Shape-Induced Variations in Aromatic Thiols Adsorption on Gold Nanoparticle: A Novel Method for Accurate Evaluation of Adsorbed Molecules

Nonspherical gold nanoparticles (GNPs) are increasingly used to enhance sensitivity and selectivity in analytical methods such as surface-enhanced Raman spectroscopy (SERS) for detecting trace biomarkers. However, there is limited research on the adsorption properties of aromatic thiols onto gold nanoparticles of different morphologies, where surface curvature varies significantly at the molecular level. In this study, we investigated the adsorption kinetics of 4-mercaptobenzoic acid, an aromatic molecule, on GNPs with different shapes using SERS. Our findings revealed significant differences in the adsorption behavior and binding site preferences of aromatic thiols on GNPs with distinct morphologies. While thiol molecules consider any surface site on nanospheres equally appealing, nanostars exhibit variations in curvature and surface energy, leading to initial binding with further repositioning from the tips of the nanostar after plasmon activation. To address these differences, we proposed a universal method to evaluate the quantity of tightly bound adsorbed molecules on GNPs independently of the particle size, shape, or concentration.