One-Pot Hydrothermal Method Preparation of Cerium-Nitrogen-Codoped Carbon Quantum Dots from Waste Longan Nucleus as a Fluorescent Sensor for Sensing Drug Rifampicin.

Currently, the large-scale application of carbon quantum dots (CQDs) is usually limited by their low quantum yield and detection limit. Herein, the abandoned longan nucleus was used as a carbon source to synthesize cerium-nitrogen-codoped carbon quantum dots (Ce/N-CQDs) with strong luminescence intensity. In this work, the fluorescent properties and fluorescent quantum yield of CQDs may be improved by the single cerium-doped carbon quantum dots (Ce-CQDs) and the single nitrogen-doped carbon quantum dots (N-CQDs). Nevertheless, the Ce/N-CQDs exhibited intense fluorescence with a high quantum yield. Compared with CQDs, the quantum yield of Ce/N-CQDs was significantly increased from 5 to 32% and showed high photostability and good water solubility. The Ce/N-CQDs can be used for the direct detection of rifampicin (RFP) in human serum. The concentration demonstrated a good linear relationship in the range of 1.0 × 10-7-9.0 × 10-6 mol/L, with a detection limit of 9.6 × 10-8 mol/L.

Five Mesoporous Lanthanide Metal-Organic Frameworks: Syntheses, Structures, and Fluorescence Sensing of Fe3+, Cr2O72-, and H2O2 and Electrochemical Sensing of Trinitrophenol.

When a multicarboxylate aromatic ligand, 3,5-di(2',4'-dicarboxylphenyl)benzoic acid (H5L), was employed, five structurally similar lanthanide metal-organic frameworks (Ln-MOFs), {[Pr10L6(OH)3Cl(H2O)6]·4C2H8N}n (1), {[Nd10L6(OH)4 (H2O)9]·4C2H8N}n (2), {[Gd10L6(OH)4(H2O)3]·4C2H8N}n (3), {[Ho10L6(OH)4 (H2O)3]·4C2H8N}n (4) and {[Er10L6(OH)4(H2O)6]·4C2H8N}n (5), were synthesized and characterized. Single-crystal X-ray structural analyses disclosed that all five Ln-MOFs crystallize in the trigonal R3 space group. They have three-dimensional mesoporous structure featuring the coexistence of binuclear and tetranuclear species as inorganic building units. The mesoporous structure of 3 was verified by the gas adsorption experiment of N2. Fluorescence analysis showed that 3 can selectively detect Fe3+, Cr2O72-, and H2O2; furthermore, it can be used for the electrochemical detection of trinitrophenol. With the merit of an excellent highly sensitive detection performance, 3 has unpredictable application prospects in future research fields.

Novel Multifunctional Samarium-Organic Framework for Fluorescence Sensing of Ag+, MnO4 -, and Cimetidine and Electrochemical Sensing of o-Nitrophenol in Aqueous Solutions.

A novel Sm-metal-organic framework (MOF) sensor with the molecular formula Sm8(HDBA)6·H2O has been prepared based on a penta-carboxyl organic ligand (H5DBA = 3,5-di(2',4'-dicarboxylphenyl)benzoic acid) and samarium nitrate under solvothermal conditions. Sm-MOF is characterized by single-crystal X-ray diffraction analysis, elemental analysis, thermogravimetric analysis, and powder X-ray diffraction analysis. Structural analysis shows that the dimer metal units are alternately connected to form a one-dimensional chain, and this chain is connected by the bridging carboxyl oxygen of the ligand H5DBA to form a two-dimensional double-layer plane, which then expands into a three-dimensional microporous framework. Fluorescence detection studies show that Sm-MOF can detect Ag+ ions, MnO4 - anions, and cimetidine tablets with high sensitivity and selectivity and can also be used to electrochemically detect o-nitrophenol in water. High-sensitivity detection capability of the Sm-MOF can enrich the application of samarium complexes in multifunctional sensors.

A Multifunctional Tb-MOF Detector for H2O2, Fe3+, Cr2O7 2-, and TPA Explosive Featuring Coexistence of Binuclear and Tetranuclear Clusters.

A novel three-dimensional microporous terbium(III) metal-organic framework (Tb-MOF) named as [Tb10 (DBA)6(OH)4(H2O)5]·(H3O)4 (1), was successfully obtained by a solvothermal method based on terbium nitrate and 5-di(2',4'-dicarboxylphenyl) benzoic acid (H5DBA). The Tb-MOF has been characterized by single crystal X-ray diffraction, elemental analysis, thermogravimetry, and fluorescence properties, and the purity was further confirmed by powder X-ray diffraction (PXRD) analysis. Structural analysis shows that there are two kinds of metal cluster species: binuclear and tetranuclear, which are linked by H5DBA ligands in two µ7 high coordination fashions into a three-dimensional microporous framework. Fluorescence studies show that the Tb-MOF can detect H2O2, Fe3+, and Cr2O7 2- with high sensitivity and selectivity and can also be used for electrochemical detection of exposed 2,4,6-trinitrophenylamine (TPA) in water. The highly selective and sensitive detection ability of the Tb-MOF might make it a potential multifunctional sensor in the future.

Water-assisted isomerization of the [H, C, N, O] system.

Ten minima of [H, C, N, O] isomers were investigated in gas phase and water solution using the polarizable continuum model at the CCSD(T)//M06-2X/6-311 + G(3df,2p) level of theory. The results show that the stability order of all isomers in water solution is HNCO > HOCN > HCNO > HONC > Y-OC(H)N > cycl-OCN(H)-a ≈ cycl-OCN(H)-b > cycl-NCO(H) > HNOC > HCON, i.e., the same as that in the gas phase. Potential energy surfaces of [H, C, N, O] system isomerization were constructed in gas phase and in water solution, showing that the isomerization of [H, C, N, O] isomers in gas phase is unfavorable because of the high barrier height. Interestingly, although the water solvent has a little impact on the isomeric mechanism, water molecules (H2O)n(n = 1-3) acting as catalyst dramatically lower the barrier height in the hydrogen transfer processes (HCNO → HONC, HNCO → HOCN, and HCON → HNOC). Water is the most abundant compound in the interstellar area. These results give new insight into the mechanism of [H, C, N, O] system isomerization in interstellar gas. Enthalpies of formation of the isomers were predicted at the CBS-QB3, G4MP2 and W1U levels.

µ-4,4'-Bipyridine-bis-[aqua-(4-hy-droxy-pyridine-2,6-dicarboxyl-ato)copper(II)].

The title compound, [Cu(2)(C(7)H(3)NO(5))(2)(C(10)H(8)N(2))(H(2)O)(2)], exhibits a centrosymmetric binuclear molecule. Each completely deprotonated 4-hy-droxy-pyridine-2,6-dicarb-oxy-lic acid mol-ecule assumes a tridentate chelating coordination mode. The square-pyramidal coordination geometry around the Cu(II) ion is completed by the bridging bipyridine ligand and an apical water molecule. Adjacent complexes are connected via O-H⋯O and C-H⋯O hydrogen bonds to generate a three-dimensional supra-molecular structure.