Research On Biosynthesis Of Ag/AgCl Nanoparticles And Its Characteristics

Nano-Ag/AgCl has many excellent properties due to its unique surface plasmon resonance effect.In this study,the green synthesis of nano-Ag/AgCl was realized by using the extracellular solution of Bacillus cereus,and its structure was characterized by transmission electron microscopy and X-ray diffraction.Besides,based on the laboratory simulation conditions and practice,the fluorescence properties,peroxidase mimic enzyme activity and antibacterial properties of nano-Ag/AgCl were further explored.This lays the foundation for exploring the practical application value of nano-Ag/AgCl and has certain economic and social benefits.The main results are as follows:(1)Bacillus cereus capable of synthesizing nano-Ag/AgCl was obtained by silver-tolerant domestication and desilverization.The synthesis site of nano-Ag/AgCl was explored,which confirmed that the extracellular fluid of Bacillus cereus could synthesize nano-Ag/AgCl.Transmission electron microscopy and X-ray diffraction characterization proved that the nano-Ag/AgCl synthesized by extracellular solution,was spherical,with an average particle size of 19.29 nm,and had good crystallinity and dispersibility.(2)The fluorescence spectrum analysis results showed that the nano-Ag/AgCl synthesized by extracellular solution had fluorescence properties and could emit blue fluorescence.Based on the selective quenching effect of Cr(?)on the fluorescence,a new method to simply and rapidly detect trace concentrations of Cr(?)has been established.The effect of pH and other metal ions on the system to check the Cr(?)has also been examined.There was a good linear relationship between Cr(?)and the fluorescence intensity of nano-Ag/AgCl.The linear equation was(F0-F)/F0=0.0026×CCr(?)+0.0318(R2=0.9751).The detection limit was 184 ?mol/L and the SNR was 3.Using this method to detect Cr(?)in Songhua River and Majiagou River,the recovery rate is between 96.93%-102.97%,which is feasible compared with spectrophotometry and has good application prospect in the field of analysis and detection.(3)The kinetic analysis results showed that the nano-Ag/AgCl synthesized in extracellular fluid had peroxidase mimic enzyme activity.Under the optimum conditions,the dry weight peroxidase mimic enzyme activity of nano-Ag/AgCl was 215.6 U/g.For linear detection of H2O2 and glucose concentrations,the ranges were 0.24-4 mmoL/L and 0.44-3.3 mmoL/L,respectively.The detection results of the glucose concentration in blood samples were close to those of glucose oxidase method,which confirmed the feasibility of nano-Ag/AgCl in the practical application of glucose detection.(4)The antibacterial experiment results showed that the nano-Ag/AgCl synthesized by extracellular fluid had antibacterial properties against E.coli.The minimum inhibitory concentration was 16 ?g/mL and the minimum bactericidal concentration was 32 ?g/mL determined by the microdilution method.When the nano-Ag/AgCl concentration was 32 ?g/mL,100%E.coli could be killed in 30 min.The results of Ag+ release measurement and X-ray energy spectrum analysis showed that the antibacterial effect of nano-Ag/AgCl was the result of the combined action of Ag+ and nano-level particle contact inhibition.The results of scanning electron microscopy and DCFH-DA fluorescence staining showed that nano-Ag/AgCl could induce intracellular reactive oxygen species to achieve antibacterial effect by disrupting cell membrane structure.