Photocatalytic TiO 2 on copper alloy for antimicrobial purposes Chi-Jen Chung a,b, *, Chung-Chien Chiang c , Chang-Hsiung Chen c , Ching-Hung Hsiao a , Hsin-I Lin a , Ping-Yen Hsieh a , Ju-Liang He a a Department of Materials Science and Engineering, Feng Chia University, 100 Wen-Hua Road, Taichung 40724, Taiwan, ROC b Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, 11 Buzih Lane, Beitun District, Taichung 40601, Taiwan, ROC c Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, 191, 38 Road, Taichung Industrial Area, Taichung 40768, Taiwan, ROC 1. Introduction The threat of device-related infection has been increasingly aware by the facts of recent global wide events of MRSA [1], enterovirus [2] and avian influenza [3] in Asia region. Unexpected multiplication of germs or other bacteria pose a serious health problem. A number of available means can exterminate bacteria in our environment, including physical (steam, high heat, or irradiation) and chemical methods. These methods of killing bacteria are time and energy consuming, and are prone to cause secondary pollution to the environment. Photocatalysts have antimicrobial capability [4,5], biocompatibility [6], and self- cleaning functionality [7]. Thus, the advantages of employing such photocatalysts to clean up the environment includes: environmental friendliness, self-regeneration and perpetuality. Matsunaga et al. in 1985 have shown that photocatalysts are capable of killing microbes, which was the first report of the antimicrobial effect of photocatalyst [8]. The hydroxyl radical produced after the photocatalyst was irradiated is a very strong oxidant and can destroy coenzymes in germs and enzymes in the respiratory system. As a result, the radical stops the reproduction of bacteria and molds, thereby inhibiting bacteria growth or preventing virus DNA multiplication [4,5]. The photocatalytic nano-anatase TiO 2 powder has a rather high specific area and is often used to remove organic substances in water, direct employing photocatalyst powder as a reaction vehicle will inevitably incur separation and recycling problems, leading to a high cost [9]. Therefore, the immobilization technology of anatase TiO 2 has become particularly important and thus the introduction of deposition technology is relevant [10]. Many methods of depositing anatase TiO 2 coating have emerged, including sol–gel processes [11–14], sputter deposition [15,16], ion beam-assisted deposition (IBAD) [17], chemical vapor deposi- tion (CVD) [18,19], and arc ion plating (AIP) [20]. However, a feasible method for the direct depositing photocatalytic TiO 2 with antimicrobial function and satisfactory mechanical properties has Applied Catalysis B: Environmental 85 (2008) 103–108 ARTICLE INFO Article history: Received 15 April 2008 Received in revised form 24 June 2008 Accepted 3 July 2008 Available online 15 July 2008 Keywords: Arc ion plating Photocatalytic Titanium dioxide Protective performance Antimicrobial ABSTRACT Photocatalytic titanium dioxide (TiO 2 ) has been developed and extensively applied due to its non- toxicity, high catalytic activity, and strong self-cleaning characteristics. The present study employs an arc ion plating technique to deposit a strongly adhered photocatalytic TiO 2 coating onto bare Cu–35Zn substrate, which is commonly used in sanitary wares. The present report aims to create a TiO 2 coating with antimicrobial function and satisfactory mechanical properties. The results indicate that arc ion plating can successfully deposit TiO 2 onto brass substrates that are precoated with Ni/Cr. The cross- sectional morphology of TiO 2 coating shows a fine and dense columnar structure of anatase with a growth rate of 5 mm/h. The surface microhardness of the specimen deposited with TiO 2 coating is 351.9 HV. The adhesive force of the coating is satisfactory with a critical load of 20.38 N and its wear resistance is far better than that of the brass substrate and Ni/Cr-precoated specimen. The coating’s wear index obtained from a Taber test is 0.26. TiO 2 coatings can act as an ideal passive film and thereby shows a high corrosion potential and low corrosion current in aqueous sodium chloride. The photocatalytic effect of anatase TiO 2 will be activated under the incident light with energy greater than the band gap energy E g , of TiO 2 (3.2 eV, 387.5 nm), thereby providing antimicrobial function. In general, the Ni/Cr-precoated specimen incorporated with a photocatalytic TiO 2 film can provide sufficient protective and antimicrobial functions to its substrate, rendering it highly feasible for commercial use. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author at: Department of Materials Science and Engineering, Feng Chia University, 100 Wen-Hua Rd, Taichung 40724, Taiwan, ROC. Tel.: +886 4245 19053; fax: +886 4245 19053. E-mail address: cjchung@seed.com.tw (C.-J. Chung). Contents lists available at ScienceDirect Applied Catalysis B: Environmental journal homepage: www.elsevier.com/locate/apcatb 0926-3373/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2008.07.009