Effect of Titanium Dioxide Film Thickness on Photocatalytic and Bactericidal Activities AgainstListeria monocytogenes (original) (raw)
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.
Biofilms, containing pathogenic bacteria, represent a recurrent economic and safety problem in food industries, due to their high resistance to cleaning and sanitizing procedures. The development of photoactive surfaces with bactericidal property could facilitate the elimination of such microbial biofilms. One solution may be to deposit a photocatalyst top-layer (TiO 2) on conventional materials used in food plants. Our aim is to study the photocatalytic activity of such layers on the adhesion and viability of different bacteria present on food plants, especially in pork meat factory: Listeria monocytogenes, Yersinia enterocolitica and Pseudomonas fragi. Glass substrates were coated with TiO 2 thin films by radio-frequency magnetron sputtering under various deposition conditions (deposition temperature T, oxygen partial pressure P O2). The characterization of the TiO 2 thin layers was performed using spectrophotometry, scanning electron microscopy and X-ray diffraction analysis. And photocatalytic activity under UVA illumination (365 nm) has been checked for all samples. Bactericidal activity has been demonstrated on the bacteria tested by enumeration of the adherent cells and in situ fluorescent labeling after three hours of contact with the thin film and a subsequent UVA illumination. Adherent bacteria with damaged bacterial cell wall were observed using a scanning electron microscopy; this can be associated with presence of oxidative stress due to the photocatalytic activity of the TiO 2 thin layer. The selected TiO 2 coating presents a photocatalytic activity leading to an oxidative stress. This activity provides bactericidal properties against different strains from the meat industry. This thin layer could be optimized by modifying anionic composition (band-gap reduction) during coating in order to be active under solar light so it could be used to fight against biofilms.
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.
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.
Applied and Environmental Microbiology, 2006
The antibacterial activity of photocatalytic titanium dioxide (TiO2) substrates is induced primarily by UV light irradiation. Recently, nitrogen- and carbon-doped TiO2 substrates were shown to exhibit photocatalytic activities under visible-light illumination. Their antibacterial activity, however, remains to be quantified. In this study, we demonstrated that nitrogen-doped TiO2 substrates have superior visible-light-induced bactericidal activity against Escherichia coli compared to pure TiO2 and carbon-doped TiO2 substrates. We also found that protein- and light-absorbing contaminants partially reduce the bactericidal activity of nitrogen-doped TiO2 substrates due to their light-shielding effects. In the pathogen-killing experiment, a significantly higher proportion of all tested pathogens, including Shigella flexneri, Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus, Streptococcus pyogenes, and Acinetobacter baumannii, were killed by visible-light-illuminated...
FEMS Microbiology Letters, 2021
Antimicrobial materials are tools used to reduce the transmission of infectious microorganisms. Photo-illuminated titania (TiO2) is a known antimicrobial material. Used as a coating on door handles and similar surfaces, it may reduce viability and colonization by pathogens and limit their spread. We tested the survival of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Saccharomyces cerevisiae on a nano-structured TiO2-based thin film, called ‘NsARC’, and on stainless steel under a variety of light wavelengths and intensities. There was significantly less survival (P <0.001) of all the organisms tested on NsARC compared to inert uncoated stainless steel under all conditions. NsARC was active in the dark and possible mechanisms for this are suggested. NsARC inhibited biofilm formation as confirmed by scanning electron microscopy. These results suggest that NsARC can be used as a self-cleaning and self-sterilizing antimicrobial surface coating for the prevention...
Processes
The antibacterial photocatalytic activity of TiO2 supported over two types of substrates, borosilicate glass tubes (TiO2/SiO2-borosilicate glass tubes (BGT)) and low-density polyethylene pellets (TiO2-LDPE pellets), which were placed in a compound parabolic collectors (CPC) reactor, was evaluated against Enterobacter cloacae and Escherichia coli under sunlight. Three solar photocatalytic systems were assessed, suspended TiO2, TiO2/SiO2-BGT and TiO2-LDPE pellets, at three initial bacterial concentrations, 1 × 105; 1 × 103; 1 × 101 CFU/mL of E. coli and total bacteria (E. cloacae and E. coli). The solar photo-inactivation of E. coli was achieved after two hours with 7.2 kJ/L of UV-A, while total bacteria required four hours and 16.5 kJ/L of UV-A. Inactivation order of E. coli was determined, as follows, suspended TiO2/sunlight (50 mg/L)…
Visible light inactivation of bacteria and fungi by modified titanium dioxide
Photochemical & Photobiological Sciences, 2007
Visible light induced photocatalytic inactivation of bacteria (Escherichia coli, Staphylococcus aureus, Enterococcus faecalis) and fungi (Candida albicans, Aspergillus niger) was tested. Carbon-doped titanium dioxide and TiO 2 modified with platinum(IV) chloride complexes were used as suspension or immobilised at the surface of plastic plates. A biocidal effect was observed under visible light irradiation in the case of E. coli in the presence of both photocatalysts. The platinum(IV) modified titania exhibited a higher inactivation effect, also in the absence of light. The mechanism of visible light induced photoinactivation is briefly discussed. The observed detrimental effect of photocatalysts on various microorganism groups decreases in the order: E. coli > S. aureus ≈ E. faecalis C. albicans ≈ A. niger. This sequence results most probably from differences in cell wall or cell membrane structures in these microorganisms and is not related to the ability of catalase production.
