Carbon quantum dots (CQDs) are promising nanostructures smaller than 10 nm that can be obtained from natural products using top-down or bottom-up methods and relatively simple equipment. The possibility of exciting them with light from the visible region of the spectrum and obtaining fluorescence and generating reactive oxygen species (ROS), makes them interesting from both a diagnostic and therapeutic point of view. This work aims at the modification of carbonate structures by means of top-down techniques with perspectives on the generation of carbon quantum dots using spinach, yerba mate and green tea as starting material and their characterization.
With the protocols based on two contemporary works, the products obtained were characterized physicochemically by absorbance and fluorescence, oxygen consumption of one of the formulations was measured, encouraging a subsequent measurement of the quantum yield of ROS and the size determination was carried out by Dynamic Light Scattering (DLS). In the case of fluorescence quantum yields, results comparable to those in the literature were obtained. This yield varied depending on the batch, starting material and purification method. The result of the determination of hydrodynamic size by DLS, showed high polydispersity in the samples, with possible formation of aggregates. However, from this experiment the need arose to carry out an independent measurement of the refractive index (n) of the samples, since a determination of this property is not recorded in the literature. It is expected in the future to confirm the presence of these aggregates by transmission electron microscopy (TEM).
With the information obtained so far, we hope to continue with the characterization of these nanoparticles and to be able to evaluate their ability to form bioimages and be used in photodynamic therapy.

Modification of carbon structures using top-down techniques for generation of quantum dots

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