High-sensitivity and low-hysteresis humidity sensor based on hydrothermally reduced graphene oxide/nanodiamond

This paper demonstrated the preparation of reduced graphene oxide/nanodiamond (rGO/ND) nanocomposite by a facile hydrothermal reduction method and its application as an ultrahigh performance humidity sensor. The synthesized rGO/ND suspension was deposited on Au interdigitated microelectrodes for sensor fabrication. The nanostructures, morphologies, and composition properties of the prepared rGO/ND nanocomposite were characterized by scanning electron microscopy (SEM), atomic force microscope (AFM), Raman spectrum, and Fourier Transform infrared spectroscopy (FTIR). The experimental results demonstrated that the rGO/ND based humidity sensor exhibited an ultrahigh sensitivity (13,086 pF/% RH), which surpasses the existed conventional humidity sensors and is more than 30 times higher than that of the pure rGO and pure ND based humidity sensors. The hysteresis characteristic of rGO/ND based humidity sensor is also dramatically improved when compared with pure rGO and pure ND based humidity sensors. Meanwhile, the sensor shows a fast response/recovery time, excellent repeatability and good long-term stability. The humidity sensing mechanism was analyzed via complex impedance spectrum (CIS). Lastly, a sensing mechanism model was established to detailedly explain the improved hysteresis properties. This research revealed that rGO/ND composite film is a promising candidate material for fabricating a high-performance humidity sensor.