Facile development of high performance QCM humidity sensor based on protonated polyethylenimine-graphene oxide nanocomposite thin film

In this paper, a protonated polyethylenimine (P-PEI)-graphene oxide (GO) nanocomposite thin film, referred as P-PEI-GO, was deposited on the quartz crystal microbalance (QCM) by a facile dipping process for the development of high performance humidity sensors. The morphological and structural characteristics of P-PEI-GO thin film were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscope. The humidity-sensing properties, such as response and recovery, sensitivity, repeatability, selectivity, humidity hysteresis and long-term stability, were investigated in a wide range of working humidity (11-97% RH). The resultant P-PEI-GO nanocomposite thin film possesses much larger specific surface area and richer hydrophilic groups than pure P-PEI film, leading to higher sensitivities and shorter response/recovery times of the sensor. Especially, the sensor preserves excellent durability, small hysteresis, good selectivity and stability compared with individual P-PEI or GO film sensor, which could be ascribed to the high mechanical modulus of GO and weak interaction between P-PEI and GO. Finally, the humidity sensing mechanism of proposed sensor was discussed in details. This research provides a feasible and effective approach to construct high performance humidity sensor operated at room temperature based on GO nanocomposites. (C) 2016 Elsevier B.V. All rights reserved.