A novel, flexible humidity sensor based on ternary nanocomposite films of Pt nanoparticles, polythiophene, and reduced graphene oxide (Pt/polythiophene/RGO) was fabricated using a simple one-pot redox synthesis. First, 2-thiophene methanol (2-TPM) was allowed to react with PtCl42– ions via an oxidative polymerization process, which released electrons that simultaneously reduce the PtCl42– ions and GO to Pt nanoparticles and RGO, respectively. The effects of the amounts of added PtCl42– ions and RGO on the electrical, flexibility, and humidity-sensing properties of the Pt/polythiophene/RGO ternary nanocomposite films were investigated. The Pt/polythiophene/RGO ternary nanocomposite films were characterized by using the Fourier transform infrared spectroscopy (FTIR), Raman, atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A Pt/polythiophene/RGO ternary nanocomposite film containing 30 mg of Pt and 0.1 g of RGO exhibited the greatest flexibility, sensitivity, and long-term stability. This flexible humidity sensor also demonstrated a wide range of working humidities, an acceptable linearity, a small hysteresis, a short response/recovery time, and a weak temperature dependence. We used complex impedance spectra to explain the humidity-sensing mechanism of the flexible sensor based on Pt/polythiophene/RGO ternary nanocomposite films and thus found that the ions (H3O+) in this system dominate the conductance process of the sensor.
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