Antibacterial and photocatalytic activity of chitosan encapsulated Ag/ZnO ternary nanocomposites

• CS/Ag/ZnO nanocomposite synthesized via wet chemistry route. • Improved chemical properties with the addition of Ag/ZnO nanoparticles. • Excellent antibacterial response to human pathogens. • Effective photocatalytic response for degradation of methylene blue dye. Nanocomposites of polymers combined with metal oxide nanoparticles have gained much attention due to their synergistic properties leading to enhanced functional ability. Herein, we report the synthesis of a nanocomposite composed of chitosan (CS) with Ag/ZnO nanoparticles produced via a wet chemistry route. The CS/Ag/ZnO nanocomposite was characterized to study its crystal structure, morphology, thermal, and chemical properties. Morphological studies revealed uniform deposition of Ag NPs (with size range of 20-50 nm) and ZnO nanoparticles (with size range of 80-100 nm) within the chitosan matrix. XRD analysis of the composite revealed a shift in peak position of chitosan and suppression of crystalline peaks of Ag and ZnO NPs. The TGA analysis confirmed better thermal stability of the composite with the infusion of Ag and ZnO NPs. FTIR and Raman analysis confirmed the molecular interaction of Ag and ZnO NPs with CS. The estimated band gap of the CS/Ag/ZnO was 2.97 eV is lower than Ag and ZnO NPs. The nanocomposite showed a remarkable antibacterial activity against human pathogens ( Staphylococcus aureus, Listeria sp., Escherichia coli, and Salmonella typhimurium ) tested using the resazurin assay with the highest potency observed for E.coli with both minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 0.1562 µg/µL. Further, the catalytic response of CS/Ag/ZnO towards the photodegradation of the methylene blue dye revealed degradation of 89.4% within 120 min under simulated sunlight, with a rate constant of K=0.0016 min -1 when compared with 70.6 % and 74.3% degradation observed for Ag NPs and ZnO NPs respectively. The bi-functional ability of the synthesized CS/Ag/ZnO composite nanomaterial is demonstrated, and prospective applications are discussed.