RESUMO
Unloaded WO3 and 0.25-1.0 wt% Pt-loaded WO3 nanoparticles were synthesized by hydrothermal method using sodium tungstate dihydrate and sodium chloride as precursors in the acidic condition and further by the impregnation method using platinum acetylacetonate. Pt-loaded WO3 films on Al2O3 substrate interdigitated with Au electrodes were prepared by spin-coating technique. The temperature has an obvious influence on the response of sensors to CO gas. In order to determine the optimal operating temperatures, the response of WO3 sensors with different Pt loading concentrations towards 50-2000 ppm of CO in air was tested as a function of operating temperature of 150-350 degrees C. It was found that 1.0 wt% Pt-loaded WO3 sensing film showed the highest response of - 469 at 2000 ppm CO (250 degrees C). Therefore an optimal operating temperature of 250 degrees C was chosen for CO detection.
RESUMO
The application of Mn-loaded ZnO nanoparticles to the design of flammable gas sensors is nowadays one of the most active research fields, due to their high activity, good adsorption characteristics and high selectivity with high response to toxic and combustible gases. It is sensitive to many gases at moderate temperature, such as C2H4, CH4 and C2H2 gases. FSP presents a new technique for 0.25-1.00 mol% Mn-loaded ZnO nanoparticles synthesis which involves only a single step. The crystallite sizes of ZnO spherical and hexagonal particles were found to be ranging from 5 to 15 nm while ZnO nanorods were seen to be 5-15 nm in width and 20-40 nm in length. In addition, very fine Mn nanoparticles were uniformly deposited on the surface of ZnO particles. The highest response for CH4 gas was -240 towards 0.50 mol% Mn-loaded ZnO at 1.0 vol.% concentration of CH4 in dry air at 300 degrees C. The response of 0.50 mol% Mn-loaded ZnO of C2H4 gas was as high as 72 for 1.0 vol.% while the response for C2H2 gas was -13 towards 0.50 mol% Mn-loaded ZnO at 1.0 vol.% concentration of C2H2 in dry air at 300 degrees C.