Bactericidal effects of titanium dioxide-based photocatalysts
Chemical Engineering Journal, 2005
The photocatalytic degradation of E. coli in water by various catalysts was investigated in a batch spiral reactor. Commercial Degussa P25 (P25), as well as novel magnetic and hydrothermally prepared photocatalysts (MPC and HPC) were investigated in a slurry system. P25 was found to be the most effective catalyst, followed by the HPC and the MPC. Cell destructions followed first order kinetics. Non-buffered samples displayed a greater bactericidal efficiency which was attributed to a decrease in electrostatic repulsions between TiO 2 and E. coli and also elevated stress on E. coli at acidic pH. Buffered (NaHCO 3 ) samples showed a decrease in bactericidal efficiency due to HCO 3 − ions competing with oxidising species and blocking (by adsorption) the TiO 2 particles. The optimum catalyst loading for P25 and HPC was 1 and 2 g/L for MPC and was attributed to mass transfer effects (bulk diffusion, available active site and shadowing). An immobilised P25 system was found to be more efficient than the MPC and comparable with the HPC in suspension. The addition of silver to the immobilised system was found to enhance the photocatalytic degradation.
HAL (Le Centre pour la Communication Scientifique Directe), 2015
Biofilms, containing pathogenic bacteria, represent a recurrent economic and safety problem in food industries, due to their high resistance to cleaning and sanitizing procedures. The development of photoactive surfaces with bactericidal property could facilitate the elimination of such microbial biofilms. One solution may be to deposit a photocatalyst top-layer (TiO 2) on conventional materials used in food plants. Our aim is to study the photocatalytic activity of such layers on the adhesion and viability of different bacteria present on food plants, especially in pork meat factory: Listeria monocytogenes, Yersinia enterocolitica and Pseudomonas fragi. Glass substrates were coated with TiO 2 thin films by radio-frequency magnetron sputtering under various deposition conditions (deposition temperature T, oxygen partial pressure P O2). The characterization of the TiO 2 thin layers was performed using spectrophotometry, scanning electron microscopy and X-ray diffraction analysis. And photocatalytic activity under UVA illumination (365 nm) has been checked for all samples. Bactericidal activity has been demonstrated on the bacteria tested by enumeration of the adherent cells and in situ fluorescent labeling after three hours of contact with the thin film and a subsequent UVA illumination. Adherent bacteria with damaged bacterial cell wall were observed using a scanning electron microscopy; this can be associated with presence of oxidative stress due to the photocatalytic activity of the TiO 2 thin layer. The selected TiO 2 coating presents a photocatalytic activity leading to an oxidative stress. This activity provides bactericidal properties against different strains from the meat industry. This thin layer could be optimized by modifying anionic composition (band-gap reduction) during coating in order to be active under solar light so it could be used to fight against biofilms.
International Conference on the Epidemiology and Control of Biological, Chemical and Physical Hazards in Pigs and Pork, 2015
Biofilms, containing pathogenic bacteria, represent a recurrent economic and safety problem in food industries, due to their high resistance to cleaning and sanitizing procedures. The development of photoactive surfaces with bactericidal property could facilitate the elimination of such microbial biofilms. One solution may be to deposit a photocatalyst top-layer (TiO 2) on conventional materials used in food plants. Our aim is to study the photocatalytic activity of such layers on the adhesion and viability of different bacteria present on food plants, especially in pork meat factory: Listeria monocytogenes, Yersinia enterocolitica and Pseudomonas fragi. Glass substrates were coated with TiO 2 thin films by radio-frequency magnetron sputtering under various deposition conditions (deposition temperature T, oxygen partial pressure P O2). The characterization of the TiO 2 thin layers was performed using spectrophotometry, scanning electron microscopy and X-ray diffraction analysis. And photocatalytic activity under UVA illumination (365 nm) has been checked for all samples. Bactericidal activity has been demonstrated on the bacteria tested by enumeration of the adherent cells and in situ fluorescent labeling after three hours of contact with the thin film and a subsequent UVA illumination. Adherent bacteria with damaged bacterial cell wall were observed using a scanning electron microscopy; this can be associated with presence of oxidative stress due to the photocatalytic activity of the TiO 2 thin layer. The selected TiO 2 coating presents a photocatalytic activity leading to an oxidative stress. This activity provides bactericidal properties against different strains from the meat industry. This thin layer could be optimized by modifying anionic composition (band-gap reduction) during coating in order to be active under solar light so it could be used to fight against biofilms.
