ABSTRACT
A novel coumarinylhydrazone fluorescent probe L was designed and synthesized from 4-(diethylamino)salicylaldehyde, its structure was characterized by NMR, IR. Fluorescence emission spectra showed that in ethanol solution, probe L could form a 1:1 complex L-Cu2+ with Cu2+ to realize the "turn-off" detection of Cu2+ with high specificity and sensitivity (3.7 × 10-7 mol/L). Meanwhile, the complex L-Cu2+ had a specific fluorescence-enhanced response to HPO42- with a detection limits down to 5.6 × 10-7 mol/L and was resistant to the effects of many common anions (NO2-, N3-, CO32-, SO32-, HPO42-, I-, Br-, F-, HCO3-, SO42-, NO3-, Cl-, CH3COO-, Cr2O72-, S2O32-, P2O74-). Detection mechanism could be HPO42- captured Cu2+ of the complex and released the free ligand L. At last, the complex L-Cu2+ was successfully applied to the determination of HPO42- in different environmental water samples, and the spiked recoveries ranged from 98.05% to 108.18% and the relative standard deviations of 0.75% ~ 2.9%, which had good application prospects.
ABSTRACT
A novel fluorescent probe QL was designed and synthesized based on Schiff base by 2-hydrazinobenzothiazole to sequentially recognize Zn2+ and glyphosate. The probe QL was capable to detect Zn2+ in DMSO solution via fluorescence enhancement, and exhibited good selectivity and anti-interference ability. The combination mode was 1:2 between probe QL and Zn2+ according to the method of job's plot, and the detection limit of probe QL for Zn2+ was found to be 4.51 × 10-8 M, which exhibited excellent sensitivity. Furthermore, the system QL-Zn2+ could detect glyphosate by causing fluorescence quenching response and with a color change from yellow to colorless for naked-eye detection. The detection limit for glyphosate was found to be 4.93 × 10-8 M, which was far below the Standards for Drinking Water Quality (GB5749-2006) acceptable limits (0.7 µg/mL for glyphosate). Notably, the probe QL and its complex QL-Zn2+ have been successfully applied to detect Zn2+ and glyphosate in water, respectively.
ABSTRACT
Fuel cells have attracted increasing attention due to their low cost, high energy density, low environmental pollution, and abundant raw materials. Oxygen reduction reaction (ORR) is a core technology of fuel cells, and the development of new electrocatalysts with high ORR performance is highly desirable. Herein, we synthesize a series of B, N co-doped hierarchical porous carbons using a soft template method with the integration of self-assembly, calcination and etching. The obtained materials exhibit hierarchical porous structures, controllable pore distribution, partial graphite structures, and B, N co-doping. They can function as the cost-effective and metal-free electrocatalysts, facilitating the diffusion of electrolyte ions and the improvement of ORR performance. Especially, the B, N co-doped porous carbon with the B-to-N molar ratio of 5 (BNC-5) displays a high ORR activity with a half-wave potential (E1/2 ) of 0.73â V, an onset potential (Eonset ) of 0.94â V, and a high limiting current density (JL ) of 5.98â mA cm-2 , superior to the N-doped C (NC) and BNC-1 (the B-to-N molar ratio=1), BNC-3 (the B-to-N molar ratio=3) and BNC-7 (the B-to-N molar ratio=7) under the identical conditions. Moreover, the BNC-5 exhibits good cycling stability after 5000 cyclic voltammetry (CV) cycles and excellent tolerance toward even 3â M methanol. This research provides a new approach for the facile synthesis of dual element-doped carbon electrocatalysts with high ORR performance.
ABSTRACT
Beyond the absence of long-range magnetic orders, the most prominent feature of the elusive quantum spin liquid (QSL) state is the existence of fractionalized spin excitations, i.e., spinons. When the system orders, the spin-wave excitation appears as the bound state of the spinon-antispinon pair. Although scarcely reported, a direct comparison between similar compounds illustrates the evolution from spinon to magnon. Here, we perform the Raman scattering on single crystals of two quantum kagome antiferromagnets, of which one is the kagome QSL candidate Cu3Zn(OH)6FBr, and another is an antiferromagnetically ordered compound EuCu3(OH)6Cl3. In Cu3Zn(OH)6FBr, we identify a unique one spinon-antispinon pair component in the E2g magnetic Raman continuum, providing strong evidence for deconfined spinon excitations. In contrast, a sharp magnon peak emerges from the one-pair spinon continuum in the Eg magnetic Raman response once EuCu3(OH)6Cl3 undergoes the antiferromagnetic order transition. From the comparative Raman studies, we can regard the magnon mode as the spinon-antispinon bound state, and the spinon confinement drives the magnetic ordering.
ABSTRACT
Excitons in monolayer transition metal dichalcogenides (TMDs) provide a paradigm of composite Boson in a two-dimensional system. This Letter reports a photoluminescence and reflectance study of excitons in monolayer molybdenum diselenide (MoSe2) with electrostatic gating. We observe the repulsive and attractive Fermi polaron modes of the band edge exciton, its excited state, and the spin-off excitons, which the simple three-particle trion model is insufficient to explain. The contrasting energy shift between the exciton and charge-bound excitons (repulsive and attractive polaron modes) and the remarkably different gate dependence of the polaron energy splitting between the ground state and the excited state excitons unambiguously support the Fermi polaron picture for excitons in monolayer TMDs.
