Biosynthesis And Characterization Of High Purity γ-MnS Nanoparticles

MnS is a p-type semiconductor with both antiferromagnetism and wide band gap,endowing it potential applications for short wavelength optoelectronic devices, solar cellsand luminescent materials. Despite successful biosynthesis of nano CdS, PbS and ZnS withextremely low solubility product, there have been no reports available on biosynthesis ofnano MnS so far because both PO43-and OH-negatively disturb reaction between Mn2+andS2-through forming Mn3(PO4)2and Mn(OH)2as undesirable impurities.In this work, high-purity MnS nanocrystals were synthesized in presence of newlyisolated Clostridiaceae sp. through two methods: Firstly, achieving high purity MnSthrough strictly controlling pH value and PO43-dose for the first time. The results showedthat hexagonal shaped γ-MnS with a diameter of2~3μm and a thickness of200~300nm was obtained by biosynthesis at0.014g/L PO43-dose and pH5.8. The γ-MnS had anobvious absorption peak at325nm and an emission peak at435nm as well asparamagnetic property with a coercivity of52.91Oe and a retentivity of4.37×10-3emu/g atambient temperature. Secondly, γ-MnS was biosynthesized by a selective precipitationbased on steric-hindrance effect of metal complex of Mn2+and eriochrome black T (EBT)at high concentration of PO43-and OH-. The dominant form of as-prepared γ-MnS wastetrakaidecahedron prismoid-like crystals with an upper width of ca.1.0μm, a bottomwidth of ca.4.0μm and a height of ca.4.0μm, having an evident absorption peak at320nm, a coercivity of37.404Oe and a retentivity of2.695×10-3emu/g.