Study of the water structure on a biomaterial surface by optical sum frequency generation (SFG)

在生物材料表面的研究中，覆盖有有机分子或金属氧化物薄膜的固体表面的水合是一个重要的问题。为了明确各种材料表面的水化结构，采用了光学和频光谱技术.研究了弱吸附于石英表面的聚合物对界面水分子结构的影响。作为聚合物，使用PEG、PPG和Pluronic L 64和17 R-4的两种类型的三嵌段共聚物。测量了石英基底与聚合物水溶液界面处水分子OH伸缩模的SF强度谱。L 64水溶液界面水的总SF强度小于其它溶液。这一结果表明，L 64水溶液具有较少数量的取向界面水分子。有人建议，吸附的L 64的亲水部分的快速运动扰乱了界面水分子的平均取向。另一方面，具有高离子强度的水溶液的界面水分子的SF强度不依赖于溶液中的聚合物的种类。后者的结果表明，离子的水合作用决定了界面水分子的结构.用SF光谱观察了二氧化钛（TiO_2）表面的水化结构。研究发现，与玻璃表面相比，酸性溶液中的TiO_2表面具有大量的取向界面水分子.氨基封端和氟烷基封端的玻璃表面也进行了研究。这些表面的水化结构是静电相互作用、氢键和疏水相互作用相互竞争的结果。

In the study of biomaterial surfaces, hydration of a solid surface covered with organic molecules or metal oxide thin film is an important problem. In order to clarify hydration structure at various materials surfaces, optical sum frequency generation (SFG) spectroscopy was used.1. The effect of polymers weakly adsorbed on a quartz surface on the structure of the interfacial water molecules was investigated. As polymers, PEG, PPG, and two types of tri-block copolymer of Pluronic L64 and 17R-4 were used. SF intensity spectra of OH stretching mode of water molecules at the interface between a quartz substrate and aqueous solutions of the polymers were measured. The total SF intensity of the interfacial water of the L64 aqueous solution was smaller than those of other solutions. This result indicates that the L64 aqueous solution has smaller number of oriented interfacial water molecules. It is suggested that the rapid motion of hydrophilic parts of the adsorbed L64 disturbs the average orientation of the interfacial water molecules. On the other hand, the SF intensity from the interfacial water molecules of aqueous solutions with high ion strength did not depend on the species of the polymers in the solutions. The latter result suggests that the hydration of ions determines the structure of the interfacial water molecules.2. Hydration structure on a titanium dioxide (TiO_2) surface was observed by SF spectroscopy. It was found that as compared with a glass surface, TiO_2 surface in acidic solution has a large amount of oriented interfacial water molecules.3. Amino-terminated and fluoroalkyl-terminated glass surfaces were also investigated. It is suggested that hydration structures on these surfaces result from competition of electrostatic interaction, hydrogen bonding, and hydrophobic interaction.