Enhanced Photocurrent Generation in Nanostructured Chromophore/Carbon Nanotube Hybrid Layer-by-Layer Multilayers

In this paper, we demonstrate photocurrent generation from nanostructured layer-by-layer (LbL) ultrathin films consisting of chromophores and single-walled carbon nanotubes (SWNT). We fabricated 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetr ( p -toluenesulfonate) (TMPyP)-SWNT/sodium copper chlorophyllin (SCC)-SWNT LbL film from noncovalently adsorbed composites. SWNT were dissolved in water-soluble cationic TMPyP and anionic SCC, and the resulting solutions were used for electrostatic LbL multilayer fabrication. The solubility of SWNT in water was studied by UV−vis absorption spectroscopy. The composites were highly dispersed owing to the π−π interactions. The fluorescence spectroscopy measurements showed efficient quenching of TMPyP and SCC fluorescence, which was due to the interaction with SWNT. In situ surface plasmon resonance spectroscopy during the LbL multilayer fabrication indicated a stepwise increase in reflectivity, implying the successive formation of nanostructured hybrid ultrathin films. Cyclic voltammetry revealed that the electroactivity of the hybrid film was enhanced by the incorporation of SWNT. The composite LbL film electrode exhibited an enhancement of photocurrent compared to a TMPyP/SCC (no SWNT) film electrode, suggesting efficient charge separation and electron transfer in the system.