%0 Journal Article %J Chemistry a European Journal %D 2011 %T Exciton-coupled charge-transfer dynamics in a porphyrin J-aggregate/TiO 2 complex %A Verma, Sandeep %A Ghosh, Amrita %A Das, Amitava %A Ghosh, Hirendra Nath %X

Exciton-coupled charge-transfer (CT) dynamics in TiO2 nanoparticles (NP) sensitized with porphyrin J-aggregates has been studied by femtosecond time-resolved transient absorption spectroscopy. J-aggregates of 5,10,15-triphenyl-20-(3,4-dihydroxyphenyl) porphyrin (TPPcat) form CT complexes on TiO2 NP surfaces. Catechol-mediated strong CT coupling between J-aggregate and TiO2 NP facilitates interfacial exciton dissociation for electron injection into the conduction band of the TiO2 nanoparticle in pulse width limited time (<80 fs). Here, the electron-transfer (<80 fs) process dominates over the intrinsic exciton-relaxation process (J-aggregates: ca. 200 fs) on account of exciton-coupled CT interaction. The parent hole on J-aggregates is delocalized through J-aggregate excitonic coherence. As a result, holes immobilized on J-aggregates are spatially less accessible to electrons injected into TiO2, and thus the back electron transfer (BET) process is slower than that of the monomer/TiO2 system. The J-aggregate/porphyrin system shows exciton spectral and temporal properties for better charge separation in strongly coupled composite systems.

%B Chemistry a European Journal %V 17 %P 3458–3464 %8 MAR %G eng %N 12 %2

Council of Scientific & Industrial Research (CSIR) - India

%3 Foreign %4 5.81 %R 10.1002/chem.201002537