Influence of Graphene Oxide (GO) Incorporation on the Structural and Antibacterial Properties of Polyaniline

Polyaniline was synthesized via chemical oxidative polymerization by adding aniline to an acidic solution, followed by ammonium persulfate. A green precipitate formed after 4 hours of stirring, which was collected, washed, and vacuum-dried. This method provides a simple way to obtain polyaniline powder. Graphene oxide (GO)-doped polyaniline (PANI) composites were synthesized via in-situ chemical oxidative polymerization. GO (10–25 w/v% of aniline) was dispersed in 0.1 M H₂SO₄ by sonication, followed by dropwise addition of aniline and ammonium persulfate. The reaction mixture was stirred for 4 hours, yielding a green precipitate. The product was washed and vacuum-dried at 60 °C to obtain GO-PANI composite powders. FTIR and XRD analyses confirmed the successful formation of GO/PANI composites. XRD patterns showed a broad peak at 2θ = 18° for pure PANI, indicating its amorphous nature, while a peak at 2θ = 20° in the composite confirmed GO incorporation. FTIR spectra revealed characteristic GO peaks at 3437, 1702, 2843, 2920, and 1640 cm⁻¹, corresponding to various oxygen-containing groups. The increase in intensity at 3437 cm⁻¹ indicated hydrogen bonding between GO and PANI. PANI peaks at 1560 and 1497 cm⁻¹ (quinoid and benzenoid rings) and a new peak at 1720 cm⁻¹ in the composite confirmed chemical interaction and successful composite formation. The antibacterial activity of pure polyaniline (PANI) and GO/PANI nanocomposites was evaluated against Escherichia coli using the disc diffusion method. Pure PANI sample showed notable antibacterial activity against E- coli, while the GO/PANI composite exhibited no response towards bacterial strain. The study highlights that the incorporation of graphene oxide into PANI reduces its antibacterial effectiveness, possibly due to reduced interaction with bacterial cells. We used the CLAIRO COMBI-Combined microbial susceptibility test discs to evaluate the antibacterial activity of our samples. This method, based on CLSI and EUCAST guidelines, allows simultaneous testing of bacterial sensitivity to 14 different antibiotics using a single disc with multiple arms. Each arm contains a specific antibiotic, enabling efficient and standardized in-vitro analysis.