Vanadium (V) was used as the central heteroatom in the synthesis of the Keggin-type Polyoxometalate {[CH3(CH2)(7)](4)N}(3)[VMo12O40] (1). This compound was characterized by elemental analysis and single-crystal X-ray diffraction. Compound 1 was used as a bulk-modifier to fabricate the chemically modified ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) carbon paste electrode (1-ILCPE) by direct mixing. The bulk-modified 1-ILCPE showed well-defined cyclic voltammograms with four reversible redox couples in H2SO4 + Na2SO4. The first wave could be ascribed to the reduction of the central V and the last three waves corresponded to the redox processes of the peripheral Mo atoms. The 1-ILCPE presents good electro-catalytic activity not only toward the oxidation Of L-cysteine, which is attributed to the function of the central V, but also toward the reduction of hydrogen peroxide, which is attributed to the function of the Mo atoms. Compared with the conventional carbon paste electrode (CPE), the excellent experimental results suggest that the newly developed paste electrode holds great promise in the design of electrochemical devices. such as sensors and biosensors. The promising results are ascribed to the use of an ionic liquid, which forms an excellent charge-transfer bridge and wide electrochemical windows in the bulk of carbon paste electrode. (C) 2009 Elsevier Ltd. All rights reserved.