Photopotential decay delay on TiO2 surface modified with p‐benzaldehydes: consequences and applications1. (19th May 2014)

• Record Type: Journal Article
• Authors: Núñez, Oswaldo; Rivas, Carlos; Vargas, Ronald; Johnson, Richard; Tor, Yitzhak; Siegel, Jay
• Is Part Of: Journal of physical organic chemistry. Volume 28:Number 3(2015:Mar.)
• Page Start: 191
• Page End: 198
• Publication Date: 2014-05-19
• Subjects: Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.3312
• Languages: English
• ISSNs: 0894-3230

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>TiO<sub>2</sub> (Anatase) surface has been modified with <italic>p</italic>‐substituted benzaldehydes (<italic>p</italic> = OCH<sub>3</sub>, CH<sub>3</sub>, H, CN, and NO<sub>2</sub>) and 4‐stilbene carboxaldehyde. Fourier transform <named-content content-type="chemicalTechnology" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">infrared spectroscopy</named-content><named-content content-type="chemicalTechnology" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">attenuated total reflectance</named-content> spectroscopy, UV–Vis reflectance spectra, and theoretical calculations indicate that the TiO<sub>2</sub> surface has been chemically modified and supported acetal formation by means of TiO<sub>2</sub>–OH reaction with the aldehyde. A steady state photocurrent was obtained during simulated UV light irradiation of the acetal‐TiO<sub>2</sub> in aqueous solution. Once the light irradiation is turned off, open‐circuit potential decay measurements were used in order to determine the electron life‐time (<italic>t<sub>n</sub></italic>). Excited electron decay is inhibited down to 1 s when the electron withdrawing delocalization capacity of the modified TiO<sub>2</sub> increases. Electron life‐time also depends on the solution reduction capacity. However, the unmodified TiO<sub>2</sub> life‐time does not. The TiO<sub>2</sub> modification results in a new series of photocatalysts that improve the organic contaminants degradation in solution because slow electron decay also induces retardation of the electron‐hole <named-content content-type="reactionType" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">recombination</named-content>. Therefore, there is a linear relationship between the electron decay life‐time and degradation rate constant. However, when electron delocalization is further increased in a way that the electron life‐time becomes ca. 7 s, degradation rate is kept constant. Therefore, the extra electron stability compromise degradation in such a way that the modified nanoparticle switches from a useful oxidant agent to a material that favors the charge carriers separation through a stable radical anion formation. Copyright © 2014 John Wiley & Sons, Ltd.</p> </abstract>