Upconversion enhancement of NaYF4:Yb3+, Tm3+ by coupling with broadband plasmonic Ag nanowires antenna

Abstract Low luminescent intensity/efficiency of upconversion nanocrystals (UCNCs) seriously limits its practical application in energy harvesting and biodetection etc. The surface plasmon modulation based on plasmonic metallic nanostructure is a promising way to largely enhance the luminescent intensity/efficiency of UCNCs. Herein, the silver nanowire network (AgNW-net)/NaYF4:Yb3+, Tm3+ composite film was prepared by the simple drop-casting method. The plasmonic AgNW-ner antenna demonstrates super-broad surface plasmon extinction band extending from 300 nm to 2500 nm, covering the excitation/emission wavelengths of UCNCs. An optimum UCL enhancement as high as 28 folds for UC visible emission and 5 folds for down-conversion near infrared emission were realized by optimizing the size of UCNCs and the excitation power. Systematic experimental studies indicate that the luminescent enhancement is due to excitation filed enhancement instead of Purcell effect. This finding provides a potential composite for harvesting near infrared solar energy.