The conventional superhydrophobic surface offered by PTFE provides no sterilization performance and is not sufficiently repellent against organic liquids. These limit PTFE's application in the field of disinfection and result a lack of durability. N-doped TiO2 photocatalyst added PTFE composite material was developed to remedy these shortcomings. This paper reports the surface characteristics, and the bactericidal and self-cleaning performance of the newly-developed composite material. The material exhibited a contact angle exceeding 150 degrees consistent with its hydrophobicity despite the inclusion of the hydrophilic N-doped TiO2. The surface free energy obtained for this composite was 5.8？mN/m. Even when exposed to a weak fluorescent light intensity (100 lx) for 24 hours, the viable cells of gram-negative E. coli on the 12% N-doped TiO2-PTFE film were reduced 5 logs. The higher bactericidal activity was also confirmed on the gram-positive MRSA. Compared with the N-doped TiO2 coating only, the inactivation rate of the composite material was significantly enhanced. Utilizing the N-doped TiO2 with the PTFE composite coating could successfully remove, by UV illumination, oleic acid adsorbed on its surface. These results demonstrate the potential applicability of the novel N-doped TiO2 photocatalyst hydrophobic composite material for both indoor antibacterial action and outdoor contamination prevention. 1. Introduction It is well known that the conventional superhydrophobic surface offered by polytetrafluoroethylene (PTFE) provides no sterilization performance and is not sufficiently repellent against organic matters. Thus, there is potential risk for bacteria to adhere to its surface more readily in ambient air, as well as organic matters is considered to reduce the durability of the superhydrophobic performance. To remedy this shortcoming, anatase titanium dioxide (TiO2), a UV light-sensitive photocatalyst added water repellent composite material has been developed in our previous study [1–5]. TiO2 was used to demonstrate the inactivation of various bacteria, such as Escherichia coli (E. coli), methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa (P. aeruginosa), Legionella pneumophila (L. pneumophila) [6–8], and Clostridium difficile spores [8]. The inclusion of TiO2 to the PTFE coating is expected to generate antimicrobial and self-cleaning properties, which would expand its scope of application. Anatase TiO2-added PTFE composite material is not only water-repellent but also exhibits self-cleaning properties. However, because
G. Yamauchu, K. Takai, and H. Saito, “PTEE based water repellent coating for telecommunication antennas,” IEICE Transactions on Electronics, vol. E83-C, no. 7, pp. 1139–1141, 2000.
G. Yamauchi, J. D. Miller, H. Saito et al., “Wetting characteristics of newly developed water-repellent material,” Colloids and Surfaces A, vol. 116, no. 1-2, pp. 125–134, 1996.
G. Yamauchi, J. D. Miller, H. Saito, et al., “Wetting characteristics of newly developed water-repellent material,” in Proceedings of the 69th Colloid and Surface Science Symposium, pp. 125–134, Salt Lake City, Utah, USA, 1995.
A. Nakajima, K. Hashimoto, T. Watanabe, K. Takai, G. Yamauchi, and A. Fujishima, “Transparent superhydrophobic thin films with self-cleaning properties,” Langmuir, vol. 16, no. 17, pp. 7044–7047, 2000.
Y. Yao, Y. Ohko, Y. Sekiguchi, A. Fujishima, and Y. Kubota, “Self-sterilization using silicone catheters coated with Ag and TiO2 nanocomposite thin film,” Journal of Biomedical Materials Research—Part B Applied Biomaterials, vol. 85, no. 2, pp. 453–460, 2008.
Y. Yao, T. Ochiai, H. Ishiguro, R. Nakano, and Y. Kubota, “Antibacterial performance of a novel photocatalytic-coated cordierite foam for use in air cleaners,” Applied Catalysis B: Environmental, vol. 106, no. 3-4, pp. 592–599, 2011.
