A RhB@Zr-MOF composite with dual-emission properties was successfully constructed, which comprises a zirconium-based metal–organic framework and the luminescent dye molecule, Rhodamine B (RhB), embedded via the encapsulation method. The fluorescence intensity ratio of the two emissions was found to be ca. 370 nm/590 nm for RhB@Zr-MOF. The fluorescence intensity values of the two emissions of RhB@Zr-MOF can also be affected by the structures of analytes containing different organic groups. Due to the existence of the dual-emission properties in RhB@Zr-MOF, the relative fluorescence intensity of the emission peaks was introduced as a detection index instead of absolute fluorescence intensity. RhB@Zr-MOF, which possesses the characteristics of a built-in self-calibrating fluorescence sensor, was investigated for detecting cations, nitroaromatics and pesticides. Aside from high sensitivity and selectivity, recyclability is the most important property for sensing pesticides. This work shows that RhB@Zr-MOF can maintain its stability after 5 cycles of detecting nitenpyram, with LOD of 0.2 μM. These results demonstrate that dye@MOFs with dual-emission properties can be employed as multifunctional fluorescence sensors for different types of analytes, and that RhB@Zr-MOF provides a new paradigm for analyte sensing.
A sensitive and accurate ratiometric fluorescent sensor (RhB@UIO-67) is constructed by simply encapsulating rhodamine B (RhB) within a zirconium-based metal–organic framework (UIO-67). Based on the inhibition effect of ligand–to-metal charge transfer, adenosine triphosphate ATP induces a significant enhancement in the MOF centre emission, but does not affect the fluorescence of RhB in the probe material at all, which are respectively employed as detection signal and reference signal to realize sensitive ratiometric fluorescence detection of ATP in human serum and urine with a detection limit (LOD) of 0.45 μM. In particular, since the introduction of the target molecules does not cause any structural degradation, the sensor can be reused. Additionally, due to fluorescence resonance energy transfer between the probe components and malachite green (MG), addition of MG results in different degrees of quenching of the fluorescence emissions of UIO-67 and RhB in the RhB@UIO-67 and thus the probe material can simultaneously serve as a sensitive ratiometric sensing platform for MG detection in aquatic products including fish and shrimp with a low LOD of 0.03 μM. Benefited from its simplicity, sensitivity, and reusability, the sensing material has a wide application potential. Graphical abstract
危险品化学品经营许可证（带存储）