Sonochemical preparation of SnS and SnS(2) nano- and micropowders and their characterization

Sonochemical production of tin(II) and tin(IV) sulfides is investigated. Different conditions of syntheses are examined: used solvent (ethanol or ethylenediamine), source of tin (SnCl(2) or SnCl(4)), the molar ratio of thioacetamide to the tin source, and time of sonication. The obtained powders are characterized by the X-ray diffraction method (PXRD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and the Tauc method. Raman and FT-IR measurements were performed for the obtained samples, which additionally confirmed the crystallinity and phase composition of the samples. The influence of experimental conditions on composition (is it SnS or SnS(2)), morphology, and on the bandgap of obtained products is elucidated. It was found that longer sonication times favor more crystalline product. Each of bandgaps is direct and most of them show typical values – c.a. 1.3 eV for SnS and 2.4 eV for SnS(2). However, there are some exceptions. Synthesized powders show a variety of forms such as needles, flower-like, rods, random agglomerates (SnS(2)) and balls (SnS). Using ethanol as a solvent led to powders of SnS(2) independently of which tin chloride is used. Sonochemistry in ethylenediamine is more diverse: this solvent protects Sn(2+) cations from oxidation so mostly SnS is obtained, while SnCl(4) does not produce powder of SnS(2) but Sn(SO(4))(2) instead or, at a higher ratio of thioacetamide to SnCl(4), green clear mixture.