Effect of strong coupling on interfacial electron transfer dynamics in dye-sensitized TiO2 semiconductor nanoparticles

Ghosh, Hirendra N. (2007) Effect of strong coupling on interfacial electron transfer dynamics in dye-sensitized TiO2 semiconductor nanoparticles Journal of Chemical Sciences, 119 (2). pp. 205-215. ISSN 0253-4134

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Official URL: http://link.springer.com/article/10.1007/s12039-00...

Related URL: http://dx.doi.org/10.1007/s12039-007-0028-2

Abstract

Dynamics of interfacial electron transfer (ET) in ruthenium polypyridyl complex [{bis-(2,2′-bpy)-(4-[2-(4′-methyl-[2,2′]bipyridinyl-4-yl)-vinyl]-benzene-1,2-diol)}ruthenium(II) hexafluorophosphate] (Ru-cat) and 5,10,15-tris phenyl-20-(3,4-dihydroxy benzene) porphyrin (TPP-cat)-sensitized TiO2 nanoparticles have been investigated using femtosecond transient absorption spectroscopic detection in the visible and near-infrared region. We have observed that both Ru-cat and TPP-cat are coupled strongly with the TiO2 nanoparticles through their pendant catechol moieties. We have observed a single exponential and pulse-width limited (<100 fs) electron injection from nonthermalized-excited states of Ru-complex. Here electron injection competes with the singlet-triplet manifold relaxation due to strong coupling of catecholate binding, which is a unique observation. Optical absorption spectra indicate that the catechol moiety interacts with TiO2 nanoparticles showing the characteristic pure catechol-TiO2 charge-transfer (CT) band in the visible region. Transient absorption studies on TPP-cat/TiO2 system exciting both the Soret band at 400 nm and the Q-band at 800 nm have been carried out to determine excitation wavelength-dependence on ET dynamics. The reaction channel for the electron-injection process has been found to be different for both the excitation wavelengths. Excitation at 800 nm, is found directly populate directly the excited CT state from where diffusion of electrons into the conduction band takes place. On the other hand, excitation at 400 nm light excites both the CT band of cat-TiO2 and also Soret band of TPP-cat.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Interfacial Electron Transfer Dynamics; Tio2 Semiconductor Nanoparticles; Transient Absorption Spectroscopy; Electron Injection; Soret Band; MLCT Singlet and Triplet States
ID Code:101911
Deposited On:01 Feb 2017 08:42
Last Modified:01 Feb 2017 08:42

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