Embedding dual fluoroprobe in metal-organic frameworks for continuous visual recognition of Pb2+ and PO43- via fluorescence 'turn-off-on' response: Agar test paper and fingerprint

A novel dual-emissive ratiometric fluorescence (RF) probe CDs/QDs@ZIF-8 has been successfully constructed by employing a simple and effective strategy for in situ encapsulating carbon dots (CDs) and thioglycolic acid-modified CdTe quantum dots (QDs) into porous metal-organic frameworks (MOFs) cage. The dual responsive colorimetric fluorescence probe was developed for the ultra-high selectivity and sensitivity continuous detection of Pb2+ (turn OFF) and PO43- (turn ON) in biological samples. Blue CDs acts as a stable internal standard emission, the emission color of CDs/QDs@ZIF-8 changes from red to blue with introducing Pb2+, fluorescence of probe is quenched because of the binding of Pb2+ ions to thioglycolic acid on the surface of probe and e- transfer from the photoexcited QDs to Pb2+ ions, color can be recovered after the adding PO43- to CDs/QDs@ZIF-8Pb(2+) system, which could take away Pb2+ ions from the surface of CDs/QDs@ZIF-8. More importantly, fabricated agar test papers was also successfully applied in visual detection of Pb2+ and PO43- in real samples, which can implement without instrument-specific calibration.