Application Of Fluorescent Carbon Quantum Dots In Microbial Photocatalysis And Imaging

With the development and progress of society,microbial pollution threatens the health of human body at all times,and the research on microbial inhibition has attracted more attention.The dependence of microorganisms on traditional antibiotics is becoming more and more obvious,so there is an urgent need for people to develop new materials to replace traditional medicines for bacteriostatic research on microorganisms.Carbon quantum dots are a new type of fluorescent carbon nanomaterials,which have attracted extensive attention due to their unique fluorescent properties,low toxicity,and good biocompatibility.In this paper,different fluorescent carbon quantum dots were synthesized by designing different materials as precursors,and successfully applied to the application research on photocatalytic bacteriostasis and biological imaging of microorganisms.The specific research contents are as follows:1.Using brewer's yeast as raw material,fluorescent carbon quantum dots(CQDs)co-doped with nitrogen,sulfur,and phosphorus were synthesized by one-step hydrothermal method,which was used for photocatalytic bacteriostasis of E.coli Bioimaging for vitality assessment.The prepared CQDs were used as photocatalytic bacteriostatic materials.The bacteriostatic activity of CQDs against E.coli(Gramnegative bacteria)was evaluated by changing the experimental conditions such as the concentration of CQDs and the time of light exposure.The results showed that CQDs had an excellent antibacterial effect against E.coli within 120 min of light,and the antibacterial rate against E.coli increased with the increase of CQDs concentration and light time.In addition,CQDs with high quantum yield(21%)have a highly negative zeta potential(-41.7 m V)and biological low toxicity,which can selectively label the dead bacteria of E.coli to show multicolor fluorescence at different excitation wavelengths.Therefore,CQDs can be used as fluorescent dyes to evaluate the bacterial viability of E.coli.2.A eutectic solvent(DES)formed by mixing choline chloride and urea as a passivating agent,and citric acid as a carbon source,was used to synthesize carbon quantum dots(N/Cl-CQDs)co-doped with nitrogen and chlorine by hydrothermal method.The fluorescence quantum yield is as high as 37%,with excellent photoluminescence performance.N/Cl-CQDs have strong photocatalytic fungal activity against Candida albicans(C.albicans),and the antibacterial activity of N/ClCQDs was evaluated by changing the experimental conditions.When the illumination time was 80 min,the antibacterial rate of N/Cl-CQDs(7 mg/m L)against C.albicans reached 100%.The excellent luminescence performance of N/Cl-CQDs can fluorescently label C.albicans,so that it can display multi-color fluorescence imaging at different excitation wavelengths.3.Nitrogen and sulfur co-doped carbon quantum dots(N/S-CQDs)with a fluorescent quantum yield of 23% were synthesized using ampicillin as a carbon precursor.The prepared N/S-CQDs have rich surface functional groups,which provides them with good cell permeability.Gram-negative bacteria Staphylococcus aureus(S.aureus)was used as the experimental bacteria to investigate the photocatalytic antibacterial activity of N/S-CQDs under visible light irradiation.The results showed that both the concentration of N/S-CQDs and the time of light affected the photocatalytic antibacterial activity against S.aureus.The concentration of N/S-CQDs was 0.7 mg/m L,and the antibacterial rate of N/S-CQDs against S.aureus after 100 minutes of light exposure was 100%.In addition,N/S-CQDs can selectively stain S.aureus and Listeria monocytogenes(L.monocytogenes)(Gram-positive bacteria),and obtain multicolor fluorescence images at different excitation wavelengths.