dorsal/arxiv
View SchemaHole Scavenging and Photo-Stimulated Recombination of Electron-Hole Pairs in Aqueous TiO2 Nanoparticles
| Authors | I. A. Shkrob, M. C. Sauer Jr |
|---|---|
| Categories | |
| ArXiv ID | physics/0405035 |
| URL | https://arxiv.org/abs/physics/0405035 |
Abstract
It is shown that 532 nm and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near IR. This photobleaching occurs within the duration of the laser pulse (3 ns FWHM); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole scavenger. When glycerol is added to the solution, some light-absorbing holes are scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not scavenged, even at high concentration of the scavenger (> 10 vol %). A reaction with chemi- and physi- sorbed glycerol would account for the prompt and the slow hole decay, respectively. The implications of these results are discussed.
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"abstract": "It is shown that 532 nm and 1064 nm laser photoexcitation of trapped\nelectrons generated by 355 nm photolysis of aqueous titania (TiO2)\nnanoparticles causes rapid photobleaching of their absorbance band in the\nvisible and near IR. This photobleaching occurs within the duration of the\nlaser pulse (3 ns FWHM); it is caused by photoinduced electron detrapping\nfollowed by rapid recombination of the resulting free electron and a trapped\nhole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm\nand ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral\ncontributions from trapped electron and hole is demonstrated using glycerol as\na selective hole scavenger. When glycerol is added to the solution, some\nlight-absorbing holes are scavenged promptly within the duration of the 355 nm\nphotoexcitation pulse, some are scavenged at a slower rate over the first 200\nns after the 355 nm pulse, and the rest are not scavenged, even at high\nconcentration of the scavenger (\u003e 10 vol %). A reaction with chemi- and physi-\nsorbed glycerol would account for the prompt and the slow hole decay,\nrespectively. The implications of these results are discussed.",
"arxiv_id": "physics/0405035",
"authors": [
"I. A. Shkrob",
"M. C. Sauer Jr"
],
"categories": [
"physics.chem-ph",
"physics.acc-ph"
],
"title": "Hole Scavenging and Photo-Stimulated Recombination of Electron-Hole Pairs in Aqueous TiO2 Nanoparticles",
"url": "https://arxiv.org/abs/physics/0405035"
},
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