Biosynthesis of Molybdenum Disulfide Nanoparticles Using The Metal-Reducing Bacterium Shewanella Oneidensis MR-1

Abstract

The bacterium Shewanella oneidensis MR-1 is a dissimilatory metal-reducing bacterium capable of performing anaerobic respiration using a metal as terminal electron acceptor. Isolated from Lake Oneida in Upstate New York, S. oneidensis MR-1 was first noted for its manganese-reducing capability, but has now been shown to reduce a range of metal ions such as Fe(III), Mn(IV), As(V) and Cr(VI), as well as sulfur anions such as thiosulfate and sulfite. In the lab, Shewanella has been grown anaerobically in media enhanced with sulfur and metal ions in order to produce several types of chalcogenide nanoparticles, such as zinc sulfide and arsenic trisulfide. Given the utility of chalcogenide materials for electronics and photonics applications, bacterially-synthesized chalcogenide nanoparticles present a tantalizing avenue for green chemistry. Compared to similar materials produced using traditional chemical synthesis methods, bacterially-synthesized nanomaterials can be produced at much lower temperatures and using fewer chemical reagents. This work presents a method of synthesizing molybdenum disulfide nanoparticles using S. oneidensis bacteria. Molybdenum disulfide is a layered semiconductor with an indirect band gap in its bulk state and a direct bandgap in its monolayer state. It also exhibits changes in its electronic properties when its surfaces are functionalized with molecules, giving it applications for both photodetection and biosensing. An anaerobic batch culture of S. oneidensis MR-1 was incubated at room temperature in the presence of molybdenum oxide, resulting in the production of molybdenum disulfide crystals less than a micron in diameter. These crystals were detected using scanning electron microscopy, transmission electron microscopy, absorbance spectroscopy and X-ray diffraction. In addition to confirming that molybdenum disulfide can be produced by Shewanella bacteria, the data collected using these methods provide insight on the size, morphology and photoresponse of nanoparticles generated this way. The findings also allow inferences to be made about how the confluence of several mechanisms present in an anaerobic Shewanella culture combine to make such a synthesis possible, while providing clues about how such processes can be further improved or extended to other materials.