Synthesis of ZnO Nanoparticles onto Sepiolite Needles and Determination of Their Sensitivity toward Humidity, NO2 and H2

This work investigated the sensitivity toward humidity, NO2 and H2 of ZnO modified sepiolite (Si12Mg8O30(OH)4.(H2O)4.8H2O). To this aim, sepiolite powder was first modified by leaching magnesium ions in HCl then by precipitating nano-sized Zn-based compounds under basic conditions. A subsequent thermal treatment at 550 °C for 1 h was performed. The powders were characterized by X-ray diffraction (XRD), specific surface area measurements, thermogravimetric and differential thermal analysis and field emission scanning electron microscopy, as well as high resolution transmission electron microscopy. The XRD patterns showed that all leached heat treated samples were made of anhydrous sepiolite and of ZnO. Sensors were then obtained by screen printing these materials onto commercial alumina substrates with Pt electrodes. All the investigated compositions were capable of detecting NO2 down to ppm level and 20 ppm H2, at an optimal working temperature of 300 °C. These detection limits are in line with the current best results reported in literature.