Co-digestive ripening assisted phase-controlled synthesis of Ag-Sn intermetallic nanoparticles and their dye degradation activity.

The Ag-Sn based system in the nano-size regime is one of the strongest candidates for lead-free solders. Besides, the investigation of several other applications of Ag-Sn nanostructures, especially in catalysis, remains scarce which makes it an interesting system to synthesize and explore its chemistry. In this report, nearly monodisperse ε-AgSn intermetallic nanoparticles were prepared by a simple and convenient solution-based process of co-digestive ripening using Ag and Sn colloids obtained by the solvated metal atom dispersion (SMAD) method. Optimization of the temperature and stoichiometric ratio between the metal elements and the use of an appropriate capping agent are crucial factors to realise phase pure intermetallic nanoparticles. AgSn nanoparticles with a size of 3.8 nm ± 0.6 nm were obtained within 12 h of reaction when tri--octylphosphine/tri--octylphosphine oxide was used as the capping agent at 205 °C. Interestingly, AgSn@SnO core-shell nanostructures were obtained by changing the capping agent to palmitic acid. These nanostructures were thoroughly characterized by powder X-ray diffraction, transmission electron microscopy (TEM and STEM-EDS), X-ray photoelectron spectroscopy and optical spectroscopy. Thereafter, Ag and AgSn nanoparticles were utilized for photocatalytic degradation of methylene blue, methyl orange and a mixture of both the dyes.