| As the prospective important materials applied potentially in many fields, nanosilver have been widely used as antibacterial material, medical material, decorative material, etc. Due to their antimicrobial activities, they are used to pilot study at against marine fouling organisms and bacteriostatic effects.There are many methods to prepare silver nanoparticles,in which the liquid-phase chemical reduction process is more controllable and easier in large-scale production. In this study, the silver colloids were prepared by the chemical reduction in liquid phase with silver nitrate, the polyethylene pyrrolidone(as protective agent),and carboxymethyl cellulose sodium(CMC) as reducer. Through controlling reduction condition, the spheroid, dispersible and the stable silver colloids were prepared, and the optimum technologic has been summarized. The dispersible and stable silver colloid was synthesized at 60℃and reaction for 6 hour(hours) in the system of C(AgNO3)=1.0 mol/L, c(PVP)/c(AgNO3)= 1:3, pH=8. The silver nanoparticles were obtained through desicecation of the colloid, and were characterized by XRD and TEM. The results showed that the product was the spherical silver particles with the mean size about 20~30nm and almost without impurity.The antibacterial and bacteriostatic effects of silver nanoparticles to two index-bacteria (the Bacillus subtilis, chlorphenol festival bacillus) have been studied qualitatively and quantitatively. The antibacterial experimental results showed that the silver nanoparticles could effectively kill and restrain bacteria. As the surface activity of nano-particle, nanosized silver would be far more antimicrobial than ordinary silver blocks or particles. The antibacterial ratio of the nano-silver was increased obviously with the increase of dosage of nano-silver particles. The antibacterial mechanics of silver was suggested that the silver ions intruded the bacterial cell and reacted with the hydrosulfide group due to electrostatic attraction between the electronegative cell membrane of bacteria and electropositive silver ions so that the bacterial protein would be curdled and the synthesis of bacterial DNA could be disturbed, and the microbe would finally lose its proliferous ability and then perish. Besides, the antibacterial effects of nanosilver were increased obviously with the increase of concentrations of nanosilver.In this study, different concentrations of nanosilver were prepared by spin coater. The antimicrobial activity of nanosilver was investigated against different alga and bacteria. As results, nanosilver coating and nanosilver/polyurethane composite coating had active effect on marine diatom, chlorella and cyanobacteria. Besides, the inhibitory effects of nanosilver were increased obviously with the increase of concentrations of nanosilver. So the effect of nanosilver would be awfully influenced by the concentration. Above all, the result of Nitzschia closterium and Synechococcus sp. were most ideal. After 14 days, the quartz glasses surface attachment amounted to 350/cm2 without nanosilver of Nitzschia closterium in their growth environment, while there was almost no attachment on the quartz glasses surface of 0.06wt% nanosilver coating. The experiment of soaking in ocean actual environment proved that nanosilver/polyurethane composite coating can be used as effective growth inhibitors in various microorganisms. From the experimental data, it can be concluded that the dosage of 0.06wt% nanosilver may be the appropriate dosage for antibacterial dope loaded with nanosilver. The antibacterial and bacteriostatic effects of nanosilver to bacteria had been investigated qualitatively. The antibacterial experimental results showed that the nanosilver could effectively restrain bacteria. |
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