Field effect transistors based on semiconductive microbially synthesized chalcogenide nanofibers

Abstract

Microbial redox activity offers a potentially transformative approach to the low-temperature synthesis of nanostructured inorganic materials. Diverse strains of the dissimilatory metal-reducing bacteria Shewanella are known to produce photoactive filamentous arsenic sulfide nanomaterials by reducing arsenate and thiosulfate in anaerobic culture conditions. Here we report in situ microscopic observations and measure the thermally activated (79 kJ mol(-1)) precipitation kinetics of high yield (504 mg per liter of culture, 82% of theoretical maximum) extracellular As2S3 nanofibers produced by Shewanella sp. strain ANA-3, and demonstrate their potential in functional devices by constructing field effect transistors (FETs) based on individual nanofibers. The use of strain ANA-3, which possesses both respiratory and detoxification arsenic reductases, resulted in significantly faster nanofiber synthesis than other strains previously tested, mutants of ANA-3 deficient in arsenic reduction, and when compared to abiotic arsenic sulfide precipitation from As(III) and S(2-). Detailed characterization by electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis and Tauc analysis of UV-vis spectrophotometry showed the biogenic precipitate to consist primarily of amorphous As2S3 nanofibers with an indirect optical band gap of 2.37 eV. X-ray diffraction also revealed the presence of crystalline As8S(9-x) minerals that, until recently, were thought to form only at higher temperatures and under hydrothermal conditions. The nanoscale FETs enabled a detailed characterization of the charge mobility (∼10(-5) cm(2) V(-1) s(-1)) and gating behavior of the heterogeneously doped nanofibers. These studies indicate that the biotransformation of metalloids and chalcogens by bacteria enables fast, efficient, sustainable synthesis of technologically relevant chalcogenides for potential electronic and optoelectronic applications.

Engineering bacteria for biogenic synthesis of chalcogenide nanomaterials

“…ANA‐3 is known to synthesize nanofibres of arsenic sulfide, as shown in Fig. C and previously reported (McFarlane et al ., ). The shape of the material was influenced by the microorganism expressing the reductase genes.…”

“…The diffrations patterns revealed overlapping crystalline phases that were produced by both E. coli and ANA‐3, such as orpiment (As 2 S 3 ), realgar (AsS) and alacranite (As 8 S 9 ). Previous reports have observed that the arsenic sulfide material crystallinity improves moderately over a period of time (Lee et al ., ; McFarlane et al ., ).…”

“…A and B), indicating a role for cellular components in the nucleation of arsenic sulfide nanomaterial. Absorbance at 375 nm (Abs 375 ) was used to quantify the formation of arsenic sulfide, as reported in previous work (McFarlane et al ., ). While there was an increase in Abs 375 for the bottle containing arsenite and sulfide as shown in Fig.…”

“…These results indicate that the compounds and molecules found that enable culture media to nucleate arsenic sulfide nanomaterials is somewhat specific to cultures of E. coli and ANA‐3. Previous reports have also found that microbes influence multiple aspects of nanomaterial formation (Singh et al ., ; McFarlane et al ., ; Hussain et al ., ).…”

e-Biologics: Fabrication of Sustainable Electronics with “Green” Biological Materials

“…The nanotubes (20 to 100 nm by ca. 30 µm) form extracellular networks, that upon aging are not only electrically conductive but also exhibit photoluminescence, photoactive, and transistor-like properties (5, 7). …”