A new family of five-coordinate lanthanide single-molecule magnets (Ln SMMs) [Dy(Mes*O)2(THF)2X] (Mes*=2,4,6-tri-tert-butylphenyl; X=Cl, 1 ; Br, 2 ; I, 3 ) is reported with energy barriers to magnetic reversal >1200 K. The five-coordinate DyIII ions have distorted square pyramidal geometries, with halide anions on the apex, and two Mes*O ligands mutually trans- to each other, and the two THF molecules forming the second trans- pair. These geometrical features lead to a large magnetic anisotropy in these complexes along the trans-Mes*O direction. QTM and Raman relaxation times are enhanced by varying the apex halide from Cl to Br to I, or by dilution in a diamagnetic yttrium analogue. 相似文献
The zinc deposition reaction onto metallic zinc has been investigated at the single particle level through the electrode-particle collision method in neutral solutions, and in respect of its dependence on the applied potential and the ionic strength of a sulphate-containing solution. Depending on the concentration of sulphate ions in solution, different amounts of metallic zinc were deposited on the single Zn nanoparticles. Specifically, insights into the electron transfer kinetics at the single particles were obtained, indicating an electrically early reactant-like transition state, which is consistent with the rate-determining partial de-hydration/de-complexation process. Such information on the reaction kinetics at the nanoscale is of vital importance for the development of more efficient and long-lasting nanostructured Zn-based negative electrodes for Zn-ion battery applications.
Herein, we report the development of an 18F‐labeled, activity‐based small‐molecule probe targeting the cancer‐associated serine hydrolase NCEH1. We undertook a focused medicinal chemistry campaign to simultaneously preserve potent and specific NCEH1 labeling in live cells and animals, while permitting facile 18F radionuclide incorporation required for PET imaging. The resulting molecule, [18F]JW199, labels active NCEH1 in live cells at nanomolar concentrations and greater than 1000‐fold selectivity relative to other serine hydrolases. [18F]JW199 displays rapid, NCEH1‐dependent accumulation in mouse tissues. Finally, we demonstrate that [18F]JW199 labels aggressive cancer tumor cells in vivo, which uncovered localized NCEH1 activity at the leading edge of triple‐negative breast cancer tumors, suggesting roles for NCEH1 in tumor aggressiveness and metastasis. 相似文献
This paper describes the extraction of 20 organochlorine pesticides (OCPs) from water samples using solid-phase microextraction (SPME). Three fused-silica fibers coated or bonded with polydimethylsiloxane (PDMS) of different film thicknesses (20-, 30-, and 100-μm) were evaluated. The extraction time, the effects of stirring and addition of NaCl to the aqueous sample, the linear range and the precision of this technique, and the effect of carryover were examined for 20 analytes and are presented here. A comparison with results using conventional liquid-liquid extraction demonstrate that the SPME technique is well suited as a fast screening technique for OCPs in water samples. 相似文献
Dibenzylidene sorbitol (DBS) is capable of gelling a variety of organic solvents and polymeric materials by forming a rigid, 3-D hydrogen-bonded network. In this work, two poly(siloxane)/poly(propylene oxide) segmented copolymers of equal composition and molecular weight, but different architectures (endblocked vs. pendant), as well as a pure poly(propylene oxide), have been gelled with DBS. We have investigated the dynamic rheological properties of these gels to ascertain the effect of copolymer architecture, PDMS comonomer and DBS concentration on network formation. 相似文献
We report the electrochemistry of amino-functionalized multiwalled carbon nanotubes (MWCNTs-NH2) in the pH range from 0.3 to 6.4 using quantitative cyclic voltammetry (CV) and single entity electrochemistry measurements, making comparison with non-functionalized MWCNTs. CV showed the latter to both catalyze the solvent (water) decomposition and to undergo irreversible electro-oxidation forming oxygen containing surface functionality. The MWCNTs-NH2 additionally undergo an irreversible oxidation to an extent which is dependent on the pH of the solution, reflecting the variable amount of deprotonated amino groups present as a function of pH. Nano-impact experiments conducted at the single particle level confirmed the oxidation of both types of MWCNTs, showing agreement with the CV. The pKa of the amino groups in MWCNTs was determined via both electrochemical methods giving consistent values of ca. 2.5.A new and generic approach to the study of the oxidation of different forms of CNTs is found by using quantitative single entity and ensemble electrochemistry measurements. 相似文献