Continuous microwave flow synthesis (CMFS) of nano-sized tin oxide: effect of precursor concentration

Abstract

Tin oxide (SnO2) nanoparticles exhibit an intense luminescent behavior under UV-light in contrast to the bulk tin oxide and therefore have become focus of many investigations. SnO2 nano-agglomerates were successfully prepared by continuous microwave flow synthesis (CMFS) method using tin chloride pentahydrate as a tin precursor. The effect of concentration of reacting species on the degree of crystallinity, particle size, lattice parameters, morphology, and photocatalytic behavior was probed. Structural and morphological features of the resulting SnO2 nano-structures were examined by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunar Emmett Tellar (BET), Transmission electron microscopy (TEM) and ultra-violet (UV/Visible) spectroscopy. From the XRD spectra the crystal structure of the synthesized product was confirmed as phase pure tetragonal cassiterite type with particle size of 4.43 nm. TEM images further confirmed the formation of highly agglomerated nanoparticles, whereas the change in concentration had no appreciable effect on the particle morphology. BET surface area measurements confirmed that the surface area of the SnO2 nanoparticles decreased with increase in Sn precursor concentration. The optical band gap values of SnO2 nanoparticles were calculated to be 3.19 eV, which is a red-shift compared with that of the bulk SnO2 (3.6 eV). The nano-agglomerates were efficient catalyst for the photodegradation of methylene blue (MB) dye. Our results indicate that the synthesized SnO2 nanoparticles can have potential applications in liquid photovoltaic, photocatalysis and sensors