Preparation and characterization of nanomaterials of tellurium, bismuth, and bismuth telluride

In order to improve the processing and performance of tellurium (Te), bismuth (Bi), and bismuth telluride (dibismuth tritelluride, Bi2Te3), which are valuable thermoelectric materials that operate near room temperature in the bulk state, a nanometer scale synthetic method, in which the starting materials are reduced with NaBH4 in the presence of protecting agents in solution under mild conditions, was used. Te nanorods having an average diameter of 10 +/- 3 nm (aspect ratio = 3.0) were prepared by reducing tellurium(IV) ethoxide in ethanol in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) under nitrogen. Although Bi nanoparticles prepared from bismuth(III) chloride by this method have an average diameter of 29 +/- 8 nm, PVP-protected Bi2Te3 nanoparticles have a really small average diameter (7 +/- 5 nm) and they are probably the smallest Bi2Te3 particles ever reported. Heat treatment of PVP-protected Bi2Te3 nanoparticles in refluxing solvents was found to improve the stability.