title: Photon flux and wavelength effects on the selectivity and product yields of the photocatalytic air oxidation of neat cyclohexane on TiO(2) particles.
abstract: Product selectivity and yields of cyclohexanol and cyclohexanone formation in the photocatalytic air oxidation of cyclohexane on TiO(2) particles were determined as a function of the irradiation wavelength (254 < or = lambda/nm < or = 366) and the photon flux (0.3 < or = I(0)/neinstein cm(-2) s(-1) < or = 5.0). Photonic efficiencies for total monooxygenated products (cyclohexanol + cyclohexanone) ranged from 10 to 25% depending on photon energy and fluency. The cyclohexanol-to-cyclohexanone ratio linearly increases with the incident photon flux at each wavelength and varies more than a magnitude order -- from 3 to 32%-at the same incident photon fluency -- 5 neinstein cm(-2) s(-1) -- by changing the irradiation wavelength from 366 to 303 nm. Experimental evidence indicates that both spectral and intensity effects emerge as a consequence of the change in the frequency of photon absorption per particle. A mechanism is proposed which accounts for the origin of the selectivity changes.
authors.affiliation: Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de Mar del Plata, B7602AYL Mar del Plata, Buenos Aires, Argentina.
authors.forename: Marta A
authors.initials: MA
authors.lastname: Brusa
authors.forename: Maria A
authors.initials: MA
authors.lastname: Grela