A smartphone-integrated nanosensor based on N, P co-doped graphene quantum dots for fluorescence detection of acid red 18 in food

Exploring graphene quantum dots (GQDs) that can be done to contaminant residue detection has been widely concerned. Herein, we develop nitrogen and phosphorus co-doped graphene quantum dots (N, P-GQDs) with a strong green emission (quantum yield: 0.582) by using the resorcinol and phosphonitrilic chloride trimer as precursors via the one-step hydrothermal method. The synthesized N, P-GQDs exhibit excellent photostability and excitation-independent characteristic. Meaningfully, N, P-GQDs exhibit good fluorescence response to acid red 18 (AR18) and possess a good linear relationship over the range of 0-50 mu M (the detection limit: 27 nM). Meanwhile, the fluorescence resonance energy transfer is considered as the possible sensing mechanism. Furthermore, a smartphone-assisted sensing platform is designed for the detection of AR18, which can realize on-site quantitative analysis and exhibit excellent on-site detection capability (the detection limit: 43 nM). There-fore, the present strategy has a prospective value for the application in the on-site monitoring of AR18.