Effect of chromium precursor on stoichiometries of Cr3S4 and Cr2S3 nanoparticles by chemical aggregation reactions

Abstract

We developed two formulations to synthesize chromium sulfide nanoparticles to analyze the effect of the chromium precursors to obtain different stoichiometries. Most works do not report samples with entangled stoichiometries. In this paper, we got a pure sample and an entangled one through slightly different formulations. There is very few information on the Raman and XPS data for chromium sulfide compounds. In this work, we support the available information through the lattice determination, indexing the diffraction patterns. The method, chemical aggregation reactions, that we utilized to prepare our material is straightforward. Besides, it is associated with short lengths of time, low costs, the number of instruments needed, precursors easy to manage and room temperature. Both formulations to elaborate the nanoparticles mentioned above differ just in the step related to the appropriate selection of the chromium source. The characterization techniques transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, were implemented to identify our nanoparticles’ chemical composition and optical properties. The first formulation leaded to an entangled composite of monoclinic Cr₃S₄ and rhombohedral Cr₂S₃ (Cr₃S₄/Cr₂S₃). The second formulation yielded a pure stoichiometry corresponding to hexagonal Cr₂S₃. The direct band gaps were found using the Tauc theory; the results were 2.73 eV for Cr₃S₄/Cr₂S₃ and 2.67 eV for Cr₂S₃. In addition, optical responses of transmission, absorption, reflection, and refractive index are presented.