Electrochemically controlled Au nanoparticle nucleation at a micro liquid/liquid interface using ferrocene as reducing agent

Gold nanoparticles (NPs) have become ubiquitous owing to their stability, plasmonic and catalytic properties, as well as biocompatibility, such that intensive research has been conducted with the aim of controlling the final NP size and morphology. Since the 1990's, the liquid/liquid interface has been a means of generating Au NPs via dissolution of Au salts in the aqueous phase and hydrophobic capping agents into the organic phase. Herein, by employing the micro interface between two electrolytic solutions (ITIES), specifically water/1,2-dichloroethane (w/DCE), Au NPs were electrolytically generated using ferrocene (Fc) dissolved in the DCE phase as both electron donor and capping agent, while KAuCl4 was dissolved in the aqueous phase. By varying the pH, Au salt:Fc concentration ratio, potential, and time of reaction, the size and morphology, 20-400 nm and spherical or cubic, respectively, can be controlled. Voltammetric analysis was used to investigate interfacial electron transfer from Fc(org) to AuCLl(4)(-)(aq). However, at open-circuit-potential and during ampemmetry highly polydisperse nanosheets, rods, and cubes were also observed. Critically, the micropipette apparatus with integrated syringe could be easily industrialized as a NP dispensing apparatus coupled with parallelization to rapidly modify substrate surfaces with size and morphologically controlled Au NPs.

Automated summary

Gold nanoparticles can be generated at the liquid/liquid interface using a micro interface between two electrolytic solutions, controlling size and morphology by adjusting pH, gold salt:Fc concentration ratio, potential, and reaction time. Voltammetric analysis is used to study electron transfer, while open-circuit potential and amperometry reveal polydisperse nanosheets, rods, and cubes. The micropipette apparatus with integrated syringe shows potential for industrialization as a NP dispensing apparatus for modifying substrate surfaces.