Nanoscale Insight into the Mechanism of a Highly Oriented\nPyrolytic Graphite Edge Surface Wetting by “Interferencing”\nWater

Abstract

The new molecular\ndynamics simulation results showing the influence\nof the edge carbon surface atoms on the wettability of a highly oriented\npyrolytic graphite (HOPG) surface with water nanodroplets are reported.\nThe conditions for the occurrence of the Wenzel effect are discussed,\nand the Cassie-to-Wenzel transition (CTWT) mechanism in the nanoscale\nis explored. This transition is detected by the application of a new\nprocedure showing that the CTWT point shifts toward larger values\nof carbon–oxygen potential well depth with the decrease in\nthe HOPG side angle. It is concluded that the Wenzel effect significantly\ncontributes to the contact angles (CAs) measured for the HOPG surfaces.\nThe Wenzel effect is also very important for the “HOPG”\nstructures possessing the disturbed C–C interlayer distance,\nand its influence on the water nanodroplet CAs is strongly pronounced.\nThe structure of water confined inside slits and on a HOPG surface\nis studied using the analysis of the density profiles, the number\nof hydrogen bonds, and, modified for the purpose of this study, structure\nfactor. The detailed analysis of all parameters describing confined\nwater leads to the conclusion about the presence of characteristic\ninterference patterns revealed as a result of long-term simulation.\nA simple model describing this effect is proposed as the starting\npoint for further considerations.