Excellent green synthesis of iron oxide decorated with carbon dots for photocatalytic degradation of rhodamine B dyes

This study presents the green synthesis of carbon dots (Cdots), magnetite nanoparticles (Fe 3 O 4 ), and their nanocomposites (Fe 3 O 4 /Cdots) for the photocatalytic degradation of Rhodamine B (RhB) dyes. Cdots were synthesized by the hydrothermal method from pineapple peel extract, while Fe 3 O 4 was prepared via the co-precipitation method using Ocimum tenuiflorum (ruku-ruku) leaf extract. The nanocomposites were fabricated through ultrasonic-assisted assembly of Cdots onto Fe 3 O 4 . X-ray diffraction confirmed the crystalline nature of Fe 3 O 4 and Fe 3 O 4 /Cdots, with crystallite sizes of 70.90 and 67.67 nm, and crystallinity degrees of 66.69% and 68.91%, respectively. FTIR analysis detected the Fe–O functional group, confirming the presence of Fe 3 O 4 post-fabrication. Functional groups such as C C, C–O, and C–O–C indicated successful incorporation of Cdots. The band gap energies were 1.84 eV for Fe 3 O 4 and 1.86 eV for Fe 3 O 4 /Cdots, suggesting good visible light absorption. SEM analysis showed irregular morphology and agglomeration in Fe₃O₄, while Fe₃O₄/Cdots exhibited a smoother surface and more uniform particle distribution. Photocatalytic tests under UV light and H 2 O 2 revealed percent degradation of RhB (10 ppm) after 120 min to be 50.85% (Cdots), 94.48% (Fe 3 O 4 ), and 87.06% (Fe 3 O 4 /Cdots). Reusability studies showed that Fe₃O₄ and Fe₃O₄/Cdots retained 75.07% and 59.72% of their initial percent degradation after five cycles. These findings highlight the potential of Fe₃O₄/Cdots as eco-friendly, reusable photocatalysts for dye-contaminated wastewater treatment.