Photooxidative self-cleaning transparent titanium dioxide films on glass

In the context of studying the feasibility of photocatalytically self-cleaning windows and windshields, clear, abrasion resistant, photocatalytic films of TiO 2 were formed on soda lime glass and on fused quartz by a sol-gel process. The rate of photooxidation of contaminant deposits was estimated by measuring the rate of decrease in the integrated IR absorbance associated with the C-H stretching vibrations of a thin solution-cast film of stearic acid under 365 nm (2.4 mW/cm 2 ) or 254 nm (0.8 mW/cm 2 ) irradiation. Approximately 3 × 10 −4 stearic acid molecules were stripped per 365 nm photon in either front- or back-illuminated soda lime glass, and 6 × 10 −4 molecules when the films were coated on fused quartz. For thin TiO 2 films on fused quartz, the rate of photooxidation, normalized by the number of photons absorbed per unit area, was independent of the wavelength. In contrast, for films on soda lime glass, the rate of photooxidation, when similarly normalized, was higher for the less penetrating wavelength. The reduced photoactivity on glass at the deeply penetrating wavelength (365 nm), as well as the greater photoefficiency on quartz than on glass, are attributed to diffusion of sodium oxide from the glass into the inner glass-contacting zone of the TiO 2 layer.

[1]  J. Fan,et al.  Transparent heat mirrors for solar-energy applications. , 1976, Applied optics.

[2]  F. Babonneau,et al.  Chemical modification of alkoxide precursors , 1988 .

[3]  D. Ulrich Better Ceramics Through Chemistry , 1988 .

[4]  N. Kotov,et al.  MONOPARTICULATE LAYERS OF TITANIUM DIOXIDE NANOCRYSTALLITES WITH CONTROLLABLE INTERPARTICLE DISTANCES , 1994 .

[5]  Anders Hagfeldt,et al.  Theoretical Models for the Action Spectrum and the Current-Voltage Characteristics of Microporous Semiconductor Films in Photoelectrochemical Cells , 1994 .

[6]  H. Bach,et al.  Kristallstruktur und optische eigenschaften von dünnen organogenen titanoxyd-schichten auf glasunterlagen , 1968 .

[7]  Aaron Wold,et al.  Photocatalytic properties of titanium dioxide (TiO2) , 1993 .

[8]  David F. Ollis,et al.  Heterogeneous photocatalytic oxidation of gas-phase organics for air purification: Acetone, 1-butanol, butyraldehyde, formaldehyde, and m-xylene oxidation , 1992 .

[9]  D. Bahnemann Ultrasmall Metal Oxide Particles: Preparation, Photophysical Characterization, and Photocatalytic Properties , 1993 .

[10]  G. Raupp,et al.  Kinetics of the gas-solid heterogeneous photocatalytic oxidation of trichloroethylene by near UV illuminated titanium dioxide , 1990 .

[11]  A. Heller,et al.  The role of oxygen in photooxidation of organic molecules on semiconductor particles , 1991 .

[12]  S. McEvoy,et al.  Photocatalytic degradation of phenol in the presence of near-UV illuminated titanium dioxide , 1992 .

[13]  M. Tomkiewicz,et al.  Titanium dioxide aerogels for photocatalytic decontamination of aquatic environments , 1993 .

[14]  M. J. Snow,et al.  Respirable particulates generated by pressurized consumer products. II. Influence of experimental conditions. , 1979, American Industrial Hygiene Association journal.

[15]  R. Naaman,et al.  Reaction between O(3P) and Organized Organic Thin Films , 1994 .

[16]  Louis E. Brus,et al.  Electronic wave functions in semiconductor clusters: experiment and theory , 1986 .

[17]  T. Kawai,et al.  Heterogeneous photocatalytic production of hydrogen and methane from ethanol and water , 1981 .