Electrocatalytic properties of [Ru(bpy)(tpy)Cl]PF6 at carbon ceramic electrode modified with nafion sol–gel composite: application to amperometric detection of l-cysteine Original Research Article

A two-step sol–gel technique was used here to prepare a carbon ceramic electrode modified with nafion and [Ru(bpy)(tpy)Cl]PF6. This involves two steps: first, forming a bulk-modified carbon ceramic electrode with nafion, and then immersing the electrode into a Ru-complex solution (electroless deposition) for a short period of time (5–25 s). Cyclic voltammograms of the resulting surface-modified carbon ceramic electrode show stable and a well-defined redox couple due to Ru(II)/Ru(III) system with surface-confined characteristic. l-Cysteine (CySH) has been chosen as a model to elucidate the electrocatalytic ability of Ru-complex nafion sol–gel composite electrode. Not only the modified electrode shows excellent catalytic activity toward l-cysteine electrooxidation in pH range 3–9, but the antifouling effect of nafion film also increases the reproducibility of results in comparison with CCE modified with homogeneous mixing of graphite powder and Ru-complex (one step sol–gel method). Under the optimized conditions in amperometry method, the concentration calibration range, detection limit and sensitivity were 0.1–100 μM, 20 nM and 50 nA/μM, respectively. The advantages of this modified electrode are good reproducibility, excellent catalytic activity, simplicity of preparation and especially its antifouling properties towards l-cysteine and its oxidation products. Additionally, it is promising as a detector in flow system or chromatography systems.