Study On Photocatalytic Inactivation Of Microorganisms And Mechanism

Microorganisms are widespread on the surface of the earth.Among them,the amount of mold spores in the air is as high as 1-100 CFU/m²,and countless bacteria are floating in the air and objects,looking for invading hosts everywhere.In recent years,microbial pollution has occurred frequently,and there have been countless cases of diseases,poisons,and cancers,which have seriously affected people’s normal lives.However,traditional sterilization methods,including ultraviolet,chlorination,and ozone sterilization,are inadequate when used.Therefore,it is urgent to find a new type of non-toxic,stable and efficient sterilization technology.In this paper,photocatalytic sterilization technology was used to explore the bactericidal ability of the research group has prepared the g-C₃N₄/Bi₄O₇ with a“Z”heterogeneous structure.In view of the structural differences of mold spores,the promotion effect of spore germination on the improvement of photocatalytic performance was studied.The inactivation process and possible mechanism of mold were explored through electron microscope and K⁺detection technology.In addition,the photocatalytic technology was applied to kill Corynespora on cucumber leaves in farmland to explore the performance of photocatalytic inactivation of Corynespora.The details are summarized as follows:（1）Preliminary study on g-C₃N₄/Bi₄O₇ used for photocatalytic inactivation of bacteria.In this chapter,the g-C₃N₄/Bi₄O₇ prepared by the research group was used as the photocatalyst to preliminarily explore its ability to inactivate bacteria under visible light and ultraviolet light irradiation.Experiments showed that there was almost no death of colonies under dark conditions.Under visible light conditions,different catalysts all showed inactivation effects.Among them,the best catalyst g-C₃N₄/Bi₄O₇-40,which inactivated all E.coli in 40 min,and inactivated about 87.3%of S.aureus in 60 min.Under ultraviolet light irradiation,the catalyst g-C₃N₄/Bi₄O₇-40 inactivate all E.coli in 25 min and all S.aureus in 30 min.（2）Germination induced visible light to improve the ability of killing mold and its mechanism.Based on the investigation of the bactericidal performance of the catalyst g-C₃N₄/Bi₄O₇,this chapter applies it to molds that are more difficult to inactivate to explore whether germination can induce an increase in bactericidal performance and its possible bactericidal mechanism.Different forms of Aspergillus fumigatus spores were treated with visible light catalysis,and the experiment found that the dormant spores did not die after 6 h of visible light irradiation.But when the dormant spores were incubated for 8～10 h to germinate,and the catalyst g-C₃N₄/Bi₄O₇-40 was irradiated for6 h to kill about 81%of Aspergillus fumigatus.Similarly,for different forms of Aspergillus nidulans spores,about 30%of the dormant spores died after 6 h of visible light irradiation,while only 4 h of photocatalysis,all germinated spores were inactivated.In addition,in this chapter,the inactivation process of the catalyst g-C₃N₄/Bi₄O₇-40 on the mold was characterized by optical microscopy,scanning electron microscopy,and confocal microscopy.The experiment clearly showed the morphology of the mold after the photocatalytic treatment for different time.Furthermore,the inactivation mechanism of mold was studied by K⁺detection technology.The experiment found that the catalyst can cause the leakage of K⁺,which is the content of the mold.Among them,the catalyst g-C₃N₄/Bi₄O₇-40 causes the most obvious effect of potassium ion leakage.In addition,during the 6 h process of photocatalytic inactivation of mold germination spores,potassium ion leakage in Aspergillus fumigatus showed a trend from slow to fast.On the contrary,potassium ion leakage in Aspergillus nidulans showed a trend from fast to slow.（3）Preliminary study on photocatalytic killing of plant fungiThis chapter performs photocatalytic treatment on the mold（corynespora）infected on cucumber leaves in actual farmland.The dark,ultraviolet,and ultraviolet+Ti O₂ were used as the control group,after 6 h of photocatalytic treatment,there was no death of Corynespora in the dark group.UV treatment alone inactivated about 17%of Corynespora;and UV photocatalytic Ti O₂ could kill all Corynespora.Furthermore,cucumber leaves were used as the experimental substrate,and after the coryneform bacteria infect the leaves,the leaves were treated in darkness,ultraviolet,and ultraviolet+Ti O₂.The experiment found that the colonies in the dark group grew well;most of the colonies in the ultraviolet light group were inactivated;and the colonies in the ultraviolet photocatalysis group were all killed.