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    Green synthesis capacitor of carbon quantum dots from Stachys euadenia
    (Wiley, 2024) Baslak, Canan; Demirel, Serkan; Dogu, Suleyman; Ozturk, Gulsah; Kocyigit, Adem; Yildirim, Murat
    Carbon quantum dots (CQDs) are a new type of carbon nanomaterial that has recently attracted great attention as a potential competitor to standard semiconductor quantum dots. There are various ways to synthesis CQDs, and one of harmless way is undoubtedly green synthesis. In this study, hydrothermal synthesis based on the green way was employed to synthesize CQDs. The CQDs were obtained using the green leaves of the Stachys euadenia plant extract, an endemic species located in Turkey. The CQDs were characterized by fluorescent and UV-Visible spectroscopy, and results confirmed blue emission (430-480 nm) and absorption around 280 nm. X-ray photoelectron spectroscopy (XPS) analysis revealed C=C, C-N and C-O interactions. X-ray diffractometer (XRD) patterns confirmed structure of carbon with a broad peak of (002) plane. High resolution tunneling electron microscopy (HRTEM) and dynamic light scattering (DLS) analysis was used to determine the shape and size of CQDs. The CQDs obtained from Stachys euadenia were employed as electrode materials for capacitor application, and they were tested in Swagelok-type cell by cyclic voltammetry (CV) measurements. CQD capacitors exhibited 2.12 F/g charge and 1.24 F/g discharge capacitances were obtained with similar to 58% coulombic efficiency rate for the first cycle. Results highlights that CQDs are synthesized successfully by green synthesis method and can be used for capacitor applications.
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    Green synthesis of carbon quantum dots from Sideritis vuralii and its application in supercapacitors
    (Elsevier, 2023) Baslak, Canan; Ozturk, Gulsah; Demirel, Serkan; Kocyigit, Adem; Dogu, Suleyman; Yildirim, Murat
    Quantum dots have good optical and electrical behaviors and can be employed in solar cells, displays and supercapacitors. When new studies in nanoparticle as well as synthesis of quantum dots are examined, it can be seen that the interest in the green synthesis approach has increased. The green synthesis approach is so prom-inent due to an environmentally friendly method and does not contain toxic chemicals at the experimental stage. In this study, we used Sideritis vuralii (S. vuralii), which is endemic in Turkey, as a source of the green synthesis approach. We synthesized carbon quantum dot (CQDs) particles with the hydrothermal method from S. vuralii plant. We performed UV-Vis spectra, fluorescence spectra, XPS and DLS analyzes for the characterization of the CQDs. According to the size and characteristics results, the CQDs were successfully synthesized from the S. vuralii plant. Furthermore, we employed CQDs as electrode for capacitor applications, and cyclic voltammetry (CV) measurements were performed. The CV measurements indicated that CQDs electrodes have rechargeable sym-metrical capacitor behaviors with 10.42 F/g charge, 8.26 F/g discharge capacitances. The green synthesized CQDs can be improved for supercapacitor applications.