Structural, optical and electron paramagnetic resonance studies on Cu-doped ZnO nanoparticles synthesized using a novel auto-combustion method

Nanocrystalline Zn1-xCuxO (x = 0, 0.02, 0.04, 0.06, 0.08) samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples were characterized using XRD, SEM, photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopies. The XRD spectra of samples reveal the hexagonal wurtzite structures of ZnO. As the copper content increases, a diffraction peak at 2 theta = 39 degrees corresponding to secondary phase of CuO ([111] crystalline face) appears when x <= 6 mol.%. PL spectra of the samples show a strong ultraviolet (UV) emission and defect related visible emissions. Cu-doping in ZnO can effectively adjust the energy level in ZnO, which leads to red shift in the emission peak position in UV region. The EPR spectra of Cu-doped ZnO nanoparticles show a distinct and broad signal at room temperature, suggesting that it may be attributed to the exchange interactions within Cu2+ ions.