Surface imprinted polymer on dual emitting MOF functionalized with blue copper nanoclusters and yellow carbon dots as a highly specific ratiometric fluorescence probe for ascorbic acid

• Preparation of an integrated ratiometry probe from surface imprinting of ZIF-8 with ascorbic acid as template and in the presence of two different fluorescence emitters. • Synthesis of stable blue CuNCs using a thiamine hydrochloride as a capping agent followed by enhancement the blue emission by encapsulation in ZIF-8. • Blue emission of CuNCs@ZIF-8 used as a reference signal and yellow emission carbon dots (Y-CDs) used as a probe for detection of ascorbic acid. • The ratiometric fluorescence probe was successfully used for detection ascorbic acid in drug samples and human serum with satisfactory accuracy and precision. The rational incorporation of metal organic frameworks (MOFs) into molecular imprinted polymers (MIPs) shows excellent potential for improving various merits from both approaches and elimination of the drawbacks of the counterparts. In this work, surface imprinted polymer on zeolitic imidazole framework-8 (ZIF-8) are presented as a highly selective probe for detection of ascorbic acid (AA). An MIP layer was surface imprinted on nano-sized ZIF-8 with AA as a template, and blue copper nanocluster (B-CuNCs) and yellow carbon dots (Y-CDs) as fluorescent signal transducers. The MIP capped ZIF-8 (MIP@ZIF-8) offered selective cavities for AA detection. The integrated system of MIP@ZIF-8 consisted of two emitters, CuNCs (λem 420 nm) used as a reference signal inserted in the pores of the ZIF-8, and yellow carbon dot (CDs, λem 560 nm) used as a probe and inserted in the polymer layer. The yellow emission of MIP@ZIF-8 nanocomposite was selectively quenched after addition of ascorbic acid, while the blue emission remained unaffected and used as an internal reference signal. The MIP@ZIF-8 ratiometry probe showed a dynamic linear response to AA in the range 4.0 µM – 22.0 µM with a detection limit 1.56 µM. The ratiometry-based fluorescence probe was successfully used for detection AA in drug samples and human serum with satisfactory recoveries of 92.5–106.11 % and 81.69 – 93.89 % respectively. Additional to high selectivity and sensitivity obtained from this MIP-MOF design, the presented probe, showed highly stability in room temperatures under well-lit room, which qualifies the probe for long-term use.