Abstract. SnO 2 was ultrasonically deposited (precipitated) in the presence of di erent amounts of graphene oxide (GO) prepared by the modi ed Hummers' method. The resulting nanocomposites were used as sensing material for the detection of 1000 ppm CO and VOCs including ethanol, acetone and toluene, and CH 4 in a temperature range of 150-300 C. The nanocomposites were characterized by Raman spectroscopy, XRD, BET surface area measurement, FT-IR, and SEM methods. It seems that SnO 2 layers were deposited on the GO surface and incorporated into the matrix. This resulted in 47% increase in the nanocomposite BET surface area. The addition of 0.1 wt% GO to SnO2 increased the response to CO by about 6 times at 300 C. 0.05 wt% GO as an optimum amount was included in SnO2 up to 2-fold enhancement in response to ethanol, and toluene was observed. At 250 C, the highest response to ethanol was obtained, which is 120, 114, 1400, and 15 times larger than the responses to CO, toluene, methane and acetone, respectively, making the sensors quite selective to ethanol. Furthermore, this sensor exhibited good response in the low concentration of ethanol.
A SnO 2 -based semiconductor thick film gas sensor was fabricated for detection of chlorinated VOCs such as dichloromethane (DCM) and trichloroethylene (TCE) at concentrations of 10 and 20 ppm respectively in the temperature range of 100-400 o C. Other semiconductors such as ZnO, CuO and Sm 2 O 3 were added in 5.0% wt to SnO 2 by co-precipitation method. The samples were characterized by TEM, XRD and BET. Characterization results showed that presence of dopants causes an increase in surface area and a decrease in the particle size of the sensing materials. Moreover, the TEM micrographs confirmed that the size of synthesized materials is less than 20 nanometers. It was found that SnO 2 -Sm 2 O 3 has the highest sensitivity to DCM, especially at low temperatures. Also sensitivity is quite high for this sensor even at a concentration as low as 0.1 ppm. However, presence of promoters suppressed the sensitivity to TCE.
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