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.
Titanium Oxide Antibacterial Surfaces in Biomedical Devices
The International Journal of Artificial Organs, 2011
Titanium oxide is a heterogeneous catalyst whose efficient photoinduced activity, related to some of its allotropic forms, paved the way for its widespread technological use. Here, we offer a comparative analysis of the use of titanium oxide as coating for materials in biomedical devices. First, we introduce the photoinduced catalytic mechanisms of TiO2 and their action on biological environment and bacteria. Second, we overview the main physical and chemical technologies for structuring suitable TiO2 coatings on biomedical devices. We then present the approaches for in vitro characterization of these surfaces. Finally, we discuss the main aspects of TiO2 photoactivated antimicrobial activity on medical devices and limitations for these types of applications.
Surface Engineering, 2007
Titanium, an otherwise perfect condenser tube material in sea water applications, is challenged by the problem of severe biofouling. Anatase, one of the two commercially important crystalline forms of titanium dioxide, possesses excellent photocatalytic activity (PCA). It has been shown in the earlier studies by the authors that anodisation of titanium produces anatase type of TiO 2 capable of photocatalytic inhibition of microbial adhesion under near UV light illumination. The present study investigates the influence of anodising voltage and anodising time on the photocatalytic inhibition of Pseudomonas sp., a frequent coloniser of natural biofilms formed on titanium surfaces. The effect of heat treatment of anodised surfaces on PCA was also studied. The results showed that heat treatment resulted in a significant enhancement of PCA. The surface oxide was characterised using glancing incidence X-ray diffraction and atomic force microscopy and the results indicate a marked increase in the cystallinity of the anatase film on the heat treated anodised surfaces. Attempts have also been made to understand the mechanism underlying the photocatalytic inactivation of the bacterial cells on TiO 2 surfaces by studying their growth characteristics.
Journal of Biomedical Science, 2009
Bactericidal activity of traditional titanium dioxide (TiO2) photocatalyst is effective only upon irradiation by ultraviolet light, which restricts the potential applications of TiO2 for use in our living environments. Recently carbon-containing TiO2 was found to be photoactive at visible-light illumination that affords the potential to overcome this problem; although, the bactericidal activity of these photocatalysts is relatively lower than conventional disinfectants. Evidenced from scanning electron microscopy and confocal Raman spectral mapping analysis, we found the interaction with bacteria was significantly enhanced in these anatase/rutile mixed-phase carbon-containing TiO2. Bacteria-killing experiments indicate that a significantly higher proportion of all tested pathogens including Staphylococcus aureus, Shigella flexneri and Acinetobacter baumannii, were eliminated by the new nanoparticle with higher bacterial interaction property. These findings suggest the created materials with high bacterial interaction ability might be a useful strategy to improve the antimicrobial activity of visible-light-activated TiO2.
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.
2017
Owing to the potential environmental applications, photocatalytic reactions occurring on the surface of photoirradiated titanium(IV) oxide (TiO2) have garnered a wide interest. One of the many usage of TiO2 as a photocatalyst is in inhibiting bacterial growth. TiO2 is generally coated onto the surface of a substrate material and the material’s photocatalytic antibacterial activity is then investigated. In the present study, TiO2-based photocatalysts were coated on the surface of stainless steels by using an automatic film applicator (AFA), which is able produce a uniform coating with controllable thickness and high resistivity. By using this method, it is also possible to directly use TiO2 powder, instead of using other TiO2 source that requires crystallization process afterwards. The TiO2 photocatalysts were firstly prepared by preparing the mixture of the coating process, which consisted of anatase TiO2 powder, polyvinyl alcohol as the binder, ammonium citrate tribasic as the stab...
Chemical Vapor Deposition, 2015
Thin films of anatase titanium dioxide are deposited on fluorine-doped tin oxide (FTO) glass substrates utilizing the electric field-assisted aerosol (EA)CVD reaction of titanium isopropoxide in toluene at 450°C. The as-deposited films are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and UV-vis spectroscopy. The photoactivity and antibacterial activity of the films are also assessed. The characterization analysis reveals that the use of an electric field affects the film microstructure, its preferential orientation, and the functional properties. XRD of the anatase films reveals that the application of electric fields causes a change in the preferential orientation of the films from (101) to (004) or (211) planes, depending on the strength of the applied field during the deposition.