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Quantum-sized ZnO nanoparticles with crystallite size about 6 nm were successfully synthesized by low temperature sol-gel process using tetraethylorthosillicate (TEOS) as capping agent to prohibit the crystallite aggregating and Ostwald ripening as well as accelerate the ZnO crystalline formation. The crystallite size was the smallest under the synthesized condition of pH = 8. The appropriate calcination temperature for as-synthesized quantum-sized ZnO was 400 °C for 1 h. The ZnO sensor exhibited the highest response of 264 to 40 ppm NO2 and the highest selectivity of 8.8 and 13.7 respectively to CO and CH4 at the same gas concentration and operating temperature of 290 °C. The mechanism of TEOS action and gas sensing were also discussed. [ABSTRACT FROM PUBLISHER]

Quantum size ZnO crystals have been synthesized successfully by a room temperature sol-gel process using oleic acid (OA) as capping agent to control the particle size. The particle size and structure of ZnO nanocrystals have been charactirized by X-ray diffraction (XRD), transmission electron microscope (TEM) and Raman spectra analysis methods. The sensor based on ZnO powder calcined at 400 °C for 1 h exhibits the highest response of 280 to NO2 and the selectivity to CO and CH4 at the same concentration reaches 31 and 49 at operating temperature of 290 °C. The effect of calcination temperature on the performance of gas sensing has also been studied. [ABSTRACT FROM PUBLISHER]