Synthesis of quantum-sized ZnO nanoparticles in different medium and their application to NO2 sensors.

Quantum-sized ZnO nanoparticles were synthesized using zinc acetate dihydrate through a sol-gel process in different mediums: water, ethanol and methanol. Three types of modifiers: tetraethyl orthosilicate (TEOS), sodium dodecyl sulfate (SDS) and oleic acid (OA) were added to control the growth of the ZnO nanoparticles and inhibit Ostwald ripening. X-ray Diffraction (XRD) analyses revealed that ZnO have a hexagonal crystal structure, the estimated average crystallite sizes of modified ZnO are in the range of 4.5-10 nm, while the crystallite sizes of non-modified ZnO are large than 20 nm. X-ray photoelectron spectroscopy (XPS) analyses obtained the surface composition and chemical states of the products of ZnO. In this paper, the obtained quantum-sized ZnO nanoparticles as a novel sensing material were used to detect NO2 in environment. The sensing tests indicated that the ZnO based sensors not only have high response to NO2 but also exhibited high selectivity to CO and CH4 at low operating temperature of 290 degrees C.