Influence of morphology on the photocatalytic and fiber optic ammonia gas sensing performance of tin oxide nanostructures by a novel microwave irradiation method

Tin oxide hexagonal-shaped nanodisks (NDs) and nanowires (NWs) were successfully prepared by one-step microwave irradiation method using cetyltrimethylammonium bromide (CTABr) and polyethylene glycol (PEG) as surfactants. The XRD pattern indicates that SnO 2 is crystalline with tetragonal rutile structure. TEM micrographs confirm SnO 2 nanodisks, approximately 100 nm in width and 20 nm in thickness, and a straight single SnO 2 nanowire with a diameter of about 30 nm and length up to several micrometers for CTAB- and PEG-assisted samples, respectively. The elemental composition and oxidation state were also confirmed through EDS and XPS analyses. Effect of morphology on the photocatalytic performance of SnO 2 nanostructures was studied toward degradation of methylene blue (MB) and rhodamine B (RhB) under visible light irradiation. For SnO 2 NDs, it was observed that 99% and 97% of MB and RhB dyes were degraded in 100 min of irradiation time. In contrary, the SnO 2 NWs showed high sensitivity (71.4 counts/ppm), fast response (35 min) and recovery time (25 min) toward ammonia gas compared to SnO 2 NDs. This could be attributed to large surface area and high adsorption of ammonia molecules on the SnO 2 surface.