Study On The Photocatalytic Sterilization Of Foodborne Pathogens Based On The Binary Synergistic System Of TiO₂ Nanotube Arrays

Water contains a large number of food-borne pathogens,and infection of water-borne diseases due to drinking water containing pathogens is still one of the important causes of high morbidity and mortality.Traditional sterilization technologies are mostly chemical sterilization methods such as chlorine-containing fungicides and ultraviolet sterilization technologies.The former is prone to produce cytotoxic,genotoxic and carcinogenic disinfection by-products that pose a threat to human health.The practical application of the latter is limited by the excessively high requirements for equipment conditions.In recent years,photocatalytic disinfection technology has gradually become an innovative strategy to replace traditional water disinfection methods.The recovery rate of the powder dosage forms photocatalyst is low,and the remaining nanoparticles in the water will also affect the ecological environment and human health,so the practical application of photocatalytic sterilization is still limited.In order to explore more efficient and stable photocatalytic water disinfection materials,improve the recovery of photocatalysts,and reduce the secondary pollution of samples,this article prepared two completely recoverable and recyclable photocatalytic antibacterial substrate materials based on the titanium dioxide nanotube arrays(TiO₂ NTAs).The experiments and research were carried out on the efficiency,mechanism and practical application of the material to kill Staphylococcus aureus and Escherichia coli under visible light irradiation.The main research contents and results are as follows:1.Preparation of MoS₂/TiO₂ Nanotube Arrays and Its Photocatalytic Sterilization PerformanceThe photocatalytic antibacterial material of molybdenum disulfide nanosheets/titanium dioxide nanotube arrays(MoS₂/TiO₂ NTAs)was synthesized by anodic oxidation and hydrothermal methods.First,the characteristics of MoS₂/TiO₂ NTAs were confirmed by characterization techniques such as scanning electron microscopy and energy spectrum analysis(SEM-EDS),high resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).Then the standard plate counting method was used to explore the photocatalytic sterilization efficiency of MoS₂/TiO₂NTAs against methicillin-resistant Staphylococcus aureus(MRSA)and Escherichia coli ATCC 25922.The research results showed that sterilization efficiency of MoS₂/TiO₂ NTAs was up to 98.5%.After 3 times of recycling,the sterilization efficiency still reached 92.1%,and it has a certain broad-spectrum and circulating disinfection effect.SEM of bacteria,live/dead cell fluorescence staining and electron spin resonance(ESR)measurement results showed that MoS₂/TiO₂ NTAs can quickly generate superoxide radicals under visible light irradiation.The strong oxidizing properties of superoxide radicals can destroy bacterial cell membranes and cause bacterial lysis and death.In addition,inductively coupled plasma mass spectrometry(ICP-MS)was used to analyze the changes in water samples before and after the material was recovered,which proved the recyclability of MoS₂/TiO₂ NTAs.The research and development of MoS₂/TiO₂ NTAs antibacterial substrate materials has confirmed the sterilization performance and recyclability of TiO₂ NTAs based materials,laying a foundation for the subsequent development of new antibacterial materials and research on photocatalytic sterilization mechanisms.2.Preparation of Direct Z-scheme Heterojunction CeO₂/TiO₂ Nanotube Arrays and Its Photocatalytic Sterilization Performance on Pathogenic BacteriaIn order to further improve the bactericidal effect of the substrate photocatalytic material,we improved the synthesis method so that the bactericidal performance of the material is comparable to that of the powder dosage forms.In this research,a direct Z-scheme heterojunction ceria nanoparticles/titanium dioxide nanotube arrays(CeO₂/TiO₂ NTAs)with excellent photocatalytic bactericidal effect was designed by electrodeposition method.The antibacterial test of MRSA and enterohemorrhagic Escherichia coli O157:H7 showed that CeO₂/TiO₂ NTAs showed the material can completely kill 7×10⁷ of pathogenic bacteria under light.The results of SEM of bacteria,intracellular ATP concentration determination,BCA protein determination and ESR determination showed that CeO₂/TiO₂ NTAs produced a large amount of active oxygen species for sterilization under light,including superoxide radicals,hydroxyl radicals and singlet oxygen.Through ultraviolet diffuse reflectance spectroscopy,photoluminescence spectroscopy and XPS technology,it was confirmed that the material has good photocatalytic performance.Through ICP-MS,cyclic sterilization test and material characterization before and after the cycle,it was proved that the material can be completely recovered and cyclically sterilized.By comparing the antibacterial performance of some powder photocatalyst,it is proved that the bactericidal effect of the CeO₂/TiO₂ NTAs can be comparable to commercial TiO₂ nanoparticles and some powder photocatalysts.In summary,CeO₂/TiO₂ NTAs have excellent photocatalytic disinfection effects and are easy to recycle,and have broad application prospects in the field of water disinfection.In addition,the sterilization test of actual river water shows that CeO₂/TiO₂ NTAs can kill microorganisms in complex water environment and realize recycling,which has broad application prospects in the field of water disinfection.