Visible-Light-Induced Bactericidal Activity of a Nitrogen-Doped Titanium Photocatalyst against Human Pathogens (original) (raw)
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Environmental Science & Technology, 2007
Nitrogen-doped titanium oxide (TiON) nanoparticle photocatalysts were synthesized by a sol-gel process, for disinfection using E. coli as target bacteria. Our work shows that the calcination atmosphere has strong effects on the composition, structure, optical, and antimicrobial properties of TiON nanoparticles. Powders calcinated in a flow of N 2 atmosphere (C-TiON) contain free carbon residue and demonstrate different structures and properties compared to the TiON powders calcinated in air. Disinfection experiments on Escherichia coli indicate that C-TiON composite photocatalyst has a much better photocatalytic activity than pure TiON photocatalyst under visible light illumination. The enhanced photocatalytic activity is related to stronger visible light absorption of the carbon-sensitized TiON.
Photocatalytic disinfection of E . coli using N-doped TiO 2 composite
2014
Heterogeneous photocatalysis is among an alternative technique for the inactivation of pathogenic microorganisms. Several researchers have achieved the successful killing of bacteria, viruses, fungi or protozoa by semiconductor photocatalysis. This study significantally provides a better understanding of the bactericidal properties of N-TiO2 by identifying specific bacterial targets and cell strcuture during disinfection in pure water. The photocatalytic inactivation of bacteria was investigated using E. coli, a well-known bacterial indicator. Firstly, the effects of the contact of N-doped TiO2 with bacterial cells in the dark on both the bacterial cultivability and the envelope integrity was carried out. Then, assessment of the deleterious effects of N-doped TiO2 on the bacteria’s permeability and cultivability was done under visible radiations exposure. In order to identify the cell structure during the inactivation of the bacteria, monitoring of atomic force microscopy was also c...
Applied Catalysis B: Environmental, 2014
The present study deals with the inactivation of Escherichia coli and Klebsiella pneumoniae in water by means of heterogeneous photocatalysis under simulated solar irradiation. For this purpose, novel Mn-, Co-and Mn/Co-doped TiO 2 catalysts were prepared. A straightforward, simple and inexpensive process has been developed based on a co-precipitation method for the synthesis of metal-doped catalysts, which were subsequently assessed in terms of their disinfection efficiency. The effect of various operating conditions, such as metal dopant (Mn-, Co-and Mn/Co), dopant concentration (0.02-1 wt%), catalyst concentration (25-250 mg/L), bacterial concentration (10 2 -10 8 CFU/mL), treatment time (up to 60 min), toxic effects on bacteria and photon flux (4.93-5.8 × 10 −7 Einstein/(L s)), was examined under simulated solar irradiation. Metal-doped TiO 2 samples were prepared reproducibly and doping shifted the optical absorption edge to the visible region. Their activity was superior to the respective of commercially available P25 titania. The reference strains of E. coli and K. pneumoniae proved to be readily inactivated during photocatalytic treatment of aqueous samples, since disinfection occurred rapidly (i.e. after only 10 min of irradiation) with the dopant concentration affecting the overall process to a certain extent. Disinfection follows a pseudo-first order kinetic rate in terms of both bacteria removal. Inactivation of the bacteria is attributed to the oxidative degradation of their cells and increase of their cell permeability and not to the potential toxicity of the metal-doped semiconductors, which did not exhibit any bactericidal properties. It has been shown that the improved activity of the Mn-, Co-, and binary Mn/Co doped TiO 2 is accredited to the fact that they can be activated in the visible part of the spectrum, in the absence of UV light (i.e. >420 nm).
World Journal of Microbiology and Biotechnology, 2009
This work focuses on the photocatalytic performances and antibacterial activity of nitrogen doped TiO 2 nanosystems with three and five layers obtained by a sol-gel route, followed by thermal treatment in oxygen or ammonia atmosphere at temperatures between 400 and 1000°C. Subsequently, the antibacterial activity of the obtained nanosystems on the Escherichia coli cells are determined and discussed. The obtained results show a significant dependence of the functional performances on the system's composition. In particular, the antimicrobial activity of nitrogen-doped TiO 2 films is correlated with the temperature of thermal treatment and illumination time with visible artificial light.
Surfaces and Interfaces, 2018
In this study, titanium dioxide (TiO 2) nano-structures including nanoparticles and nano-wires are synthesized on the glass substrate at temperatures of 300, 400 and 500°C using thermal chemical vapor deposition technique. Doping with nitrogen are done in three different temperatures including 300, 400, 500°C to obtain optimum nitrogen doping content. To investigate the optical properties, crystalline structure, morphology, thickness and chemical components of the nano-structures, UV-Visible spectrometer, X-Ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy are used, respectively. Results show that the temperature and location of substrate play a significant impact on the morphology and structure of as-grown TiO 2 nano-structures. The crystal structure of the obtained layers including TiO 2 nano-structures on the glass are consisted anatase and rutile crystalline phases. The atomic percentage of nitrogen in TiO 2 nano-structures at a doping temperature of 400°C increase in comparison to the other two doping temperatures. In addition, observing the peak of TiN and Ti 3.72 O 8.00 N 2.24 structures in the X-Ray pattern at doping temperature of 400°C, refer to dope TiO 2 nano-structures with a significant amount of nitrogen. Moreover, the reduction of band gap at about 0.4 eV, for N-TiO 2 nano-structures grown at 400°C, confirms the enhancement of photo-catalytic activity in the visible region. Antibacterial properties of pure titanium dioxide and doped with nitrogen were examined under dark, sunlight and UV light for E. Coli bacteria. The results show that growth of E. Coli bacteria significantly reduces in solution using N-TiO 2 /glass system treated at 400°C in NH 3 /N 2 ambient under sunlight due to down shifting of TiO 2 band gap in compared with other samples.
