Ethylene glycol mediated synthesis of SnS quantum dots and their application towards degradation of eosin yellow and brilliant green dyes under solar irradiation

Abstract

SnS (tin sulfide) quantum dots (QDs) were synthesized by a chemical coprecipitation method using ethylene glycol as a solvent and capping agent and thiourea as a sulfur source at a temperature of 160 °C, 4 h. The as synthesized SnS QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis-NIR spectroscopy and FT-Raman spectroscopy. XRD patterns show the formation of single phase SnS QDs with rhombohedral structure. Ethylene glycol mediated synthesis resulted 2.5–3 nm SnS QDs. The UV-Vis-NIR optical absorption spectra of the SnS QDs displayed that the SnS QDs possess an absorption profile across the whole visible-light and near-infrared region. The direct band gap and indirect band gap energy for SnS QDs are found to be 1.17 eV and 1.11 eV, respectively. FT-Raman spectra of SnS QDs demonstrate vibrational modes at 73, 97, 162, 188, 222 cm⁻¹. The Brunauer–Emmett–Teller (BET) surface area of SnS QDs was found to be 5.63 m² g⁻¹. SnS QDs showed powerful photodegradation activity towards degradation of eosin yellow and brilliant green dyes under sunlight. The enhanced photocatalytic activity of SnS QDs is attributed to improved visible light absorption and efficient separation of photogenerated charge carriers. In addition, the quenching effects of different quenchers suggest that superoxide radicals play a major role in the photodegradation process.