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Photon Energy and Photon Intermittence Effects on the Quantum Efficiency of Photoinduced Oxidations in Crystalline and Metastable TiO_2 Colloidal Nanoparticles

Grela, M. A. and Colussi, A. J. (1999) Photon Energy and Photon Intermittence Effects on the Quantum Efficiency of Photoinduced Oxidations in Crystalline and Metastable TiO_2 Colloidal Nanoparticles. Journal of Physical Chemistry B, 103 (14). pp. 2614-2619. ISSN 1520-6106. doi:10.1021/jp9829492. https://resolver.caltech.edu/CaltechAUTHORS:20150623-154800791

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Abstract

We report quantum yields φ-NP for the photocatalytic oxidation of 3-nitrophenol (NP) in clear, aerated, aqueous colloids of crystalline or metastable TiO2 nanoparticles as a function of photon wavelength (254 ≤ λ/nm ≤ 366) and photon absorption intermittence I_(ap) (0.002 ≤ I_(ap)/photons particle^(-1) s^(-1) ≤ 2). φ-NP's vary as φ_(-NP) ∝ I_(ap)^-(0.21±0.05) at all λ's in metastable TiO_2 sols and are ∼20 times smaller than the I_(ap)-independent φ_(-NP)'s determined in crystalline suspensions. Higher energy photons are always more efficient. We infer that (1) hyperthermal holes are able to capture electrons from NP while being deactivated in both types of particles, (2) thermalized electrons and holes are trapped in metastable particles within nanoseconds and persist as such for minutes, and (3) shallower traps become populated at larger I_(ap)'s. The similar action spectra of φ_(-NP) and φ_(-S) for nonchelating NP and bidentate salicylate (S) [E_0(NP/NP^(+•)) ≈ E_0(S^-/S^•) ≈ 2.8 V vs NHE], in the presence or absence of phosphate as a competing ligand, are evidence that hot carrier effects are indeed associated with outer-sphere interfacial redox reactions. Our data support k_(SC,max) ≥ 6 × 10^5 cm s^(-1) for h + NP → NP^(.+), which is close to the adiabatic coupling limit.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1021/jp9829492DOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp9829492PublisherArticle
ORCID:
AuthorORCID
Colussi, A. J.0000-0002-3400-4101
Additional Information:© 1999 American Chemical Society. Received: July 10, 1998; In Final Form: January 30, 1999. This work was financially supported by the National Research Council of Argentina (CONICET). Ignacio Gil Torró (University of Valencia, Spain) collaborated with this project as a fellow of the Instituto de Cooperación Iberoamericano.
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Funding AgencyGrant Number
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)UNSPECIFIED
Issue or Number:14
DOI:10.1021/jp9829492
Record Number:CaltechAUTHORS:20150623-154800791
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150623-154800791
Official Citation:Photon Energy and Photon Intermittence Effects on the Quantum Efficiency of Photoinduced Oxidations in Crystalline and Metastable TiO_2 Colloidal Nanoparticles M. A. Grela and and A. J. Colussi The Journal of Physical Chemistry B 1999 103 (14), 2614-2619 DOI: 10.1021/jp9829492
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58495
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:28 Jul 2015 19:40
Last Modified:10 Nov 2021 22:06

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