Zinc Sulfide Nanoparticles From Pseudomonas Putida Nm-1 Exhibiting Photocatalytic Activities And Their Applications

In recent years,zinc sulfide nanoparticles have attracted great attention due to their unique size,optical and electrical effects.The synthesis of zinc sulfide nanoparticles by microorganisms has the advantages of low cost,mild reaction conditions and environmental protection.In this paper,a strain of Pseudomonas putida,nm-1,was isolated from the mud of an ecological lake in Xilinhaote,Inner Mongolia.The strain was cultured in a medium containing Zn and S.The nanoparticles produced by the strain were obtained by centrifuging,crushing,washing with distilled water and vacuum drying for many times.Its composition,structure and morphology were characterized by transmission electron microscopy(TEM),X-ray electron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR).The particle was identified as ZnS nanoparticles.The ZnS nanoparticles extracted from bacterial cells have good decolorization effect on methylene blue dye under xenon lamp simulated light.The experimental results show that the decolorization effect of the nanoparticles on methylene blue dye is related to the concentration of nanoparticles and dye,and can be reused.The mechanism of degradation of methylene blue by nanoparticles is related to the electron-hole pairs produced by the electron transition in valence band of ZnS nanoparticles under irradiation.Electrons(e-)combine with dissolved oxygen(O2)in water to form superoxide anion(·O2-),and holes(h+)combine with H2O to form hydroxyl radicals(·OH),which decompose dyes into small molecules of acids,H2 and C02.The ZnS nanoparticles extracted from bacterial cells undergo electron transitions in valence bands on the surface of the particles under light.Escherichia coli can use the escaped electrons to promote the growth of E.coli.The ZnS nanoparticles can convert the light energy into the chemical energy used by E.coli through photocatalysis.The results showed that adding ascorbic acid to the suspension of ZnS nanoparticles could promote the growth of E.coli,and adding p-benzoquinone could inhibit the growth of E.coli.The light intensity and wavelength of different light sources are all factors affecting the growth rate of E.coli.