| Summary: | <p>The mechanism of organothiol (OT) binding to gold has remained controversial for decades. There are three mechanisms proposed for OT binding to gold surfaces. The first is the radical pathway in which the sulfur-bound hydrogen atoms (RS-H) are released as hydrogen atoms which eventually converted into hydrogen gas. Second is the deprotonation pathway in which the sulfur-bound hydrogen atoms leave as protons. Third is direct adsorption in which the RS-H bonds remain intact on the gold surface. This study demonstrates a combined pH and surface enhanced Raman spectroscopic study of organothiol binding to citrate- and borohydride-reduced gold nanoparticles (AuNPs) in polar (water), moderately polar (dichloromethane), and nonpolar (toluene,hexane) solvents. Thiol deprotonation provides a unified pathway for OT binding to AuNPs regardless of solvent polarity of the ligand binding solutions. This work should contribute to resolve the long-standing debate on the fate of the sulfur-bound hydrogen of organothiols self-assembled on gold.</p>
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