Effects of Surface Chemistry on Structure and Thermodynamics of Water Layers at Solid-Vapor Interfaces
Effects of Surface Chemistry on Structure and Thermodynamics of Water Layers at Solid-Vapor Interfaces
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DOI：
10.1021/jp806815p
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发表时间：
2009-02-12
影响因子：
3.7
通讯作者：
Kim, Seong H.
中科院分区：
文献类型：
--
作者：
Asay, David B.;Barnette, Anna L.;Kim, Seong H.
利用衰减全反射红外光谱研究了表面化学对吸附水层等温线厚度和结构以及等量吸附热和吸附熵的影响。亲水性程度似乎明显改变了氧化硅表面吸附的水层的结构和热力学性质。在覆盖有硅烷醇基团的高亲水性氧化硅表面上，低湿度下吸附的水层在3230 cm(-1)处表现出OH伸缩峰（类固体水结构的特征），吸附等量热远高于冰升华潜热。随着表面硅烷醇基团浓度的降低，水的初始等量吸附热和固体状水的量均减少。在低湿度下吸附在亲水表面上的水层似乎比本体水具有低得多的熵，而部分甲基化表面上的水层的熵并不比本体水低很多。在高湿度下，液态水结构在吸附层中占主导地位。讨论了高等量吸附热和低熵的可能起源。
The effects of surface chemistry on the isotherm thickness and structure of the adsorbed water layer as well as the isosteric heat of adsorption and entropy of adsorption were studied using attenuated total reflection infrared spectroscopy. The degree of hydrophilicity seems to distinctively change the structure and thermodynamic properties of the water layers adsorbed on silicon oxide surfaces. On the highly hydrophilic silicon oxide surface covered with silanol groups, the water layer adsorbed at low humidities exhibits the OH stretching peak at 3230 cm(-1) (characteristic of a solid-like water structure), and the isosteric heat of adsorption is much higher than the latent heat of ice sublimation. As the concentration of surface silanol groups decreases, both the initial isosteric heat of adsorption of water and the amount of solid-like water decrease. The water layer adsorbed on the hydrophilic surface at low humidities seems to have much lower entropies than bulk water, while the entropy of the water layer on the partially methylated surface is not much lower than that of bulk water. At high humidities, the liquid water structure becomes dominant in the adsorbed layer. The possible origins of high isosteric heat of adsorption and low entropy are discussed.