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(Dec. 12) Spectroscopic Studies of Europium-Doped Calcium Fluoride Nanoparticles

Last updated :2018-12-07

Topic: Spectroscopic Studies of Europium-Doped Calcium Fluoride Nanoparticle
Speaker: Professor Michael F. Reid
(University of Canterbury, New Zealand)
Host: Professor LIANG Hongbin
Time: 16:00-17:00, Wednesday, December 12, 2018
Venue: A402, Fulan Academic Center, Fong Shing Hall, Guangzhou South Campus, SYSU

Abstract:
Lanthanide-doped luminescent nanoparticles are important candidates for low-toxicity imaging agents and intracellular nano-thermometers for biomedical applications. Lanthanide ions doped into bulk CaF2 crystals are known to form a variety of sites, and to form clusters at concentrations as low as 0.01 mol%, becoming the dominant centre by 0.1 mol%. This clustering gives enhanced energy transfer, promising significant improvements in applications requiring up-conversion or down-conversion via energy transfer.

Previous work on lanthanide-doped CaF2 nanoparticles has made use of low-resolution spectroscopy at high temperatures, and was therefore unable to clearly discriminate between the different sites. Indeed, work on sodium-stabilized Eu3+-doped CaF2 nanoparticles makes the assumption that the sites are predominately C4v(F-), though sodium is known to suppress C4v(F-) sites in bulk crystals.

In this work we present high resolution laser spectroscopy of CaF2:Eu3+ nano-particles at cryogenic temperatures (10 K), including site-selective excitation, emission, and lifetime measurements. Samples include core-only and core-shell particles with a variety of concentrations and preparation techniques. C4v(F-) sites appear to be suppressed in these materials. An enhancement of Oh and C2v(Na+), sites, and evidence of cluster and surface sites is observed.

About the speaker:
In 1981, Professor Michael F. Reid obtained the Doctor of Philosophy Degree in University of Canterbury (New Zealand). After graduation, he has worded in University of Virginia for three years, then in University of Hong Kong for seven years. In 1993, he returned to New Zealand and worked in University of Canterbury. His main research interests are the electronic structure and the transition intensities of visible and UV transitions within 4fn configurations and between the 4fn and 4fn-15d configurations of lanthanide (rare-earth) ions in various compounds. Currently, he focuses on the understanding of materials that have potential for quantum-information applications, and on nanoparticles for biomedical imaging. Up to now, he has published more than 160 papers (eg: J. Phys. Chem. C; Phys. Rev. B: Condens. Matter; Appl. Phys. Lett.) and some chapters of several books. His researches are summarized in the following:
(1) Electronic structure and optical properties of lanthanide (rare-earth) materials;
(2) Quantum-information candidate materials;
(3) Nano-particles for biomedical imaging.