Dong W
Université de Lyon, CNRS, Ecole Normale Supérieure de Lyon, Université Lyon 1, Laboratoire de Chimie, UMR 5182, 69364 Lyon Cedex 07, France;
College of Chemistry and Chemical Engineering, Hunan University, 410082 Changsha, China.
Proc Natl Acad Sci U S A. 2021 Jan 19;118(3). doi: 10.1073/pnas.2019873118.
As a system shrinks down in size, more and more molecules are found in its surface region, so surface contribution becomes a large or even a dominant part of its thermodynamic potentials. Surface tension is a venerable scientific concept; Gibbs defined it as the excess of grand potential of an inhomogeneous system with respect to its bulk value per interface area [J. W. Gibbs, "The Collected Works" in (1928), Vol. 1]. The mechanical definition expresses it in terms of pressure tensor. So far, it has been believed the two definitions always give the same result. We show that the equivalence can break down for fluids confined in narrow pores. New concepts of integral and differential surface tensions, along with integral and differential adsorptions, need to be introduced for extending Gibbs thermodynamics of interfaces. We derived two generalized Gibbs adsorption equations. These concepts are indispensable for an adequate description of nanoscale systems. We also find a relation between integral surface tension and Derjaguin's disjoining pressure. This lays down the basis for measuring integral and differential surface tensions from disjoining pressure by using an atomic force microscope.
随着系统尺寸的减小，越来越多的分子出现在其表面区域，因此表面贡献成为其热力学势的一个很大甚至主导的部分。表面张力是一个古老的科学概念；吉布斯将其定义为非均匀系统的巨势相对于其每单位界面面积的体相值的超额部分[J. W. 吉布斯，《文集》（1928年），第1卷]。力学定义用压力张量来表述它。到目前为止，人们一直认为这两种定义总是给出相同的结果。我们表明，对于限制在狭窄孔隙中的流体，这种等效性可能会失效。需要引入积分和微分表面张力以及积分和微分吸附的新概念，以扩展界面的吉布斯热力学。我们推导了两个广义吉布斯吸附方程。这些概念对于充分描述纳米尺度系统是必不可少的。我们还发现了积分表面张力与德亚金分离压力之间的关系。这为通过使用原子力显微镜从分离压力测量积分和微分表面张力奠定了基础。
