Microstructural and optical investigations on sonochemically synthesized Cu doped ZnO nanobricks

Abstract Copper doped ZnO (ZnO:Cu) nanoparticles were synthesized by sonochemical method varying the doping concentration. Copper nitrate was taken as the dopant source and its concentration was varied as 0.001, 0.002 and 0.003 M and added to 0.2 M zinc nitrate to prepare ZnO:Cu nanoparticles. Systematic investigations like X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) were carried out to understand the microstructural properties. XRD result revealed the formation of wurtzite phase of ZnO with average crystallite size in the range of 23–57 nm. Further, an increase in the crystallite size of ZnO:Cu was observed with the increase in doping concentration. The result obtained from XRD was also supported by the results obtained from electron microscopic measurements. Moreover, formation of brick like nanostructures of ZnO:Cu was observed from the images obtained from these studies. X-ray photo-electron spectroscopic (XPS) studies showed the presence of Cu 2p levels in the spectra. This confirmed the divalent state of Cu ions in ZnO. UV absorption spectra revealed the absorption wavelength around 370 nm with a remarkable red shift of absorption band with the increase in doping concentration. But, the Fourier transform infrared (FTIR) spectroscopy showed a linear decrease in transmittance of IR light with increasing Cu content in ZnO. Photo-luminescence (PL) spectra recorded at two excitation wavelengths such as; 293 and 354 nm showed prominent emission bands in the UV and visible regions among which the blue emission is dominant. This has been well supported by the XPS data.