Ahmed Bilal, Kumar Sumeet, Ojha Animesh K, Donfack P, Materny A
Department of Physics, Motilal Nehru National Institute of Technology Allahabad, 211004, India.
Department of Physics, Motilal Nehru National Institute of Technology Allahabad, 211004, India; Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
Spectrochim Acta A Mol Biomol Spectrosc. 2017 Mar 15;175:250-261. doi: 10.1016/j.saa.2016.11.044. Epub 2016 Nov 28.
In this work, we have performed a facile and controlled synthesis of WO nanorods and sheets in different crystal phases (triclinic, orthorhombic and monoclinic) of WO using the sol-gel method. The detailed structures of the synthesized materials were examined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy measurements. The shapes and crystal phases of the WO nanostructures were found to be highly dependent on the calcination temperature. The variation in crystalline phases and shapes is modified the electronic structure of the samples, which causes a variation in the value of optical band gap. The value of the Raman line intensity ratio I/I has been successfully used to identify the structural transition from the triclinic to the orthorhombic phase of WO. The PL spectra of the synthesized products excited at wavelengths 380, 400, and 420nm exhibit intense emission peaks that cover the complete visible range (blue-green-red). The emission peaks at ~460 and ~486nm were caused by the near band-edge and band to band transition, respectively. The peaks in spectral range 500-600nm might be originated from the presence of oxygen vacancies lying within the energy band gap. The synthesized WO nanostructures showed improved photocatalytic activity for the photodegradation of MB dye. The enhanced photocatalytic activity of WO nanosheets compared to WO nanorods for photodegradation of methylene blue (MB) dye could be due to the shape of the nanostructured WO. The sheet type of structure provides more active surface for the interaction of dye molecules compared to the rods, which results in a more efficient degradation of the dye molecules.
在本工作中，我们采用溶胶-凝胶法，以简便且可控的方式合成了处于不同晶体相（三斜晶系、正交晶系和单斜晶系）的WO纳米棒和纳米片。通过X射线粉末衍射（XRD）、透射电子显微镜（TEM）和拉曼光谱测量对合成材料的详细结构进行了研究。发现WO纳米结构的形状和晶体相高度依赖于煅烧温度。晶相和形状的变化改变了样品的电子结构，这导致光学带隙值发生变化。拉曼线强度比I/I的值已成功用于识别WO从三斜晶系到正交晶系的结构转变。在波长380、400和420nm激发下合成产物的PL光谱显示出覆盖整个可见光范围（蓝-绿-红）的强发射峰。分别在460和486nm处的发射峰是由近带边和带间跃迁引起的。光谱范围500 - 600nm内的峰可能源于能带隙内存在的氧空位。合成的WO纳米结构对亚甲基蓝（MB）染料的光降解表现出增强的光催化活性。与WO纳米棒相比，WO纳米片对亚甲基蓝（MB）染料光降解的光催化活性增强可能归因于纳米结构WO的形状。与棒状结构相比，片状结构为染料分子的相互作用提供了更多的活性表面，这导致染料分子的降解更有效。
