Green synthesis of carbon dots from medicinal herbs by microwave assisted method: Physicochemical and optical properties

Carbon dots (CDs), a type of nanoparticle, exhibited adjustable physicochemical and optical characteristics. In the present study, microwave method was used for the synthesis of green carbon dots. A surge in interest was observed in the one-pot green synthesis methods that used renewable materials, instead of employing hazardous chemicals, for the generation of carbon dots. Coleus amboinicus and Scallion (spring onion) were used as readily available precursors for the production of green carbon dots. The structural properties and crystalline nature of the prepared carbon dots were examined by the X-ray diffraction (XRD) analysis. The elemental composition of the green carbon dots was determined using the EDAX spectrum. The morphological features of the carbon dots were analyzed via. Field Emission Scanning Electron Microscopy (FE-SEM). Fourier Transform Infrared Spectroscopy (FT-IR) was carried out for the investigation of the presence of functional groups in the synthesized carbon dots. UV-Vis absorption spectroscopy was employed to study the optical properties of the generated carbon dots. The UV-Vis spectra confirmed successful synthesis of carbon dots viz. CD1 (C. amboinicus synthesized carbon dots) and CD2 (Scallion synthesized carbon dots) with distinct absorption peaks, though CD2 showed partial synthesis. FT-IR analysis revealed functional groups like -OH, -COOH and -C=O, enhancing hydrophilicity and biocompatibility. XRD patterns indicated an amorphous nature for CD1, while CD2 showed impurities due to incomplete synthesis. FE-SEM images displayed spherical morphologies and EDX analysis verified the presence of carbon and oxygen, confirming synthesis with some impurities in CD2.