DOI: 10.1002/cphc.201200845 Application of Boron-Doped Diamond Microelectrodes for Dental Treatment with Pinpoint Ozone-Water Production Tsuyoshi Ochiai,* [a, b] Yuya Ishii, [c] Shoko Tago, [a] Masayuki Hara, [a] Takuya Sato, [d] Kazuo Hirota, [d] Kazuya Nakata, [a, b] Taketoshi Murakami, [a] Yasuaki Einaga, [c, e] and Akira Fujishima [a, b] Ozone is known to act as a powerful antimicrobial agent against bacteria, fungi, and viruses. The strong oxidation ability of ozone induces the destruction of bacterial cell walls, cyto- plasmic membranes, and biomolecules on the bacterial cell surface. [1–3] Recently, ozone has received growing attention as a useful tool for dental treatment. [4–7] Ozone has a severely dis- ruptive effect on cariogenic bacteria, resulting in the elimina- tion of acidogenic bacteria. However, while laboratory studies suggest a promising potential of ozone in dentistry, this has not been fully realised in clinical studies to date. In this study, a novel pinpoint ozone-water production unit for dental treat- ment using boron-doped diamond (BDD) microelectrodes was developed. The application of BDD electrodes is promising for electrolyzing water to produce ozone, because of their superi- or chemical and dimensional stability, as well as their large overpotential for the oxygen-evolution reaction. [8, 9] Escherichia coli (E. coli ) and Enterococcus faecalis (E. faecalis) were used as test bacteria to assess the disinfection efficiency of the units. The BDD microelectrodes were prepared by method report- ed previously which has already been established for applica- tions in in vivo detection. [10] The BDD thin film was deposited on a prepared tungsten wire using a microwave-plasma-assist- ed chemical-vapor deposition system. Prior to BDD deposition, the tungsten wire was shaped by electrochemical etching to achieve a very small wire diameter. The as-prepared BDD- coated tungsten wires can then be used to fabricate micro- electrodes with very small wire diameters (500 mm). A scanning electron microscopy (SEM) image of such a fabri- cated BDD microelectrode shows that the wire diameter is small (500 mm) with the polycrystalline diamond grain size being approximately 2 mm (Figure 1 a). The Raman spectrum (excitation wavelength: 532 nm) of the BDD microelectrode shows one clear peak at 1333 cm 1 for sp 3 carbon bonds indi- cating that the BDD thin film is of good quality (Figure 1 b). The broad peak before the sp 3 carbon peak is attributed to the high boron-doping concentration. According to the Raman spectrum, the boron-to-carbon ratio in the BDD microelectrode is estimated to be almost 1 % by comparison of previously re- ported data. [11] A detailed interpretation of the Raman spec- trum is mentioned in ref. [11]. The SEM image and Raman spectrum indicate that by optimizing the deposition conditions qualitatively similar BDDs, in terms of morphology and crystal- line structure, can be deposited on different types and sizes of substrates. Figure 2 shows the schematic image and photograph of the ozone-water production unit which has been prepared in anal- ogy to the electrolytic water ejecting apparatus reported by Ki- taori et al. [12] A strip of an ion-exchange membrane (Nafion  ; thickness, 0.05 mm; width, 1 mm) was spirally wound around the BDD microelectrode which was used as an anode. A com- mercial Pt wire (0.3 mmf) was wound as a cathode on the ion- exchange membrane to unite the anode, the membrane, and the cathode. When a DC voltage was applied between the Figure 1. SEM image (a) and Raman spectrum (b) of a BDD microelectrode. [a] Dr. T. Ochiai, S. Tago, Dr. M. Hara, Dr. K. Nakata, T. Murakami, Prof. Dr. A. Fujishima Photocatalyst Group Kanagawa Academy of Science and Technology KSP EAST 412, 3-2-1 Sakado, Takatsu-ku, Kawasaki City Kanagawa, 213-0012 (Japan) Fax: (+ 81) 44-819-2070 E-mail : pg-ochiai@newkast.or.jp [b] Dr. T. Ochiai, Dr. K. Nakata, Prof. Dr. A. Fujishima Division of Photocatalyst for Energy and Environment Research Institute for Science and Technology Tokyo University of Science 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan) [c] Y. Ishii, Prof. Dr. Y. Einaga Department of Chemistry, Faculty of Science and Technology Keio University 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522 (Japan) [d] T. Sato, Prof. Dr. K. Hirota Research & Development Department GC CORPORATION 76-1 Hasunuma-cho, Itabashi-ku, Tokyo 174-8585 (Japan) [e] Prof. Dr. Y. Einaga JST-CREST 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522 (Japan)  2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ChemPhysChem 2013, 14, 2094 – 2096 2094 CHEMPHYSCHEM COMMUNICATIONS