Effects of plasmonic field due to gold nanoparticles and magnetic field on photocurrents of zinc porphyrin–viologen linked compound-gold nanoparticle composite films

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Composite films of zinc-porphyrin–viologen (ZnP–V2+) linked compound containing six methylene group [ZnP(6)V]–gold nanoparticles (AuNP) were fabricated by combining electrostatic layer-by-layer adsorption and the Langmuir–Blodgett method. The anodic photocurrents of the ZnP(6)V–AuNP composite films are higher than those of the ZnP(6)V films. The large photocurrents in ZnP(6)V–AuNP composite films are most likely attributable to the combination of localized surface plasmon resonance due to AuNP and photoinduced intramolecular electron transfer from excited state of ZnP to V2+. The photocurrents of the ZnP(6)V–AuNP composite films increase in the presence of magnetic field. The photocurrents increase with low magnetic fields (B ≤ 150 mT) and are almost constant under high magnetic fields (B ≥ 150 mT). Magnetic field effects (MFEs) were clearly observed for both ZnP(6)V–AuNP composite films and ZnP(6)V films. The MFEs can be explained by a radical pair mechanism.