Xingming Kou

A highly selective fluorescent sensor for mercury ion (II) based on azathia‐crown ether possessing a dansyl moiety

An intramolecular charge transfer (ICT) fluorescent sensor 1 using a dansyl moiety as the fluorophore and an azathia-crown ether as the receptor was designed, synthesized and characterized. The ions-selective signaling behaviors of the sensor 1 were investigated in CH(3) CN-H(2) O (1:1, v/v) by fluorescence spectroscopy. It exhibited remarkable fluorescence quenching upon addition of Hg(2+), which was attributed to the 1:1 complex formation between 1 and Hg(2+), while other selected metal ions induced basically no spectral changes. The sensor 1 showed a rapid and linear response towards Hg(2+) in the concentration range from 5.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) with the detection limit of 1.0 × 10(-7) mol L(-1). Furthermore, the whole process could be carried out in a wide pH range of 2.0-8.0 and was not disturbed by other metal ions. Thus, the sensor 1 was used for practical determination of Hg(2+) in different water samples with satisfactory results.

Comparative kinetics of carboxylic esters hydrolysis catalyzed by the zinc(II) complex of a macrocyclic Schiff base ligand

The comparative kinetic investigation of the hydrolysis of p-nitrophenyl picolinate (PNPP) and p-nitrophenyl acetate (PNPA) catalyzed by the tetracoordinate macrocyclic Schiff base complex of zinc(II) (1) at 30 °C is reported. The results indicate that the (1) catalyzed hydrolyses of PNPP and PNPA are acid-base catalytic processes and that the active species is the metal bound hydroxide ion, namely, ZnL—OH−. (1) promoted hydrolysis of PNPP proceeds much faster than that of PNPA. At pH 7.51, the apparent second-order rate constants kc for hydrolysis of PNPP and PNPA are 0.254 and 7.28 × 10−3 mol−1 dm3 s−1, respectively. The difference in hydrolytic rates may be attributed to the difference of hydrolytic mechanisms by which the PNPP and PNPA operate. The reasons are discussed in detail.

Studies on the reaction kinetics and the mechanism of hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) catalyzed by oxamido-bridged dinuclear copper(II) complexes in micellar solution

Oxamido-bridged dinuclear copper(II) complexes, used as symmetric two-center catalysts for the cleavage of BNPP, were synthesized and characterized. The reaction kinetics and the mechanism of hydrolysis of BNPP catalyzed by metallomicelles, made from complex (A) or (B) and a surfactant (LSS or CTAB), were investigated. A kinetic mathematical model for BNPP cleavage was also proposed. The results showed that the reaction rate for the catalytic hydrolysis of BNPP, compared with spontaneous hydrolysis of BNPP, increased by a factor of ca. 1 × 106 due to the synergistic effect of two copper ions in the complex and the local concentration effect of the micelle. The study indicates that the metallomicelle-containing oxamido-bridged dinuclear copper(II) complex may be a potential catalyst for the hydrolysis of BNPP.

One-step Synthesis of Highly Luminescent Nitrogen-doped Carbon Dots for Selective and Sensitive Detection of Mercury(II) Ions and Cellular Imaging

In this paper, nitrogen-doped carbon dots (N-CDs) with high quantum yield (QY) of 40.5% were prepared through a facile and straightforward hydrothermal route. The as-prepared N-CDs exhibited excellent photoluminescence properties, good water-solublity and photostability, negligible cytotoxicity and favourable biocompatibility. Such N-CDs were found to serve as an effective fluorescent sensor for selective and sensitive detection of Hg(2+) in a wide linear response concentration range of 0 - 8 μM with a limit of detection (LOD) of 0.087 μM and could be applied to the determination of Hg(2+) in environmental water samples. The corresponding mechanisms were discussed in detail. Moreover, another attractive finding was that the N-CDs showed satisfactory performance in bioimaging before and after the addition of Hg(2+) in human lung cancer PC14 cells. With excellent sensitivity, selectivity and biocompatibility, such cheap carbonmaterials are potentially suitable for monitoring of Hg(2+) in environmental applications and promising for biological applications.

Metallomicellar Catalytic Hydrolysis of Bis(4‐nitrophenyl) Phosphate by CuIINiII Heterodinuclear Complexes in Brij35 Micellar Solution

The hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP) catalyzed by metallomicelles formed from three asymmetry oxamido‐bridged Cu(II)Ni(II) heterodinuclear complexes containing different diamine groups and Brij35 micelle has been investigated kinetically in the pH range of 6.0–10.0 at 25°C. The results indicate that these complexes show relative high reactivity in Brij35 micellar solutions. Complex III exhibited a more effective catalytic function than complex I and complex II for the hydrolysis of BNPP, which was attributed to the different structure of the diamine group in the complex. The apparent rate constants (k obsd ) of BNPP hydrolysis increased with the increasing pH values of reaction media and then reached saturation near pH 9.0. The kinetic and thermodynamic parameters (K and k) were obtained, and the studies show that the hydrolysis of BNPP involves a bifunctional mechanism and is an intramolecular nucleophilic reaction. In the reaction systems, the kinetically active species has been determined to be the aquo‐hydroxo form of the complex CuNi(H2O)OH in Brij35 micellar solution.

