Synthesis of tin oxide nanocrystalline phases via use of tin(II) halide precursors

Nanocrystalline tin oxides are synthesized via precipitation from heated solutions as well as from a novel above-solution vapor deposition route that occurs at low temperatures and atmospheric pressure. Crystalline phases are characterized via powder X-ray diffraction. Samples precipitated from reactions of SnCl2 are found to exist primarily as mixtures of tetragonal SnO and tetragonal SnO2 or tetragonal SnO2 and tin(II) oxyhydroxide (Sn6O4(OH)(4)), depending on reaction conditions. A mixed tin(II)/tin(IV) sample is shown to produce a rarely observed form of the intermediate oxide Sn3O4 upon annealing in air at 600 degreesC. SnBr2 exclusively forms tetragonal SnO2 via precipitation. Variation in the solvent composition with SnBr2 is shown to result in vapor deposition of SnO2 at temperatures below 160 degreesC. The average crystallite sizes of the vapor-deposited material are approximate to3 nm and grow slowly upon heating. Partially hydrolyzed SnBr4 is proposed as the vapor deposition intermediate based on variations in precursor/solvent combinations along with FTIR and GC-MS analysis of the reaction solution removed prior to the onset of deposition.