Visual detection of Auramine O using dual-signal ratiometric fluorescent nanopaper sensor combined portable smartphone

The misuse of additives is a major problem for global food safety, and of particular concern is Auramine O (AO). Although the analysis of AO by fluorescent carbon dots (CDs) has been extensively explored, the development of effective sensitivity enhancement and portable detection solutions based on CDs remains a significant challenge. Herein, we developed a dual-signal ratiometric fluorescent probe (RFP) integrated with fluorescent nanopaper and smartphone application, which has been used to achieve portable visualization and quantitative detection of AO in food and drug samples. The specific response analysis model (RFP) for AO detection was constructed using fluorescence resonance energy transfer and electrostatic attraction between B-CDs and O-CDs. Within a concentration range of 0.0–10.0 μM, achieving a detection limit as low as 12.3 nM. Furthermore, a laboratory device that incorporates portable fluorescent nanopaper into a smartphone was developed to record the color information response ratio (R/B) in combination with the ColorColl application, enabling visual quantitative measurement of AO. This is powerful construction of RFP, which avoids time-consuming synthesis and complex modification. It directly demonstrates the superiority of proportional fluorescence detection over single wavelength detection. This work provides a referable perspective for preliminary monitoring and rapid on-site detection of harmful factors such as AO in food and drug samples.