Structural and optical properties of ZnO nanoclusters supported on mesoporous silica

Abstract

This paper reports on structural and optical properties of ZnO nanoclusters embedded in mesoporous silica (MPS) an inorganic host matrix. Small angle X-Ray Diffraction (SAXRD), Wide angle X-Ray Diffraction (XRD), N2-Sorption (BET), Scanning Electron Microscopy/Energy Dispersive spectroscopy (SEM/EDS), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet – visible spectroscopy (UV–Vis.) and Photoluminescence (PL) spectroscopy were used to characterize the samples. The UV-Vis absorption and PL spectra show a strong blue shift due to the quantum confinement effect of ZnO semiconductor nanoparticles. On excitation with 318 nm light source, ZnO/MPS nanocomposite shows emission peaks at 344, 372, 455, 485 and 512 nm. The emission peaks at 372 and 485 nm are the contribution of mesoporous silica. The PL band at 344 nm is attributed to the band gap luminescence of ZnO which is smaller than the previous reports. We suppose that the emission at 455 nm is not the blue shifted green emission but it is due to the formation of Zn-O-Si bonds at the interface. Singly ionized oxygen vacancies in ZnO nanocrystals are responsible for the green emission at 512 nm..