Optical, microstructural, and magnetic hyperthermia properties of green-synthesized Fe3O4/carbon dots nanocomposites utilizing Moringa oleifera extract and watermelon rinds

Cancer therapy with targeted-localized heating is one of the breakthroughs in the biomedical field. The incor-poration of magnetic nanoparticles and fluorescent nanoparticles was one of the crucial issues for magnetic hyperthermia applications. This research investigates the magnetic hyperthermia properties of green-synthesized Fe3O4/CDs. Fe3O4 nanoparticles were synthesized using the coprecipitation method with Moringa oleifera leaf extract as a reducing agent and stabilizer. In contrast, CDs were synthesized using a hydrothermal method with watermelon rind waste as a carbon source. X-ray diffraction analysis confirmed the presence of cubic inverse spinel and a reduction in crystallite size with increasing CDs concentration. Transmission electron microscopy revealed particle size distributions of 9.7 nm for Fe3O4 and 7.5 nm for Fe3O4/CDs. Scanning electron microscopy showed that CDs were distributed on the surface of Fe3O4. The detection of characteristic Fe-O, C--C, C-O, and C-O-C bonds indicated the presence of CDs on the surface of Fe3O4. Ultraviolet-visible spectroscopy spectra absorption peaks at 282 nm for CDs and 193 nm for Fe3O4. Photoluminescence spectra indicated shifts from 509 to 505 nm in excitation wavelength for both CDs and Fe3O4/CDs, situated within the green region of visible light. The vibrating sample magnetometer revealed that the nanocomposites displayed characteristics of soft ferro-magnetic materials. Furthermore, the specific absorption rate (SAR) value of Fe3O4/CDs was found to be dependent on magnetization. The SAR value of Fe3O4/CDs decreased as the concentration of CDs increased, and the frequency and strength of the AMF increased. Therefore, these results can promote Fe3O4/CDs nano-composites as a promising candidate for magnetic hyperthermia applications.