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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >A relationship between structural and electronic order-disorder effects and optical properties in crystalline TiO2 nanomaterials
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A relationship between structural and electronic order-disorder effects and optical properties in crystalline TiO2 nanomaterials

机译：晶体TiO2纳米材料的结构和电子有序无序效应与光学性质之间的关系

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The focus of this paper is on the analysis of the structural and electronic order-disorder effects at long, medium and short ranges of titanium dioxide (TiO2) nanoparticles synthesized by the sol-gel process followed by the microwave-assisted solvothermal (MAS) method at low temperatures and short reaction times. X-ray diffraction (XRD), Rietveld refinement, micro-Raman (MR) spectroscopy, transmission electron microscopy (TEM) and X-ray spectroscopy (EDX) were used to characterize the TiO2 nanoparticles. Optical properties were investigated by ultraviolet-visible (UV-vis) and photoluminescence (PL) measurements performed at room temperature. XRD and Rietveld refinement confirmed the presence of the anatase and brookite phases; nonetheless anatase is the major phase. The X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of only Ti4+ but the nonstoichiometry revealed that TiO2 NPs contain defects assigned to oxygen vacancies that lead to structural and electronic order-disorder effects observed by band gap narrowing and PL wide band emission. These intermediary energy levels (shallow and deep levels) created within the band gap act as acceptors/ donors of electrons and recombination centers. The oxygen vacancies (VOx, VO center dot and VO center dot center dot) responsible by degree of structural order-disorder are related to distortions (tilts) on the [TiO6] octahedron and changes in the bond lengths and bond angles between oxygen and titanium atoms that gave rise to new species of cluster makers such as [TiO6]', [TiO5 center dot V-O(x)], [TiO5 center dot VO center dot] and [TiO5 center dot VO center dot center dot]. This structural transformation is consistent with a redistribution of electron density from highly ordered [TiO6](x) clusters which form distorted [TiO6]' as well as complex [TiO5 center dot V-O(x)], [TiO5 center dot VO center dot] and [TiO5 center dot VO center dot center dot] clusters assigned to oxygen vacancies which were understood as displacements in the oxygen atoms' position in the bond lengths (Ti-O).
机译：本文的重点是分析通过溶胶-凝胶法和微波辅助溶剂热法（MAS）合成的二氧化钛（TiO2）纳米粒子在长，中和短范围内的结构和电子有序无序效应在低温和短反应时间下。使用X射线衍射（XRD），Rietveld精制，微拉曼（MR）光谱，透射电子显微镜（TEM）和X射线光谱（EDX）表征TiO2纳米颗粒。通过在室温下进行紫外-可见（UV-vis）和光致发光（PL）测量来研究光学性质。 XRD和Rietveld精制证实了锐钛矿和板钛矿相的存在。尽管如此，锐钛矿是主要阶段。 X射线光电子能谱（XPS）分析显示仅存在Ti4 +，但非化学计量显示TiO2 NPs包含与氧空位有关的缺陷，这些缺陷导致通过带隙变窄和PL宽带发射观察到的结构和电子有序无序效应。带隙内产生的这些中间能级（浅和深能级）充当电子和复合中心的受体/供体。与结构有序度有关的氧空位（VOx，VO中心点和VO中心点中心点）与[TiO6]八面体的变形（倾斜）以及氧和钛之间的键长和键角的变化有关原子产生了新的簇制造子，例如[TiO6]'，[TiO5中心点VO（x）]，[TiO5中心点VO中心点]和[TiO5中心点VO中心点中心点]。这种结构转变与高度畸变的[TiO6]（x）团簇形成畸变的[TiO6]'以及复杂的[TiO5中心点VO（x）]，[TiO5中心点VO中心点]的电子密度重新分布是一致的和[TiO5中心点VO中心点中心点]簇分配给氧空位，这被理解为键长（Ti-O）中氧原子位置的位移。

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