Metal-organic frameworks (MOFs) have emerged as very fascinating functional materials due to their diversity nature. A nanocomposite consisting of copper nanoparticles dispersed within a carbon matrix (Cu NPs@C) is prepared through a one-pot thermolysis of copper-based metal-organic framework precursors. Cu NPs@C can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to form a colored product in the presence of H2 O2 . As a peroxidase mimic, Cu NPs@C not only has the advantages of low cost, high stability, and easy preparation, but also follows Michaelis-Menten behaviors and shows strong affinity to H2 O2 . As the Cu NPs' surfaces are free from stabilizing agent, Cu NPs@C exhibited a higher affinity to H2 O2 than horseradish peroxidase. On the basis of the inhibitory effect of ascorbic acid (AA) on oxidation of TMB, this system serves as a colorimetric method for the detection of AA, suggesting that the present work would expand the potential applications of MOF-derived nanocomposites in biomedical fields.

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The metal-organic coordination polymers with tunable structures and properties have been rapidly emerging as very important functional materials. In this work, we prepared terbium (Tb(3+))-based coordination polymer nanoparticles (CPNPs) by employing adenine (Ad) as bridging ligands. The CPNPs was further used as a receptor reagent for ciprofloxacin (CF) detection in aqueous solution. Addition of CF induces a typical emission of Tb(3+) due to the formation of Ad/Tb-CF complex and the sensitization of CF. The fluorescent intensity of Tb(3+) was enhanced linearly with increasing the CF concentration from 60 nM to 14 μM. The detection limit for CF in aqueous solution is 60 nM. The Ad/Tb CPNPs was successfully applied to detect CF in tablet and urine samples and showed a satisfactory result. Compared with other methods, the proposed method is advantageous because that it provides a very simple strategy for CF detection, which does not require complicated sample pretreatment processes or special reaction media. The proposed strategy could be contributed to expand the potential applications of lanthanide coordination polymers in biological and environmental fields.

Lanthanide coordination polymers have recently emerged as very fascinating sensing materials due to their tunable structures and unique optical properties. However, a major problem concerning the applications of lanthanide coordination polymers for fluorescent sensing is their unselective recognition to analytes. In this work, a direct post-modification strategy was employed to prepare functionalized lanthanide coordination polymer nanoparticles (Phe/Tb-CPBA CPNPs) with specific response ability to hydrogen peroxide (H2O2) by using phenylalanine (Phe) as bridging ligands, terbium ions (Tb(3+)) as metal nodes and carboxyphenylboronic acids (CPBAs) as guest ligands. Phe/Tb-CPBA CPNPs emit a strong green fluorescence due to the removal of coordinated water molecules and the sensitization effect of CPBA. Upon the addition of H2O2, however, the quenched fluorescence of Phe/Tb-CPBA CPNPs can be observed owing to an intramolecular charge transfer effect. This finding led to a method for the quantitation of H2O2 in the 6 μM to 1 mM concentration range and with a detection limit at 2 μM. Because of the chemoselective H2O2-mediated oxidative deboronation, Phe/Tb-CPBA CPNPs as fluorescent sensors exhibit excellent selectivity to H2O2. Furthermore, Phe/Tb-CPBA CPNPs were successfully used to measure the level of H2O2 in urine samples and showed satisfactory results. We envision that the presented strategy could be extended to design other functionalized coordination polymers with desired functions for various biomedical applications.

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