Preparation and Characterization of Carbon Quantum Dots from Salvia rosmarinus (Rosemary) Plant via Hydrothermal Synthesis Method

Abstract

In this study, Carbon Quantum Dots (CQDs) were synthesized via hydrothermal synthesis (CQDs) from the rosemary (Salvia Rosmarinus) plant as a natural carbon source. Dried and ground rosemary extracts were subjected to hydrothermal reaction at 200 °C for 18 h. CQD solutions were obtained by two purification methods involving high-speed centrifugation and 22 μm injector filter methods. The obtained CQDs were characterized by UV–Vis spectroscopy (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy to analyze their optical and surface chemical properties. UV-Vis analyses revealed that CQDs produced by both purification methods exhibited absorption in the range of 260–320 nm. The lower absorbance values observed after the 22 μm injector filtration process compared to the centrifuged samples showed that the purification method affected the particle size and optical properties. FTIR results proved the presence of hydroxyl (-OH), carboxyl (-COOH), carbonyl (C=O), double bond (C=C) and epoxy (C–O–C) groups on the surface of CQDs. The sharper and more distinct IR bands observed in the CQD samples purified by high-speed centrifugation indicate a more homogeneous and pure structure. As a result of the findings obtained, it is seen that the rosemary plant can be used as an environmentally friendly carbon source by the hydrothermal method, and synthesized CQDs have the potential to be used in biosensors, imaging, and other biomedical applications.