Electrochemical Oxidation and Deposition of Metal Nanoclusters and Nanoparticles at Electrodes and Electrode-Molecule Junctions

Here we describe the direct electrodeposition of Au nanoclusters (NCs) in the 1-2 nm diameter range on indium tin oxide coated glass electrodes (glass/ITO) by electroreduction of ionic Au complexes in the absence and presence of phosphine stabilizers. Anodic stripping voltammetry, UV-vis spectroscopy, and x-ray photoelectron spectroscopy confirms the size and coverage of the Au NCs. The Au NCs have unique reactivity and stability due to their small size. Metal nanoparticle (NP) oxidation and deposition occur directly at electrode/molecule/NP junctions with slower kinetics compared to direct processes on the electrode surface but faster kinetics compared to electrode/molecule systems with no NPs. A variety of junctions and electrochemical processes are possible using molecular assembly and NP electrophoretic deposition at electrode surfaces. Finally, the use of seed-mediate growth of metal NPs allows pM detection limits of metal ions in solution for electrochemical sensing applications. Nanoscale electrochemical processes are fascinating from a fundamental perspective but also have potential applications in catalysis, nanoelectronics, sensing, and energy.