Supercapacitor behaviors of carbon quantum dots by green synthesis method from tea fermented with kombucha

Quantum dots have good optical and electronic behaviors due to their smaller size and having changeable properties depending on the size owing to quantum confinement effect. They can be used in various applications such as solar cells, drug delivery, displays and supercapacitors. In this study, carbon quantum dots (CQD) with nitrogen containing have been synthesized by green synthesize technique from the Kombucha fungus and characterized by HRTEM, XRD, XPS, particle sizer, luminescence and UV–Vis spectrometers. While the XRD results confirmed the crystalline structure of the CQDs, HRTEM results revealed the size of CQDs as 5 nm. The luminescence spectroscopy results showed blue-green emission. The UV–Vis spectrometer affirmed absorption peaks of the carbon at around 250–330 nm wavelengths. The CQDs were used as electrode materials for supercapacitor structure and characterized by electrochemical analysis to determine charge-discharge profiles and capacity. The results revealed that the green synthesized CQDs can be employed and improved for supercapacitor applications.