Ratiometric detection of I- using a dysprosium-based metal-organic framework with a single emission center.

In this study, a dysprosium-based metal-organic framework (MOF) sensor (Dy-MOF) was developed for the ratiometric detection of I- in aqueous medium. Upon excitation at 230 nm, Dy-MOF shows two dominant emission bands at 464 nm and 574 nm assigned to (4F, 4D)5/2 → 6H9/2 + 6F11/2 and 4F9/2 → 6H13/2 transition of Dy3+, respectively, which have different sensitivities toward iodide ions. The introduction of I- slightly weakened the blue emission at 464 nm and significantly quenched the yellow emission at 574 nm. Thus, ratiometric sensing for iodide was realized using the yellow-to-blue intensity ratio of Dy3+. Dy-MOF exhibits superior sensing behavior towards I- with high selectivity, sensitivity and low detection limit (24 nM). This study also provides a strategy for the construction of a ratiometric sensor with dual-emission bands originating from only one emission center.

A ratiometric luminescence sensing platform based on lanthanide-based silica nanoparticles for selective and sensitive detection of Fe3+ and Cu2+ ions.

Detection of Fe(III) and Cu(II) in water is highly desirable because their abnormal levels can cause serious harm to human health and environmental safety. In this work, a ratiometric luminescence sensing platform based on lanthanide-based silica nanoparticles was constructed for the detection of Fe3+ and Cu2+ ions. The terbium-silica nanoparticles (named SiO2@Tb) with dual-emission signals were successfully prepared by grafting Tb3+ ions onto trimellitic anhydride (TMA) functionalized silica nanospheres. It can serve as a ratiometric fluorescent probe for the detection of Fe3+ and Cu2+ ions in water with the green emission of Tb3+ ions as a response signal and the blue emission of silica nanospheres as the reference signal. Significantly, an easy-to-differentiate color change for visual detection was also realized. SiO2@Tb shows high sensitivity even in very low concentration regions towards the sensing of Fe3+ and Cu2+ with low detection limits of 0.75 µM and 0.91 µM, respectively. Moreover, the mechanism for the luminescence quenching of SiO2@Tb was systematically investigated, and was attributed to the synergetic effect of the absorption competition quenching (ACQ) mechanism and cation exchange. This study demonstrates that SiO2@Tb can be employed as a promising fluorescent probe for the detection of Fe3+ and Cu2+ ions, and the combination of lanthanide ions with silica nanoparticles is an effective strategy to construct a ratiometric fluorescent sensing platform for the determination of analytes in environmental detection.

A terbium(III) lanthanide-organic framework as a selective and sensitive iodide/bromide sensor in aqueous medium.

A potent luminescent sensor for the detection of iodide ions was developed based on a terbium(iii)-based lanthanide-organic framework [Tb(cpia)(H2O)2]n·nH2O (1), which was prepared under hydrothermal conditions using the 5-(4-carboxyphenoxy)isophthalic acid (H3cpia) bridging ligand. Compound 1 exhibits superior luminescence quenching behavior towards I- with high sensitivity and selectivity among various anions and shows real-time response. Moreover, the mechanism of the selective luminescence quenching response for I- can be mainly explained by the absorption competition between 1 and I-. According to this quenching mechanism, we find that compound 1 can also detect Br- by adjusting the excitation wavelength. Significantly, this work could serve as a general guidance for the design and synthesis of pollutant sensors.

5,7,13,15-Tetra-oxo-2,2,10,10-tetra-kis-(trifluoro-meth-yl)-4,8,12,16-tetra-oxa-1(1,4),3(1,4),6(1,2),9(1,4),11(1,4),14(1,2)-hexa-benzenahexa-deca-phane tetra-hydro-furan monosolvate.

The title compound, C(46)H(24)F(12)O(8)·C(4)H(8)O, consists of a cyclic aryl ester dimer and a tetra-hydro-furan mol-ecule. In the structure of the cyclic dimer, one carbonyl group stretches above the cavity and the other below.

