Co2+ doped ZnO nanoflowers grown by hydrothermal method

Undoped zinc oxide (ZnO) and cobalt doped ZnO nanostructures without any surfactant were grown by hydrothermal method by varying the process parameters such as molarity of precursors and time of growth. X-ray diffraction spectra of the sample show wurtzite ZnO without any secondary Co phases. SEM image confirms the formation of hexagonal shaped rods and these rods assembled like a flower. Inductively coupled plasma atomic emission spectroscopic (ICP AES) studies confirm the incorporation of cobalt in the ZnO nanostructures. The electronic structure as well as the optical properties of ZnO:Co2+ have been characterized. In the energy range below the band gap, the optical absorption spectra show the internal d–d transitions related to Co2+ incorporated on the Zn site in ZnO lattice. The g-values of ZnO:Co samples obtained from electron paramagnetic resonance confirms the incorporation of Co2+ in ZnO. Photoluminescence (PL) studies shows that these nanostructures exhibit a blue luminescence on excitation with wavelength 350 nm due to the Zn interstitial related defects.