Self-assemblies of organothiols (OT) and thiolated biomolecules onto gold and silver have remained as one of the most active research areas in nanoscience and molecular interfacial phenomena.  One common belief is that organothiol forms monolayer adsorption onto gold and silver surfaces, and the structure and properties of the organothiols on gold and silver are similar.   However, recent researches conducted in our lab with a series of aromatic and alkyl thiols reveals that OT adsorption, desorption, and reactions on gold nanoparticle (AuNPs) in water can be significantly different from that on silver nanoparticles (AgNPs) in water.  OTs form monolayer adsorption onto AuNPs by releasing the sulfur-bound hydrogen as a proton and acidifying the ligand binding solution, but the aromatic OTs continuously reacts with AgNPs until total consumption of AgNP or OTs occurs.  These reactions convert AgNPs into insoluble RS-Ag complexes, inducing no detectable pH change in the OT/AgNP solutions.  On the other hand, long-chain alkanethiols adopt monolayer adsorption on both AuNPs and AgNPs, and the alkanethiols are drastically better ordered on AgNPs than on AuNPs.  Sodium borohydride induces organothiol desorption or desulfurization from both AuNPs and AgNPs.  However, the OT desorption and desulfurization efficiencies on AgNPs are significantly lower than that on AuNPs, and the effect of the sodium borohydride on the morphology for the as-synthesized colloidal AgNPs are markedly different for AuNPs.  In addition to providing a side-by-side comparison of the OT adsorption, desorption, and reaction on AuNPs versus on AgNPs, a unifying mechanism will be discussed in this presentation for those stark differences in the structure and properties between OT on AuNPs and AgNPs.

Comparative study of organothiol adsorptions, desorptions, and reactions on gold and silver nanoparticles in water

248th National Meeting (2014)

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