The structural modification of metal–organic frameworks (MOFs) is of vital importance in many fields, especially in sensing with enhanced performance, while the efficient synthesis of functionalized MOF nanoparticles toward small molecule detection remains challenging. Here, a general cellulose nanofibril (CNF)-induced in situ one-step strategy was proposed for the synthesis of dual-ligand-functionalized europium-based MOF (EuMOF@CNF) nanoparticles under an effective regulation of the crystallization kinetics in hydrothermal synthesis. Based on the unique dual-ligand structure, the obtained EuMOF featured a tunable antenna effect and laid a good foundation for fluorescence-sensing materials. Benefiting from the superior self-assembly properties of CNFs and the tunable antenna effect of EuMOF@CNF, flexible sensing films were constructed, showing excellent mechanical properties (72 MPa for stress and 3.8% for strain) and tunable luminescence properties and achieving instant (1 s) and sensitive fluorescence sensing of sarin analogue vapor with a significantly low limit of detection (LOD, 2.8 ppb) and robust selectivity against a wide range of common interferents (>14 types), especially independent of common acids. We believe that this pioneering design of EuMOF with tunable antenna effects would positively advance the development of high-performance MOF-based fluorescent materials and devices.
α-Ketoglutaric acid (α-KA) is an important endogenous metabolite in the Krebs cycle and considered a critical marker for various diseases. Several approaches for identifying α-KA have been reported. However, most of them are limited to single-signal transduction modes in one assay and working in the suspension state, which easily cause quantification errors and lead to false-positive detection results. Herein, a multivalue-responsive and semi-solid EuMOF-gel (EuMOG) logic biosensor is first designed and fabricated, which can realize the specific, rapid, and easy-to-differentiate naked-eye detection of the disease-associated marker of α-KA in serum through implementing one-to-two logic operation with three multicolor gates. The implementation of one-to-two logic operation can be rationally achieved by assembling 2,6-naphthalenedicarboxylic acid as both the energy donor and blue-colored output 1, photoactive Eu3+ ions as the red-emissive output 2, and α-KA stimuli as an input and energy blocker between the dual spectrum-resolved outputs into one unit. With the specific input of α-KA among various analytes, the binary code of the logic decoder switches from (0,1) to (1,0) with an obvious color change from red to cyan. Moreover, by integrating the output chromaticity into the logical operations, the concentration levels of α-KA could be easily evaluated with the intelligent EuMOG detector, which has three multicolor gates in parallel encoding low (0,1), normal (1,1), and danger (1,0) statuses. Such multivalued logic biosensor provides a facile strategy to improve the analysis reliability of disease-associated biomarkers.
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