Surface modification of TiO{sub 2} nanoparticles with carotenoids. EPR study
- Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Chemistry
- Inst. of Chemical Kinetics and Combustion, Novosibirsk (Russian Federation)
Among the semiconductors, titanium dioxide is the most suitable for many environmental applications. EPR measurements demonstrate efficient charge separation on carotenoid-modified titanium dioxide nanoparticles (7 nm). Strong complexation of carotenoids containing terminal carboxy groups ({minus}CO{sub 2}H) with the TiO{sub 2} surface leads to electron transfer from the adsorbed carotenoid molecule to the surface trapping site. For these systems, EPR signals of the carotenoid radical cations Car{sup {sm_bullet}+} and the electrons trapped on the TiO{sub 2} are observed before irradiation (77 K). Their UV-visible spectra show an absorption band with a maximum near 650 nm that is characteristic of the trapped electrons. Surface modification of the TiO{sub 2} by other carotenoids results in the formation of a complex with an optical absorption band near 545 nm. These systems form charge-separated pairs [Car{sup {sm_bullet}+}{hor_ellipsis}TiO{sub 2}(e{sup {minus}}{sub tr}){sub surf}. TiO{sub 2}(e{sup {minus}}{sub tr}){sub latt}] only upon 365--600 nm illumination at 77 K. Complexation of the TiO{sub 2} colloids with carotenoids enhances spatial charge separation, shifts the absorption threshold into the visible region, and thus greatly improves the reducing ability of the semiconductor. Photoreduction of acceptor molecules such as 2,5-dichloro-1,4-benzoquinone, nitrobenzene, and oxygen is demonstrated.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-86ER13465
- OSTI ID:
- 351600
- Journal Information:
- Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Vol. 103, Issue 22; Other Information: PBD: 3 Jun 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Investigation of surface modification of nanostructured TiO{sub 2} with EPR spectroscopy
Using site-directed mutagenesis to probe the role of the D2 carotenoid in the secondary electron-transfer pathway of photosystem II