Ultrasound-assisted facile synthesis of tin sulfide (SnS) nanostructures and their structural, optical, and morphological studies

Abstract

In this study, we report the synthesis of tin sulfide (SnS) nanostructures via an ultrasonic-assisted sol–gel method, varying sulfur concentrations through different thiourea ratios. The formation of these nanostructures was confirmed through X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and optical analysis. The SnS nanostructures exhibited a polycrystalline orthorhombic structure. The crystallite size of sample D1 was estimated at 3.30 nm, while increasing the molar concentration of thiourea in samples D2 and D3 resulted in reduced crystallite sizes of 3.14 nm and 3.08 nm, respectively. This size reduction suggests that thiourea plays a critical role in the nucleation and growth process during synthesis, where higher thiourea concentrations increase nucleation sites by providing excess of sulfur ions, thereby limiting crystallite growth. SEM images revealed that ultrasonic waves induce the transformation of disordered particle orientations into well-ordered nanospheres. The particle size consistently decreased with higher thiourea concentrations, forming larger clusters as individual particles aggregated into defined spherical structures. Energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of Sn and S in the nanostructures, while Raman spectroscopy showed vibrational modes at 214 and 315 cm⁻¹, indicating the successful formation of SnS nanostructures. Optical transmission studies revealed that the ultrasound-assisted SnS nanostructures possess a direct bandgap ranging from 1.85 to 1.87 eV, which falls within the visible light region. The bandgap variation with increasing thiourea concentration highlights the potential of these nanostructures for photovoltaic applications, offering improved conversion efficiency. Overall, the ultrasound-assisted synthesis route demonstrates significant promise for producing SnS nanostructures with tailored optical properties suitable for energy-related applications.