Electrode substrate could impact the self-assembly structure of alkylthiol monolayer and further electron transfer of redox species through monolayer. In present paper gold nanoparticle modified electrode (nanogold electrode) was obtained and used for dodecanethiol (DDT) assembly. The cyclic voltammogram of DDT modified electrode in ferricyanide plus methylene blue (MB) solution revealed that MB could be used as an electron mediator to reduce ferricyanide. This mediation reduction of ferricyanide by MB on nanogold electrode was found to be largely improved than that on planar gold electrode. The voltammetric peak of this mediation reduction occurred at the potential of -0.38 V on nanogold electrode; however, no voltammetric peak was found on the planar gold electrode. This enhanced mediation reduction could be attributed to the larger surface area of nanogold electrode than that of planar gold electrode. Also, the less-densely packed assembly structure of DDT monolayer and gold nanoparticle on nanogold electrode maybe play an important role in this mediation reduction process. The self-assembly structure of DDT monolayer on electrode was also characterized by the cyclic voltammetry in solely MB, solely ferricyanide solution, and reductive desorption in KOH solution. (c) 2006 Elsevier B.V. All rights reserved.