Preparation of yttrium oxysulfide phosphor nanoparticles with infrared-to-green and -blue upconversion emission using an emulsion liquid membrane system

Abstract

Yttrium oxysulfide upconverting phosphor nanoparticles, doped with Yb as a sensitizer and Er (or Ho, Tm) as an activator, have been prepared via a solid–gas reaction using precursor oxalate particles obtained in an emulsion liquid membrane (ELM, water-in-oil-in-water (W/O/W) emulsion) system. The resulting Y 2O 2S:Yb, Er particles, mainly smaller than 50 nm in diameter, demonstrated green upconversion emission under infrared excitation ( λ ex=980 nm) via a two-photon process. Distinct green and blue upconversion emission were also demonstrated under the same infrared excitation from Y 2O 2S:Yb, Ho and Y 2O 2S:Yb, Tm nanoparticles, respectively. These upconverting phosphor nanoparticles, together with Y 2O 3:Yb, Er infrared-to-red upconverting phosphor particles, with different emission under the same infrared excitation may be applied to the luminescent reporter materials for the detection of the targeted analyte in multiplexed assays.