Effects of Silver Nanoparticles on Photoelectrochemical Responses of Organic Dyes

The electrostatic layer-by-layer adsorption technique was used to fabricate silver nanoparticle (AgP)-organic dye composite films on indium-tin-oxide (ITO) electrodes. The degree of immobilization for the AgPs on the ITO electrode could be controlled by changing the immersion time of the electrode in the AgP aqueous colloidal solution. Porphyrin and phthalocyanine were selected as the dye molecules here because the former has a strong absorption band around the plasmon band of isolated AgPs, while the latter has one around the plasmon band of aggregated AgPs (interparticle plasmon coupling). Remarkable enhancement in the photocurrent action and fluorescence excitation spectra was observed for both dyes when considerable amounts of AgPs were deposited onto the ITO electrode. The Raman scattering measurements suggested the effects of enhanced electric fields resulting from localized surface plasmon resonance and light scattering on the photocurrent enhancement.