Nanoarchitecture of semiconductor titania nanosheets revealed by polarization-dependent total reflection fluorescence X-ray absorption fine structure
Nanoarchitecture of semiconductor titania nanosheets revealed by polarization-dependent total reflection fluorescence X-ray absorption fine structure
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DOI：
10.1021/jp047766w
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发表时间：
2004-09-02
影响因子：
3.3
通讯作者：
Sasaki, T
中科院分区：
文献类型：
--
作者：
Fukuda, K;Nakai, I;Sasaki, T
利用X射线吸收精细结构（XAFS）分析，利用两种不同的几何排列，s-和p-偏振的单层二氧化钛纳米片的纳米结构进行了研究。在使用同步辐射X射线的全反射荧光模式中，对于通过静电自组装沉积的厚度仅为10埃的纳米片的单层膜，以高产率检测到XAFS信号。由于纳米片的二维各向异性，获得的扩展X射线吸收精细结构振荡依赖于偏振。这种依赖性有助于分析纳米片结构，这是进行的基础上的自由能力场（FEFF）模拟的母体层状钛酸盐。单层纳米片的EXAFS数据得到了满意的曲线拟合。所获得的结果揭示了当与母体层状钛酸盐的晶体结构数据相比时，一些原子间距离的伸长，特别是具有沿纳米片法线沿着的组分的那些原子间距离的伸长。这种结构改性导致剥离后片厚度膨胀4%，这可以通过减轻带负电荷的纳米片中的钛离子与其抗衡阳离子之间的静电排斥来理解。
The nanoarchitecture of unilamellar titania nanosheets was studied by X-ray absorption fine structure (XAFS) analysis utilizing two different geometrical arrangements, s- and p-polarization. In total reflection fluorescence mode using synchrotron radiation X-ray, an XAFS signal was detected in high yield for monolayer films of nanosheets having a thickness of only similar to10 Angstrom, which were deposited via electrostatic self-assembly. Obtained extended X-ray absorption fine structure oscillations were dependent on the polarization due to the two-dimensional anisotropy of the nanosheets. This dependence was helpful in analysis of the nanosheet architecture, which was conducted on the basis of free energy force field (FEFF) simulations of the parent layered titanate. Satisfactory curve-fitting of the EXAFS data of the unilamellar nanosheet was achieved. The obtained results revealed the elongation of some interatomic distances, particularly those having a component along the nanosheet normal, when compared with the crystal structure data for the parent layered titanate. This structural modification led to 4% expansion in sheet thickness upon exfoliation, which can be understood by mitigation of electrostatic repulsion between titanium ions in the negatively charged nanosheet and its countercations.