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Tb 3+ - and Eu 3+ -Doped Lanthanum Oxysulfide Nanocrystals. Gelatin-Templated Synthesis and Luminescence Properties

2008; American Chemical Society; Volume: 112; Issue: 7 Linguagem: Inglês

10.1021/jp0764687

1932-7455

Zhigang Liu, Xudong Sun, Shukun Xu, Jingbao Lian, Xiaodong Li, Zhimeng Xiu, Qiang Li, Di Huo, Ji‐Guang Li,

Crystal Structures and Properties

Tb3+- and Eu3+-doped lanthanum oxysulfide nanocrystals (NCs) with homogeneous grain size have been prepared by a gel-network coprecipitation method using gelatin as the template and ammonium sulfate as the sulfurizing agent and a following reduction process at relatively low temperatures (750 °C) in a H2 atmosphere. The products were characterized using thermogravimetry−differential thermal analysis (TG−DTA), X-ray diffractometry (XRD), and transmission electron microscopy (TEM). The gelatin template can act as a "nanoreactor", which is beneficial to the dispersion and size control of the coprecipitation product. The high decomposition temperature (about 482 °C) of the gelatin network is advantageous to prevent aggregation of the newly formed (LaO)2SO4 NCs during calcination of the coprecipitation product. Single hexagonal phase La2O2S NCs were obtained by reduction of the (LaO)2SO4 powder, and the NCs are equiaxial in shape with particle sizes ranging from 40 to 50 nm. The photoluminescence spectra and time-resolved spectra of the La2O2S:Tb(Eu) in phosphate buffer were investigated. The results show that the La2O2S:Tb NCs have a strong luminescence at 544 nm, whose intensity decreases along with decreasing particle size. Concentration quenching occurs when the Tb concentration reaches 8 mol %. The fluorescence color of the La2O2S:Eu NCs depends on the concentration of Eu3+ ions. The red emission (at 625 nm) from 5D0 transition has a much longer decay time than the green emission from 5D1 transition of the La2O2S:Eu NCs. The Tb3+- and the Eu3+-doped La2O2S NCs have respective fluorescence lifetimes of 1.10 and 0.41 ms in phosphate buffer, allowing their potential applications in biological labeling.