Interfacial Thermal Transport of Gold Surfaces Coated with Heterogeneous Monolayers in a Binary Solvent

Gold nanoparticles play a key role in thermoplasmonics due to their efficient light-to-heat conversion and their potential for chemical group functionalization. In this study, we investigate the interfacial thermal transport properties of gold surfaces coated with heterogeneous layers in contact with ethanol-water cosolvents commonly used in catalysis. By employing nonequilibrium molecular dynamics simulations, we quantify the thermal transport characteristics of water-ethanol mixtures at relevant experimental concentrations. Our simulations show excellent agreement with experimental Soret coefficients and reveal that ethanol tends to accumulate in the hot regions at experimentally relevant ethanol-water weight fractions. However, the composition of the solvent layers in contact with the hot gold surfaces is primarily influenced by the interfacial interactions between the substrate and solvent. We examine the interfacial thermal conductance of gold surfaces coated with self-assembled monolayers, including hexanethiol (hydrophobic), mercaptohexanol (hydrophilic), and catalytic units designed to offer an immobilized form of PdCl₂-(diphosphine). Our findings indicate that the preferential adsorption of ethanol (on hydrophobic surfaces) or water (on hydrophilic surfaces) significantly alters the interfacial thermal conductance. These results help explain recent observations in plasmonic sensing experiments. Furthermore, we demonstrate that in heterogeneous surfaces incorporating hydrophobic spacers and catalytic units, enhanced heat transport occurs, leading to significant temperature differences among the catalytic units, spacers, and the surrounding solvent at nanometer length scales. These insights improve our understanding of thermal and mass transport at catalytic surfaces and will inform the extensive research on thermoplasmonic applications of gold nanomaterials.