Fabrication of a highly sensitive flexible humidity sensor based on Pt/polythiophene/reduced graphene oxide ternary nanocomposite films using a simple one-pot method

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 PtCl₄^2– ions via an oxidative polymerization process, which released electrons that simultaneously reduce the PtCl₄^2– ions and GO to Pt nanoparticles and RGO, respectively. The effects of the amounts of added PtCl₄^2– 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.