title: 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(2)O(2)S:Yb,Er particles, mainly smaller than 50 nm in diameter, demonstrated green upconversion emission under infrared excitation (lambdaex = 980 nm) via a two-photon process. Distinct green and blue upconversion emission were also demonstrated under the same infrared excitation from Y(2)O(2)S:Yb,Ho and Y(2)O(2)S:Yb,Tm nanoparticles, respectively. These upconverting phosphor nanoparticles, together with Y(2)O(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.
authors.affiliation: Research Center for Solar Energy Chemistry and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. hirai@cheng.es.osaka-u.ac.jp
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hirai
authors.forename: Takuya
authors.initials: T
authors.lastname: Orikoshi