Evaluation of the Adsorption States of H2O on Oxide Surfaces by Vibrational Absorption: Near- and Mid-Infrared Spectroscopy
Evaluation of the Adsorption States of H2O on Oxide Surfaces by Vibrational Absorption: Near- and Mid-Infrared Spectroscopy
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通过振动吸收评估 H2O 在氧化物表面的吸附状态：近红外和中红外光谱
DOI：
10.1255/jnirs.843
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发表时间：
2009
影响因子：
1.8
通讯作者：
M. Anpo
中科院分区：
文献类型：
--
作者：
M. Takeuchi;G. Martra;S. Coluccia;M. Anpo
使用振动吸收光谱、傅里叶变换红外 (FT-IR)、近红外 (NIR) 以及 H2O 分子分子间氢键的吸附等温线分析研究了 H2O 分子与各种氧化物表面的相互作用。近红外区域 H2O 分子基本振动模式的组合谱带提供了有关其分子间氢键的非常有用的信息。还研究了固体表面的物理化学性质，例如亲水性或疏水性，因为它们与“氢键H2O”和“无氢键H2O”的分布观点有关。研究发现，与 TiO2 或 Al2O3 相比，SiO2 表面吸附的水和烃分子量较少，表现出疏水性。由于H2O分子与SiO2表面之间的相互作用较小以及分子间氢键的贡献较小，吸附在SiO2表面上的少量H2O分子使其能够展开形成H2O薄层。这些结果清楚地表明疏水性 SiO2 表面对 H2O 分子表现出高润湿性。另一方面，发现大量的H2O分子和碳氢化合物不仅吸附在表面羟基上，而且吸附在TiO2或Al2O3表面的阳离子（Ti4+或Al3+）位点上，表明TiO2或Al2O3表面同时表现出亲水和亲油特性。此外，由于 H2O 分子的分子间氢键的巨大贡献，大量的 H2O 分子被发现在 TiO2 或 Al2O3 表面上形成聚集的大体积 H2O 网络。结果表明，TiO2或Al2O3表面可以吸附大量的H2O和碳氢化合物，对H2O分子表现出较低的润湿性。氧化物表面的亲水性或疏水性是通过客体分子和主体固体表面之间的直接相互作用来指示的，并且可以通过分子水平的振动吸收（FT-IR和NIR）和吸附等温线测量来分析这些相互作用。此外，我们讨论了固体表面的润湿性，该润湿性是由水滴的接触角以及水与氧化物表面的宏观相互作用决定的，在氧化物表面上不仅有水，而且碳氢化合物分子也被吸附在空气中直至饱和。
The interactions of H2O molecules with various oxide surfaces were investigated using vibrational absorption spectroscopies, Fourier transform infrared (FT-IR), near infrared (NIR) and an analysis of the adsorption isotherms with regard to the intermolecular hydrogen bonds for H2O molecules. The combination bands of the fundamental vibration modes for H2O molecules in the NIR region provided very useful information on their intermolecular hydrogen bonds. The physicochemical properties of the solid surfaces such as hydrophilicity or hydrophobicity were also investigated as they relate to the viewpoint of the distribution of “hydrogen-bonded H2O” and the “hydrogen bond-free H2O”. It was found that SiO2 surfaces adsorb smaller amounts of H2O and hydrocarbon molecules as compared to TiO2 or Al2O3, showing hydrophobicity. The smaller amounts of H2O molecules adsorbed on the SiO2 surfaces enabled them to spread out to form H2O thin layers due to the small interaction between the H2O molecules and SiO2 surface as well as the small contribution of the intermolecular hydrogen bonds. These results clearly indicate that the hydrophobic SiO2 surfaces show high wettability against the H2O molecules. On the other hand, larger amounts of H2O molecules and hydrocarbons were found to adsorb not only on the surface hydroxyl groups but also on the cationic (Ti4+ or Al3+) sites of the TiO2 or Al2O3 surfaces, suggesting that TiO2 or Al2O3 surfaces show both hydrophilic and oleophilic properties. Moreover, larger amounts of H2O molecules were found to form aggregated bulky H2O networks on TiO2 or Al2O3 surfaces due to the large contribution of the intermolecular hydrogen bonds of the H2O molecules. The results revealed that TiO2 or Al2O3 surfaces, on which large amounts of H2O and hydrocarbons can adsorb, show low wettability against H2O molecules. The hydrophilic or hydrophobic properties of oxide surfaces are indicated by the direct interaction between the guest molecules and host solid surfaces and these interactions can be analysed by vibrational absorption (FT-IR and NIR) and adsorption isotherm measurements at the molecular level. Moreover, we discuss the wettability of solid surfaces as determined by the contact angle of the H2O droplets and by the macroscopic interaction of H2O with oxide surfaces on which not only H2O but also hydrocarbon molecules are adsorbed in air until saturation.