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

• Acid leaching of sepiolite to partially remove Mg2 + ions
• Different oxide/hydroxide nanoparticles were formed onto sepiolite grains.
• Sensors prepared in the form of pellets with screen-printed gold electrodes
• Tungsten doped sepiolite showed a significant response towards humidity.

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 (TG–DTA) combined with X-ray diffraction (XRD), nitrogen adsorption at − 196 °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 °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.

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