Novel trapping system for size wise sorting of SnO2 nanoparticles synthesized from pyrolysis of ultrasonically atomized spray for gas sensing

High-purity, nanostructured SnO2 powders were synthesized using an ultrasonic spray pyrolysis technique. Ultrasonic generator was used to convert aqueous solution (0.1 M/0.5 M/0.75 M) of SnCl4·5H2O into very fine droplets. When droplets pass through two zone furnace, they would be pyrolysed and nanoparticles of SnO2 would form. Simple but novel trap system (with traps) was employed for size wise sorting of the nanoparticles. It was observed that the most of larger and heavier particles could reside in Trap-1 and smaller and lighter nanoparticles could move respectively to Trap-2, Trap-3 and finally to Trap-4. For each powder, mean size was smaller and size distribution was narrower in case of particles in Trap-4 as compared to particles in previous traps. Size of nanoparticles was also observed to be dependent on precursor concentration. Mean size was observed to be decreasing and size distribution was observed to be narrower with the decrease in precursor concentration. It is also clear from scanning electron microscopy (SEM) and transmission electron microscope (TEM) images that some of the powder exists in the form of agglomerated spheres and remaining in the form of nanocrystallites. Structural properties of the nanoparticles were investigated using X-ray diffraction (XRD). Results are discussed and interpreted.