A sensitive lateral flow test strip sensor for visual detection of acid red 18 in food using bicentric-emission carbon dots

Hazardous synthetic colorants have found widespread use in food production, and excessive consumption of these pigments can pose potential risks to human health. In this study, we propose an ultrasensitive fluorescence method for the analysis of Acid Red 18 (AR18) in food products. The method is based on the nitrogen-doped carbon dots (N-CDs) derived from tris and resorcinol through a hydrothermal way. The as-synthesized N-CDs exhibit two emission centers at 425 nm and 541 nm, corresponding to the excitation wavelengths of 377 nm and 465 nm, respectively. Upon the addition of AR18, the fluorescence intensity at 541 nm significantly decreases with a simultaneous, though less pronounced, reduction in the intensity at 425 nm, which is attributed to the localization of fluorescence resonance energy transfer (L-FRET). Specifically, a novel ratiometric fluorescent probe was constructed based on the extracted data from the 3D fluorescence excitation-emission matrix. This probe demonstrates a wide linear range from 0.0539 to 30 μM and a low limit of detection (LOD) of 53.9 nM. For practical applications, a portable fluorescent sensor based on a lateral flow test strip (LFTS) was designed for real-time monitoring of AR18. Color channel values were determined using a smartphone application, resulting in a satisfactory LOD of 75.3 nM. Furthermore, the suitability of the proposed ratiometric fluorescent probe was validated through the detection of AR18 in real food samples, consistently achieving recovery rates in the range of 99.7-101.4%. This research not only expands the scope of CDs in sensing fields, but also provides an effective strategy for the development of an excellent platform for real-time AR18 detection, contributing to public food safety.