Interactions and Competitive Adsorption at Solid/Liquid Interface*

Broadness in vibrational spectrum is usually associated with heterogeneity of surrounding environment. At solid/liquid interface, surface-sensitive sum-frequency generation spectroscopy (SFG) has shown wide distributions of frequency shifts of sapphire surface hydroxyl groups with several liquids in contact. Even though the shifts were associated with the interfacial interactions, the origin of variation and a physical picture of interfacial interactions are elusive in experiments. To better understand the interfacial interactions, we perform molecular dynamics (MD) simulations of liquid molecules (acetone, chloroform, and dimethylformamide) in contact with sapphire. The energy distribution profiles from MD correlate well with the experimental SFG spectra, highlighting the ability to interpret spectroscopic features with the physical insights gained from MD simulations. Further, we use MD simulations to gain insights into the preferential adsorption of acetone from acetone-chloroform binary mixtures on sapphire. The current study paves the way for the theoretical understanding of adsorption, which can benefit the development of new technologies in adhesion, coatings, and medicine.