‐ray diffraction and transmission electron microscopy. Furthermore, vibrational studies have been carried out using Raman spectroscopic technique. Specific Raman peaks have been observed in the CuO and Co3O4 nanostructures, and the full width at half maximum (FWHM) of the peaks indicates a small particle size of the nanocrystals.

Highlights

  • Nanocrystalline semiconductor particles have drawn considerable interest in recent years because of their special properties such as a large surface to volume ratio, increased activity, special electronic properties, and unique optical properties as compared to those of the bulk materials [1, 2]

  • The results show that the nanoparticles have high dispersion and narrow size distribution

  • The line scans of atomic force microscopy (AFM) images of the nanocrystals (NCs) sprayed on GaAs substrates confirm the results of both X-ray diffraction and transmission electron microscopy

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Summary

Introduction

Nanocrystalline semiconductor particles have drawn considerable interest in recent years because of their special properties such as a large surface to volume ratio, increased activity, special electronic properties, and unique optical properties as compared to those of the bulk materials [1, 2]. The oxides of transition metals represent an important class of semiconductors, which have applications in magnetic storage media, solar energy transformation, electronics, and catalysis [4]. CuO is known as ptype semiconductor, which makes it a promising material for gas sensors, magnetic storage media, solar energy transformation, electronics, semiconductors, varistors, and catalysis [7]. The CuO exhibits high activity for photocatalysis of H2 evolution reaction (HER) in oxalic acid solution under simulated sunlight irradiation [8]. Hybrid material consisting of Co3O4 nanocrystals grown on reduced graphene oxide is a high-performance bifunctional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) [10]. Microwave irradiation has shown very rapid growth in its application to material science due to its unique reaction effects such as rapid volumetric heating and the consequent dramatic increase in reaction rates. The product has good crystallinity, uniform morphology, and high purity as demonstrated by Xray diffraction, TEM, and Raman spectroscopy

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