Abstract

This study presents the green synthesis of carbon dots (Cdots), magnetite nanoparticles (Fe₃O₄), and their nanocomposites (Fe₃O₄/Cdots) for the photocatalytic degradation of Rhodamine B (RhB) dyes. Cdots were synthesized by the hydrothermal method from pineapple peel extract, while Fe₃O₄ 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 Fe₃O₄. X-ray diffraction confirmed the crystalline nature of Fe₃O₄ and Fe₃O₄/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 Fe₃O₄ 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 Fe₃O₄ and 1.86 eV for Fe₃O₄/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 H₂O₂ revealed percent degradation of RhB (10 ppm) after 120 min to be 50.85% (Cdots), 94.48% (Fe₃O₄), and 87.06% (Fe₃O₄/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.

Credit: Mahardiani et al., Next Materials, 12, 101992 (2026), https://doi.org/10.1016/j.nxmate.2026.101992. © 2026 The Authors. Licensed under CC BY 4.0.