| Black Phosphorus(BP)is the most stable allotrope of phosphorus with adjustable band gaps,can fill the gap between graphene and transition metal halide compounds.At the same time,Black Phosphorus nanosheets(BPNSs)also has high current-carrying mobility,can directly convert electrical signals to optical signals,is a rare photoelectronic material.Therefore,it has a wide range of application prospects.Water is one of the environmental endpoints of BPNSs,but its aquatic biological toxicity has not been systematically revealed.Especially,the biological effects and cell damage mechanisms of primary producer algae exposed to BPNSs have not been fully explained.Therefore,it has important scientific significance for water environmental health assessment and BPNSs discharge management to explore the toxic effects of BPNSs on algae.In this paper,two layers of BPNSs(BP-1 and BP-2)were prepared,and characterize the physical and chemical properties.Then,we selected model organism Chlorella vulgaris and Scenedesmus obliquus as test organisms.The toxic effects of BP-1 and BP-2 on algae cells and the mechanism of cell damage were studied.The main research contents are as follows:(1)Two layers of BPNSs(BP-1,BP-2)were prepared by liquid phase stripping method.FE-SEM,TEM and AFM analysis showed that BPNSs was a lamellar nanomaterial,and the thickness of BP-1 and BP-2 were 80.86±22.75 nm and 30.76±21.84 nm,respectively.The lateral size were 546.88±180.73 nm and 154.64±50.35 nm,respectively.The thickness and lateral size of BP-1 were both larger than that of BP-2.(2)The inhibition on the growth of C.vulgaris and S.obliquus by BPNSs.Both BP-1 and BP-2 inhibited the growth and proliferation of algae(inhibition degree BP-1>BP-2).After 120h exposure,the relative survival rates of C.vulgaris in 15 mg/L BP-1 and BP-2 groups were 45.05%and 73.67%,respectively,the relative survival rates in 45 mg/L group were 18.86%and 36.90%,respectively,and the relative survival rates in 75 mg/L group were 4.60%and 12.64%.The EC50 of BP-1 and BP-2 treatment groups were 23.20 mg/L and 43.58 mg/L,respectively.After 120h exposure,the relative survival rates of S.obliquus in 15 mg/L BP-1 and BP-2 groups were 45.79%and 63.99%,respectively,in 45 mg/L group were 25.63%and 42.76%,respectively,and in 75 mg/L group were 12.74%and 14.48%.The EC50 of BP-1 and BP-2 treatment groups were 50.49 mg/L and 60.70 mg/L,respectively.(3)Inhibition of photosynthesis on C.vulgaris and S.obliquus by BPNSs.The contents of chlorophyll a and carotenoid in algae cells were decreased,indicated that photosynthesis was inhibited(BP-1>BP-2).(4)Oxidative damage mechanism on C.vulgaris and S.obliquus by BPNSs.Under BPNSs exposure,ROS levels in C.vulgaris and S.obliquus increased,and algal cells produced oxidative stress response(Damage degree BP-1>BP-2).At the same time,the activities of SOD and CAT in cells increased significantly to resist the oxidative damage.The results showed that BPNSs could cause lipid peroxidation and damage of cell membrane.(5)The physical damage mechanism on C.vulgaris and S.obliquus by BPNSs.Microscopic observation showed that BPNSs adsorbed and aggregated on the surface and surrounding of algal cells,forming physical shading effect,affecting the absorption of light energy by algal cells and inhibiting their photosynthesis.FE-SEM and TEM were used to observe the microscopic morphology of C.vulgaris and S.obliquus.It was found that BPNSs could cause physical damage to algal cells.Its sharp edges could cut through cell walls and membranes,damaged cell integrity and caused content flow out.(6)Metabonomics and flow cytometry of algal cells exposed to BPNSs.BPNSs inhibited intracellular protein synthesis by disturbing the intracellular amino acid metabolism pathway,and meanwhile its nitrogen curing process was disturbed,thus inhibited the normal growth of algae.Flow cytometry analysis showed that BPNSs could destroy cell integrity,lead to cell wall and cell membrane rupture,and the effect of BP-1 was stronger than that of BP-2. |
PDF Full Text Request