Smartphone-assisted fluorimetric and colorimetric dual-recognition sensing platform based on nitrogen-doped carbon dots for visual monitoring of acid red 18 in food

The widespread presence of acid red 18 (AR18) in the environment has raised concerns about the potential risks on human health and ecosystems. Herein, upon addition of AR18, nitrogen doped carbon dots (N-CDs) synthesized with catechol and 3, 3-diaminobenzidine exhibit interactive behavior with AR18. Therein, the emission peaks at 490 nm and 410 nm are quenched by internal filtering effect (IFE) and fluorescence resonance energy transfer (FRET). Notably, the former experiences a rapid decline due to robust FRET efficiencies. On this basis, a N-CDs-based fluorimetric and colorimetric sensor is developed for sensitive and selective detection of AR18 in concentrations ranging from 0.053 to 100 μM with a low detection limit (LOD) of 53 nM. In addition, a smartphone-based dual-recognition device, integrated with composite film that enhances liquid collection in determination zone, is aimed at the sensitive detection of AR18 in food samples. The LODs are determined to be 131 nM and 122 nM respectively under fluorimetric and colorimetric conditions. Concomitantly, the device exhibits satisfying accuracy and precision for practical applications. Therefore, this newly developed dual-recognition device provides reliable means to detect the presence of AR18, demonstrating promising potential for on-site monitoring and intelligent sensing applications.