P. S. M. Dunlop, C. P. Sheeran, J. A. Byrne, M. A. S. McMahon, M. A. Boyle, and K. G. McGuigan, “Inactivation of clinically relevant pathogens by photocatalytic coatings,” Journal of Photochemistry and Photobiology A: Chemistry, vol. 216, no. 2–4, pp. 303–310, 2010.
G. Yamauchi, H. Saito, and K. Takai, “Surface characterization of a new water repellent coating material,” in Proceedings of the International Conference on Surface Characterization of Adsorption & Interfacial Reaction, p. 121, Cona, Hawaii, USA, 1998.
G. Yamauchi, Y. Riko, Y. Yasuno, T. Shimizu, and N. Funakoshi, “Water-repellent coating for mobile phone microphones,” in Proceedings of the Nano and Hybrid Coatings Conference, pp. 1–6, Manchester, UK, 2005.
Y. Yasuno, Y. Riko, N. Funakoshi, T. Shimizu, and G. Yamauchi, “Environmentally robust electret condenser microphone,” IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E89-A, no. 8, pp. 2226–2229, 2006.
D. Gruson, G. Hilbert, F. Vargas et al., “Rotation and restricted use of antibiotics in a medical intensive care unit: impact on the incidence of ventilator-associated pneumonia caused by antibiotic-resistant gram-negative bacteria,” American Journal of Respiratory and Critical Care Medicine, vol. 162, no. 3 I, pp. 837–843, 2000.
R. Nakamura, T. Tanaka, and Y. Nakato, “Mechanism for visible light responses in anodic photocurrents at N-doped TiO2 film electrodes,” Journal of Physical Chemistry B, vol. 108, no. 30, pp. 10617–10620, 2004.
H. Shima, Ed., “Fine ceramics (advanced ceramics, advanced technical ceramics)—Test method for antibacterial activity of photocatalytic products under photoirradiation and efficacy,” JIS R 1702, Japanese Standards Association, Tokyo, Japan, 2006.
“Fine ceramics (advanced ceramics, advanced technical ceramics)—Test method for self-cleaning performance of photocatalytic materials—Part 1: measurement of water contact angle,” JIS R 1703-1, Japanese Standards Association, Tokyo, Japan, 2007.
G. Yamauchi, J. D. Miller, H. Saito, K. Takai, H. Takazawa, and T. Ueda, “The wetting characteristics of PTFE particulate composites,” Materials Transactions, vol. 37, no. 4, pp. 721–728, 1996.
J. D. Edgeworth, D. F. Treacher, and S. J. Eykyn, “A 25-year study of nosocomial bacteremia in an adult intensive care unit,” Critical Care Medicine, vol. 27, no. 8, pp. 1648–1650, 1999.
S. M. Smith, R. H.K. Eng, P. Bais, P. Fan-Havard, and F. Tecson-Tumang, “Epidemiology of ciprofloxacin resistance among patients with methicillin-resistant Staphylococcus aureus,” Journal of Antimicrobial Chemotherapy, vol. 26, no. 4, pp. 567–572, 1990.
G. Gogniat, M. Thyssen, M. Denis, C. Pulgarin, and S. Dukan, “The bactericidal effect of TiO2 photocatalysis involves adsorption onto catalyst and the loss of membrane integrity,” FEMS Microbiology Letters, vol. 258, no. 1, pp. 18–24, 2006.
P. C. Maness, S. Smolinski, D. M. Blake, Z. Huang, E. J. Wolfrum, and W. A. Jacoby, “Bactericidal activity of photocatalytic TiO2 reaction: toward an understanding of its killing mechanism,” Applied and Environmental Microbiology, vol. 65, no. 9, pp. 4094–4098, 1999.
J. Rathousky, V. Kalousek, M. Kolá？, J. Jirkovsky, and P. Barták, “A study into the self-cleaning surface properties—the photocatalytic decomposition of oleic acid,” Catalysis Today, vol. 161, no. 1, pp. 202–208, 2011.
