Nature463, 1061-1065 (25 February 2010) | doi:10.1038/nature08777; Received 25 June 2009; Accepted 15 December 2009
Simultaneous phase and size control of upconversion nanocrystals through lanthanide doping
Feng Wang1, Yu Han2, Chin Seong Lim3, Yunhao Lu4, Juan Wang1, Jun Xu5, Hongyu Chen5, Chun Zhang1,4, Minghui Hong3,6 & Xiaogang Liu1
Department of Chemistry, National University of Singapore, 117543, Singapore
Membrane Research Centre, Division of Chemical and Life Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
Optical Materials and Systems Division, Data Storage Institute, A*STAR, 117608, Singapore
Department of Physics, National University of Singapore, 117543, Singapore
Division of Chemistry and Biological Chemistry, Nanyang Technological University, 637371 Singapore
Department of Electrical and Computer Engineering, National University of Singapore, 117543 Singapore
Correspondence to: Xiaogang Liu1 Correspondence and requests for materials should be addressed to X.L. (Email: chmlx@nus.edu.sg).
Doping is a widely applied technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield hybrid materials with desirable properties and functions. For nanocrystalline materials, doping is of fundamental importance in stabilizing a specific crystallographic phase1, modifying electronic properties2, 3, 4, modulating magnetism5 as well as tuning emission properties6, 7, 8, 9. Here we describe a material system in which doping influences the growth process to give simultaneous control over the crystallographic phase, size and optical emission properties of the resulting nanocrystals. We show that NaYF4 nanocrystals can be rationally tuned in size (down to ten nanometres), phase (cubic or hexagonal) and upconversion10, 11, 12 emission colour (green to blue) through use of trivalent lanthanide dopant ions introduced at precisely defined concentrations. We use first-principles calculations to confirm that the influence of lanthanide doping on crystal phase and size arises from a strong dependence on the size and dipole polarizability of the substitutional dopant ion. Our results suggest that the doping-induced structural and size transition, demonstrated here in NaYF4 upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels12 to volumetric three-dimensional displays13.
