ABSTRACT

Figure 12.1 (a, b) Low-magnification and (c) high-magnification SEM images of SnO, (d, e) TEM images of the SnO nanoplates with the SAED pattern inserted, and SEM images of the (f) single-layer and (g) multilayer SnO2 nanoplates after annealing. Reproduced from Adv. Funct. Mater., 19, pp. 2453-2456 (2009). Copyright © 2009, Wiley-VCH [1]. Abbreviations: SEM, scanning electron microscopy; TEM, transmission electron microscopy; SAED, selected area electron diffraction. Due to the large surface area of the transformed SnO2 nanoplates, the film fabricated using these nanoplates as the building blocks was very promising for the application in ethanol sensors. Ethanol gas sensing was measured in a closed chamber (shown in Fig. 12.2a), and the sensing behavior was performed at 350°C. Figure 12.2b shows the response and recovery characteristics of the single-layer (rectangles) and multilayer (triangles) SnO2 nanoplates when exposed to ethanol at decreasing and increasing concentrations. R and R0 are the resistance values of the sensors in mixed ethanol-air vapor and in air, respectively. The sensing properties were very reproducible, and the sensors showed almost exactly the same response whether they were exposed to decreasing or increasing ethanol concentrations. The sensitivities of the multilayer SnO2nanoplates were about twice that of the single-layer SnO2 nanoplates, which was attributed to the large surface area of the multilayer SnO2 nanoplates. The facile fabrication of SnO2 nanoplates with high surface/volume ratio directly on the Si substrate offered vast advantages over other competing methods for the fabrication of high-sensitivity SnO2 sensors.