A ‘‘Turn-on’’ Al(III)-Mediated Fluorescent Micro-Probe for Quercetin Sensing

Quercetin (Qr) is a common flavonoid widely found in plants with promising pharmacological activities. It is thus worthwhile to design a convenient method for its detection. In this work, a specific Al 3+ -regulated poly(cyclotriphosphazene- co -curcumin) (PC-Al) micro-probe was designed for real-time detection of Qr, therein significant “turn-on” fluorescence was observed after addition of Qr to PC-Al. Under optimal conditions, the probe has a detection limit of 23.2 nM for Qr sensing with good linearity in the range of 0–5 × 10 −5 M. Moreover, real-time applications of the PC-Al probe in red wine, orange juice, and honey samples were validated. Furthermore, assisted by a consumer smartphone sensing platform, the sensor shows an excellent linear response between the red/blue ratio (R/B) of the two color channels in the picture and the concentration of Qr in the range of 1–120 μM, achieving quantitative detection of Qr. The introduction of smartphone system to realize convenient detection of Qr demonstrates good application prospects of this Al 3+ -mediated fluorescence probe.