Fabrication of tin disulfide/graphene oxide nanoflower on flexible substrate for ultrasensitive humidity sensing with ultralow hysteresis and good reversibility

Flexible humidity sensors with ultrafast response are great importance in the promising wearable devices. In this paper, a novel nanocomposite of tin disulfide/graphene oxide nanoflower (SnS2/GO) was first synthesized for constructing humidity sensors. The nanostructural, morphological and compositional properties of the SnS2/GO hybrid were characterized by XRD, XPS, FT-IR, SEM, TEM and EDS. The humidity experiment found that SnS2/GO (in the wt% ratio of 1:2.5) has the most excellent response. The humidity sensing results revealed the SnS2/GO film sensor has ultrahigh response, negligible hysteresis, favorable reversibility and ultrafast response/recovery behavior, which outstrips the individual SnS2 or GO film sensor. The potential mechanism of water molecule adsorption was revealed, and the complex impedance spectroscopy and Bode diagrams were used to further explain the sensing mechanisms of the SnS2/GO composite. Moreover, the impedance changes caused by the bending effect, human respiration and fingertip approaching/retracting behavior were investigated, which demonstrate a great potential of the SnS2/GO sensor in humidity sensing for wearable applications.