Development of a NS-CDs/fluorescein ratiometric fluorescent sensor-integrated smartphone platform for rapid and specific detection of Mn( <scp>vii</scp> ) and captopril

The construction of a ratiometric fluorescent sensor based on nitrogen-doped carbon dots (NS-CDs) and fluorescein has been reported for the detection of Mn(VII) and captopril. The detection mechanisms for Mn(VII) and captopril are based on the inner filter effect (IFE) and a redox reaction, respectively. The sensor showed good linearity in the detection range of 0.12-100 μM for Mn(VII) and 0.52-300 μM for captopril, with limits of detection (LODs) of 0.12 μM and 0.52 μM, respectively. Furthermore, a smartphone-based platform for the detection of Mn(VII) and captopril was developed, based on the dual-signal response of color and fluorescence intensity. The system displayed linear signal changes with increasing Mn(VII) and captopril concentrations in the ranges of 0.32-100 μM and 0.52-300 μM, with LODs of 0.32 μM and 0.52 μM, respectively. Finally, the ratiometric sensor was validated for the determination of Mn(VII) and captopril in herb and captopril tablet samples, demonstrating its broad applicability and versatility as a portable, sensitive, and specific detector for Mn(VII) and captopril in various sample types. Overall, our ratiometric fluorescent sensor has potential as a portable, on-site detector for Mn(VII) and captopril analysis.