RESUMEN

Rapid and quantitative detection of isoquercitrin (Isq) has been attracting much attention due to its outstanding pharmacological and physiological activities. Herein, an interesting 48-metal Zn(II)-Nd(III) nanocluster (1, molecular sizes 1.3 × 2.8 × 3.1 nm) with salen-type Schiff base ligand was constructed as molecular sensor for the luminescence detection of Isq. 1 exhibits visible ligand-centered emission and NIR luminescence of Nd(III), and shows ratiometric fluorescence response to Isq with high sensitivity even in the presence of other interferences. The fluorescence sensing behavior can be expressed by a second-order equation I1060nm/I480nm = A*[Isq]2 + B*[Isq] + C, which is used to quantitatively analyze the Isq concentrations in DMF and FCS. The LODs to Isq for the ligand-centered and lanthanide emissions of 1 in DMF are 0.21 µM and 0.11 nM, respectively. The quenching of the ligand-centered emission of 1 caused by Isq is attributed to the competitive absorption of light energy and "inner effect", while, the luminescence enhancement is due to the "antenna effect".

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A near-infrared luminescent Cd(II)-Nd(III) nanocluster 1 (molecular dimensions of 1.0 nm × 2.2 nm × 2.2 nm) was obtained using a Schiff base ligand. It can be used as a sensor for the wavelength-dependent detection of rutin even in the presence of other interference, which can be expressed by the third-order equation IEx470 nm/IEx395 nm = A[Rut]3 + B[Rut]2 + C[Rut] + D. 1 is used to analyze the Rut concentrations quantitatively in CH3CN and fetal calf serum (FCS). For the determination of Rut concentrations in FCS, the ranges of recovery and relative standard deviations are 99.06-104.70% and 2.30-4.15%, respectively.

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A high-nuclearity Zn(II)-Eu(III) nanocluster was synthesized for the rapid and quantitative luminescence detection of neopterin as an inflammatory marker.

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A near-IR-luminescent octanuclear Yb(III) complex 1 was constructed from a new dodecadentate Schiff base ligand, which is used in the rapid and reliable wavelength-dependent detection of aloe emodin (AE) with high sensitivity even in the presence of other interferences.

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An interesting 48-metal Zn(II)-Yb(III) nanocluster (1) with a size of about 1.3 × 2.8 × 3.1 nm was constructed by carbonate templates from a Schiff base ligand. It exhibits ligand-centered emission and near-infrared (NIR) luminescence of Yb(III), which are used in the dual-emissive detection of rutin (Rut) with high sensitivity even in the presence of other interferences. The response behavior can be expressed by the second-order equation I980 nm/I510 nm = A*[Rut]2 + B*[Rut] + C, and the limits of detection to Rut for the emissions of 1 are 2.23 µM and 0.20 nM.

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A luminescent 56-metal Cd(II)-Sm(III) nanocluster (1, molecular sizes: 4.5 × 2.7 × 2.7 nm) was constructed from a flexible Schiff base ligand, and its crystal structure was determined using the X-ray diffraction method. It shows a rapid triple-emissive response to 2,6-dichloro-4-nitroaniline (DCN, a common pesticide) with high sensitivity and selectivity, which can be used to quantitatively analyze the DCN concentrations in fruit extracts. The limits of detection (LODs) of 1 to DCN for the visible ligand-centered and Sm(III) emissions and NIR Sm(III) luminescence are from 0.95 µM to 2.81 µM.

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A Cd(II)-Tb(III) nanocluster {[Cd10Tb9L8(OH)16(OAc)23(H2O)3][Cd10Tb9L8(OH)16(OAc)23(H2O)4]}·3H2O (1), which contains two crystallographically independent components, was constructed from a tridentate ligand (HL, 3-ethoxysalicylaldehyde). It exhibits rapid and reliable excitation wavelength-dependent luminescence response to 2,6-dipicolinic acid (DPA) [limit of detection = 0.23 nM], which is not influenced by aromatic carboxylates, amino acids, and ions. The test papers of 1 can be used to check DPA in solution. The equation IEx272nm/IEx329nm = 0.0109 × [DPA]2 + 0.106 × [DPA] + 2.39 of 1 for the luminescence response could be used to quantitatively measure the concentration of DPA in tap water. 1 displays rapid and stable luminescence response to DPA, with the sensing times shorter than 5 s and no changes for the lanthanide luminescence over 24 h.

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Two NIR luminescent Zn(II)/Cd(II)-Yb(III) complexes were obtained by the use of a Schiff base ligand with a binaphthyl backbone. Cd(II)-Yb(III) complex 2 has a triangular structure and exhibits interesting luminescent sensing activity to antibiotics, in particular to ciprofloxacin (CPFX) and norfloxacin (NFX) due to the inner filter effect. The limits of the detection of 2 to CPFX and NFX are 0.18 and 0.36 µM, respectively, and the fluorescence sensitivity is not changed with the existence of other antibiotics tested in this study.

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