Novel organic–inorganic hybrid material based on tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate and Dawson-type tungstophosphate K7[H4PW18O62]·18H2O as a bifuctional hydrogen peroxide electrocatalyst for biosensors

In this study, we synthesized a new hybrid material using Wells–Dawson K7[H4PW18O62]·18H2O (PW18) and tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate ([Ru(bpy)3]Cl2·6H2O). CHN elemental analyses depicted that 1 mol of [H4PW18O62]7− reacts with 3 mol of [Ru(bpy)3]2+ to form K[Ru(bpy)3]3H4PW18O62. By adding the mild reducing agent (KI), CHN analyses illustrated that 1 mol of [H4PW18O62]7− reacts with only 1 mol of [Ru(bpy)3]2+ to yield K5[Ru(bpy)3]H4PW18O62 hybrid material. FT-IR spectra showed the presence of both [Ru(bpy)3]2+ cation and the Dawson anion. K5[Ru(bpy)3]H4PW18O62 was immobilized on glassy carbon (GC) electrode and the modified electrode was subjected to cyclic voltammetry and amperometry in presence of hydrogen peroxide (H2O2) and found to exhibit a notable bifunctional catalytic activity towards the oxidation and the reduction of H2O2 at neutral pH and at reasonably low cathodic and anodic potentials. Reductive determination was found to be more efficient than the oxidative detection. The resulting H2O2 sensor K5[Ru(bpy)3]H4PW18O62/GC based reductive detection at −0.4 V vs. Ag/AgCl has a sensitivity of ∼0.78 μA/mM mm2, fast response time (<5 s), low detection limit (<0.5 μM), high selectivity towards endogenous interferences such as uric acid, acetaminophen and ascorbic acid, a linear range from 0.5 μM to at least 90 mM H2O2 and was stable for at least 5 weeks. This type of hybrid catalysts could be of great relevance for applications in oxidase based biosensors.