Advanced

Photoinduced electron transfer between a carotenoid and TiO2 nanoparticle

Pan, Jie LU ; Benko, Gabor LU ; Xu, YH; Pascher, Torbjörn LU ; Sun, LC; Sundström, Villy LU and Polivka, Tomas LU (2002) In Journal of the American Chemical Society 124(46). p.13949-13957
Abstract
The dynamics of photoinduced electron injection and recombination between all-trans-8'-apo-beta-caroten-8'-oic acid (ACOA) and a TiO2 Colloidal nanoparticle have been studied by means of transient absorption spectroscopy. We observed an ultrafast (similar to360 fs) electron injection from the initially excited S-2 state of ACOA into the TiO2 conduction band with a quantum yield of similar to40%. As a result, the ACOA(.+) radical cation was formed, as demonstrated by its intense absorption band centered at 840 nm. Because of the competing S-2-S-1 internal conversion, similar to60% of the S-2-state population relaxes to the S-1 state. Although the S-1 state is thermodynamically favorable to donate electrons to the TiO2, no evidence was found... (More)
The dynamics of photoinduced electron injection and recombination between all-trans-8'-apo-beta-caroten-8'-oic acid (ACOA) and a TiO2 Colloidal nanoparticle have been studied by means of transient absorption spectroscopy. We observed an ultrafast (similar to360 fs) electron injection from the initially excited S-2 state of ACOA into the TiO2 conduction band with a quantum yield of similar to40%. As a result, the ACOA(.+) radical cation was formed, as demonstrated by its intense absorption band centered at 840 nm. Because of the competing S-2-S-1 internal conversion, similar to60% of the S-2-state population relaxes to the S-1 state. Although the S-1 state is thermodynamically favorable to donate electrons to the TiO2, no evidence was found for electron injection from the ACOA S, state, most likely as a result of a complicated electronic nature of the S, state, which decays with a similar to18 ps time constant to the ground state. The charge recombination between the injected electrons and the ACOA(.+) was found to be a highly nonexponential process extending from picoseconds to microseconds. Besides the usual pathway of charge recombination forming the ACOA ground state, about half of the ACOA(.+) recombines via the ACOA triplet state, which was monitored by its absorption band at 530 nm. This second channel of recombination proceeds on the nanosecond time scale, and the formed triplet state decays to the ground state with a lifetime of similar to7.3 mus. By examination of the process of photoinduced electron transfer in a carotenoid-semiconductor system, the results provide an insight into the photophysical properties of carotenoids, as well as evidence that the interfacial electron injection occurs from the initially populated excited state prior to electronic and nuclear relaxation of the carotenoid molecule. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
124
issue
46
pages
13949 - 13957
publisher
The American Chemical Society
external identifiers
  • wos:000179269800057
  • scopus:0037145995
ISSN
1520-5126
DOI
10.1021/ja0279186
language
English
LU publication?
yes
id
8b6b31f6-3fe8-4b32-87be-e9eeec786255 (old id 323401)
date added to LUP
2007-11-08 09:44:33
date last changed
2017-12-10 04:36:22
@article{8b6b31f6-3fe8-4b32-87be-e9eeec786255,
  abstract     = {The dynamics of photoinduced electron injection and recombination between all-trans-8'-apo-beta-caroten-8'-oic acid (ACOA) and a TiO2 Colloidal nanoparticle have been studied by means of transient absorption spectroscopy. We observed an ultrafast (similar to360 fs) electron injection from the initially excited S-2 state of ACOA into the TiO2 conduction band with a quantum yield of similar to40%. As a result, the ACOA(.+) radical cation was formed, as demonstrated by its intense absorption band centered at 840 nm. Because of the competing S-2-S-1 internal conversion, similar to60% of the S-2-state population relaxes to the S-1 state. Although the S-1 state is thermodynamically favorable to donate electrons to the TiO2, no evidence was found for electron injection from the ACOA S, state, most likely as a result of a complicated electronic nature of the S, state, which decays with a similar to18 ps time constant to the ground state. The charge recombination between the injected electrons and the ACOA(.+) was found to be a highly nonexponential process extending from picoseconds to microseconds. Besides the usual pathway of charge recombination forming the ACOA ground state, about half of the ACOA(.+) recombines via the ACOA triplet state, which was monitored by its absorption band at 530 nm. This second channel of recombination proceeds on the nanosecond time scale, and the formed triplet state decays to the ground state with a lifetime of similar to7.3 mus. By examination of the process of photoinduced electron transfer in a carotenoid-semiconductor system, the results provide an insight into the photophysical properties of carotenoids, as well as evidence that the interfacial electron injection occurs from the initially populated excited state prior to electronic and nuclear relaxation of the carotenoid molecule.},
  author       = {Pan, Jie and Benko, Gabor and Xu, YH and Pascher, Torbjörn and Sun, LC and Sundström, Villy and Polivka, Tomas},
  issn         = {1520-5126},
  language     = {eng},
  number       = {46},
  pages        = {13949--13957},
  publisher    = {The American Chemical Society},
  series       = {Journal of the American Chemical Society},
  title        = {Photoinduced electron transfer between a carotenoid and TiO2 nanoparticle},
  url          = {http://dx.doi.org/10.1021/ja0279186},
  volume       = {124},
  year         = {2002},
}