Core size effects on electrodeposition of gold nanoparticles attached with biferrocene derivatives

Biferrocene-modified gold nanoparticles(Au_n-BFc) comprising 1.7, 2.2 and 2.9 nmin average core diameter, d,were synthesized by a substitution reaction of octylthiolate-covered nanoparticles with biferrocene-terminatedalkanethiol, 1-(9-thiononyl-1-one)-1, 1-biferrocene (BFcS).All sizes of Au_n-BFc undergo two-stepoxidation reactions in 0.1 mol dm^-3Bu₄NClO₄-CH₂Cl₂and consecutive potential scans including the second oxidationprocess lead to the formation of an adhesive redox-active goldnanoparticle film on an electrode. The thickness of theAu_n-BFc film is controllable by thenumber of potential scans. The scanning tunneling microscopeimages reveal that the Au_n-BFc (d = 2.9 nm) film forms many domains ofthe assembled Au_n-BFcs, especially theparticles are isotropically assembled in line.