Photostability and antimicrobial study of different phases of TiO2 thin films Endrika Widyastuti1, Jue-Liang Hsu2, Claire Chung3, and Ying Chieh Lee 4,5*
1 Department of Food science and Biotechnology, Faculty of Agricultural Technology, Universitas Brawijaya, Malang 65145, Indonesia- endrika_w[at]ub.ac.id
2 Department of Biological Science and Technology, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan- jlhsu[at]mail.npust.edu.tw
3 Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA- cchung43[at]jh.edu
4 Institute of Precision Electronic Components, National Sun Yat-sen University, Kaohsiung 804, Taiwan
5 Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung 804, Taiwan- yc56[at]mail.nsysu.edu.tw
Abstract
Direct current magnetron sputtering was used for generating titanium thin films on glass substrates. In order to develop TiO2 thin films, Ti thin films were thermally oxidized to promote oxygen diffusion from the air to the thin film layer. The influence of oxidation temperature on Ti thin film^s structural, morphological, photocatalytic, photostability, and antimicrobial properties has been addressed in this study. X-ray diffraction (XRD) showed that the non-stochiometric TiO2 (Ti0.895O.77) was found at a 400 oC oxidation temperature. However, increased oxidation temperatures will transform Ti0.895O.77 into the anatase/rutile TiO2 phase. Moreover, the mixed anatase-rutile phase on Ti thermally oxidized at 500 oC exhibits 54% photocatalytic performance under UV irradiation, with high photostability after five degradation cycles. The optical and photocatalytic properties of these thin films depend on the film^s phase structure and morphology, which are affected by oxidation temperature. The rate of microbial inhibition increased considerably (p < 0.05) with increasing irradiation time against effectiveness values of around 98.70, 99.87, and 93.67 % for E. coli, S. aureus, and C. albicans, respectively. These findings suggest that a critical factor in producing effective photocatalytic activity and antimicrobial effectiveness of Ti thin films is thermal oxidation temperature. Therefore, the thermal oxidation process for oxide surface growth of Ti to form TiO2 gives a simpler, more efficient, and better cost-effective method.
Keywords: Thermal oxidation- Photostability- TiO2 thin films- Irradiation time
