Fast and facile sonochemical synthesis of Mg- and Zn-doped PbS nanospheres: optical properties and photocatalytic activity

In this work, Mg²⁺- and Zn²⁺-doped PbS nanopowders were synthesized simply and quickly by a sonochemical method. The nanopowders were characterized by X-ray diffraction, wavelength dispersive X-ray fluorescence, scanning electron microscopy, and ultraviolet–visible spectroscopy. The photocatalytic activity was estimated by methylene blue dye degradation. The sonochemical method produces crystalline PbS particles with cubic structure and free of secondary phases. The use of polyvinylpyrrolidone as a surfactant, and reaction medium at pH 13, results in the formation of nanospheres with diameter ranging from 31.4 to 114.5 nm. Doping favors the absorption of radiation in the visible region, and consequently, reduces the optical bandgap of the PbS. Photocatalytic assays show that magnesium and zinc codoping results in 80% reduction of methylene blue concentration after 180 min, while undoped PbS achieves only 42%. Tests with charge scavengers indicate that holes (h⁺) act as the main mechanism in the photocatalytic process.