Bismuth sulphide-polymer nanocomposites from a highly soluble bismuth xanthate precursor

Bismuth sulphide nanocrystal-polymer hybrid layers are of interest for various optoelectronic, thermoelectric or sensing applications. In this work, we present a ligand-free in situ route for the formation of Bi2S3 nanorods directly within a polymer matrix. For this purpose, we introduce a novel bismuth xanthate (bismuth(III) O-3,3-dimethylbutan-2-yl dithiocarbonate), which is highly soluble in non-polar organic solvents. The analysis of the crystal structure revealed that the prepared bismuth xanthate crystallises in the monoclinic space group C2/c and forms dimers. The bismuth xanthate can be converted into nanocrystalline Bi2S3 with an orthorhombic crystal structure via a thermally induced solid state reaction at moderate temperatures below 200 degrees C. In combination with the high solubility in non-polar solvents this synthetic route for Bi2S3 is of particular interest for the preparation of Bi2S3-polymer nanocomposites as exemplarily investigated on Bi2S3-poly(methyl methacrylate) and Bi2S3-poly(3-hexylthiophene-2,5-diyl) (P3HT) nanocomposite layers. Atomic force and transmission electron microscopy revealed that Bi2S3 nanorods are dispersed in the polymer matrix. Photoluminescence experiments showed a quenching of the P3HT fluorescence with increasing Bi2S3 content in the hybrid layer.