One-pot ultrasound synthesis of polyaniline–ZnO and its synergistic effect on microbial activity

Abstract

In this investigation, an eco-friendly ultrasonic-assisted green synthesis was employed to synthesize a polyaniline–zinc oxide (PANI–ZnO) nanocomposite with particle sizes ranging from 50 to 60 nm. Zinc oxide (ZnO) nanoparticles were synthesised using a low-cost coprecipitation approach, and the PANI–ZnO nanocomposite was formed in situ using an ultrasound, single-step oxidative polymerisation process. This approach promoted a uniform dispersion of the ZnO nanoparticles inside the polyaniline matrix, which improved the physicochemical interactions between the organic and inorganic phases. The structural, morphological, thermal, optical, and electrical properties of the nanocomposite were thoroughly investigated using ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and electrical conductivity measurements. UV-vis and FTIR analyses showed the nanocomposite's effective production and interaction with ZnO and PANI functional groups. SEM scans revealed that the ZnO nanoparticles were uniformly dispersed throughout the PANI matrix, with no agglomeration. XRD patterns demonstrated that the crystalline character of ZnO was preserved within the composite, while TGA results indicated that the nanocomposite was more thermally stable than pure PANI. Electrical conductivity experiments revealed that the addition of ZnO altered charge transport capabilities, increasing the composite's suitability for electronic applications. Furthermore, the antibacterial activity of the PANI–ZnO nanocomposite was tested against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Salmonella typhi (S. typhi). The nanocomposite exhibited better antibacterial activity against E. coli and S. aureus but reduced activity against S. typhi. The observed antibacterial behaviour was due to the synergistic interaction between the ZnO nanoparticles and the PANI matrix, which resulted in improved disruption of bacterial cell membranes. Overall, the PANI–ZnO nanocomposite synthesised via this green, ultrasonic technique showed remarkable multifunctional capabilities, making it a feasible option for applications in antimicrobial materials, sensors, and electronic devices.