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.

Bis(2,2-dinitro-prop-yl)formal.

The complete mol-ecule of the title compound [systematic name: bis(2,2-dinitro-prop-oxy)methane], C(7)H(12)N(4)O(10), which was synthesized by the condensation reaction between 2,2-dinitro-propanol and paraformaldehyde in methyl-ene chloride, is generated by crystallographic twofold symmetry with one C atom lying on the rotation axis. In the crystal structure, mol-ecules are linked into chains running parallel to the b axis by inter-molecular C-H⋯O hydrogen-bond inter-actions, generating rings of graph-set motif R(2) (2)(14).

A novel p-nitroaniline fluorescent sensor based on molecular recognition of carboxymethyl-ß-cyclodextrin-capped ZnO/ZnS/MgO nanocomposites.

Carboxymethyl-ß-cyclodextrin (CMCD)-capped ZnO/ZnS/MgO nanocomposites, which combined water-soluble host molecules with multi-shelled nanocrystals, have been prepared. The nanocomposites have good fluorescence performance and host-guest complexation. Thus, a novel fluorescent sensor for the determination of p-nitroaniline based on the molecular recognition of water-soluble CMCD-capped ZnO/ZnS/MgO nanocomposites has been proposed. Factors affecting the p-nitroaniline detection were investigated, and the optimum conditions were determined. Under the optimum conditions, the relative fluorescence intensity of CMCD-capped ZnO/ZnS/MgO nanocomposites was linearly proportional to the concentration of p-nitroaniline over the range from 8.33 × 10(-7) to 5.83 × 10(-5) mol L(-1) with a correlation coefficient of 0.9967 and a detection limit of 6.38 × 10(-7) mol L(-1). The proposed method was successfully applied to the determination of p-nitroaniline in water samples. The related mechanisms were also discussed.