Versatile functional properties of polyindole/CuO nanocomposites for dielectric and environmental sensing...

Conductive polyindole/copper oxide (PInCuO) nanocomposites (NCs) were synthesized via oxidative in situ polymerization. Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analyses confirmed the successful incorporation of CuO nanoparticles and their crystallinity within the polymer matrix. UV-Vis analysis revealed enhanced optical conductivity, a reduced optical bandgap, and an increased refractive index with CuO addition, showing optimal effects at 7 wt% loading. Field-emission scanning electron microscopy (FE-SEM) images revealed a uniform nanoparticle dispersion at this concentration, whereas higher loadings led to agglomeration. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed that the incorporation of CuO significantly improved the phase transition temperature and thermal stability of the NCs. The impact of nanofiller concentration, frequency, and temperature on the electrical, dielectric, and modulus properties was systematically investigated. Dielectric analysis showed a substantial increase in the dielectric constant with increasing filler content, with the NC containing 7 wt% CuO (PInCuO7) exhibiting the highest charge storage capacity. Moreover, PInCuO7 exhibited the highest AC conductivity of 3.5 × 10⁻⁵ S/cm at room temperature and 10⁶ Hz, significantly surpassing that of pristine PIn (2.7 × 10⁻⁶ S/cm). The activation energy from Arrhenius plots was significantly lower for PInCuO7 (0.054 eV) compared to PIn (0.174 eV), indicating enhanced charge carrier mobility due to the effective dispersion of CuO. Additionally, PInCuO NCs exhibited improved ammonia sensing performance over PIn, underscoring the critical role of CuO in enhancing optical, electrical, and sensing properties of the nanocomposites. These findings highlight the potential of PInCuO NCs for advanced applications in optoelectronics, energy storage, and gas sensing.