Controlled synthesis of basic bismuth nitrate by reverse microemulsion

Basic bismuth nitrate (BBN) with different shapes and dimensionalities were controllably synthesised in reverse microemulsion stabilised by TritonX-100. The obtained products were characterised by thermogravimetry differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD and TG-DSC detections revealed that the as-prepared BBN had the composition Bi₆O₆(OH)₂(NO₃)₄·2H₂O. The TEM results indicated that 1D nanorods, 2D hexagonal nanoplates and irregular nanosheets of BBN were obtained by changing the water content (w, molar ratio of water to surfactant). At low w, most of the products were nanorods with 100-200 nm in diameter and 3-7 μm in length. Hexagonal nanoplates with the side length of 250-350 nm were formed at higher w. When w further increased to 10, irregular nanosheets with 2-8 μm in size were found. The morphology of products was also sensitive to the surfactant concentration and reaction time. It was found that the growth of BBN nanoplates is a function of time. The possible formation mechanism of these nanostructures was also discussed.