Coatings, 2014
In damp environments, indoor building materials are among the main proliferation substrates for microorganisms. Photocatalytic coatings, including nanoparticles of TiO 2 , could be a way to prevent microbial proliferation or, at least, to significantly reduce the amount of microorganisms that grow on indoor building materials. Previous works involving TiO 2 have already shown the inactivation of bacteria by the photocatalysis process. This paper studies the inactivation of Escherichia coli bacteria by photocatalysis involving TiO 2 nanoparticles alone or in transparent coatings (varnishes) and investigates different parameters that significantly influence the antibacterial activity. The antibacterial activity of TiO 2 was evaluated through two types of experiments under UV irradiation: (I) in slurry with physiological water (stirred suspension); and (II) in a drop deposited on a glass plate. The results confirmed the difference in antibacterial activity between simple drop-deposited inoculum and inoculum spread under a plastic film, which increased the probability of contact between TiO 2 and bacteria (forced contact). In addition, the major effect of the nature of the suspension on the photocatalytic disinfection ability was highlighted. Experiments were also carried out at the surface of transparent coatings formulated using nanoparticles of TiO 2 . The results showed significant antibacterial activities after 2 h and 4 h and suggested that improving the formulation would increase efficiency.
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2015
Commercially available polypropylene foil was pretreated with a low temperature oxygen plasma and covered with a thin film of nanocrystalline titanium dioxide by dip coating. The films were then photosensitized by titanium(iv) surface charge transfer complexes formed by impregnation with catechol. The photoactivity of the coatings up to 460 nm was confirmed by photoelectrochemical measurements. The photoinactivation of Escherichia coli and Staphylococcus aureus was evaluated by a glass adhesion test based on ISO 27447:2009(E) in the presence of visible light. The coating showed good antimicrobial activity induced by light from a light-emitting diode (405 nm), in particular towards E. coli ATCC 25922 strain. Adaptation of ISO 27447:2009(E) to assess bacterial photoinactivation by photocatalytic coatings will allow this procedure to be applied for the comparison of photoactivity under a range of irradiation conditions.
Beilstein Journal of Nanotechnology, 2013
Pure anatase, nanosized and Sn 4+ ion doped titanium dioxide (TiO 2 ) particulates (TiO 2 -Sn 4+ ) were synthesized by hydrothermal process. TiO 2 -Sn 4+ was used to coat glass surfaces to investigate the photocatalytic antibacterial effect of Sn 4+ doping to TiO 2 against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus). Relationship between solid ratio of TiO 2 -Sn 4+ in coatings and antibacterial activity was reported. The particulates and the films were characterized using particle size analyzer, zeta potential analyzer, Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), SEM, AAS and UV/VIS/NIR techniques. The results showed that TiO 2 -Sn 4+ is fully anatase crystalline form and easily dispersed in water. Increasing the solid ratio of TiO 2 -Sn 4+ from 10 to 50% in the coating solution increased antibacterial effect.
Songklanakarin Journal of Science and Technology
Titanium dioxide photocatalysts were synthesized by sol-gel process, by varying the reaction conditions, acids, water content, and trivalent (Al, B) dopants. The characterizations of products were determined by XRD, SEM, BET, and UV-vis spectroscopy. The samples were mainly amorphous with a small amount of anatase, rutile, or a mixture of anatase and rutile, with a crystallite sizes of about 5-10 nm. The antibacterial activity of the synthesized TiO2 samples were investigated qualitatively and semi-quantitatively. Five types of bacteria, Escherichia coli ATCC25922, Psudomonas aeruginosa ATCC27853,Bacillus subtilis BGA, Staphylococcus aureus ATCC25923, and methicillin-resistant S. aureus (MRSA) DMST 2054, were used for the inactivation experiment employing the agar dilution method. All the synthesized samples showed inactivation activity with varying degree of efficiency. Two of them showed a much higher activity than Degussa P25.
Photobactericidal effects of TiO2 thin films at low temperatures—A preliminary study
Journal of Photochemistry and Photobiology A: Chemistry, 2010
The efficacy of TiO 2 photocatalysis for the destruction of pathogenic bacteria has been demonstrated by a number of groups over the past two decades. Pathogenic bacteria represent a significant hazard for the food and drink industry. Current practices in this industry dictate that rigorous sanitizing regimes must be regularly implemented resulting in lost production time. The incorporation of a TiO 2 antibacterial surface coating in this setting would be highly desirable. In this paper we report a preliminary study of the efficacy of a TiO 2 coating, doped with the lanthanide, neodymium, at low temperature conditions such as those utilised in the food and drink sector. The rapid destruction of Staphylococcus aureus, a common foodborne pathogen, was observed using TiO 2 films coated to glass and steel substrates.