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.