Anderson A, Ashurst W R
Department of Chemical Engineering, Auburn University, 212 Ross Hall, Auburn, Alabama 36849, USA.
Langmuir. 2009 Oct 6;25(19):11549-54. doi: 10.1021/la901459b.
Evidence suggests that in order for a surface to support an extensive water structure, it must possess sufficient Lewis cites so that water-surface interactions are favored over water-water interactions. In this paper we use ATR-FTIR to comparatively study, as a function of relative humidity, the water structure that exists on three surfaces: silicon, PEG-modified silicon, and a highly hydroxylated silica film which is formed from the room temperature, vapor phase hydrolysis of tetrachlorosilane. Results indicate that the PEG-modified silicon surface supports a water structure nearly 2.5 times as extensive as that which exists on unmodified silicon surfaces, which is an expected result in light of previous molecular dynamics simulations that indicate extensive hydrogen bonding between PEG monolayers and water molecules. The silica layer supports a water structure that is nearly an order of magnitude more extensive than that which exists on clean silicon surfaces and approximately 3.5 times more extensive than is adsorbed on PEG-modified silicon surfaces at similar relative humidities. Furthermore, the water layer on the silica surface exists mostly in an "ice-like" structure which is also more strongly hydrogen bonded than that which exists on clean silicon and PEG-modified silicon surfaces.
有证据表明，为使一个表面能够支撑广泛的水结构，它必须拥有足够的路易斯位点，以使水与表面的相互作用优于水与水之间的相互作用。在本文中，我们使用衰减全反射傅里叶变换红外光谱（ATR-FTIR），作为相对湿度的函数，比较研究在三种表面上存在的水结构：硅、聚乙二醇（PEG）修饰的硅，以及通过四氯化硅在室温下的气相水解形成的高度羟基化二氧化硅薄膜。结果表明，PEG修饰的硅表面支撑的水结构几乎是未修饰硅表面上存在的水结构的2.5倍，鉴于之前的分子动力学模拟表明PEG单分子层与水分子之间存在广泛的氢键，这是一个预期的结果。二氧化硅层支撑的水结构比干净硅表面上存在的水结构几乎大一个数量级，并且在相似的相对湿度下，比吸附在PEG修饰的硅表面上的水结构大约大3.5倍。此外，二氧化硅表面上的水层大多以“类冰”结构存在，其氢键结合也比干净硅表面和PEG修饰的硅表面上的水层更强。
