Phytochemical mediated synthesis of ZnO:Dy3+ nanophosphors: Judd–Ofelt analysis, structural and spectroscopic properties

In the present work, ZnO:Dy3+ nanophosphors were synthesized by a simple, cost effective and eco-friendly route using the aqueous extract of Azadirachta Indica leaves. The prepared ZnO:Dy3+ nanophosphors were characterized using X-ray diffraction (XRD), Fourier Transformed Infra-Red (FTIR), Raman, UV-VIS diffuse reflectance (UVDR) spectroscopy and Photoluminescence (PL), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). TEM and X-ray diffraction analyses reveal the hexagonal wurtzite structure of the ZnO nanoparticles in the prepared samples. UV-VIS-NIR spectrum of the ZnO:Dy3+ nanophosphor was analysed on the basis of Judd–Ofelt (J-O) theory and the J–O intensity parameters (Ωλ) were calculated. The radiative properties, such as radiative transition probability, branching ratio, stimulated emission cross-section and optical gain were investigated using the J–O intensity parameters. The photo luminescence emission spectra (PLE) of the Dy3+ doped samples exhibits three emission bands relative to 4F9/2→ 6H15/2 (478 nm), 4F9/2→ 6H13/2 (572 nm) and 4F9/2→ 6H11/2 (663 nm) transitions of Dy3+ ions respectively. The CIE chromaticity color coordinate shows that the ZnO:Dy3+ nanophosphors can be useful for white luminescence applications. The result indicates that the prepared phosphors produce white light emission and can be used for near ultraviolet excited white light emitting diode (NUV WLED) applications.