Structural and optical properties of Cu doped ZnO aerogels synthesized in supercritical ethanol

Abstract

Undoped and copper doped ZnO aerogels have been synthesized by the sol–gel method followed by supercritical drying in ethanol. The dopant contents in the aerogels were 1, 2, 3, 4 and 5 at.%. The as-obtained products were analyzed without any additional heat or chemical treatments. The XRD measurements revealed that aerogels have good polycrystalline ZnO hexagonal wurtzite structure with high crystalline quality. The data analysis showed that the crystallite sizes of ZnO and Cu-doped ZnO nanoparticles were within the range of 32–38 nm and the Cu dopant uniformly substitute for Zn sites. ATG measurements and EDAX studies showed that the aerogels have the extreme purity. SEM images revealed a snow-like morphology of the aerogels and the agglomeration state of the nanoparticles was not affected by Cu concentration. Optical absorption spectra showed a red shift of the absorption edge due to the merging of an impurity band into the conduction band. As the Cu content increases, the visible photoluminescence intensity decreases due to the scattering of the excitation radiation by surface-adsorbed dopant atoms and the non-radiative recombination process introduced by Cu impurity. The photoluminescence spectra of all aerogels showed one UV emission at 388 nm and a broad visible luminescence (490–650 nm) formed with two green (510 and 545 nm) and orange (612 nm) emissions. No shift observed with Cu concentration in emission positions in Cu-doped ZnO aerogels synthesized in supercritical ethanol.