PNNL

Abstract

This paper describes the novel production of extensive filamentous, arsenic-sulfide (As-S) nanotubes (20 - 100 nm dia. X ~30 µm length) resulting from the dissimilatoryreduction of thiosulfate and arsenate by the bacterium Shewanella sp. HN-41. While there have been several reports of bacterial-produced nanowires composed entirely of biological macromolecules, here we report for the first time the biogenic formation ofphotosensitive and electroconductive nanotubes comprised of crystalline As-S and bacterial extracellular polymeric substances (EPS). To our knowledge, there have been no previous reports of the synthesis of such a material either by chemical or biological means. The biogenic As-S nanotubes reported here represent a significant advancement as building blocks for the production of nanodevices because of their high aspect ratios and unique size dependent properties. We characterized the structural evolution of the bacterial As-S nanotubes formed by strain HN-41 using XAFS spectra as well as XRD analyses, as a function of time and extent of bacterial reduction. In addition, we characterized the electrical and photoconductive properties of the As-S nanotubes. Upon aging, the As-S nanotubes behaved as metals and semiconductors in terms of their electrical and photoconductive properties, respectively. These results indicate that the dissimilatory bacterium Shewanella may be an excellent biological tool to bioengineer As-S nanotubes, which may provide useful materials for novel nano- and optoelectronic devices.