Electrocatalytic oxidation of GMP on an ITO electrode modified by the photodeposition of Pd nanoparticles onto a monolayer TiO2 nanosheets/[Ru(phen)2(dC18bpy)]2+ hybrid film

An indium tin oxide (ITO) electrode coated with monolayer TiO2/[Ru(phen)2(dC18bpy)]2+ (phen = 1,10-phenanthroline, dC18bpy = 4,4′-dioctadecyl-2,2′-bipyridyl) hybrid film (denoted as ITO/TiO2-Ru) has been prepared using the modified Langmuir-Blodgett (LB) method, and the electrocatalytic oxidation of mononucleotide of guanosine 5′-monophosphate (GMP) on an ITO/TiO2-Ru electrode after Pd-photodeposition (denoted as ITO/TiO2-Ru/Pd) has been studied. Atomic force microscopy reveals that the single-layered hybrid film of TiO2 nanosheets/[Ru(phen)2(dC18bpy)]2+ is closely packed at a surface pressure of 25 mN m−1 and has a thickness of (3.20 ± 0.5) nm. X-ray photoelectron spectra show the formation of Pd nanoparticles on the surface of hybrid film with radii of 20–200 nm by the reduction of [Pd(NH3)4]2+ under light irradiation. When it is applied to oxidize GMP, a larger catalytic oxidative current is achieved on the ITO/TiO2-Ru/Pd electrode at the external potential above 700 mV (vs. Ag|AgCl|KCl) in comparison with the naked ITO electrode and ITO/TiO2-Ru electrode. Such a result indicates that the Pd nanoparticles are able to hamper the combination of electron hole pairs and reduce the counterwork of insulating long alkyl chains of amphiphilic Ru(II) complexes, and thus develops the electron transfer efficiency and produces the enhanced redox current.