Barium ferrite-chitosan nanocomposite for efficient photothermal heating and broad-spectrum antibacterial activity
Nanocrystalline BaFe₂O₄ was synthesized via a modified combustion method and incorporated into chitosan to develop BaFe₂O₄–chitosan nanocomposites with varying polymer loadings. X-ray diffraction confirmed the formation of single-phase orthorhombic BaFe₂O₄ with lattice parameters of a ≈ 4.58 Å, b ≈ 11.04 Å, and c ≈ 8.08 Å, and crystallite sizes ranging from 27 to 30 nm. FTIR and SEM–EDX analyses verified the successful incorporation of chitosan and the uniform dispersion of BaFe₂O₄ within the biopolymer. Thermal analysis confirmed the high thermal stability of BaFe₂O₄ and demonstrated that the BaFe₂O₄–chitosan nanocomposite undergoes characteristic polymer degradation between 200 and 400 °C, while preserving a stable ferrite framework with approximately 65% residual mass at 900 °C. Optical measurements revealed strong visible–NIR absorption that increased with chitosan content, accompanied by a reduction in band gap from 2.27 eV for pure BaFe₂O₄ to approximately 2.0 eV for the 80% chitosan composite. Under sunlight irradiation, the composites exhibited excellent photothermal performance, with BaFe₂O₄+80CS reaching a temperature of approximately 62 °C and achieving photothermal conversion efficiencies exceeding 80%. Antibacterial tests demonstrated more than 90% inhibition of Streptococcus pyogenes and Acinetobacter baumannii in the absence of NIR irradiation, while photothermal activation (808 nm, 5 min) enabled complete bacterial eradication in the high-chitosan composites. The novelty of this work lies in demonstrating, for the first time, a synergistic BaFe₂O₄–chitosan system that combines magnetic photothermal heating with the intrinsic antimicrobial activity of a biopolymer to achieve rapid, light-triggered, antibiotic-free bacterial disinfection. This multifunctional nanocomposite shows strong potential for biomedical applications, including photothermal antimicrobial coatings and light-activated disinfection systems for environmental applications.