Nanoscale zerovalent iron (nZVI) likely finds its application in source zone remediation. Two approaches to modify nZVI have been reported: bimetal (Fe-Me) and sulfidated nZVI (S-nZVI). However, previous research has primarily focused on enhancing particle reactivity with these two modifications under more plume-like conditions. In this study, we systematically compared the trichloroethene (TCE) dechlorination pathway, rate, and electron selectivity of Fe-Me (Me: Pd, Ni, Cu, and Ag), S-nZVI, and nZVI with excess TCE simulating source zone conditions. TCE dechlorination on Fe-Me was primarily via hydrogenolysis while that on S-nZVI and nZVI was mainly via β-elimination. The surface-area normalized TCE reduction rate ( k) of Fe-Pd, S-nZVI, Fe-Ni, Fe-Cu, and Fe-Ag were ∼6800-, 190-, 130-, 20-, and 8-fold greater than nZVI. All bimetallic modification enhanced the competing hydrogen evolution reaction (HER) while sulfidation inhibited HER. Fe-Cu and Fe-Ag negligibly enhanced electron utilization efficiency (ε) while Fe-Pd, Fe-Ni, and S-nZVI dramatically increased ε from 2% to ∼100%, 69%, and 72%, respectively. Adsorbed atomic hydrogen was identified to be responsible for the TCE dechlorination on Fe-Me but not on S-nZVI. The enhanced dechlorination rate along with the reduced HER of S-nZVI can be explained by that FeS conducting major electrons mediated TCE dechlorination while Fe oxides conducting minor electrons mediated HER.
Color-stable light-emitting diodes based on quasi-2D PEA- and BA-perovskite with DMA as a co-ligand afford sky-blue (490 nm) and bluish green (499 nm) emission with a maximum luminance of 2825 and 7760 cd m−2 respectively.
It is demonstrated that, via surface treatment of CsPbBr3 perovskite quantum dots (PeQDs) by introducing small amount of organic ammonium chlorides possessing short alkyl chain (C ≤ 4) in methyl acetate in the typical purification process, the emission can be tuned from green to blue region with boosted photoluminescence quantum yield (PLQY). The Cl− mainly works on the surface of PeQDs to fill bromide vacancy, which generates a passivated mixed‐halide surface and avoids formation of defects deep within bandgap. Meanwhile, the replacement of initial long‐chain ligands with short chain ammonium moiety benefits the film PLQY. Accordingly, a standard blue emission of 461 nm with a high film PLQY of 52% is accessed and the corresponding colloidal shows a PLQY of 80% at 456 nm. This method is also proved to be a versatile tool to boost the PLQY of PeQDs by using short chain ammonium halides bearing the same X with the initial CsPbX3. A near‐unity colloidal PLQY of 97% and 98% is achieved for CsPbBr3 and CsPbI3 respectively. Quantum dots light‐emitting diode (QLED) with treated CsPbBr3 affords a standard blue electroluminescence of 459 nm and a maximum external quantum efficiency of 0.3%.
Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional molecules represents an extremely useful process in organic synthesis. Herein, we describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio-and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcohols. Control experiments demonstrated that the key to this high reactivity and selectivity is the addition of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex molecules. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be especially useful in a lead optimization program.
Zn0.997WO4: Pr(3+)(0.003) and different concentrations (0.1 mol% to 0.9 mol%) of Pr, Li co-doped ZnWO4 red phosphors were prepared by means of solid-state reaction process. The crystalline, surface morphology and luminescent properties of Zn0.997WO4: Pr(3+)(0.003) and Zn(1-x-y)WO4: xPr(3+), yLi(+) phosphors were investigated by the X-ray diffraction patterns (XRD), scanning electron microscope (SEM) and fluorescent measurements. From powder XRD analysis, the formation of monoclinic structure with C(2/h) point-group symmetry and P(2/c) space group of the as-synthesized samples is confirmed. The SEM image showed that surface morphology of the phosphor powder is irregular cylindricality. The luminescent spectra are dominated by the red emission peaks at 607, 621 and 643 nm, respectively, radiated from the (1)D2→(3)H4, (3)P0→(3)H6 and (3)P0→(3)F2 transitions of Pr(3+) ions. The concentrations of the highest luminescent intensity is determined at 0.3 mol% Pr(3+) and 0.3 mol% Li co-doped ZnWO4 powder crystal, and the peak intensity is improved more than 3 times in comparison with that of 0.3 mol% Pr(3+) single-doped ZnWO4. The enhanced luminescence comes from the improved crystalline and from the charge compensation of Li(+) ions. The decay curve and CIE chromaticity coordinates of as-prepared samples are also studied in detail.
The mild base-promoted C−H bonds functionalization of amides to obtain α,β-unsaturated imines in good yields with high chemoselectivities was achieved. Control experiments show this process involves [2 + 2] cyclization/ring-cleavage reorganization.
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