title: Monodispersed LaF3 nanocrystals: shape-controllable synthesis, excitation-power-dependent multi-color tuning and intense near-infrared upconversion emission.
abstract: In this study, monodispersed and high-quality hexagonal phase LaF3 nanocrystals with different shapes and sizes were synthesized by a solvothermal method using oleic acid as the stabilizing agent. The as-prepared LaF3 nanocrystals were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD), and analysis of the upconversion spectra. The TEM results reveal that the samples present high uniformity and monodispersity and are self-assembled into a two-dimensional ordered array. Moreover, the shape, size and structure of the nanocrystals can be readily tuned by adjusting the NaF content. With increasing content of NaF, the shape of the LaF3 nanocrystals changed from particle to rod and the size gradually increased. More importantly, high NaF content favors the formation of one-dimensional nanorods. High Y b(3+) and Er(3+) content is beneficial to synthesizing the hexagonal phase of NaLaF4 nanocrystals. Furthermore, the TEM results show that the shape and size of the LaF3 nanocrystals can also be tuned by doping lanthanide ions, which provides a new route for size and shape control of nanocrystals. In addition, LaF3 nanocrystals co-doped with Y b(3+)/Tm(3+) present efficient near-infrared (NIR)-NIR upconversion luminescence. More importantly, the upconversion luminescent colors can be readily tuned from blue-white to blue by adjusting the excitation power. Therefore, it is expected that these LaF3 nanocrystals with well-controlled shape, size and NIR-NIR upconversion emission have potential applications in biomedical imaging fields.
authors.affiliation: College of Physics and Information Science and Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of the Ministry of Education, Hunan Normal University, Changsha, Hunan, People's Republic of China. Faculty of Materials, Optoelectronics and Physics, Key Laboratory of Low-dimensional Materials and Application Technology (Ministry of Education), Xiangtan University, Xiangtan 411105, People's Republic of China.
authors.forename: Ling
authors.initials: L
authors.lastname: Rao
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Guozhong
authors.initials: G
authors.lastname: Ren
authors.forename: Haibo
authors.initials: H
authors.lastname: Wang
authors.forename: Zhigao
authors.initials: Z
authors.lastname: Yi
authors.forename: Hongrong
authors.initials: H
authors.lastname: Liu
authors.forename: Songjun
authors.initials: S
authors.lastname: Zeng
mesh_terms: D003116:Color; D003460:Crystallization; D003952:Diagnostic Imaging; D005459:Fluorides / Q000737:chemistry*; D007477:Ions; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D049449:Luminescence; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry*; D019301:Oleic Acid / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D019265:Spectroscopy, Near-Infrared; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D007477:Ions; D028581:Lanthanoid Series Elements; D010087:Oxides; D012997:Solvents; C083668:lanthanum trifluoride; D019301:Oleic Acid; D007811:Lanthanum; D005459:Fluorides