Carbon Quantum Dots Interactions with Pyrogallol, Benzoic Acid, and Gallic Acid: A Study on Their Non-Covalent Nature

Understanding the interactions between carbon quantum dots (<b>CDs</b>) and promising food preservatives (<b>FPs</b>), like pyrogallol (<b>PG</b>), benzoic acid (<b>BA</b>), and gallic acid (<b>GA</b>), is highly relevant. This knowledge is crucial for designing <b>CD</b>-based sensors capable of determining the safe levels of these molecules in food and beverages. Additionally, such sensors could be exploited in the development of sustainable, intelligent packaging that controls food shelf life. Based on those considerations, in this study, we post-functionalized blue-emitting <b>CDs</b>, prepared according to a synthetic approach previously developed, with the <b>FP</b> molecules <b>PG</b>, <b>BA</b>, and <b>GA</b> to obtain <b>CD-(FP)</b> systems. UV-vis absorption and FTIR spectroscopy confirmed the presence of the <b>FP</b> molecules on the <b>CD</b> surface. The appearance of a new vibrational band at 1196 cm^-1 in the FTIR spectra of all <b>CD-(FP)</b> systems suggested that the three <b>FP</b> molecules interact with the <b>CD</b> surface via electronic interactions between the aromatic and delocalized electron systems. Further electrochemical analyses of the <b>CD-(PG)</b> and <b>CD-(GA)</b> systems show that the interactions between <b>PG</b> and <b>GA</b> benzene rings and <b>CDs</b> prevent their oxidation to the corresponding quinone forms.