Biomass-Derived Lenthionine Enhanced by Radical Receptor for Rechargeable Lithium Battery.

Organic compounds with tunable structures and high capacities are promising electrode materials for batteries. Cyclic organosulfide (i. e., lenthionine), as a natural material that can provide excellent ratio of effective atoms (S) and non-efficient atoms (C, H, and others), has a high theoretical specific capacity of 853.6 mAh g-1 . However, the multiphase transformation causes rapid capacity decay and hysteresis of charge/discharge voltage plateaus. To overcome these issues, a receptor, phenyl disulfide (PDS), was introduced to truncate subsequent transformations directly from the source and change the reaction path, inhibit the capacity decay, and improve the cycling stability. After 500 cycles, the capacity retention was 81.1 % with PDS, which was in sharp contrast to that (35.6 %) of the control cell. This study helps to understand the electrochemistry mechanism of biomass-derived lenthionine used as a high-capacity cathode material for rechargeable lithium batteries, also offering a strategy to overcome its inherent issues.

Momentum-Dark Intervalley Exciton in Monolayer Tungsten Diselenide Brightened via Chiral Phonon.

Inversion symmetry breaking and 3-fold rotation symmetry grant the valley degree of freedom to the robust exciton in monolayer transition-metal dichalcogenides, which can be exploited for valleytronics applications. However, the short lifetime of the exciton significantly constrains the possible applications. In contrast, the dark exciton could be long-lived but does not necessarily possess the valley degree of freedom. In this work, we report the identification of the momentum-dark, intervalley exciton in monolayer WSe2 through low-temperature magneto-photoluminescence spectra. Interestingly, the intervalley exciton is brightened through the emission of a chiral phonon at the corners of the Brillouin zone (K point), and the pseudoangular momentum of the phonon is transferred to the emitted photon to preserve the valley information. The chiral phonon energy is determined to be ∼23 meV, based on the experimentally extracted exchange interaction (∼7 meV), in excellent agreement with the theoretical expectation of 24.6 meV. The long-lived intervalley exciton with valley degree of freedom adds an exciting quasiparticle for valleytronics, and the coupling between the chiral phonon and intervalley exciton furnishes a venue for valley spin manipulation.

Nondegenerate Chiral Phonons in Graphene/Hexagonal Boron Nitride Heterostructure from First-Principles Calculations.

Triggered by the recent successful observation of previously predicted phonon chirality in the monolayer tungsten diselenide [ Science 2018 , 359 , 579 ], we systematically study the chiral phonons in the classical heterostructure of graphene/hexagonal boron nitride (G/ h-BN) by first-principles calculations. It is found that the broken inversion symmetry and the interlayer interaction of G/ h-BN not only open the phononic gaps but also lift the degeneracy of left-handed and right-handed chiral phonons at the first-Brillouin-zone corners (valleys). At valleys, the hybridization makes chiral phonon modes solely contributed from one individual layer. Moreover, we demonstrate that the vertical stress is effective to tune the degenerated phononic gap while keeping the valley-phonon chirality of G/ h-BN heterostructure, which is favorable for the Raman or ultrafast infrared spectroscopy measurement. We also analyze the pseudoangular momentum of valley-phonon modes, which provide important references for the excitation and measurement of the chiral phonons in the process of electronic intervalley scattering. Collectively, our results on the chiral phonons in the G/ h-BN heterostructure system could stimulate more experimental and theoretical studies and promote the future applications on the phonon-chirality-based phononics.

Preparation of Ce-PbO(2) modified electrode and its application in detection of anilines.

The effect of Ce(III) on the morphology and structure of lead dioxide (PbO(2)) modified electrode was studied in this paper. The results obtained by cyclic voltammetry (CV), X-ray diffractometion (XRD) and scanning tunneling micrograph (STM) indicated that the Ce-doped PbO(2) film consisted of a mixture of alpha- and beta-PbO(2) crystallographic phases and the content of alpha-phase was higher than that in undoped PbO(2) film. PbO(2) crystal grains in nanometric size were formed on the electrode surface by doping with Ce. So that the specific surface areas and catalytic active sites of the modified electrode were increased. Hence the catalytic activity of the Ce-PbO(2) modified electrode was evidently greater than the undoped PbO(2) modified electrode. When the Ce-PbO(2) modified electrode was applied as an analytical sensor to determine aniline compounds, the linearity was in the range of 5x10(-5) to 1x10(-3)mol/l and the detection limit was 1x10(-5)mol/l.

