Green synthesis of carbon dots from Nigella sativa seeds for supercapacitor application

Abstract

The synthesis of carbon dots (CDs) from sources such as coal and phenolic resins requires the use of chemicals that sometimes are hazardous to the environment. Several studies have highlighted the significance of using natural and biomass sources in ecologically friendly CDs synthesis. This strategy guarantees their accessibility, environmental friendliness and cost-effectiveness. In this work, we report the synthesis of CDs from Nigella sativa seeds for supercapacitor application. A hydrothermal technique was adopted for this experiment. The structural, size distribution, fluorescence, and electrochemical properties of the synthesized CDs were studied using an X-ray diffraction (XRD) spectroscope, Transition electron microscope (TEM), spectrofluorometer and potentiostat, respectively. The TEM revealed distinct scattered quasi-spherical dots on the surface and the estimated size distribution ranges from 6.08 to 9.91 nm. The fluorescence spectra revealed that CDs have green light emission, which redshifts as the excitation wavelength increases. The electrochemical measurement confirms that CDs exhibited an electrical double layer (EDL) capacitance behavior with an areal capacitance of 2.82 mF/cm2 at 5.21 μA/cm2 current density. To the best of our knowledge, this is the first report on the fabrication of supercapacitor from CD derived from Nigella sativa seeds.