Thiol-Capped Gold Nanoparticles on Graphite:  Spontaneous Adsorption and Electrochemically Induced Release

Gold nanoparticle-(AuNP)-modified carbon graphite surfaces have been prepared by simple immersion of highly oriented pyrolytic graphite (HOPG) in hexane solutions containing 3 nm diameter butanethiol- or nonanethiol-capped nanoparticles. The AuNP adsorb on the HOPG surface free of unbounded thiols, remaining unchanged with time. The amount of adsorbed thiol-protected AuNP depends on concentration and time. The reductive desorption of thiols from the AuNP produces an efficient release of more than 90% of the AuNP from the carbon surface to the aqueous solution. The remaining thiol-free Au nanoparticles do not sinter on the HOPG, forming stable and electrochemically active islands. These results could open interesting possibilities for easy transfer of thiol-capped metallic NP from one environment to another, for controlled release of biomolecules from metallic NP, and for the preparation of catalytic or decontamination systems on large area C surfaces.