Biosynthesis of high-purity γ-MnS nanoparticle by newly isolated Clostridiaceae sp. and its properties characterization

MnS is a p-type semiconductor with both antiferromagnetism and wide band gap, endowing it potential applications for short wavelength optoelectronic devices, solar cells and luminescent materials. Despite successful biosynthesis of nano CdS, PbS and ZnS with extremely low solubility product, there have been no reports available on biosynthesis of nano MnS so far because both PO₄ ^3- and OH^- negatively disturb reaction between Mn²⁺ and S^2- through forming Mn₃(PO₄)₂ and Mn(OH)₂ as undesirable impurities. In this work, high-purity MnS nanocrystals were synthesized in presence of newly isolated Clostridiaceae sp. through strictly controlling pH value and PO₄ ^3- dose for the first time. The results showed that hexagonal-shaped γ-MnS with a diameter of 2-3 μm and a thickness of 200-300 nm was obtained by biosynthesis at 0.014 g/L PO₄ ^3- dose and pH 5.8. The hexagonal-shaped particle possessed dense and uniform texture. The γ-MnS had an obvious absorption peak at 325 nm and an emission peak at 435 nm as well as paramagnetic property with a coercivity of 52.91 Oe and a retentivity of 4.37 × 10^-3 emu/g at ambient temperature. The studies demonstrated that biosynthesis was qualified for preparation of nano metal sulfites with relatively high solubility product like MnS, widening its application spectrum.