Highly selective and sensitive fluorescent determination of Fe3+ within alcoholic beverages with 1,5-diphenylcarbazone-functionalized graphene quantum dots

Abstract

Herein, we report the synthesis of graphene quantum dots (GQDs) functionalized with 1,5-diphenylcarbazone for the selective quantification of Fe in wine, via front-face fluorescence. Crystalline GQDs are obtained via a clean and relatively size-controlled synthesis based on the electrochemical exfoliation from a graphene foam. The product of the synthesis was later functionalized to solely detect Fe3+ amongst various other ions present within the sample. The detection is based on quenching the fluorescence emission from the functionalized nanomaterial in the presence of the analyte, which follows a linear relationship with the concentration of the analyte, consistent with the Stern-Volmer model. Diverse parameters involved in the measurements, including the pH and excitation wavelength, were optimized, giving place to limits of detection (LOD) of 0.014 mg L−1 and 0.11 mg L−1 in waters and white wines, respectively. A soft UV-based digestion and a profound analysis of interferences were key factors to achieve such LODs. Furthermore, front-face fluorescence measurements improved the applicability of the method by avoiding the commonly occurring matrix shielding effects. We believe that the sensitive, selective, and fast detection of Fe3+ within real (i.e.; wine) samples represents a major step forward in the field.