ZnO-SnO2 nanotubes surface engineered by Ag nanoparticles: synthesis, characterization, and highly enhanced HCHO gas sensing properties

Novel Ag nanoparticles (NPs) coated ZnO-SnO2 nanotubes (NTs, diameter similar to 250 nm, wall thickness similar to 20 nm) were fabricated using a facile electrospinning technique together with a seed-mediated growth procedure, and the amount of surface Ag NPs was systematically controlled. They were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis spectra and X-ray photoelectron spectroscopy (XPS) techniques, which showed that strong interactions occurred between the ZnO-SnO2 NTs and the Ag NPs. The sensing properties of the Ag coated ZnO-SnO2 NTs for HCHO gas were carefully studied and the results indicated that the sensing properties were significantly modified by the coating of Ag NPs, including a considerably decreased working temperature, a highly improved response and shortened response dynamics. The 10% Ag coated NTs gas sensor was the optimum sensor, demonstrating an enhanced response of similar to 6 times that of the ZnO-SnO2 NTs, while the working temperature was decreased by about 140 degrees C. Additionally, it showed a very low detection limit (9 ppb) for HCHO. The main reason for the enhanced HCHO gas sensing properties was attributed to spillover effects between the Ag NPs and ZnO-SnO2 NTs. Overall, the Ag coated ZnO-SnO2 NTs synthesized through electrospinning make a promising ppb-level HCHO sensor and an effective indoor HCHO detector.