Flaxseed‐Derived Rhamnogalacturonan as a Biogenic Stabilizer for CuO Nanoparticles With Photocatalytic, Antimicrobial, and Pollutant‐Sensing Applications

ABSTRACT The study presents the green synthesis of copper oxide nanoparticles (CuO NPs) using the rhamnogalacturonan‐rich mucilage from flaxseed ( Linum usitatissimum ) as a natural stabilizing agent. The CuO NPs were characterized using spectroscopic techniques, including UV‐Visible spectroscopy, FTIR, SEM, and XRD. The UV analysis revealed a sharp band at 294 nm with an energy band gap of 4.27 eV; hence, the prepared CuO NPs are semiconductor materials. FTIR spectrum revealed an intense peak at 590 cm −1 , attributed to Cu‐O bonds. SEM analysis discovered that the CuO NPs were non‐spherical, polydispersed, and agglomerated. The XRD analysis showed a monoclinic crystal structure with crystallite sizes of 11–31 nm. The photocatalytic activity of CuO NPs was responsible for the decomposition of 87.2% methylene blue (MB) in sunlight following pseudo‐first‐order (k = 0.01708 min −1 ) kinetics. The CuO NPs depicted significant antimicrobial activity and complete biofilm inhibition at 100 µ g/mL against Bacillus licheniformis, Escherichia coli , and Pseudomonas aeruginosa . In addition, CuO NPs acted as sensors for heavy metal ions such as Pb 2+ and Fe 2+ . The study suggests the potential of rhamnogalacturonan‐capped CuO NPs for successful use in antibacterial applications, environmental remediation, and pollutant detection.