Substitution of a metal center of phosphomolybdate, PMo12O403- (PMo12), or its tungsten analogue with dirhodium(II) and subsequent stabilization of gold nanoparticles, AuNPs, with Rh2PMo11 are demonstrated. The AuNP-Rh2PMo11 mediates oxidations but adsorbs too weakly for direct modification of electrode materials. Stability in quiescent solution was achieved by modifying glassy carbon (GC) with 3-aminopropyltriethoxysilane (APTES) and then electrostatically assembling AuNP-Rh2PMo11. At GC vertical bar APTES vertical bar AuNP-Rh2PMo11, cyclic voltammetry showed the expected set of three reversible peak-pairs for PMo11 in the range -0.2 to 0.6 vs. (Ag/AgCl)/V and the reversible Rh-II,Rh-III couple at 1.0 vs. (Ag/AgCl)/V. The presence of AuNPs increased the current for the reduction of bromate by a factor of 2.5 relative to that at GC vertical bar Rh2PMo11, and the electrocatalytic oxidation of methionine displayed characteristics of synergism between the AuNP and Rh-II. To stabilize AuNP-Rh2PMo11 on a surface in a flow system, GC was modified by electrochemically assisted deposition of a sol-gel with templated 10-nm pores prior to immobilizing the catalyst in the pores. The resulting electrode permitted determination of bromate by flow-injection amperometry with a detection limit of 4.0 x 10(-8) mol dm(-3). (C) 2010 Elsevier Ltd. All rights reserved.