Dual-emitting dye-CDs@MOFs for selective and sensitive identification of antibiotics and MnO4− in water

Abstract

It is highly challenging to create a novel fluorescent material that can quickly and credibly differentiate between polluting ions and organic matter in water monitoring. Here, a dual-emissive fluorescent platform based on a novel RhB-CDs@1 (RhB = rhodamine B, CDs = carbon dots, 1 = [Cu₂L(OH⁻)]_n, L = 1,3-bis(4′-carboxylic acid benzyloxy)benzoic acid) composite is constructed by introducing CDs and RhB into metal–organic frameworks (MOFs). The RhB-CDs@1 probe acts as a dual-emitting ratio sensor that not only avoids the errors caused by environmental and instrumental instability, but also has the advantages of MOFs that can aggregate the analytes. Interestingly, this probe has different responses to different types of antibiotic, and it especially shows rapid and sensitive identification of quinolones, tetracyclines and nitrofurans in water (the detection limit is as low as 25 ppb for ciprofloxacin; 44 ppb for norfloxacin; 65 ppb for nitrofurazone; 74 ppb for nitrofurantoin; 777 ppb for tetracycline). Similarly, an efficient ratiometric fluorescent probe for MnO₄⁻ was designed based on different fluorescence responses to MnO₄⁻ ions in different acid and base conditions (MnO₄⁻, H⁺ and OH⁻), and a Boolean logic operation was constructed. All of the results indicate that the RhB-CDs@1 probes have merits of outstanding specific surface area and strong molecular/ionic recognition that are promising for the simultaneous selective recognition and detection of antibiotics or MnO₄⁻, providing application prospects in the monitoring of water quality.