Study on the effect of electromagnetic impulse on neurotransmitter metabolism in nerve cells by high-performance liquid chromatography-electrochemical detection coupled with microdialysis.

In this paper, a reverse-phase high-performance liquid chromatographic method using a chemically modified electrode coupled with microdialysis was developed to study the effect of electromagnetic impulse (EMI) on monoamine neurotransmitter metabolism in nerve cells. To detect the monoamines and their metabolites, a poly (para-aminobenzoic acid) (P-pABA)-modified electrode was prepared. The modified electrode exhibited efficiently electrocatalytic oxidation for monoamines and their metabolites with relatively high sensitivity, stability, and long life. Nerve cells were primarily cultured. EMI was radiated to three experimental model nerve cells: (i) on mature nerve cells, (ii) on the culture medium, and (iii) on juvenile nerve cells for various periods of time. Then the levels of monoamines in the culture medium were detected by high-performance liquid chromatography-electrochemical detection. The data indicated that electromagnetic fields could influence neurotransmitter metabolism by direct effect on nerve cells or effect on the nutrient medium and that the effect was not only relevant with the length of radiation time, but also with the growing state of the nerve cells.

Amperometric determination of glutathione and cysteine on a Pd-IrO(2) modified electrode with high performance liquid chromatography in rat brain microdialysate.

A Pd/IrO(2) co-electrodeposited glassy carbon electrode was prepared and the electrochemical behavior of glutathione (GSH) at this chemically modified electrode (CME) has been studied by cyclic voltammetry (CV). The results indicated that the modified electrode efficiently exhibited electrocatalytic oxidation for GSH with relatively high sensitivity, stability, and long-life. Coupled with high-performance liquid chromatography (HPLC), the Pd/IrO(2) modified electrode was utilized for the electrochemical detection (ECD) of the thiocompounds, glutathione and cysteine (Cys). The peak currents were linear with the substance concentrations in the range of 1.0 x 10(-5) mol L(-1) to 8.0 x 10(-4) mol L(-1) for GSH and 4.0 x 10(-6) mol L(-1) to 2.0 x 10(-4) mol L(-1) for Cys. The detection limits were 2.0 x 10(-6) mol L(-1) for GSH and 5.0 x 10(-7) mol L(-1) for Cys with S/N of 3. The method has been successfully applied to assess the contents of GSH and Cys in rat brain microdialysates.

Amperometric sensor for glucose and hypoxanthine based on a PdIrO(2) modified electrode by a co-crosslinking bienzymic system.

A glassy carbon electrode (GCE) modified with Pd/IrO(2) provides excellent electrocatalytic oxidation of hydrogen peroxide. Glucose oxidase (GOD) and xanthine oxidase (XOD) were co-immobilized on the modified electrode with a thin film Nafion coated on the enzyme layer to form a glucose (Glu)/hypoxanthine (Hx) sensor, without interference from electroactive species such as ascorbic acid (AA) and uric acid (UA). Its response was evaluated with respect to the enzyme amount on the electrode, pH and temperature of the electrolyte. The prepared bienzymic biosensor, used as the detector of HPLC gave a detection limit of 1.0x10(-6) mol l(-1) Glu and 2.0x10(-7) mol l(-1) Hx (Hx) with a linear concentration range of 5.0x10(-6)-2.5x10(-3) mol l(-1) and 1.0x10(-6)-5.0x10(-4) mol l(-1), respectively. Coupled with microdialysis, it was used to monitor the concentrations of Glu and Hx in rat brain.

Amperometric determination of morphine on cobalt hexacyanoferrate modified electrode in rat brain microdialysates.

The analysis of morphine in biological fluids is of vital interest in monitoring opiate abuse and in drug abuse research. In this paper, a cobalt hexacyanoferrate (CoHCF) chemically modified electrode (CME) was prepared. The electrochemical behavior of morphine at this modified electrode has been studied by cyclic voltammetry (CV). The results indicated that the modified electrode exhibited efficiently electrocatalytic oxidation for morphine with relatively high sensitivity and stability. The CoHCF CME was employed as the detector of high-performance liquid chromatography (HPLC). The peak current was linearly related to the morphine concentration in the range of 1.0x10(-6) M to 5.0x10(-4) M at +0.60 V (vs. Ag/AgCl) with a detection limit of 5.0x10(-7) M (S/N of 3). Typical intra-day reproducibility (n=5) of 2.0% and inter-day reproducibility (n=5) of 3.8% were obtained at the 2.0x10(-5) M level. This method was for the first time applied to study the pharmacokinetics of morphine in rat brain after an intravenous administration of morphine (25 mgkg(-1)).