Microstructure, Optical and Electrical Properties of Cu-Cu₂O Core-Shell Nanostructures

Abstract

Composites of nanometre-sized copper core–copper oxide (Cu-Cu₂O) shell with different diameters were synthesized by a facile one step co-solvent technique. By the analysis of X-ray diffraction (XRD) and transmission electron microscope (TEM) data, the resultant particles were confirmed to be pure and nanocrystalline in nature. The perfect core-shell structure of nanocrystalline Cu-Cu₂O was confirmed by using high resolution TEM. The presence of pure Cu and Cu₂O was further confirmed from optical absorbance spectrum and Fourier transform infrared (FT-IR) spectroscopy. The tailoring of position of optical absorption peaks, originating from Cu or Cu₂O nanoparticles, is possible by modulating the oil to water ratio, which controls the size of the composite particles and thickness of Cu₂O. Drastic change of electrical resistivity with change in thickness of shell, has been observed. Variation of resistivity with temperature delineates a semiconducting nature with two distinct activation processes. Results demonstrate that the activation energies for the core-shell nanostructure composites were found to be smaller than the bulk Cu₂O. Photoluminescence spectrum further confirms the semiconducting nature of the composite. In addition, the kinetic of core-shell morphology formation is also discussed briefly.