Carbon-based Quantum Dots Modified Titanium Dioxide Nanomaterials And Their Applications On Photocatalytic Degradation And Antibacterial

The rapid development of urbanization not only significantly improved our living standards but also caused increasingly serious environmental pollution.Organic pollutants and pathogenic microorganisms in industrial wastewater and from human life damaged the ecological environment,and threatened human life and health.On one hand,a large number of pharmaceutical compounds,including antibiotics,have been detected in sewage discharged from cities,medical industry and animal husbandry.However,due to their stable chemical properties and non-biodegraded,it is difficult to remove them completely by conventional water treatment processes.On the other hand,a large number of pathogenic microorganisms in sewage also pose a huge threat to aquatic ecosystems and human health.The semiconductor photocatalysis technology has been applied to degrade organic pollutants and kill pathogenic microorganisms,which is an important development direction of water treatment technology.As a typical semiconductor material,the low-cost Ti O₂ possesses stable chemical property,low cytotoxicity,and will not cause secondary pollution,which is considered to be an ideal photocatalyst in sewage treatment.However,the band gap of Ti O₂ is too wide?3.2e V?and its maximum absorption wavelength is only 387 nm,so it can only absorb ultraviolet light that accounts for about 4%of solar spectrum.Secondly,the high recombination rate of photoexcited charges results in a lower photocatalytic activity.In decades,the photocatalytic activity of Ti O₂has been improved through doping,constructing heterojunction and other methods.However,most of materials used for Ti O₂ doping are expensive noble metals or highly cytotoxic metal-containing semiconductors.Therefore,choosing a metal-free carbon material for enhancing the photocatalytic performance of Ti O₂ has become a hotspot research direction.In this paper,carbon quantum dots and carbon nitride quantum dots were used to modify Ti O₂ to improve the sunlight absorption and hinder the recombination of photo-generated carriers,thereby to improve the photocatalytic performance for degradation of organic poluttants and disinfection.The main contents are as follows:?1?Ti O₂ nanosheets?TNSs?with dominant?001?facet were successfully synthesized using HF and ethanol as modifiers through hydrothermal process.TNSs own higher photocatalytic activity than commercial Ti O₂,and the photocatalytic activity was further enhanced after being modified by CQDs.Under simulated sunlight condition,the TNSs-CQDs composite can degrade 96.5%ciprofloxacin within 120 min and kill more than 99.9%E.coli and S.aureus in180 min.In addition,the active species of TNSs-CQDs reaction system were proved to be h⁺,·OH and·O₂^-by free radical capture experiment and EPR,and·O₂^-was the main active species of the reaction?2?Highly-efficient Ti O₂/CN-QDs photocatalyst was successfully prepared by hybridizing commercial P25 with g-C₃N₄ quantum dots?CN-QDs?that were synthesized by thermal polymerization.Under simulated sunlight,Ti O₂/CN-QDs can degrade 97.7%ciprofloxacin within 120 min,and kill 100%E.coli and S.aureus within 180 min.Moreover,the active species of the Ti O₂/CN-QDs reaction system were confirmed to be h⁺,·OH and·O₂^-through free radical capture experiment an EPR,and·O₂^-was the main active species of the reaction.