Sterilisation performances of amorphous TiO2 cardboard and textile based photocatalysts Alexis EVSTRATOV *, Cristian CHIS, Jean-Marie TAULEMESSE, Pierre GAUDON Ecole des Mines d’Alès, 6, av. de Clavières, Alès, 30319 Cedex, France * Tel: +33 (0)4 66 78 27 56, Fax: +33 (0)4 66 78 27 0, E-mail address:
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Abstract: The deep sterilisation (destruction) of genetically reinforced Escherichia Coli bacteria over the surfaces of cardboard and textile based composite materials containing amorphous TiO2 aggregates was studied. The morphologies of TiO2 species were characterized by scanning electron microscopy (SEM) and their crystalline state was investigated by X-ray Diffraction (XRD) analysis. Keywords: photocatalysis, amorphous TiO2, bacteria removal. Introduction Recently, some researches have been dedicated to the study of the sterilization capacities of photoexcited titanium dioxide being actually the most wide-spread photocatalyst [e.g. 1, 2]. However, all currently applied photocatalytic materials contain crystalline micro- or nanometric semiconductor species as active components in free or supported form. From the practical point of view, the composite photocatalytic materials are better adapted for application but the task of perfectly crystallized active phase elaboration over different supports remains a technological problem [3,4], particularly for soft matrix as natural and synthetic polymers. In our previous works [5-7] it was shown that the amorphous TiO2 composites manifest important photocatalytic activities overcoming the one of commercial Degussa P25 as reference active product. This study presents some preliminary results of cardboard and textile based amorphous TiO2 composites application as efficient bacteria removal photocatalysts. Experimental Cardboard and textile (cotton) supports containing amorphous TiO2 nano- and microaggregates grown in situ were used as test samples. Genetically modified Escherichia coli (source – INRA, France) were selected as test bacteria. Non-modified cardboard and textile were used as control samples. After three minutes of bacterial impregnation, the samples were exposed to UV-A irradiation (Vilber-Lourmat T-6L “black light” lamp, λ = 365 nm, electric power = 6W ) for 7 min. Afterwards the bacteria from all the test samples were transferred to Petrie dishes containing nutritive gel and conserved in dark for 20 hours at 35°C in order to promote the development of bacterial colonies.
Results and discussion Two Petri dishes were used as recipients. The results obtained for cardboard supports are exposed in the figure 1-a. It can be seen that in the dish sector N (right side) containing nonmodified cardboard exposed to UV-light, approximately 1500 bacterial colonies mushroomed in 20 hours of incubation. In sector M containing UV-exposed amorphous TiO2-cardboard samples, only 80 colonies were found. The figure 1-b presents the results concerned the modified textile anti-bacterial capacities. In this case, 123 bacterial colonies were developed at the active surface (sector M, right side) whereas 1200 colonies mushroomed over an initial textile surface (sector N, left side). For both modified supports, the bacteria removal efficiencies reach the level of 90 – 95 %. a)
b) M
80
N
1500
N
1200
M
123
Figure 1: Bacterial colony development in Petri dishes: a). cardboard support; b). textile support.
Conclusion The amorphous TiO2 cardboard and textile based photocatalysts manifest significant sterilisation capacities under UV-A irradiation. These soft support based composite materials seem to be promising sterilization agents of a new generation. References [1] J. H. Lee, M. Kang, S.J. Choung, K. Ogino, S. Miyata, M.S. Kim, J.Y. Park, J.B. Kim,The preparation of TiO2 nanometer photocatalyst film by a hydrothermal method and its sterilization performance for Giardia lamblia, Water Research 38, (2004) 713–719. [2] D. Blake, P.C Maness, Z. Huang, E.J. Wolfrum, J. Huang, Application of the photocatalytic chemistry of titanium dioxide to disinfection and the killing of cancer cells, Separation and Purification Methods 28 (1999) 1-50. [3] N. Kaliwoh, J.Y. Zhang, and I.W. Boyd, Titanium dioxide films prepared by photo-induced sol-gel processing using 172 nm excimer lamps, Surface & Coatings Technology 125 (2000) 424-427. [4] Z.M. Wang, Q. Fang, J.Y. Zhang, J.X. Wu, Y. Di, W. Chen, M.L. Chen and I.W. Boyd, Growth of titanium silicate thin films by photo-induced chemical vapour Deposition, Thin Solid Films 453-454 (2004) 167-171. [5] A. Evstratov, C. Chis, P. Gaudon, B. Ducourant, P. Jouffrey, 2005, Structures composites nanométriques en
état amorphe en tant que photocatalyseurs d’une nouvelle génération, Récents Progrès en Génie des Procédés 92 (2005) Section L-14, 1-8. [6] C. Chis, A. Evstratov, P. Gaudon, P. Jouffrey, Nanosized Composite Structures in an Amorphous State as Efficient Photocatalysts for Indoor Air Conditioning, Ozone & Related Oxidants (2005) Sec. VIII.5, 1-10. [7] A. Evstratov, C. Chis, A. Malygin, A. Malkov, P. Gaudon, J.M. Taulemesse, C.B. Lopez, P. Jouffrey, Pronounced Photocatalytic Activity of Nanosized TiO2 Composite Structures in Amorphous State, Topics in Catalysis (2005) in press
