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 Iap (0.002 ≤ Iap/photons particle-1 s-1 ≤ 2). φ-NP's vary as φ-NP ∝ Iap-0.21±0.05 at all λ's in metastable TiO2 sols and are ∼20 times smaller than the Iap-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 Iap's. The similar action spectra of φ-NP and φ-S for nonchelating NP and bidentate salicylate (S) [E0(NP/NP+•) ≈ E0(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 kSC,max ≥ 6 × 105 cm s-1 for h + NP → NP.+, which is close to the adiabatic coupling limit.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
