Microstructural effect on the antimicrobial efficacy of arc ion plated TiO 2
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H.I. Lin and J.L. He Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan, Republic of China (Received 21 April 2007; accepted 16 July 2007)
Photocatalytic titanium dioxide coatings prepared via various processes have been developed for antimicrobial purposes. Among them is arc ion plating, which may provide more advantages than other processes such as high growth rate, strong film adhesion, as well as the ability to obtain anatase phase at a low deposition temperature. This research involves an arc ion plating method to produce TiO2 film on stainless steel. Antimicrobial efficacy is examined as a function of coating parameters. The experimental results show that the deposited film mainly consists of a rutile phase at an initial growth stage, followed by the growth of an anatase phase at a later stage. By increasing oxygen partial pressure, an increased volume of anatase phase is obtained. The volume of anatase phase is found to strongly and positively affect antimicrobial efficiency. Such an arc ion plated TiO2 coating can be potentially served for antimicrobial treatment of medical equipment.
I. INTRODUCTION
As opposed to essential antimicrobial materials through the addition of copper or silver,1–4 photocatalytic titanium oxide has received great interest for antimicrobial applications for years because of its many advantages over other materials, such as chemical stability, non-toxicity, and long-term durability. Antimicrobial behavior of TiO2 is known to be activated by its photocatalysis property that was first discovered by Fujishima and Honda in 1972.5 Photocatalytic splitting of water on anatase TiO2 crystal was found. This has led to tremendous research on the photocatalytic mechanism and improvement of the microstructure.6–8 The photocatalytic process of TiO2 involves the generation of electron-hole pairs when exposed to light.9 Aggressive oxygen radicals are generated by the electron attack, and the hole accelerates hydroxyl radical formation. These radicals eventually attack bacteria or viruses by inhibiting deoxyribonucleic acid (DNA) clonal processing.10–12 Knowing that photocatalytic events occur heterogeneously to the TiO2 surface and on the near surface, a
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Address all correspondence to this author. e-mail [email protected] DOI: 10.1557/JMR.2007.0388 J. Mater. Res., Vol. 22, No. 11, Nov 2007
variety of attempts have been made to prepare TiO2 by coating. The substrate provides the integrity of TiO2, whereas TiO2 permanently serves its photocatalytic function, as well as its antimicrobial function on the substrate surface. Wet processes such as sol-gel preparation9,13 and coprecipitation,14 dry processes such as sputter deposition15 and evaporation deposition16 are capable of providing photocatalytic properties or antimicrobial performance. Unfortunately, the methods reported above require post heat treatment to a temperature of at least 350 °C to allow anatase phase growth that the photocatalytic properties or antimicrobial performance rely on. Arc
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