Near-IR Emission and upconversion luminescent properties of Tb3+/Yb3+ Co-doped HfO2/SiO2 nanoparticles

Abstract The luminescent characteristics of spherical hafnia/silica (HfO2/SiO2) nanoparticles (NPʼs) co-doped with Tb3+/Yb3+ were analysed. These NPʼs were synthesized using the spray pyrolysis technique. The addition of SiO2 and Tb3+/Yb3+ was found to induce a cubic phase in HfO2. The luminescent spectra presented the characteristic emission peaks for inter-electronic energy levels transitions of the Tb3+ and Yb3+ ions, with an excitation band centred at 270 nm. Under solid-state laser excitation at 980 nm an upconversion emission related to the Tb3+ ion was observed. The maximum emission peak in the visible region was at 543 nm, associated with 5D4 → 7F5 transitions of the Tb3+ ions and an IR emission peak at 970 nm (2F5/2 → 2F7/2) pertaining to Yb3+, with irradiation at 270 nm (UV). The energy transfer mechanism from Tb3+→Yb3+ (excitation at 270 nm), is discussed based on the time decay of the luminescence intensity analysis and the energy transfer efficiency (ηET) and was determined to be in the range of 29.2%–40.8%.