Humic acid nanosheets decorated by tin oxide nanoparticles and there humidity sensing behavior

A novel resistive type humidity sensor based on humic acid nanosheets decorated by tin oxide nanoparticles is reported in the present work. The humic acid nanosheets have been extracted from Leonardite via acid base treatment followed by centrifugation. The SnO2 nanoparticles were incorporated in humic acid nanosheets using SnCl2. The microstructure and morphology of the as prepared samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). The results confirm the successful formation of tin oxide nanoparticles anchored and uniformly distributed over humic acid nanosheets. The surface investigations showed a crumpled, fluffy and wrinkled morphology. Humidity sensing properties of the as prepared nanocomposite has been studied. Saturated salt solutions were used to control the relative humidity. The sensing response has been measured in the relative humidity range 12.4 up to 97.1% at the room temperature. It has been found that the sensor impedance decreases as the relative humidity increases with good linearity (-0.19319 +/- 0.01264). The prepared sensor exhibited a fast response and recovery time. The present type of humidity sensor opens a new generation of low cost, fast response and environmentally friend humidity sensors.