Bismuth sulfide nanorods by thermal decomposition of a complex: Effect of reaction temperature on microstructural and optical properties

Abstract

Bismuth sulfide nanorods have been prepared by thermolysis of a bismuth dithiocarbamate complex, as a single-source precursor, in a mixture of solvents (oleylamine, 1-dodecanethiol, and 1-octadecene) at various temperatures. Bismuth sulfide nanorods denoted as BS(120), BS(150), BS(180), BS(200), and BS(220) have been obtained at the specified temperatures (°C). They have been characterized by X-ray diffraction analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV/Vis spectrophotometry, and photoluminescence (PL) spectroscopy. The effect of temperature on the microstructural and optical properties of the obtained Bi2S3 has been studied. The results show that interactions of the N–H group of oleylamine and the S–H group of dodecanethiol with the nanoparticles are temperature-dependent. The crystallite sizes of the nanoparticles were calculated using the Scherrer equation, Williamson–Hall (W–H) analysis, and Rietveld analysis, which yielded values in the ranges 20.1–45.9, 20.9–26.6, and 23.0–29.6 nm, respectively. Analysis of the microstrain in crystals of the nanoparticles showed that while the strain therein was due to contraction of the nanoparticles obtained at 180 °C, the strains at other temperatures were due to expansion, thereby confirming the effect of temperature on the nature of the defects in Bi2S3 crystals. The lattice strains were estimated by the W–H and Rietveld analyses to be in the ranges 3.19 × 10−5–1.04 × 10−4 and 0.008–0.067, respectively. The crystallite sizes and lattice strains estimated by both W–H and Rietveld analyses were mutually consistent, showing similar trends. SEM and TEM analyses showed that the nanorods were aggregated into longer rods at 120 and 150 °C, whereas shorter rods were obtained at 180 and 220 °C, suggesting a change in preferential growth direction. The widths and lengths of the nanorods were estimated as 20.97–41.25 nm and 79.4–111.0 nm, respectively, giving aspect ratios in the range 1.92–5.52. The band-gap energies of the nanorods varied in the range 1.08–0.78 eV, which can be related to differences in tail state width as observed in the absorption spectra. Calculation of texture coefficients showed preferential growth in the (111), (020), and (321) directions.