Microstructures and Dielectric Permittivity Properties of Fe3O4/Cdots Nanocomposites Synthesized by Green Route Utilizing Moringa Oleifera Extract and Watermelon Peel
Mareta Fidya Latifa, Adhistinka Jiananda, Aldi Riyanto, Emi Kurnia Sari, Friska Suryani Sitorus, Nurul Imani Istiqomah, Edi Suharyadi*

Department of Physics, Universitas Gadjah Mada, Yogyakarta, Indonesia

*Corresponding author: esuharyadi[at]ugm.ac.id

Abstract

Dielectric materials are highly useful for storing electrical energy due to their insulating and polarization properties in response to external electric fields. Among the other materials, magnetite has shown promise as a dielectric material due to their good magnetic properties, low toxicity, and biocompatibility. However, the weakness of Fe3O4 which has low stability and easy agglomeration requires a modification on its surface, by using Carbon dots (Cdots). This research investigates the dielectric properties of Fe3O4/Cdots obtained through green synthesis method. In this multidisciplinary research, Fe3O4 nanoparticles were synthesized using the coprecipitation method with Moringa oleifera leaf extract as a reducing and stabilizing agent. In contrast, Cdots were synthesized using hydrothermal method with watermelon peel waste as carbon source. The Fe3O4 composite nanoparticles were characterized using X ray diffraction (XRD), scanning electron microscopy energy dispersive X ray (SEM/EDX), ultraviolet visible spectroscopy (UV Vis), and impedance spectroscopy to determine their crystal structure, morphology, optical properties, and dielectric properties. The XRD spectra revealed the existence of cubic inverse spinel and a reduction in crystal size as the concentration of Cdots increased, measuring 10.4 and 6.9 nm, respectively. SEM/EDX revealed that the sample is composed of Fe, O, and C elements, has a spherical shape with Cdots distributed on the surface of Fe3O4. The UV Vis spectrum showed the absorption peak of Cdots at 282 nm. In addition, the Fe3O4 absorption peak is identical to the Fe3O4/Cdots absorption peak at 193 nm. The increase in band gap energy from 2.96 to 3.33 eV is related to the increase in Cdots concentration. In the frequency range of 10 to 900 kHz, dielectric property tests demonstrated peak dielectric permittivity values (both real and imaginary) in the 10 ml Fe3O4/Cdots sample. These values reached 314 and 104, respectively, at a 10 kHz frequency. A substantial decrease was observed between 10 kHz and 200 kHz, followed by a relatively stable pattern up to 900 kHz. The loss tangent value obtained has a value <0.5, which means that the addition of Cdots has an effect on reducing the energy loss stored in Fe3O4. Based on this, Fe3O4/Cdots material can be used as a good dielectric material.

Keywords: Dielectric material- Fe3O4/Cdots- Green synthesis- Magnetic- Nanoparticles

Topic: Material Physics