Molecular Structure and Dielectric Anisotropy of Ethanol-Water Mixtures within Heterogeneous Graphene/silica Interface

Abstract

Heterogeneous graphene/silica interfaces, integrating hydrophobic and hydrophilic domains, have shown great potential for applications in interfacial capacitive and electrostatic environments. The structures and properties of intercalating molecules within the hybrid interlayer become crucial for regulating the interfacial systems. Herein, molecular simulations were employed to systematically investigate the behavior of amphiphilic ethanol-water mixtures within the hybrid graphene-silica nanochannels. Interfacial asymmetry induces local demixing under weak confinement and promotes directional molecular alignment under strong confinement. The structural features differ markedly from those observed in symmetric graphene slits. We present the first elucidation of the out-of-plane dielectric properties of mixture fluids under asymmetric environments. Spatially resolved charge and polarization distributions lead to dielectric anisotropy within the hybrid interlayer channels, highlighting interfacial asymmetry. The interfacial effective dielectric responses increase with pore width and exhibit clear variation with the mixture concentration. In strongly confined regimes, the dielectric permittivity shows greater sensitivity to pore size under asymmetric systems, as compared with symmetric systems. Moreover, a scaling relation between dielectric permittivity and channel size was developed to describe the dielectric behavior under the heterogeneous nanochannels. This work offers further understanding of confined organization and behavior in hybrid interfaces, which is relevant to nanoscale electrostatic applications.