Fabrication of carbon quantum dots by microemulsion route: Dual functional materials for energy storage and environmental treatment

In this research, Carbon quantum dots (CQDs) were synthesized by the microemulsion method with a variation of 1- 5 wt. % multi-walled carbon nanotubes (MWCNTs). Varying percentages of MWCNTs affected morphological, structural, antibacterial, photocatalytic, dielectric, electrochemical and optical properties of CQDs. X-ray diffractometer confirmed the formation of the cubic phase of carbon. SEM revealed a granular and a cloud like surface morphology that was not uniform, with a significant number of grain boundaries. FTIR spectroscopy was used to examine the different functional groups. As MWCNTs concentration increased, the band gap of CQDs reduced from 3.89 to 3.5 eV. These CQDs were suitable as absorbing layers for solar panels due to their reduced band gap and ability to absorb the visible portion of the electromagnetic spectrum. The dielectric properties of all CQDs were also examined. AC conductivity was increased with the increased MWCNTs content. Utilizing these CQDs considerably improved the efficiency of supercapacitors, resulting in specific capacitance ranging from 1007.81 to 4531.25 Fg^-1 with high energy and power density. This led to the manufacturing of supercapacitors in modern electrical devices. Furthermore, increasing MWCNTs concentration enhanced the photocatalytic properties of CQDs. These synthesized nanoparticles exhibit improved photocatalytic activity due to increased UV–VIS light absorption and decreased recombination of photoinduced electron-hole pairs. CQDs have strong antibacterial activity, especially against salmonella enterica. These CQDs have significance in supercapacitors and water treatment.