Elaboration and characterization of modified sepiolites and their humidity sensing features for environmental monitoring

After precipitation under basic conditions and subsequent thermal treatment, different oxide/hydroxide nanoparticles (based on W4+, Co2+, Cu2+, Gd3+, La3+, Mn2+, Nd3+, Sm3+, Sr2+, Y3+ and Zn2+) were formed onto sepiolite grains. Thermogravimetric-Differential Thermal Analysis (TO-DTA) combined with X-ray diffraction (XRD), nitrogen adsorption at -196 degrees C, Field Emission-Scanning Electron Microscopy (FE-SEM), Diffuse Reflectance UV-visible (DR-UV-vis) spectroscopy and Infra-Red (IR) spectroscopy were used to study the particle size distribution, the morphology and the composition of the modified sepiolites. Humidity sensors were prepared in the form of pellets, where powders were uniaxially pressed and thermally treated at 550 degrees C for 1 h then, gold electrodes were screen-printed. Among the different studied compositions, tungsten-doped sepiolite exhibited a significant response towards relative humidity (RH) at room temperature starting from 40% RH.