Synchronous fluorescence sensing and discrimination of azo food colorants based on dual-emission carbon dots and its sensing application in electrospuns films.

The extensive use of azo food colorants has heightened public health concern, underscoring the need for advanced sensing methods to accurately quantify these compounds in food products. Herein, a ratiometric fluorescent sensor employing dual-emission carbon dots (DC-CDs) is developed for the sensitive detection and differentiation of azo colorants. The DC-CDs are synthesized from tris (hydroxymethyl) aminomethane and 2, 5-diaminobenzenesulfonic acid via a solvothermal method. At a wavelength interval of 120 nm, the synchronous fluorescence spectrum of DC-CDs displays two well-defined emission peaks at 320 nm and 470 nm. Upon addition of azo food colorants, the fluorescence signals at 320 and 470 nm are both quenched due to the combined effects of inner filter effect (IFE) and fluorescence resonance energy transfer (FRET). Accordingly, DC-CDs provide the limits of detection (LODs) of 43 nM, 56 nM, 76 nM and 49 nM for sunset yellow (SY), tartrazine (Tar), allura red (AR) and azorubine (AZ), respectively. Furthermore, mixtures of azo food colorants can be effectively distinguished through the combined use of hierarchical cluster analysis (HCA), principal components analysis (PCA) and linear discriminant analysis (LDA). For practical applications, DC-CDs are encapsulated into an electrospun film to fabricate a smartphone-assisted sensing platform for the on-site determination of azo food colorants in real commercial food samples, yielding satisfactory recoveries (96.7%-103.1%) with relative standard deviations below 5.92%. This work integrates dual-emission synchronous fluorescence analysis with an electrospun film platform, offering a sensitive and feasible approach for the on-site analysis of azo food colorants.