title: Facile synthesis of intense green light emitting LiGdF4:Yb,Er-based upconversion bipyramidal nanocrystals and their polymer composites.
abstract: A pathway for achieving intense green light emitting LiGdF4:Yb,Er upconversion nanophosphors (UCNPs) via Y(3+) doping is demonstrated. It was revealed that Y(3+) doping initiated the formation of a tetragonal phase and affected the particle size. Single tetragonal-phase LiGd0.4Y0.4F4:Yb(18%),Er(2%) (LGY0.4F:Yb,Er) UCNPs exhibited strong upconversion (UC) green luminescence and tetragonal bipyramidal morphologies. They showed 1325 and 325-fold higher photoluminescence intensity than the 0 and 80 mol% Y(3+)-doped LiGdF4:Yb,Er UCNPs, respectively. Additionally the particle size (edge length) of LiGdF4:Yb,Er-based upconversion tetragonal bipyramids (UCTBs) was controlled from 60.5 nm to an ultrasmall size of 9.3 nm with varying Y(3+) doping concentration. In an LGY0.4F:Yb,Er UCTB, uniform distribution of all constituent elements was directly confirmed by using high-angle annular dark-field scanning transmission electron microscopy and energy-filtered transmission electron microscopy (EFTEM) image analyses. In particular, existence of activator Er(3+) ions with extremely small quantity was clearly seen over a particle on the EFTEM image. Moreover, the LGY0.4F:Yb,Er UCTBs were successfully incorporated into the polydimethylsiloxane (PDMS) polymer and the highly transparent UCTB-PDMS composites showed bright green light under the excitation of 980 nm infrared light.
authors.affiliation: Molecular Recognition Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea. msekorea@kist.re.kr.
authors.forename: Hyejin
authors.initials: H
authors.lastname: Na
authors.forename: Jong Seok
authors.initials: JS
authors.lastname: Jeong
authors.forename: Hye Jung
authors.initials: HJ
authors.lastname: Chang
authors.forename: Hyun You
authors.initials: HY
authors.lastname: Kim
authors.forename: Kyoungja
authors.initials: K
authors.lastname: Woo
authors.forename: Kipil
authors.initials: K
authors.lastname: Lim
authors.forename: K Andre
authors.initials: KA
authors.lastname: Mkhoyan
authors.forename: Ho Seong
authors.initials: HS
authors.lastname: Jang