Takeuchi Masato, Martra Gianmario, Coluccia Salvatore, Anpo Masakazu
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1, Gakuen-cho, Sakai, Osaka 599-8531, Japan.
J Phys Chem B. 2005 Apr 21;109(15):7387-91. doi: 10.1021/jp040630d.
The overtone and combination bands of the fundamental vibration modes (nu(1), symmetric stretching; nu(2), bending; and nu(3), asymmetric stretching) attributed to the H(2)O molecules adsorbed on a TiO(2) surface could be observed in the near-infrared (NIR) region. Especially, two absorption bands attributed to the combination (nu(2) + nu(3)) and (nu(1) + nu(3)) modes of the H(2)O molecules adsorbed on the TiO(2) surface were observed at around 1940 and 1450 nm, respectively. From detailed investigations on the (nu(2) + nu(3)) combination band, it was found that H(2)O molecules absorbed on a TiO(2) surface aggregate to form clusters due to the high surface tension of H(2)O arising from the intermolecular hydrogen bonds, and the hydrogen-bonded H(2)O in the bulk part of the cluster and the hydrogen-bond-free H(2)O in the outside spherical part of the cluster could be easily distinguished. Furthermore, it was quantitatively confirmed that the relaxation of the surface energy accompanying the adsorption of H(2)O on the TiO(2) surface stabilized the adsorption states of the hydrogen-bonded H(2)O molecules, while on the other hand, the hydrogen-bond-free H(2)O molecules became unstable as compared to the liquid-phase H(2)O molecules.
在近红外（NIR）区域可以观察到吸附在TiO₂表面的H₂O分子的基本振动模式（ν₁，对称伸缩；ν₂，弯曲；ν₃，不对称伸缩）的泛音和组合带。特别是，分别在1940和1450 nm左右观察到了归因于吸附在TiO₂表面的H₂O分子的（ν₂ + ν₃）和（ν₁ + ν₃）模式的两个吸收带。通过对（ν₂ + ν₃）组合带的详细研究发现，由于分子间氢键导致的H₂O的高表面张力，吸附在TiO₂表面的H₂O分子聚集形成簇，并且簇主体部分中氢键结合的H₂O和簇外部球形部分中无氢键的H₂O可以很容易地区分开来。此外，定量证实了H₂O吸附在TiO₂表面时表面能的弛豫稳定了氢键结合的H₂O分子的吸附状态，而另一方面，无氢键的H₂O分子与液相H₂O分子相比变得不稳定。
