Engineering Dielectric Transition and Surface Polarity in Hydrothermally Synthesized MXene-PbO-PANI Nanocomposites

In this study, Ti₃C₂Tₓ MXene-based nanocomposites were synthesized via hydrothermal-assisted in situ polymerization with polyaniline (PANI) and lead oxide (PbO), offering a novel approach to tune the dielectric transition behavior and surface polarity. Three different hybrid structures were prepared and characterized in detail: Ti₃C₂Tₓ MXene/PANI, Ti₃C₂Tₓ MXene₀.₁₈:PbO, and Ti₃C₂Tₓ MXene₀.₀₃:PbO₀.₈₆:PANI₀.₁₁. XRD and SEM-EDX analyses confirmed the presence of α-PbO and β-PbO phases and the homogeneous distribution of MXene layers. At the same time, AFM results showed a reduction in surface roughness after hybrid formation. According to contact angle measurements, pure PANI showed the highest hydrophilic behavior (38.0°), while the MXene₀.₁₈:PbO system exhibited weaker hydrophilicity (67.6°), and the MXene: PbO: PANI hybrid showed moderate wettability (49.7°). Dielectric measurements performed over the frequency range of 200 Hz–10 MHz and the temperature range of 30–140 °C revealed two distinct polarization mechanisms. The MXene₀.₁₈:PbO system showed a negative dielectric constant and a DC conductivity value of 35 mS cm⁻¹ due to its metallic character. At the same time, the MXene: PbO: PANI hybrid exhibited positive dielectric behavior due to temperature-activated dipole orientation and a DC conductivity value of 140 nS cm⁻¹ at 50 °C. The results show that varying composition ratios and structural arrangements can precisely adjust dielectric properties, conductivity, and surface polarity. With these properties, the developed MXene-based nanocomposites stand out as strong candidate materials for capacitive systems, sensor applications, and energy-efficient electronic components.