Synthesize and Optical properties of ZnO: Eu Microspheres Based Nano-sheets at Direct and Indirect Excitation

Europium (Eu) doped ZnO microsphere based nano-sheets were synthesized through hydrothermal method. Effects of different concentrations of Europium on structural and optical properties of ZnO nano-sheets were investigated in detail. Prepared un-doped and Eu-doped ZnO samples were characterized using X-Ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy at fluorescence and phosphorescence modes. Results for XRD and EDX showed Eu ions were successfully incorporated into ZnO nanostructures. Fluorescence Spectroscopy indicated that indirect excitation of Eu ions was more effective than direct excitation, which is attributed to an efficient absorption process at UV wavelengths in ZnO host and energy transfer from photon generated electron-hole pair in the ZnO nano-sheets to Eu ions at indirect excitations. Phosphorescence spectroscopy also showed a sharp red luminescence from intra 4f transitions of Eu3+ ions at excitation wavelengths of 395nm and 464nm which was consistent with XRD and EDX results