通过探针分子芘研究超临界CO_2流体密度不均一性

近年来超临界CO2在环境地球科学领域应用广泛,在这些研究应用中,CO2流体在超临界状态下的溶剂化特性起到了十分重要的作用。在超临界高密度压缩区域里,体系温度和压力的稍许变化都会导致流体密度的突变,因此通过有效的探针分子研究超临界CO2流体的异常溶剂化行为具有重要的理论和应用价值。文中从新的角度运用荧光探针分子芘在温度308.15K和不同压力下研究超临界CO2性质,与以往采用的参照线方法有所不同,文中所提出的参照点模型手段引入序参量方法和新定义的溶剂化作用参量,测定近临界区超临界CO2流体局域密度增强的变化。文中同时讨论了3段密度区域模型(three-density regionmodel)、局域密度不均一性以及探针芘在超临界CO2中的分子间相互作用。将荧光探针分子研究的流体局域密度增强与热力学测试的流体等温压缩系数进行综合对比,有助于更好地从微观和宏观两方面理解超临界CO2的特性。

Solvent density inhomogeneities in supercritical CO2 by pyrene probe

In recent years supercritical CO2 (SC CO2) has been widely used in environmental Earth sciences and the solvating properties of SC CO2 in the compressible region play a very important role in applications. In this supercritical region the fluid density may vary dramatically with modest changes in temperature and pressure. Understanding the unusual solvation behavior of SC CO2 by the efficient probe molecular is very critical to the theory and application of supercritical science and technology. A new view is represented in this article on the technique by fluorescence probe pyrene in SC CO2 at 308.15 K and different pressures. The order parameter methods and the new concept of the solvent effect have been introduced in proposed mode approach of the reference point, different from the traditional method by reference line, to estimate the local density enhancement change for SC CO2 near the critical region. Three-density region model, solvent density inhomogeneities and intermolecular interactions of probe pyrene in SC CO2 are also discussed. Combining the local density enhancements by the fluorescence indicator method and isothermal compressibility by the thermodynamic measurement, we can better understand the unusual behavior of SC CO2 from microscopic and macroscopic views.