Universidade Estadual Paulista, P.O. Box 355, CEP, 14801-907 Araraquara, São Paulo, Brazil.
Inorg Chem. 2012 Oct 15;51(20):10675-87. doi: 10.1021/ic300948n. Epub 2012 Sep 21.
In this paper, we report our initial research to obtain hexagonal rod-like elongated silver tungstate (α-Ag(2)WO(4)) microcrystals by different methods [sonochemistry (SC), coprecipitation (CP), and conventional hydrothermal (CH)] and to study their cluster coordination and optical properties. These microcrystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinements, Fourier transform infrared (FT-IR), X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopies. The shape and average size of these α-Ag(2)WO(4) microcrystals were observed by field-emission scanning electron microscopy (FE-SEM). The optical properties of these microcrystals were investigated by ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) measurements. XRD patterns and Rietveld refinement data confirmed that α-Ag(2)WO(4) microcrystals have an orthorhombic structure. FT-IR spectra exhibited four IR-active modes in a range from 250 to 1000 cm(-1). XANES spectra at the W L(3)-edge showed distorted octahedral [WO(6)] clusters in the lattice, while EXAFS analyses confirmed that W atoms are coordinated by six O atoms. FE-SEM images suggest that the α-Ag(2)WO(4) microcrystals grow by aggregation and the Ostwald ripening process. PL properties of α-Ag(2)WO(4) microcrystals decrease with an increase in the optical band-gap values (3.19-3.23 eV). Finally, we observed that large hexagonal rod-like α-Ag(2)WO(4) microcrystals prepared by the SC method exhibited a major PL emission intensity relative to α-Ag(2)WO(4) microcrystals prepared by the CP and CH methods.
本文报道了我们通过不同方法[声化学（SC）、共沉淀（CP）和常规水热（CH）]获得六方棒状拉长的钨酸银（α-Ag2WO4）微晶的初步研究，并研究了它们的团簇配位和光学性质。这些微晶通过 X 射线衍射（XRD）、Rietveld 精修、傅里叶变换红外（FT-IR）、X 射线吸收近边结构（XANES）和扩展 X 射线吸收精细结构（EXAFS）光谱进行结构表征。这些α-Ag2WO4 微晶的形状和平均尺寸通过场发射扫描电子显微镜（FE-SEM）观察。通过紫外可见（UV-vis）光谱和光致发光（PL）测量研究了这些微晶的光学性质。XRD 图谱和 Rietveld 精修数据证实α-Ag2WO4 微晶具有正交结构。FT-IR 光谱在 250 至 1000 cm-1 范围内显示出四个 IR 活性模式。W L（3）-边的 XANES 光谱显示晶格中存在扭曲的八面体[WO6]簇，而 EXAFS 分析证实 W 原子由六个 O 原子配位。FE-SEM 图像表明α-Ag2WO4 微晶通过聚集和奥斯特瓦尔德熟化过程生长。α-Ag2WO4 微晶的 PL 性质随光学带隙值（3.19-3.23 eV）的增加而降低。最后，我们观察到通过 SC 方法制备的大六方棒状α-Ag2WO4 微晶相对于 CP 和 CH 方法制备的α-Ag2WO4 微晶表现出较大的 PL 发射强度。
