Photocatalytic bactericidal effect of TiO2 thin film on plant pathogens (original) (raw)
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Photocatalytic Bactericidal Effect of TiO 2 Thin Films Produced by Cathodic Arc Deposition Method
Key Engineering Materials, 2004
Many plant pathogens such as Enterobacter spp., Pythium spp., and Fusarium spp. can be transmitted by irrigation water. The conventional bactericidal methods often apply chemical pesticides to the water. However, synthetic pesticides are hazardous to animals and the environment. Photochemical disinfection of plant pathogens with TiO 2 thin film might offer an alternative method to disinfect plant pathogens from water. In this study, photocatalytic inactivation of Enterobacter cloacae SM1 and Erwinia carotovora subsp. carotovora ZL1 was evaluated on glass substrates coated with TiO 2 thin film using the sol-gel process. The bactericidal activity was examined with 2, 3, 5-triphenyl tetrazolium chloride (TTC), an indicator of cell viability. The inhibition rates of TiO 2 thin film against E. cloacae SM1 and E. carotovora subsp. carotovora ZL1 bacteria treated with ultraviolet A (UV-A) light irradiation for 60 min were 99.5% and 99.9%, respectively. The disinfection efficiency with TiO 2 thin film is relatively constant at pH values in the range of 5.8 to 8.0. The results suggested that photocatalytic phytopathogen inactivation with TiO 2 thin film has the potential for use as a new tool for plant protection in recycled water systems.
Surface and Coatings Technology, 2007
Synthetic pesticides have been used to control plant diseases or pests for a long time. The public has been affected by many problems such as environmental pollution and health issues from synthetic pesticide use in agriculture. It has consequently become necessary to develop alternative methods for the control of plant diseases. The TiO 2 photocatalyst technique has potential for agricultural application because it will not form dangerous compounds. However, UV is only about 3% of the light existing in the solar spectrum. This limits TiO 2 photocatalytic disinfection application under visible light irradiation. Our current research emphasizes the improvement of TiO 2 thin film photocatalytic efficiency under visible light (λ N 400 nm) by doping a novel photosensitive dye (5, 10, 15, 20-tetraphenyl-21H, 23H-porphine nickel, TPPN) using the sol-gel method. These results showed that the TiO 2 thin film doped with 200 μM of TPPN had high indigo dye photodegrading efficiency. The inhibition rates of TiO 2 /TPPN thin film illuminated by visible light against phytopathogenic bacteria including Enterobacter cloacae SM1, Erwinia carotovora subsp. carotovora 3 and E. carotovora subsp. carotovora 7 which induced severe soft/basal rot disease in vegetable crops were all more than 90%. These evidence suggest that the TiO 2 /TPPN thin film under visible light irradiation has the potential for direct application to plant protection in irrigation water systems.
The antibacterial photocatalytic activity of TiO 2 supported over two types of substrates, borosilicate glass tubes (TiO 2 /SiO 2-borosilicate glass tubes (BGT)) and low-density polyethylene pellets (TiO 2-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 TiO 2 , TiO 2 /SiO 2-BGT and TiO 2-LDPE pellets, at three initial bacterial concentrations, 1 × 10 5 ; 1 × 10 3 ; 1 × 10 1 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 TiO 2 /sunlight (50 mg/L) > TiO 2-LDPE pellets/sunlight (52 mg/L) > TiO 2 /SiO 2-BGT/sunlight (59 mg/L), the best E. coli. inactivation rate was obtained with TiO 2-LDPE pellets/sunlight, within 4.5 kJ/L and 90 min. The highest total bacteria inactivation rate was found for TiO 2 /sunlight (50 mg/L) and TiO 2-LDPE pellets/sunlight (52 mg/L), within 11.2 kJ/L and 180 min. TiO 2 deposited over LDPE pellets was the most effective material, which can be successfully used for water disinfection applications. Bacterial regrowth was assessed 24 h after all photocatalytic treatments, none of those microorganisms showed any recovery above the detection limit (2 CFU/mL).
Photocatalytic bactericidal effect of TiO2 film on fish pathogens
Surface and Coatings Technology, 2008
In this research, fish bacteria pathogens, Streptococcus iniae and Edwardsiella tarda, are deposited on TiO 2 film and radiated with 500 μW/cm 2 of ultraviolet A (UV-A, 360 nm). The bacteria viability is estimated using 2, 3, 5-triphenyl tetrazolium chloride (TTC) and inhibition efficiency calculated. The results show that bacteria inhibition efficiency in UV-A radiated TiO 2 film groups is significantly higher than that of UV-A radiated only groups. Regardless of fish pathogen species, inhibition efficiency of higher than 96% is found in the TiO 2 coated experimental groups that are exposed in 90 min of UV-A radiation. These results suggest that combined use of UV-A and TiO 2 can enhance bactericidal effects on fish pathogens in fish farm.
A Review on TiO 2 Photocatalytic Disinfection of Water with Pathogenic Micro-organisms
During disinfection, the formation of byproducts such as trihalomethanes and other chlorinated byproducts are a major concern. The best alternative to avoid the byproducts formation is photocatalysis. In the past two decades, the studies on photocatalysis have been done using a semiconductor for the treatment of air and water. Among the various semiconductors, TiO 2 is used in various industries as it gives the highest efficiency with the highest stability at a lower cost. This is a powerful process used for disinfecting environment contaminated with pathogenic microorganisms. In this study, a review of previous developments made in the TiO 2 photocatalysis for the disinfection of water contaminated with pathogenic microorganisms is carried out. This paper concludes that TiO 2 photocatalysis can be used in different ways either in suspension or in the form of thin films to disinfect water contaminated with pathogenic microorganisms presenting a potential hazard to animals and human ...
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.
Environmental and Climate Technologies
Water contamination by various bacteria, viruses and other pathogens is a great threat to human health. Amongst other Advanced Oxidation Processes TiO2 photocatalysis is considered as one of the most efficient treatment for the polluted wastewater disinfection. Usually, the wastewater produced by higher risk objects, such as hospitals, implicates diverse contaminants, but efficiency of most of the Advanced Oxidation Processes is tested by using only single pathogens and information on inactivation of bacteria mixtures is still limited. In this study, photocatalytical inactivation of three commonly found bacterial pathogens (gram-positive (Micrococcus luteus) and gram-negative (Salmonella enterica, Escherichia coli)) was investigated. Efficiency of traditional photocatalytic disinfection process using single bacterial pathogens was compared to the one observed for their mixtures. The impact of photocatalytical process parameters and treatment time on bacteria disinfection efficiency ...
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...
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.