Plasmonic enhancement of the upconversion fluorescence in YVO₄:Yb³⁺, Er³⁺ nanocrystals based on the porous Ag film.

The upconversion luminescence (UCL) enhancement based on the surface plasmonic resonance (SPR) of noble metals is a promising way to improve UCL efficiency. However, it is still a challenge to achieve stable and effective UCL enhancement. Here, we present the preparation of the porous Ag/YVO4:Yb(3+), Er(3+) composite film via a simple double annealing method. It is exciting to observe that a maximum 36-fold ((2)H11/2-(4)I15/2) and 30-fold ((4)S3/2-(4)I15/2) UCL enhancement in the porous Ag/YVO4:Yb(3+), Er(3+) composite film, attributed to the effective coupling between SPR and the excitation light by adjusting the SPR peak to the excitation wavelength, controlling the effective coupling distance and improving the scattering-absorption ratio. Furthermore, the enhancement factor strongly depended on the excitation power and the Er(3+) concentration.