Catalytic cleavage of p-nitrophenyl picolinate by metallomicelles made up of copper(II) complexes of small molecular ligands bearing hydroxyl or carboxyl groups

The esterolytic activities of Cu2+ complexes (Cu2+L1, Cu2+L2 and Cu2+L3) of three small molecular ligands: N-(2-hydroxyethyl)ethylenediamine (L1), 2,2′-iminodiethanol (L2) and iminodiacetic acid (L3), in the presence of the nonionic micelle (Brij35) towards the substrate p-nitrophenyl picolinate (PNPP) have been investigated. The catalytic reactivity order is: Cu2+L1 > Cu2+L2 > Cu2+L3, which can be attributed to the similarity of and the difference between their catalytic mechanisms, most likely resulting from the analogy and the discrepancy of the structure of the three complexes. The critical feature of the catalytic process is, quite likely, the formation of a ternary complex involving a binary metal ion complex and the substrate, followed by pseudo-intramolecular nucleophilic attack of the alcoholic hydroxyl (for Cu2+L1 and Cu2+L2) or metal ion bound hydroxide ion (for Cu2+L3), at carbonyl of the substrate. Detailed kinetic analyses are given for the hydrolysis of PNPP catalyzed by the three complexes.

A highly sensitive luminescent probe based on Ru(II)-bipyridine complex for Cu 2+ , l -Histidine detection and cellular imaging

A ruthenium(II) bipyridyl complex conjugated with functionalized Schiff base (RuA) has been synthesized and functioned as a luminescent probe. The luminescence of RuA was greatly quenched by Cu2+ due to its molecular coordination with paramagnetic Cu2+. Subsequently, the addition of l-Histidine can turn on the luminescence of the RuA-Cu(II) ensemble, which can be attributed to the replacement of RuA in RuA-Cu(II) ensemble by l-Histidine. On the basis of the quenching and recovery of the luminescence of RuA, we proposed a rapid and highly sensitive on-off-on luminescent assay for sensing Cu2+ and l-Histidine in aqueous solution. Under the optimal conditions, Cu2+ and l-Histidine can be detected in the concentration range of 5 nM-9.0 μM and 50 nM-30 μM, respectively, and the corresponding detection limits were calculated to be 0.35 and 0.44 nM (S/N=3), separately. The proposed luminescent probe has been successfully utilized for the analysis of Cu2+ and l-Histidine in real samples (drinking water and biological fluids). Furthermore, the probe revealed good photostability, low cytotoxicity and excellent permeability, making it a suitable candidate for cell imaging and labeling in vitro.

A Novel Pyrene Fluorescent Sensor Based on the π–π Interaction Between Pyrene and Graphene of Graphene–Cadmium Telluride Quantum Dot Nanocomposites

In this article, water-soluble graphene–cadmium telluride quantum dot nanocomposites were fabricated through the synthesis of cadmium telluride quantum dots in the presence of graphene aqueous dispersion. It was found that pyrene could remarkably quench fluorescence of graphene–cadmium telluride quantum dot nanocomposites. On this basis, a novel method for the determination of pyrene was developed. Factors affecting the pyrene detection were investigated, and the optimum conditions were determined. Under the optimum conditions, a linear relationship could be established between the quenching of fluorescence intensity of graphene–cadmium telluride quantum dot nanocomposites and the pyrene concentration in the range of 6.00 × 10−8–2.00 × 10−6 mol L−1 with a correlation coefficient of 0.9959. The detection limit was 4.02 × 10−8 mol L−1. Furthermore, the nanocomposites were applied to practical determination of pyrene in different water samples with satisfactory results.

Bis(2,2-dinitro­prop­yl)formal

The complete molecule of the title compound [systematic name: bis(2,2-dinitropropoxy)methane], C7H12N4O10, which was synthesized by the condensation reaction between 2,2-dinitropropanol and paraformaldehyde in methylene chloride, is generated by crystallographic twofold symmetry with one C atom lying on the rotation axis. In the crystal structure, molecules are linked into chains running parallel to the b axis by intermolecular C—H⋯O hydrogen-bond interactions, generating rings of graph-set motif R 2 2(14).