%0 Journal Article
%T Intense Red Upconversion Emission and Shape Controlled Synthesis of Gd2O3:Yb/Er Nanocrystals
%A Zhigao Yi
%A Boyun Wen
%A Chao Qian
%A Haibo Wang
%A Ling Rao
%A Hongrong Liu
%A Songjun Zeng
%J Advances in Condensed Matter Physics
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/509374
%X Yb/Er codoped Gd(OH)3 was synthesized firstly via a simple hydrothermal treatment of the corresponding nitrate in the presence of alkali by tuning the pH values. The Gd2O3:Yb/Er nanocrystals were obtained via sintering the corresponding hydroxides precursors. The as-prepared samples were characterized by the typical X-ray diffraction, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, and spectrophotometer. The results revealed that two shapes of the as-prepared Gd2O3:Yb/Er nanocrystals can be readily tuned from lemon-like particle to rod-like structure via tuning pH values from 7 to 14. Moreover, compared with the samples prepared at pH 7, the Gd2O3:Yb/Er nanocrystals prepared at pH 14 exhibit enhanced red upconversion emission and higher upconversion luminescence intensity under the excitation of 980£¿nm laser. 1. Introduction Rare-earth (RE) doped upconversion (UC) nanocrystals have been comprehensively used in high-quality lighting devices, magnets, and other functional materials due to their optical, electronic, and chemical properties arising from the 4f shell of their ions [1¨C6]. These capabilities are highly sensitive to the bonding states of RE ions. RE doping induced photoluminescence property in fluorides, and oxides systems have been universally reported [7¨C11]. For instance, Yb/Tm codoped Y2O3 nanocrystals can achieve remarkable green UC luminescent emission [8]. In Yb/Er codoped Lu2O3 system, UC spectra revealed that simultaneous green and red emissions can be obtained [11]. However, the intense UC emission located in the red region by doping Yb/Er is an enormous challenge owing to the fact that Yb/Er codoped UC materials have a multipeak emissions nature. Recently, Li¡¯s group have developed a simple and controlled synthetic method [3¨C5], in which the shape transformation, phase evolution, and UC emission tuning of a series of RE oxides nanocrystals can be reached by simply adjusting reaction parameters, such as pH value, reaction time, and temperature. Among various developed RE-based oxides UC nanomaterials, gadolinium oxide (Gd2O3) has its unique UC luminescent and magnetic properties. Therefore, RE (Nd3+, Er3+, and Tm3+) doped Gd2O3 nanocrystals have been selected for optical and magnetic studies, because of their high chemical durability, photothermal and photochemical stabilities, low photon-energy, and unpaired electrons of the 4f shell [12¨C17]. Of course, there are also many investigations of the UC luminescence nanocrystals mainly focused on the RE doped Gd2O3 with phase/structure
%U http://www.hindawi.com/journals/acmp/2013/509374/