title: Remarkably enhanced photoluminescence of hexagonal GdPO4.nH2O:Eu with decreasing size.
abstract: The hexagonal rhabdophane-type GdPO(4) hydrate (GdPO(4).nH(2)O) was synthesized via a simple hydrothermal process. The size and morphology of the products can be tunable by adjusting the pH of reaction systems through the addition of aqueous NaOH. The nanorods with a width of 50-100 nm and a length of about 1 microm were obtained in the absence of NaOH (pH = 2), while a significant reduction of size (width: approximately 10 nm, length: approximately 50 nm) was observed for the product synthesized in the presence of NaOH (pH = 10). Surprisingly, the small-sized product exhibits a remarkably enhanced photoluminescence quantum yield and long excited state lifetime in comparison with those of the large-sized product. This abnormal luminescence phenomenon is discussed and explained. The EDS and XPS measurements revealed the presence of Na(+) in the small-sized samples. These Na(+) cations were probably bonded to the surface O(2-) dangling bonds, which thus reduces the number of surface defects that usually serve as the nonradiative energy transfer center channels. A considerable reduction of surface defect centers results in the increase of the emission efficiency and excited state lifetime in a small-sized sample. Obviously, the controlled synthesis of rare-earth-doped nanoparticles with a small size, but with relatively strong luminescence, is significant for their applications in the areas of technologies including optoelectronics, sensing and bioimaging.
authors: Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, People's Republic of China. lusz@ciomp.ac.cn
authors: Shaozhe
authors: S
authors: Lu
authors: Jiahua
authors: J
authors: Zhang
authors: Jishen
authors: J
authors: Zhang
authors: Haifeng
authors: H
authors: Zhao
authors: Yongshi
authors: Y
authors: Luo
authors: Xinguang
authors: X
authors: Ren
mesh_terms: D005063:Europium / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D008163:Luminescent Measurements / Q000379:methods; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D010710:Phosphates / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D010710:Phosphates; D005063:Europium; D012972:Sodium Hydroxide; D005682:Gadolinium