Carrageenan bionanocomposite films incorporating Ag and Zn-Doped CeO₂ nanoparticles for active food packaging applications

Abstract

• This research examines the effects of incorporating Ag and Zn as dopants into CeO₂ NPs and their subsequent impact on the mechanical properties, hydrophobicity, and antibacterial activity of carrageenan-based bionanocomposite films. The synthesis of CeO₂ NPs doped with varying concentrations of Ag and Zn, was achieved using the green synthesis method with green tea extract as a reducing agent. Characterization techniques like XRD, TEM, PSA, and Zeta potential analysis confirmed the successful doping and stability of the nanoparticles. • The carrageenan-based bioplastic without nanomaterial addition exhibits a good hydrophobicity with a WCA value of 109.90° due to the incorporation of montmorillonite because clay tends to increase the hydrophobicity of bioplastic. However, adding hydrophilic CeO₂ NPs decreases the bioplastic's water resistance, while adding Ag and Zn doped CeO₂ NPs further decreases the water resistance. Bionanocomposite with Zn-Doped CeO₂ NPs has a better water resistance than Ag-Doped CeO₂ NPs with a WCA value of 84.25° versus 68.19° due to the hydrophobic nature of ZnO. • Doping CeO₂ NPs with Ag and Zn leads to the formation of oxygen vacancies, which contribute to the generation of ROS that induce oxidative stress in bacteria, thereby enhancing antibacterial activity. The inherent antibacterial properties of Ag, Zn, and their oxides byproducts further enhance the effectiveness of the Doped CeO₂ NPs with Ag and its oxides (AgO, Ag₂O) exhibit superior antibacterial activity compared to Zn and ZnO. Overall, Zn and Ag-Doped CeO₂ NPs exhibited superior antibacterial activity than undoped CeO₂ NPs. • The antibacterial activity test shows that all sample variations tend to have a stronger antibacterial activity against E. coli (Gram-negative) than B. cereus (Gram-positive). The 20 wt% Ag-Doped CeO 2 NPs nanocomposite exhibited the highest antibacterial activity, slightly better than amoxicillin used as a positive control. The strong antibacterial activity of the Ag-Doped CeO₂ NPs nanocomposite may be attributed to Ag's intrinsic strong antimicrobial properties and silver oxides due to the generation of silver ions (Ag⁺) and ROS. • The addition of CeO₂ NPs, as well as Ag and Zn-Doped CeO₂ NPs, to the bionanocomposites can increase tensile strength and young's modulus. Ag-Doped CeO₂ NPs have better tensile strength due to good dispersibility and very small particle size. The study concludes that Ag and Zn-Doped CeO₂ nanoparticles are promising additives for developing effective and sustainable active food packaging materials. The increasing demand for sustainable and safe food packaging has led to the exploration of bio-based materials and advanced packaging technologies. This study investigates the incorporation of silver (Ag) and zinc (Zn) doped cerium oxide nanoparticles (CeO₂ NPs) into carrageenan-based bionanocomposite films to enhance their antimicrobial properties, mechanical strength, and hydrophobicity. The synthesis of CeO₂ NPs, doped with varying concentrations of Ag and Zn, was achieved using the green synthesis method with green tea extract as a reducing agent. Characterization techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and Zeta potential analysis confirmed the successful doping and stability of the nanoparticles. The bionanocomposites were evaluated for their mechanical properties, water contact angle, and antibacterial activity against Escherichia coli and Bacillus cereus . Mechanical testing revealed that the addition of CeO₂ NPs, particularly Ag-doped CeO₂ NPs, significantly improved the tensile strength and Young's modulus of the bionanocomposites. Hydrophobicity assessments showed that Zn-doped CeO₂ NPs enhanced water resistance compared to Ag-doped CeO₂ NPs, making them more suitable for food packaging applications. Zn and Ag-doped CeO₂ NPs exhibited superior antibacterial activity compared to undoped CeO₂ NPs, with 20 wt% Ag-doped NPs showing the highest antibacterial activity compared to Amoxicillin as positive control and other variations. The study concludes that Zn and Ag-doped CeO₂ NPs are promising additives for developing effective and sustainable active food packaging materials.