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摘要
Mesoporous (mp-)Al2O3 powders, which were prepared by microwave-assisted solvothermal treatment of aluminum secondary butoxide in 1-propanol at 110 degrees C followed by firing at 700 degrees C in air, were loaded with l wt% MO (CeO2, CuO, Fe2O3, Mn2O3, NiO or RuO2, l <= 20 (wt%)) by impregnation with the constituent metal salt in the aqueous solution followed by firing at 700 degrees C in air. Thereafter the mp-Al2O3 powders loaded with and without MO were further co-loaded with noble metal nanoparticles, which were synthesized by sonochemical reduction. The VOC-sensing properties of the adsorption/combustion-type gas sensors fabricated by MEMS technology and drop coating technique utilizing the mN(1)/nN(2)/mp-Al2O3, 1.0Pt/mp-Al2O3 and 1.0Pt/lMO/mp-Al2O3 (N-1, N-2: Au, Pd and Pt, m and n: the amount of N-1 and N-2 nanoparticles loaded, m + n =1.0 (wt%)) obtained as sensor materials were investigated in this study. The general ethanol response (Delta V-MAX) of all mAu/nPt/mp-Al2O3 sensors was smaller than that of the 0.2Au/0.8Pd/mp-Al2O3 sensor, which showed the largest Delta V-MAX among mAu/nPd/mp-Al2O3 sensors in our previous study. In the series of mPt/nPd/mp-Al2O3 sensors, on the other hand, the 0.8Pt/0.2Pd/mp-Al2O3 sensor showed larger Delta V-MAX to ethanol than that of the 0.2Au/0.8Pd/mp-Al2O3 sensor. Moreover, the Delta V-MAX of the PtImp-Al2O3 sensor to ethanol was slightly larger than of the 0.8Pt/0.2Pd/mp-Al2O3 sensor. The co-loading of 10 wt% MO with 1.0 wt% Pt nanoparticles onto the mp-Al2O3 was effective in improving the Delta V-MAX to ethanol of the Pt/mp-Al2O3 sensor in some cases, and the 1.0Pt/10CeO(2)/mp-Al2O3 sensor showed the largest Delta V-MAX to ethanol among all the 1.0Pt/10MO/mp-Al2O3 sensors tested. The Delta V-MAX of the 1.0Pt/1OCeO(2)/mp-Al2O3 sensor to other VOCs (acetone, ethyl acetate, benzene, toluene and o-xylene) was relatively smaller than that to ethanol, but the shape of the differential sensor-signal profiles largely depended on the kind of VOCs and thus detailed analyses by the differential processing may have an advantage in the VOC-selective detection. On the other hand, integral processing of the sensor-signal profiles showed that the magnitude of the approximately integrated dynamic response (IDR), which was largely dependent on the amount of VOCs adsorbed on the mp-Al2O3, may provide an indication of the quantitative VOC detection. Furthermore, the control of the amount of CeO2 loaded and the value of low temperature at pulse-driven heating enabled the 1.0Pt/lCeO(2)/mp-Al2O3 sensors to detect a small amount of VOCs in comparison with general catalytic combustion-type gas sensors, because of the large IDR to the VOCs at a low-concentration range.
- 出版日期2015-12-1