Magnetic solid-phase extraction of hydrophobic analytes in environmental samples by a surface hydrophilic carbon-ferromagnetic nanocomposite.

A new sorbent of carbon-ferromagnetic nanocomposite was proposed for the extraction of polycyclic aromatic hydrocarbons (PAHs) in environmental samples. The sorbent was specially designed with a hydrophobic sublayer and a hydrophilic surface, which endows the sorbent some unique features. The former shows high extraction capability for the PAHs and the latter provides benign compatibility with the sample matrix. The sorbent can be easily dispersed in aqueous solutions for extraction and no additional stirring or shaking was necessary to facilitate the dispersion, which may bring operational convenience especially for on-site sampling and extraction. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: 10mg of nanoparticles, 40mmol/L of sodium chloride, 30min of extraction time without shaking, hexane as the desorption solvent and 15min as the desorption-sonication time. The results demonstrate that enrichment factors ranging from 35- to 133-fold were obtained for the analytes. The limits of detection and the limits of quantification are in the range of 0.015-0.335ng/mL and 0.05-1.14ng/mL, respectively. Finally, the new sorbent was successfully used for the extraction of PAHs in lake water samples.

Dextran gadolinium complexes as contrast agents for magnetic resonance imaging to sentinel lymph nodes.

PURPOSE: The aim was to investigate three dextran gadolinium complexes Dextran-DTPA-Gd as the potential MRI contrast agents in lymphatic system. METHODS: Three dextran gadolinium complexes Dextran-DTPA-Gd containing differing amounts of Gd-DTPA were synthesized by the incorporation of Gd-DTPA to the hydroxyl groups of dextran. These dextran ligands and gadolinium complexes were characterized, and their properties in vitro and in vivo were also evaluated. RESULTS: Dextran-DTPA-Gd demonstrated obviously higher relaxation effectiveness than that of Gd-DTPA. The result of in vitro cytotoxicity assay showed that these macromolecular ligands and their corresponding gadolinium complexes had low cytotoxicity to HeLa cells. Dextran-DTPA-Gd greatly enhanced the contrast of MR images of normal politeal lymph nodes and reactive hyperplasia of politeal lymph nodes in rabbits and provided prolonged duration in lymphatic system with lower injection doses than that of Gd-DTPA. However, Dextran-DTPA-Gd displayed low signal enhancements in MR images of politeal lymph nodes with VX2 carcinoma in rabbits during the detection time. CONCLUSIONS: These dextran gadolinium complexes Dextran-DTPA-Gd can be taken up selectively by lymphatic system and showed the potential as MRI contrast agents in lymphatic system.

Synthesis of penetrable macroporous silica spheres for high-performance liquid chromatography.

Silica microspheres have been synthesized by phase separation and sol-gel transition coupled with emulsion method. The as-obtained material is characterized by scanning electron microscopy, nitrogen sorption, elemental analysis and particle size distribution measurements. The results demonstrated that the material featured with hierarchically porous structure, possessing both mesopores and penetrable macropores. The mesopores provide large surface area while the macropores traverse the silica particles, which may facilitate fast mass transfer as well as guarantee low backpressure when such materials are used for packed high-performance liquid chromatography (HPLC) column. Therefore, their preliminary applications as HPLC packings in fast separation and low-pressure separation have been attempted in the present study. Benzene, benzaldehyde and benzyl alcohol were separated within two minutes on the silica column at a flow rate of 7 mL min(-1). Vitamin E mixtures can also be baseline separated at a high flow rate of 8 mL min(-1). In addition, thirteen aromatic hydrocarbons were well separated on the octadecyl-bonded silica (ODS) column. In comparison with a commercial Kromasil ODS column, the pressure of the proposed column is much lower (<1/2) under the same chromatographic conditions, while comparable separation efficiency can be achieved.