Covalent immobilization of phosphonium-based ionic liquid onto modified graphitic carbon nitride for visible-light photodegradation and antibacterial applications

چکیده مقاله

The rapid growth of industrialization and subsequent environmental pollution emphasizes the need for the introduction of photocatalysts that efficiently decompose both natural and synthetic contaminants in wastewater treatment processes. To achieve a superior nanophotocatalyst, ZnO-modified g-C₃N₄ was synthesized through simple calcination-hydrothermal techniques and then covalently linked to a phosphonium-based ionic liquid. For the first time, the ultrasound-assisted synthesis of [Ph₃PC₂H₄Br][Br] was reported by reacting triphenylphosphine with 1,2-dibromoethane. The photocatalytic property of the designed ZnO/g-C₃N₄/[Ph₃PC₂H₄][Br] was evaluated through the degradation of the water-soluble dyes Eriochrome Black T (EBT) and Methyl Violet (MV). An optical bandgap of 2.19 eV was assessed using diffuse reflectance spectroscopy, making the proposed nanocomposite suitable for the visible light photodegradation process. The EBT cationic dye exhibited higher efficiency (90.9 %) when 45 mg of ZnO/g-C₃N₄/[Ph₃PC₂H₄][Br] nanocomposite was present at pH = 10. The kinetic study revealed that the maximum observed rate constant (k = 0.0176 min−1) led to the highest photocatalytic activity (90.9 %). The results indicate that benzoic acid, when used as a scavenger, significantly reduces the photocatalytic activity, highlighting the essential role of •OH radicals in the process. In the next step, the antibacterial activity was evaluated to determine the susceptibility of Staphylococcus aureus and Escherichia coli strains to the synthesized nanocomposites. The results demonstrate the significant impact of the IL on antibacterial activity, revealing that the ZnO/g-C₃N₄/[Ph₃PC₂H₄][Br] nanocomposite can serve as an effective antibacterial agent, particularly against Gram-positive pathogens.