Sonochemical synthesis of chalcone-functionalized SnS and SnS₂ with improved sonocatalytic activity

Herein we present a novel method of functionalization of sonochemically obtained SnS and SnS₂. For that purpose, a yellow-orange synthetic dye, chalcone 1,5-bis-(4-dimethylamino-phenyl)-penta-1,4-dien-3-one, was obtained via ultrasound-assisted synthesis based on the Claisen-Schmidt condensation. Then it was applied in the sonochemical synthesis of SnS and SnS₂ microparticles using two distinct polar protic solvents - methanol and ethanol. In each of syntheses (regardless the addition of chalcone) nanocrystalline SnS₂ phase was identified. In two cases (starting from SnCl₂ and using methanol as solvent regardless the addition of chalcone) also more crystalline SnS phase was observed. SEM images showed that the addition of chalcone to the reaction mixture significantly affects the morphology of product, for example microparticles with near ideal spherical shape or SnS/SnS₂ heterostructure were observed. Tauc investigations revealed the band gap widening due to the quantum confinement effect. The estimated band gap values were in the range of 1.94-4.05 eV. The addition of chalcone generally increased the band gap value. All prepared materials were tested in terms of their sonocatalytic activity towards degradation of model organic azo-dye and it was found that the chalcone-modified tin sulphide obtained from SnCl₂ in methanol, containing SnS/SnS₂ heterostructure, allowed for significant improvement of degradation (64%) in comparison with the unmodified sample (3%).