Organotin(IV) triazolates as molecular precursors for pure-phase, nanosized SnS/SnO₂ through pyrolysis

Abstract

The thermal decomposition of organotin(IV) triazolates of general formula R₂SnL₂ (R = methyl (1), n-butyl (2), n-octyl (3) and phenyl (4)) and R₃SnL (R = Me (5); and L = anion of 3-amino-5-mercapto-1,2,4-triazole) provides a simple route to prepare nanosized semiconductors, SnS and SnO₂ in nitrogen and air atmosphere, respectively, at low temperature 600-700ºC. The crystallite average size of the residues determined by X-ray diffraction line broadening is found in the range of 6-63 nm. The particle size of the residues obtained by the pyrolysis of 2 and 4 (in nitrogen) has also been determined by tunneling electron microscope and found to be in the range 2-55 nm. The surface morphology of these residues has been determined by scanning electron microscopy. The thermogravimetric analysis shows that the weight loss observed in nitrogen is higher than that expected for the formation of SnS as end-product. This indicates the partial loss of the residue to the gas phase due to sublimation at higher temperature. Kinetic studies of 2 and 4 in air indicate the first order kinetics for the decomposition process. The X-ray diffraction, SEM and TEM results of the residues along with kinetic parameters show that 5 and 2 are the best precursors for production of pure phase nanosized SnO₂ followed by 3 in air whereas 4 is the best precursor for SnS followed by 2 in nitrogen. These compounds are much better precursors for production of pure phase nanosized SnO₂/SnS as compared to diorganotin(IV) thiadiazolates.