Remarkably enhanced upconversion luminescence in hybrid of Ag film/colloidal crystal/NaYF4:Er/Yb nanorods

NaYF4:Er/Yb nanorods, colloidal crystal (CC) and Ag nanoparticles were obtained by solvothermal, self-assembly and hydrothermal methods, respectively. The hybrid structure of NaYF4:Er/Yb nanorods-colloidal crystal-Ag film (Ag-CC-NaYF4:Er/Yb) with low cost and large area was prepared for upconversion luminescence (UCL). The UCL enhancement was achieved by synergistic use of local reflection of incident light by colloidal crystal and reflection of incident light by Ag film. Compare with that of NaYF4:Er/Yb nanorods, the UCL intensity of Ag-CC-NaYF4:Er/Yb was increased by 33.2-folds. The UCL enhancement mechanism in Ag-CC-NaYF4:Er/Yb was investigated systematically. Our work has certain guiding value for promoting the application of upconversion nanocrystals in the fields of anti-counterfeiting, biological imaging, display and so on.