A novel green approach for fabricating visible, light sensitive nano-broccoli-like antimony trisulfide by marine Sb(v)-reducing bacteria: Revealing potential self-purification in coastal zones

Antimony trisulfide (Sb2S3) is industrially important for processes ranging from a semiconductor dopant through batteries to a flame retardant. Approaches for fabricating Sb2S3 nanostructures or thin films are by chemical or physicochemical methods, while there have been no report focused on the biological synthesis of nano Sb2S3. In the present study, we fabricated nano-broccoli-like Sb2S3 using Sb(V) reducing bacteria. Thirty four marine and terrestrial strains are capable of fabricating Sb2S3 after 1-5 days of incubation in different selective media. The nano-broccoli-like bio-Sb2S3 was light sensitive between 400-550 nm, acting as a photo-catalyst with the bandgap energy of 1.84 eV. Moreover, kinetic and mechanism studies demonstrated that a k value of similar to 0.27 h(-1) with an R-2 = 0.99. The bio-Sb2S3 supplemented system exhibited approximately 18.4 times higher photo-catalytic activity for degrading methyl orange (MO) to SO42-, CO2 and H2O compared with that of control system, which had a k value of similar to 0.015 h(-1) (R-2=0.99) under visible light. Bacterial community shift analyses showed that the addition of S or Fe species to the media significantly changed the bacterial communities driven by antimony stress. From this work it appears Clostridia, Bacilli and Gammaproteobacteria from marine sediment are potentially ideal candidates for fabricating bio-Sb2S3 due to their excellent electron transfer capability. Based on the above results, we propose a potential visible light bacterially catalyzed self-purification of both heavy metal and persistent organic contamination polluted coastal waters.