The up-conversion luminescent properties and silver-modified luminescent enhancement of YVO4:Yb3+, Er3+ NPs

Abstract

In this paper, the unique up-conversion luminescence (UCL) properties of as-prepared and annealing YVO₄:Yb³⁺, Er³⁺ nanoparticles (NPs, ∼100 nm) and the corresponding YVO₄:Yb³⁺, Er³⁺@Ag hybrids under 980 nm excitation were systemically studied through power-dependent, temperature-dependent emission spectra and dynamics. It is interesting to determine that the radiative transition rate of ²H_11/2/⁴S_3/2–⁴I_15/2 for Er³⁺ ions in YVO₄ is about an order of magnitude faster than that in the other hosts due to the wave function coupling with the 3d orbital of V⁵⁺ and, thus, the up-conversion (UC) green emissions of YVO₄:Yb³⁺, Er³⁺ NPs is efficient. In addition, efficient novel UC broad band centering around 630 nm (1.97 eV) was observed in YVO₄:Yb³⁺, Er³⁺ powders, which was attributed to defect emissions related to oxygen vacancies near V⁵⁺ sites in the lattices of YVO₄. In as-prepared YVO₄:Yb³⁺, Er³⁺@Ag hybrids colloids, more than one order UCL enhancement than YVO₄:Yb³⁺, Er³⁺ was observed. Powder and the annealing samples lead the UCL enhancement effect to disappear. The main UCL enhancement mechanism of YVO₄:Yb³⁺, Er³⁺@Ag hybrids colloids was attributed to prevent YVO₄:Yb³⁺, Er³⁺ interaction with the solution, instead of surface plasmon enhancement (SPE) effect.