Influence of doping group I elements on structural, optical and magnetic properties of nanocrystalline ZnO

Pure ZnO and group-I elements doped ZnO nanocrystals were synthesized by solution combustion method. The XRD analysis reveals that all the ZnO doped nanocrystals have hexagonal wurtzite crystal structure. Scanning electron microscopy reveals the growth of rod like structure for Na doped sample. The UV–Vis absorption results show that the band gap of ZnO doped nanocrystals is red shifted with decrease in crystallite size. A sharp peak at 434 cm−1 was observed in Raman spectra which correspond to the high frequency E2 mode of ZnO. Photoluminescence properties of pure and group-I elements doped ZnO nanocrystallites have strong blue emission at 421 nm. The peak positions were found to be almost same even after the addition of alkali metal ions owing to the variation in the nanostructure and difference in ionic radii. Vibrating sample magnetometer studies show that the doping of group-I elements show ferromagnetic behavior compared to pure ZnO samples which are paramagnetic. Our investigations make, hence, useful contributions to nano-photonics, luminescence and optoelectronic devices.