Upconversion emission enhancement by porous silver films with ultra-broad plasmon absorption

Abstract

Abstract: Surface plasmon effects of Ag nanostructures are being extensively applied to enhance upconversion (UC) luminescence properties of rare-earth-ion-doped nanoparticles. However, the plasmonic absorption bands from various Ag nanostructures are generally located at a visible region that cannot couple effectively with the 980 nm near infrared excitation light, resulting in a smaller UC emission enhancement factor. In this paper, we present a facile method to fabricate the porous Ag films with tunable and ultra-broad surface plasmonic absorption by using a polystyrene microsphere as a hard template, and then investigate the influence of tunable surface plasmonic absorption (SPA) on the UC emission. About 10 and 60-fold UC emission enhancement of NaYF4: Yb3+, Er3+ nanoparticles was obtained on the Ag films with narrow and ultra-broad SPA ranging from 350 to 1400 nm, respectively. The UC emission increases 60 fold at the surface of porous Ag film with the ultra-broad plasmonic absorption, which is attributed to efficient coupling between the ultra-broad SPA and the 980 nm near infrared excitation light and UC emission. The results demonstrate Ag film with ultra-broad plasmonic absorption is more appropriate as a substrate for the enhancement of UC emission in comparison with the narrow plasmonic absorption Ag film.