Richard Thierry, Mercury Lionel, Poulet François, d'Hendecourt Louis
UMR-CNRS 8148, IDES, Université Paris-Sud, Bât. 504, 91405 Orsay, France.
J Colloid Interface Sci. 2006 Dec 1;304(1):125-36. doi: 10.1016/j.jcis.2006.08.036. Epub 2006 Aug 24.
We present experimental data acquired by diffuse reflectance infrared spectroscopy in the mid-IR (4000-400 cm(-1)), on micrometric-sized mineral grain powders. The spectral evolution of the OH-stretching band is followed when the adsorbed water film is thinned under dry conditions, from high to low hydration states. The IR bands are found to be characteristic of the degree of adsorption/confinement of the liquid water. The OH-stretching band is shifted toward shorter wavenumbers than in bulk water, showing that a significant portion of adsorbed water has a higher intermolecular bonding energy. Complementary treatment of the kinetics of water desorption, varying with the surface forces in the water film, confirms the relationships of these bands with the constrained water state. We distinguish different water types obeying liquid-liquid interactions (free and capillary water) or dominated by solid-water interactions (confined and adsorbed water). Part of this study is devoted to mesoporous silica MCM-41, of interest due to the restricted geometries of its mesopores (4.7 nm) favouring the confined water state. The methodology allows us to distinguish bulk and adsorbed/confined water, using spectral analysis coupled with an understanding of the dynamic behaviour of the desorption process.
我们展示了通过中红外（4000 - 400 cm⁻¹）漫反射红外光谱法获取的关于微米级矿物颗粒粉末的实验数据。当吸附水膜在干燥条件下从高水合状态变薄至低水合状态时，跟踪了OH伸缩带的光谱演变。发现红外波段是液态水吸附/受限程度的特征。OH伸缩带向比体相水更短的波数移动，表明很大一部分吸附水具有更高的分子间键能。对随水膜表面力变化的水解吸动力学进行的补充处理，证实了这些波段与受限水状态的关系。我们区分了遵循液 - 液相互作用的不同水类型（自由水和毛细水）或由固 - 水相互作用主导的水类型（受限水和吸附水）。本研究的一部分致力于介孔二氧化硅MCM - 41，因其4.7纳米的介孔受限几何结构有利于受限水状态而备受关注。该方法使我们能够通过光谱分析并结合对解吸过程动态行为的理解来区分体相水和吸附/受限水。
