Local Structures of Methanol -Water Binary Solutions Studied by Soft X-ray Absorption Spectroscopy
Local Structures of Methanol -Water Binary Solutions Studied by Soft X-ray Absorption Spectroscopy
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软X射线吸收光谱研究甲醇-水二元溶液的局部结构
DOI：
10.1021/jp4091602
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发表时间：
2014
期刊：
影响因子：
3.3
通讯作者：
N. Kosugi
中科院分区：
文献类型：
--
作者：
M. Nagasaka;K. Mochizuki;V. Leloup;N. Kosugi
液态甲醇显示一维和二维（1D/2D）氢键（HB）网络，液态水显示三维（3D）HB网络。在C-K边软X射线吸收谱（XAS）中，我们清楚地发现了不同浓度的甲醇-水二元溶液（CH_3OH）_X（H_2 O）_（1-X）中甲基周围的三种不同局域结构。借助分子动力学模拟，我们讨论了C-K边XAS谱中甲基疏水相互作用的浓度依赖性。在富甲醇区I（1.0 >X> 0.7），少量的水分子分别存在于甲醇团簇的一维/二维HB网络周围。在区域II（0.7 >X> 0.3），由于甲醇-水混合三维网络结构的增加，甲基的疏水作用占主导地位。在富水区域III（0.3 >X> 0.05）中，甲醇分子分别嵌入水的主导3D HB网络中。另一方面，在O K边缘XAS的前边缘功能显示几乎线性的浓度依赖性。这表明甲醇与水之间的HB相互作用与水-水和甲醇-甲醇之间的HB相互作用几乎相同。
Liquid methanol shows one- and two-dimensional (1D/2D) hydrogen bond (HB) networks, and liquid water shows three-dimensional (3D) HB networks. We have clearly found three different local structures around the methyl group of methanol–water binary solutions (CH3OH)X(H2O)1–Xat different concentrations in C K-edge soft X-ray absorption spectroscopy (XAS). With the help of molecular dynamics simulations, we have discussed the concentration dependence of the hydrophobic interaction at the methyl group in the C K-edge XAS spectra. In the methanol-rich region I (1.0 >X> 0.7), a small amount of water molecules exists separately around dominant 1D/2D HB networks of methanol clusters. In the region II (0.7 >X> 0.3), the hydrophobic interaction of the methyl group is dominant due to the increase of mixed methanol–water 3D network structures. In the water-rich region III (0.3 >X> 0.05), methanol molecules are separately embedded in dominant 3D HB networks of water. On the other hand, the pre-edge feature in the O K-edge XAS shows almost linear concentration dependence. It means the HB interaction between methanol and water is almost the same as that of water–water and of methanol–methanol.