Embedding Ag or Au nanoparticles within the nano-sized wall of YbPO4:Er3+ inverse opals and resulting enhanced upconversion luminescence

Metal nanoparticles preparation in the interior of nanoscale skeleton of inverse opals made up of crystallized matrix is more difficult than the preparation of pure inverse opals. In the present work, the Ag or Au nanoparticles embedded YbPO4:Er3+ inverse opals were prepared by a simple approach, which involved the infiltration of opal template by using the transparent YbPO4:Er3+ sol including silver nitrate or chloroauric acid and the sintering at high temperature. The 20-30 nm Au or 5-10 nm Ag nanoparticles were formed in the interior of nanoscale skeleton in the YbPO4:Er3+ inverse opals, and the Ag or Au nanoparticles embedded YbPO4:Er3+ inverse opals were prepared. The influence of Ag or Au nanoparticles on the upconversion photoluminescence of YbPO4:Er3+ inverse opal was studied, and the upconversion luminescence enhancement induced by the Ag or Au nanoparticles was observed. The mechanisms of upconversion luminescence enhancement of YbPO4:Er3+ inverse opals induced by Ag or Au nanoparticles were discussed. The enhancement of upconversion luminescence induced by Ag nanoparticles was attributed to the enhancement of the excitation field, and the enhancement of upconversion emission induced by Au nanoparticles was related to the increasing of the radiation decay rate of Er3+.