Photoelectrochemical sensing of dopamine using gold-TiO2 nanocomposites and visible-light illumination

A photoelectrochemical (PEC) method was developed for the determination of dopamine. It is making use of a composite prepared from gold nanoparticles and TiO 2 (type P25) and placed on a fluorine-doped tin oxide (FTO) electrode. The composites are used for photoelectrical detection with improved electron transfer efficiency for photoproduction and with improved photoelectrical conversion efficiency. This is due to the excellent electrical conductivity and surface plasmon resonance absorption by gold nanoparticles, and also by the photocatalytic effect of TiO 2 . Dopamine binds easily to the surface of the composites and acts as an electron donor. This electrode gives a strongly enhanced photocurrent which increases linearly in the 0.1 to 100 μM dopamine concentration range and has a 23 nM detection limit (at S/ N  = 3). The electrode was operated over 15 cycles of light-on and light-off states every 20 s under visible-light illumination, and the sensor indicates good stability. In addition, it is selective over several possible interferents including uric acid, L-cysteine, glutathione, ascorbic acid and glucose. A new gold/P25 composite-based photoelectrochemical sensing scheme for dopamine is described. Under visible light irradiation, the photocurrent response is increased with the increasing concentration of dopamine (DA).