Disinfection of surfaces by photocatalytic oxidation with titanium dioxide and UVA light

• Published in: Chemosphere (Oxford) Vol. 53; no. 1; pp. 71 - 77
• Main Authors: Kühn, Klaus P., Chaberny, Iris F., Massholder, Karl, Stickler, Manfred, Benz, Volker W., Sonntag, Hans-Günther, Erdinger, Lothar
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-10-2003; Elsevier
• Subjects: Antibacterial effects; Bacteria - drug effects; Bacteria - radiation effects; Biological and medical sciences; Candida albicans; Disinfection - methods; Enterococcus faecium; Ergonomics. Workplace layout. Occupational psychology; Escherichia coli; Free Radicals; Fundamental and applied biological sciences. Psychology; Kinetic; Light-guiding materials; Medical sciences; Microbiology; Microscopy, Electron, Scanning; Miscellaneous; Occupational medicine; Photocatalysis; Photolysis; Pseudomonas aeruginosa; Public health. Hygiene-occupational medicine; Sampling, pollutant analysis method, on the work place; Staphylococcus aureus; Titanium - pharmacology; Ultraviolet Rays; UV-irradiation; Free radicals; Antibacterial effects; Kinetic; UV-irradiation; Light-guiding materials; Photocatalysis; Pseudomonadales; Candida albicans; Medical equipment; UVA radiation; Microbiology; Escherichia coli; Laboratory; Fungi; Bacteria; Micrococcales; Pseudomonadaceae; Pseudomonas aeruginosa; Micrococcaceae; Fungi Imperfecti; Biological contamination; Staphylococcus aureus; Enterobacteriaceae; Thallophyta; Disinfection; Occupational hygiene; Surface treatment; Streptococcaceae; Enterococcus faecium; Metabolic inactivation; Titanium oxide; Photooxidation
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/S0045-6535(03)00362-X

Particularly in microbiological laboratories and areas in intensive medical use, regular and thorough disinfection of surfaces is required in order to reduce the numbers of bacteria and to prevent bacterial transmission. The conventional methods of disinfection with wiping are not effective in the longer term, cannot be standardized, are time- and staff-intensive and use aggressive chemicals. Disinfection with hard ultraviolet C (UVC) light is usually not satisfactory, as the depth of penetration is inadequate and there are occupational medicine risks. Photocatalytic oxidation on surfaces coated with titanium dioxide (TiO
2) might offer a possible alternative. In the presence of water and oxygen, highly reactive OH-radicals are generated by TiO
2 and mild ultraviolet A (UVA). These radicals are able to destroy bacteria, and may therefore be effective in reducing bacterial contamination. Direct irradiation with UVC however can produce areas of shadow in which bacteria are not inactivated. Using targeted light guidance and a light-guiding sheet (out of a UVA-transmittant, Plexiglas
®, for example), as in the method described in the present study, bacterial inactivation over the entire area is possible. The effectiveness of the method was demonstrated using bacteria relevant to hygiene such as
Escherichia coli,
Pseudomonas aeruginosa,
Staphylococcus aureus and
Enterococcus faecium. For these bacteria, a reduction efficiency (RE) more than 6
log
10 steps in 60 min was observed. Using
Candida albicans, a RE of 2
log
10 steps in 60 min was seen. Light and scanning electron microscopic examinations suggest that the germ destruction achieved takes place through direct damage to cell walls caused by OH-radicals.