Optimization of sensitizer concentration for upconversion photoluminescence of Yb3+/Er3+: La10W22O81 nanophosphor rods. Issue 4 (15th February 2021) - Kumar, K. Naveen
Abstract: Yb 3+ /Er 3+ codoped La10 W22 O81 (LWO) nanophosphor rods have been successfully synthesized by a facile hydrothermal assisted solid state reaction method, and their upconversion photoluminescence properties were systematically studied. X-ray diffraction patterns revealed that the nanophosphors have an orthorhombic structure with space group Pbcn (60). A microflowers-like morphology with irregular hexagonal nanorods was observed using field emission scanning electron microscopy for the Yb 3+ (2 mol%)/Er 3+ (2 mol%):LWO nanophosphor. The shape and size of the nanophosphor and the elements along with their ionic states in the material were confirmed by TEM and XPS studies, respectively. A green upconversion emission was observed in the Er 3+ : LWO nanophosphors under 980 nm laser excitation. A significant improvement in upconversion emission has been observed in the Er 3+ : LWO nanophosphors by increasing the Er 3+ ion concentration. A decrease in the upconversion emission occurred due to concentration quenching when the doping concentration of Er 3+ ions was greater than 2 mol%. An optimized Er 3+ (2 mol%): LWO nanophosphor exhibited a strong near infrared emission at 1.53 μm by 980 nm excitation. The green upconversion emission of Er 3+ (2 mol%): LWO was remarkably enhanced by co-doping with Yb 3+ ions under 980 nm excitation because of energy transfer from Yb 3+ to Er 3+ . The naked eye observed this upconversion emission when co-doping with 2 mol% Yb 3+ . In order to obtain the high upconversion green emission, the optimized sensitizer concentration of Yb 3+ ions was found to be 2 mol%. The upconversion emission trends were studied as a function of stimulating laser power for an optimized sample. Moreover, the NIR emission intensity has also been enhanced by co-doping with Yb 3+ ions due to energy transfer from Yb 3+ to Er 3+ . The energy transfer dynamics were systematically elucidated by energy level scheme. Colorimetric coordinates were determined for Er 3+ and Yb 3+ /Er 3+ : LWO nanophosphors. The energy transfer mechanism was well explained and substantiated by several fluorescence dynamics of upconversion emission spectra and CIE coordinates. The results demonstrated that the co-doped Yb 3+ (2 mol%)/Er 3+ (2 mol%): LWO nanophosphor material is found to be a suitable candidate for the novel upconversion photonic devices.