Influence of metal (Ag, Cd, Cu)-doping on the optical properties of ZnO nanopowder: Variation of band gap

Metal doped ZnO (MZO, metal = Ag, Cd, Cu) with different metal ion doped concentrations were synthesized by sol-gel method. The structural and optical properties were characterized by UV–Vis spectroscopy and Fourier transform infrared (FT-IR). With metal ion doping content increase, a red shift in band gap is observed. The red shift in band edge absorption peak in UV-Vis absorbance spectrum with increasing metal content also confirm the doping of metal in ZnO nanostructure. The band gap of ZnO resistivity was also changed according to the metal doping amounts and a kind of dopant. The results showed that each metal ion that has closer ionic radius to Zn 2+ could change optical band gap more than other.