Gong Jia-You, Chen Yen-Chi, Huang Yi-Ting, Tsai Ming-Chien, Yu Kuo-Pin
Institute of Environmental and Occupational Health Sciences, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Taipei, 11221, Taiwan.
Photochem Photobiol Sci. 2014 Sep;13(9):1305-10. doi: 10.1039/c4pp00054d.
Fungal spores are known as critical indoor allergens, and indoor air purification techniques including photocatalytic disinfection using titanium dioxide (TiO2), ultraviolet germicidal irradiation (UVGI) and ozonation, have been considerably investigated. However, most of the research is in regard to photocatalytic disinfection, focused on the anti-bacterial efficacy of TiO2 nanoparticles (NPs). Furthermore, some research even showed that the photocatalytic antifungal efficacy of TiO2 NPs may not be that significant. Thus, investigating the reasons behind the non-significant antifungal efficacy of TiO2 photocatalytic disinfection and enhancing the antifungal efficacy is indispensable. In this study, ozone was employed to improve the photocatalytic antifungal efficacy of the TiO2 NPs and nano-metal supported on TiO2 NPs. The commercial TiO2 NPs (Degussa (Evonik) P25) served as a good support, and incipient wetness impregnation was successfully exploited to prepare oxidized nano-metals (Ag, Cu and Ni) in this study. There were two surfaces (quartz and putty) used in the inactivation experiments of Aspergillus niger spores which were manipulated under two conditions: exposed to ultraviolet (UVC) light , and exposed to UVC and ozone simultaneously. The SEM images demonstrated that the spores were sheltered from UVC light in the microcracks between TiO2 agglomerates. When irradiating with UVC, the A. niger spores on the two testing surfaces, without TiO2 NPs, were inactivated faster than those with TiO2 NPs, implying a "sun block" effect of this material and a lower photocatalytic antifungal efficacy than UVGI. On both surfaces, the inactivation rate constants (k) of A. niger spores exposed to UVC and ozone simultaneously (on quartz: k = 2.09-6.94 h(-1), on putty: k = 3.17-6.66 h(-1)) were better than those exposed to only UVC (on quartz: k = 1.80-5.89 h(-1); on putty: k = 2.97-3.98 h(-1)), indicating ozone can enhance the UVGI antifungal efficacy.
真菌孢子是重要的室内过敏原，包括使用二氧化钛（TiO₂）的光催化消毒、紫外线杀菌照射（UVGI）和臭氧处理在内的室内空气净化技术已得到大量研究。然而，大多数研究集中在光催化消毒方面，重点是TiO₂纳米颗粒（NPs）的抗菌效果。此外，一些研究甚至表明TiO₂ NPs的光催化抗真菌效果可能并不显著。因此，探究TiO₂光催化消毒抗真菌效果不显著的原因并提高其抗真菌效果是必不可少的。在本研究中，采用臭氧来提高TiO₂ NPs以及负载在TiO₂ NPs上的纳米金属的光催化抗真菌效果。商用TiO₂ NPs（德固赛（赢创）P25）是一种良好的载体，本研究成功利用初湿浸渍法制备了氧化态的纳米金属（Ag、Cu和Ni）。在黑曲霉孢子的灭活实验中使用了两种表面（石英和腻子），实验在两种条件下进行：暴露于紫外线（UVC）光下，以及同时暴露于UVC和臭氧中。扫描电子显微镜（SEM）图像表明，孢子在TiO₂团聚体之间的微裂缝中受到UVC光的遮蔽。在用UVC照射时，两个测试表面上没有TiO₂ NPs的黑曲霉孢子比有TiO₂ NPs的孢子灭活得更快，这意味着这种材料具有“防晒”作用，且其光催化抗真菌效果低于UVGI。在两个表面上，同时暴露于UVC和臭氧的黑曲霉孢子的灭活速率常数（k）（在石英上：k = 2.09 - 6.94 h⁻¹，在腻子上：k = 3.17 - 6.66 h⁻¹）优于仅暴露于UVC的情况（在石英上：k = 1.80 - 5.89 h⁻¹；在腻子上：k = 2.97 - 3.98 h⁻¹），这表明臭氧可以增强UVGI的抗真菌效果。
