论文标题
在亲水和疏水界面上的水结构:限制在周期性介孔(有机)硅中的水的拉曼光谱法
Structure of Water at Hydrophilic and Hydrophobic Interfaces: Raman Spectroscopy of Water Confined in Periodic Mesoporous (Organo)Silicas
论文作者
论文摘要
通过拉曼振动光谱学研究了限制在亲水性中性二氧化硅(MCM-41)和疏水性苯桥周期性周期性有机硅(PMO)中的水结构的温度依赖性。对于毛细管填充的孔(75%的相对湿度,RH),OH伸直的区域由位于孔的核心部分中的液体水的贡献主导。它采用了散装的结构,该结构受到限制和表面疏水性的适度破坏。对于部分填充的毛孔(33%RH),不可冻结的吸附膜的结构与毛细管填充的孔中的结构根本不同。一个显着的特征是即使在低温(-120 {\ textDegree} c)中,不存在低密度无定形冰的拉曼光谱指纹。其次,其他带揭示了指向不同水/固体和水/蒸气界面的水羟基。对于MCM-41,它们对应于用二氧化硅作用的弱H键供体的水分子,以及悬挂在孔隙中心的悬挂羟基。对于苯桥接的PMO,我们发现了另一种类型的悬挂羟基,我们将其归因于疏水固体界面的水。
The temperature dependence of the structure of water confined in hydrophilic mesostructured porous silica (MCM-41) and hydrophobic benzene-bridged periodic mesoporous organosilicas (PMO) is studied by Raman vibrational spectroscopy. For capillary filled pores (75% relative humidity, RH), the OH-stretching region is dominated by the contribution from liquid water situated in the core part of the pore. It adopts a bulk-like structure that is modestly disrupted by confinement and surface hydrophobicity. For partially filled pores (33% RH), the structure of the non-freezable adsorbed film radically differs from that found in capillary filled pores. A first remarkable feature is the absence of the Raman spectral fingerprint of low density amorphous ice, even at low temperature (-120{\textdegree}C). Secondly, additional bands reveal water hydroxyls groups pointing towards the different water/solid and water/vapor interfaces. For MCM-41, they correspond to water molecules acting as weak H-bond donors with silica, and dangling hydroxyl groups oriented towards the empty center of the pore. For benzene-bridged PMO, we found an additional type of dangling hydroxyl groups, which we attribute to water at hydrophobic solid interface.