Organic bromide-assisted one-pot synthesis of Bi₂S₃ nanorods using DMSO as a sulfur supply

Metal sulfide semiconductor nanorods have attracted much attention because of their potential use as a photo-responsive component of optical/electrical devices. In the present study, we report a simple solvothermal method of the Bi₂S₃ nanorod synthesis exploiting dimethyl sulfoxide (DMSO) as both a solvent and a sulfur source in the presence of an organic bromide such as tetraethylammonium bromide (Et₄NBr). The organic bromide conducts dual roles; it promotes the decomposition of DMSO to produce reactive sulfur species and reacts with Bi species to produce an intermediate product of bismuth oxybromide (BiOBr) that reacts further with the sulfur compounds. These dual roles of organic bromide facilitate the synthesis of Bi₂S₃ nanorod without extra sulfur sources. The production of Bi₂S₃ nanorods is successful when the organic bromide is used, but not when KBr is used, and is dependent upon the amount of organic bromide. With controlled parameters of reaction temperature and time, production of BiOBr intermediates and growth of Bi₂S₃ nanorod from the surface of BiOBr are observed along with the identification of the organic sulfur-Bi complexes during the synthesis. Based on the experimental outcomes, the process of the Bi₂S₃ nanorod synthesis is proposed. The synthesized Bi₂S₃ nanorods have a band gap energy of 1.5 eV along with a photoresponse time of 920 ms, thus demonstrating semiconductor photosensitivity.