Graphene-Nanoplatelet-Induced π–π Ordering in Electrodeposited Graphene/PANI Nanocomposite Thin Films: Bandgap Narrowing, Dielectric-Loss Modulation, and Enhanced Charge Transport

Camphorsulfonic-acid-doped polyaniline/graphene nanoplatelet (PANI/GNPs) thin films were electrodeposited on indium tin oxide to determine how GNP loading affects film structure and optical, dielectric, and electrical properties. Pristine PANI and composite films were prepared at a constant cell bias using GNP feed loadings of 6, 12, and 18 wt.% relative to aniline. White-light interferometry and scanning electron microscopy revealed a non-monotonic morphological evolution: low GNP loading increased surface roughness, whereas higher loadings produced more consolidated but heterogeneous structures, consistent with changes in PANI growth around the graphene nanoplatelets. FTIR spectra retained the characteristic PANI backbone and emeraldine-salt-related bands; changes in band width and intensity were consistent with altered chain packing and non-covalent interactions at PANI/GNP interfaces. UV–Vis–NIR measurements showed reduced transmittance, enhanced optical attenuation, and changes in refractive-index dispersion. The optical bandgap estimated using the direct-transition Tauc model decreased from 2.49 eV for pristine PANI to 2.17 eV at 18 wt.% GNP feed loading. The calculated surface and volume energy-loss functions increased with GNP loading, indicating changes in the optical dielectric response. Reported room-temperature DC conductivity increased from 0.9 to 1.5 S cm−1, consistent with improved charge transport through the PANI/GNP network. Analysis of X-ray diffraction in q-space identified additional ordered scattering features in the composite films, including characteristic spacings of approximately 3.22–3.26 Å tentatively associated with stacking of the graphene layers within GNPs. These results link GNP feed loading to changes in film morphology, optical response, and electrical transport, supporting further investigation of PANI/GNP coatings for optoelectronic and sensing applications.