振动光谱揭示的硅胶表面吸附的十二胺和水的状态。

States of adsorbed dodecyl amine and water at a silica surface as revealed by vibrational spectroscopy.

机构信息

Department of Metallurgical Engineering, College of Mines and Earth Sciences, University of Utah, Salt Lake City, Utah 84112, USA.

出版信息

Langmuir. 2010 Mar 2;26(5):3407-14. doi: 10.1021/la9031943.

DOI:10.1021/la9031943

PMID:20025239

Abstract

States of adsorbed dodecylamine (DDA) at a silica surface have been studied as a function of pH by vibrational spectroscopy (SFVS, FTIR), contact angle measurements, and molecular dynamics (MD) simulations. The results show that the state of adsorbed DDA at a silica surface varies significantly at different pH values. At pH 6.30, there is no pronounced adsorption of DDA cations and the surface is hydrophilic. At pH 10.0, the vibrational spectroscopy results together with contact angle measurements and MD simulations suggest that amine is adsorbed as a well organized monolayer, the hemimicelle structure. Under these conditions, dehydration occurs based on SFVS analysis and the silica surface becomes hydrophobic. In the case of pH 12.3, it has been confirmed that continued adsorption of DDA neutral molecules occurs with the amine surface state changing from a monolayer to a bilayer or a micellar surface state as revealed both from SFVS analysis and MD simulations. At this high pH, extensive surface hydration is evident from SFVS results and the silica surface becomes hydrophilic.

摘要

已通过振动光谱（SFVS、FTIR）、接触角测量和分子动力学（MD）模拟研究了二氧化硅表面上吸附的十二胺（DDA）的状态随 pH 值的变化。结果表明，二氧化硅表面上吸附的 DDA 状态在不同 pH 值下有显著差异。在 pH 6.30 时，DDA 阳离子没有明显吸附，表面亲水。在 pH 10.0 时，振动光谱结果结合接触角测量和 MD 模拟表明，胺以组织良好的单层，即半胶束结构吸附。在这些条件下，根据 SFVS 分析发生脱水，二氧化硅表面变得疏水。在 pH 12.3 的情况下，已经证实 DDA 中性分子的继续吸附发生，并且从 SFVS 分析和 MD 模拟中可以看出，胺表面状态从单层变为双层或胶束表面状态。在这种高 pH 值下，SFVS 结果表明表面广泛水合，二氧化硅表面亲水。