Synthesis and Analysis of Fluorescent Carbon Dots Derived from Plant Material

An investigation was carried out on the fluorescent properties of nanoparticles made by a hydrothermal method from an ethanolic extract of mulberry leaves. Our analysis confirmed the presence of carbon dot nanostructures exhibiting fluorescence emission peaking at 670 nm (excited at 405 nm) with a quantum yield of 45%. Photobleaching of the nanoparticles upon quasi-continuous excitation at 405 nm was observed with 10–20 s irradiation. Without illumination, partial fluorescence recovery was detected consisting of several percent within one minute and over 25% after 16 h in darkness. Comparative spectral analysis of the initial leaf extract and the synthesized red-luminescent carbon dot fraction revealed similarities, suggesting the presence of unbound organic molecules with chromophore groups in the medium. The chromophores were found to accumulate in erythrocyte membranes, enabling cell visualization. However, these chromophores were found to be both cytotoxic and phototoxic. Thus, the synthesis of carbon dots from multicomponent plant extracts may result in incomplete carbonization and degradation of the chromophores, which can significantly alter our interpretation of the optical properties of these nanostructures.