Comparative investigation of three types of ethanol sensor based on NiO-SnO2 composite nanofibers

NiO-SnO2 composite nanofibers were synthesized via electrospinning techniques and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Three types of sensor were applied to investigate the sensing properties of these nanofibers. Sensors A were fabricated by mixing the nanofibers with deionized water, and then grinding and coating them on ceramic tubes to form indirect heated gas sensors. Microsensors B (with an area of 600 mu mx200 mu m) were formed by spinning nanofibers on Si substrates with Pt signal electrodes and Pt heaters. Sensors C were fabricated by spinning nanofibers on plane ceramic substrates (with a large area of 13.4 mmx7 mm) with Ag-Pd signal electrodes only. The operating temperatures of sensors A and B were controlled by adjusting heater currents, and the operating temperatures of sensors C were controlled by adjusting an external temperature control device. Experimental results show that sensors C possess the highest sensing properties, such as high response values (about 42 to 100 mu L/L ethanol), quick response/recovery speeds (the response and recovery times were 4 and 7 s, respectively), and excellent consistencies. These phenomena were explained by the retained fiber morphology and suitable sensor area. The presented results can provide some useful information for the design and optimization of one-dimensional nanomaterial-based gas sensors.