Due to their ability of emitting light at higher energy than the one used for excitation, rare earth-activated up-converting (UC) materials have attracted much attention of scientific and industrial interest. Their narrow emission bandwidth, long emission lifetime and impressive photo-stability permit them to have an enormous application including biomedicine, photodetector, light harvesting and color display. However, their poor luminescent efficiency limits the development of UC based technology. In this context, localized surface plasmon resonance (LSPR) has been demonstrated as an important strategy to improve UC fluorescence efficiency. Herein, we use LSPR induced by gold nanoparticles (NPs) to ameliorate UC photoluminescence (PL) of fluoride-oxyfluoride based nanophosphor transparent films. We provide a simple method to implant gold NPs in nanophosphor films through the preparation of a viscous paste made of both YF/YOF:Yb-Er UC and gold NPs. The LSPR of gold NPs is selected to be resonant with the emission band of UCNPs. We observe the UCPL enhancement and its plasmonic origin is confirmed by analyzing the emission spectra and the decay dynamics of gold-contained UC nanophosphor films. In addition, based on the changes obtained in the quadratic dependence of the UCPL intensity on the excitation power, we provide a discussion on the influence of LSPRs on the interplay between excitation and relation processes of UCNPs.

References.

1. Enhanced up-conversion photoluminescence in fluoride-oxyfluoride nanophosphor films by embedding gold nanoparticles. Thi Tuyen Ngo, Gabriel Lozano and Hernán Míguez. Under revision.

2. Highly Versatile Upconverting Oxyfluoride-Based Nanophosphor Films. Thi Tuyen Ngo, Elena Cabello-Olmo, Encarnación Arroyo, Ana I. Becerro, Manuel Ocaña, Gabriel Lozano and Hernán Míguez. ACS Appl. Mater. Interfaces 2021, 13, 25, 30051–30060