Herein we demonstrate tungsten oxide (WO3 nanostructures based resistive type sensors for hydrogen sulfide (H2S) gas sensing utility. The WO3 dynamic layers have been deposited upon alumina substrates pre-patterned with gold (Au) interdigitated electrodes. For comparative study, two distinct WO3 nanostructures (S-425 and S-450) have been synthesized using Aerosol Assisted Chemical Vapor Deposition (AACVD) technique at varied deposition temperatures i.e., 425 and 450 °C, respectively. The gas detecting properties of both sensors were investigated against varied concentration (0–60 ppm) of H2S gas levels. The electrical resistance of fabricated gas detectors has been observed at DC bias of 5 V and low operating temperature 250 °C. Specifically, when concentration of H2S gas increases from 0–10 ppm, average resistance of the S-425 and S-450 gas sensors was observed to decrease by 96.5% and 97.6%, respectively. In general, the sensing mechanism of gas sensors proposed in this work can be associated with ionosorption of oxygen species over WO3 nanostructured surfaces. However, the significantly enhanced sensing performance of S-450 sensor may be attributed to improved crystallinity in its structure and improved ions adsorption/desorption kinetics at nanorods surface morphology.

No abstract

No abstract

Well-defined CoFe 2 O 4 nanoparticles with an average grain size of about 50 nm were successfully synthesized by a combustion method employing different ratios of fuel to cations within the range 0-2.67. The as-prepared powders were characterized and investigated by TG, XRD, IR, SEM, TEM and VSM methods, and via isopropanol conversion at 250-450The results showed that increasing the ratio between fuel and cations stimulated the formation of cobalt ferrite due to the increasing flame temperature. Changing the fuel/cation ratio brought about modifications in the structure, surface activity, selectivity and magnetic properties of the investigated solids. A fuel/cation ratio of 2 led to the formation of catalyst having a high activity (49%) and magnetization (77.54 emu/g). All the solids investigated behaved as dehydrogenation catalysts leading to the formation of acetone as the major product. The fuel/cation ratio did not alter the mechanism of dehydrogenation of isopropanol, but increased the concentration of active sites involved in the catalyzed reaction.

No abstract