Impact of double-chain surfactant stabilizer on the free active surface sites of gold nanoparticles

Abstract Positive and negative charged stabilizing ligands, for example, ammonium surfactants and citrate, influence the catalytic activity of AuNPs greatly, due to their different electrostatic attraction ability with substrates. However, as for the more decisive factor in AuNPs catalyzed reactions, the free active surface sites of AuNPs influenced by different kinds of ammonium surfactants has not been studied yet. In this work, we prepared double chain and mono chain ammonium surfactants capped gold nanoparticles, DDAB-Au and CTAB-Au, and put them into the reduction reaction of uranine by NaBH4. Compared to CTAB-Au, DDAB-Au favors the adsorption of BH4− and generation of metal hydride on the active sites. As a result, DDAB-Au catalyzed reduction of uranine could give shorter induction time. We attribute this phenomenon to a weaker binding affinity of DDAB to the active sites of AuNPs, resulting from the more flexible, less polar and low charge-to-molecular weight ratio properties of DDAB. Fast responding time is one of important criteria in analytical chemistry and sensor chemistry. With dramatic fluorescence changes, some DDAB-Au catalyzed reactions would facilitate the related studies in the fields of catalysis, analysis and biosensors.