Synthesis and Characterization of CuO Nanoparticles from Kappaphycus alvarezii Derived Carrageenan for the Photocatalytic Degradation of Methylene Blue Dye

The present study investigates the synthesis and characterization of copper oxide (CuO) nanoparticles embedded in carrageenan matrices derived from green and brown strains of Kappaphycus alvarezii. The CuO-carrageenan nanoparticles (CuO-CRGg and CuO-CRGb) exhibit distinct absorption peaks at 295 nm and 301 nm, respectively suggesting variations in particle size distribution and crystallinity. Morphological analysis through SEM reveals the agglomerated structures with average particle sizes of 93 nm for CuO-CRGg and 106 nm for CuO-CRGb. FTIR analysis indicates the presence of functional groups including 3,6-anhydrogalactose from carrageenan, whereas the XRD analysis shows the average crystalline sizes of 26 nm and 27 nm for CuO-CRGg and CuO-CRGb, respectively. The energy levels associated with CuO-CRGg and CuO-CRGb nanoparticles are confirmed with a characteric peak at 4.20 and 4.12 eV, respectively suggesting wide bandgap semiconductor properties. The CuO-CRGb nanoparticles demonstrate higher photocatalytic efficiency under UV light (89.76%) compared to visible light (55.21%), with rate constants of 0.035 min–1 and a half-life of 4.04 min. Whereas CuO-CRGg nanoparticles exhibit efficiencies of 86.87% under UV light and 64.38% under visible light, with a rate constant of 0.033 min–1 and a half-life of 4.12 min under UV light and 0.011 min–1 and a half-life of 5.15 min under visible light.