Low temperature quaternary microemulsion synthesis of Bi2S3 nanospheres and nanorods

Two different morphologies of bismuth sulphide (Bi2S3), nanospheres and nanorods, were obtained in W/O microemulsions (cyclohexane / Triton X-100 / n-pentanol / water) as a reaction medium. The structural characterization of the Bi2S3 nanoparticulates was performed using transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The difference in morphology was achieved by adjusting reactant concentrations. The Bi2S3 nanospheres have bimodal size distribution with sizes in the range 2-5 nm and 20-40 nm while the diameter of nanorods is in between 5 and 20 nm and their length is in the range from 150 to 400 nm. Both kinds of nanostructures are well-crystalline although they were prepared at 60 degrees C without any further thermal treatment. Based on optical measurements the band gaps were estimated to be 1.5 and 1.57 eV for nanospheres and nanorods, respectively. These values are larger compared to the bulk material as a consequence of reduced dimensionality of the Bi2S3 nanostructures.