Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba, Ibaraki 305-8565, Japan.
J Phys Chem B. 2011 May 19;115(19):6111-8. doi: 10.1021/jp201722f. Epub 2011 Apr 19.
A water-in-supercritical CO(2) microemulsion is a reverse micelle encapsulating a nanometer-size water droplet dispersed in supercritical CO(2). In the microemulsion solution, water exists not only in the reverse micelle but also in the solvent CO(2). For quantitative analysis of the water distribution, near-infrared spectra of water + CO(2) and water + surfactant + CO(2) mixtures were measured over a wide range of water/CO(2) ratios from 0.1 to 1.0 wt% at 60 °C and 30.0 MPa. The stretching combination band of water was decomposed into two components, a sharp one peaked at 7194 cm(-1) assigned to monomeric water dissolved in CO(2) and a broad one around 7000 cm(-1) corresponding to aggregated water in the microemulsion. Integrated molar absorptivities of these types of water were negligibly different from each other, despite the different hydrogen-bonding environments. The spectral decomposition revealed that water is distributed mainly into CO(2) at water contents smaller than 0.5 wt% and then is introduced into the microemulsion after saturation of water in CO(2) and full hydration of the surfactant headgroup.
超临界 CO(2)中的水-反胶束微乳液是一种反向胶束，其中包含分散在超临界 CO(2)中的纳米级水滴。在微乳液溶液中，水不仅存在于反向胶束中，还存在于溶剂 CO(2)中。为了定量分析水的分布，在 60°C 和 30.0 MPa 下，从 0.1 到 1.0 wt%的宽水/CO(2)比范围内，测量了水+CO(2)和水+表面活性剂+CO(2)混合物的近红外光谱。水的伸缩组合带分解为两个组分，一个在 7194 cm(-1)处尖锐的峰，归属于溶解在 CO(2)中的单体水，另一个在 7000 cm(-1)左右的宽峰，对应于微乳液中的聚集水。尽管存在不同的氢键环境，但这些类型的水的积分摩尔吸光率彼此之间差异可以忽略不计。光谱分解表明，水在含水量小于 0.5 wt%时主要分布在 CO(2)中，然后在 CO(2)中达到水饱和和表面活性剂头基完全水合后，被引入到微乳液中。
