Structure of the Submonolayer of Ethanol Adsorption on a Vapor/Fused Silica Interface Studied with Sum Frequency Vibrational Spectroscopy
Structure of the Submonolayer of Ethanol Adsorption on a Vapor/Fused Silica Interface Studied with Sum Frequency Vibrational Spectroscopy
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用和频振动光谱研究蒸汽/熔融石英界面上乙醇吸附的亚单层结构
DOI：
10.1021/jp510706u
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发表时间：
2015
影响因子：
2.9
通讯作者：
Shen Y. Ron
中科院分区：
文献类型：
--
作者：
Xu Huijie;Zhang Donghua;Hu Jun;Tian Chuanshan;Shen Y. Ron
用CH和OH伸缩区的和频振动光谱研究了不同乙醇分压下乙醇在熔融石英表面的吸附。结果表明，在低乙醇蒸气压下，吸附态乙醇分子的甲基平均偏离表面法线约为45°，接近饱和蒸气压时平均偏离表面法线约为39°.光谱随乙醇蒸气压的变化和推导的吸附等温线表明，乙醇分子在二氧化硅上有两个不同的吸附位点：一个是乙醇分子可以强氢键结合的硅醇基团位点，另一个是乙醇分子可以弱氢键结合的硅氧烷（Si-O-Si）基团位点.由于乙醇和水之间的竞争吸附，蒸汽中的水的存在显著降低了乙醇在二氧化硅上的表面覆盖。
Sum-frequency vibrational spectroscopy in the CH and OH stretch region was used to study ethanol adsorption on fused silica from vapor of different ethanol partial pressures. It was found that the adsorbed ethanol molecules were oriented with their methyl group tilted away from the surface normal by an average angle of ∼45° at low ethanol vapor pressures and ∼39° when approaching saturated vapor pressure. The spectral change with ethanol vapor pressure and the deduced adsorption isotherm show that ethanol molecules have two distinct adsorption sites on silica: One is the silanol group site to which an ethanol molecule can be strongly hydrogen-bonded, and the other is the siloxane (Si–O–Si) group site to which an ethanol molecule can be weakly bonded. The presence of water in vapor significantly reduced the surface coverage of ethanol on silica due to competitive adsorption between ethanol and water.