An Ultra-Long-Life Lithium-Rich Li1.2Mn0.6Ni0.2O2 Cathode by Three-in-One Surface Modification for Lithium-Ion Batteries

Voltage decay and capacity fading are the main challenges for the commercialization of Li-rich Mn-based layered oxides (LLOs). Now, a three-in-one surface treatment is designed via the pyrolysis of urea to improve the voltage and capacity stability of Li_1.2Mn_0.6Ni_0.2O₂ (LMNO), by which oxygen vacancies, spinel phase integration, and N-doped carbon nanolayers are synchronously built on the surface of LMNO microspheres. Oxygen vacancies and spinel phase integration suppress irreversible O₂ release and help lithium ion diffusion, while N-doped carbon nanolayer mitigates the corrosion of electrolyte with excellent conductivity. The electrochemical performance of LMNO after the treatment improves significantly; the capacity retention rate after 500 cycles at 1 C is still as high as 89.9 % with a very small voltage fading rate of 1.09 mV cycle⁻¹. This three-in-one surface treatment strategy can suppress the voltage decay and capacity fading of LLOs.     

Electrochemical Synthesis of Thienoacene Derivatives: Transition-Metal-Free Dehydrogenative C−S Coupling Promoted by a Halogen Mediator

The first electrochemical dehydrogenative C−S bond formation leading to thienoacene derivatives is described. Several thienoacene derivatives were synthesized by dehydrogenative C−H/S−H coupling. The addition of ⁿBu₄NBr, which catalytically promoted the reaction as a halogen mediator, was essential.     

Single-molecule nanopore sensing of actin dynamics and drug binding

Actin is a key protein in the dynamic processes within the eukaryotic cell. To date, methods exploring the molecular state of actin are limited to insights gained from structural approaches, providing a snapshot of protein folding, or methods that require chemical modifications compromising actin monomer thermostability. Nanopore sensing permits label-free investigation of native proteins and is ideally suited to study proteins such as actin that require specialised buffers and cofactors. Using nanopores, we determined the state of actin at the macromolecular level (filamentous or globular) and in its monomeric form bound to inhibitors. We revealed urea-dependent and voltage-dependent transitional states and observed the unfolding process within which sub-populations of transient actin oligomers are visible. We detected, in real-time, filament-growth, and drug-binding at the single-molecule level demonstrating the promise of nanopore sensing for in-depth understanding of protein folding landscapes and for drug discovery.

Nanopipettes were used for real-time investigation into actin dynamics and drug binding at single-molecule resolution, showing promise for a better understanding of the mechanism of protein–protein interactions and drug discovery.     

Investigation of electro-oxidation activity of Pt-CNTs/GC electrodes

The morphology and structure of Pt-CNTs/ GC electrodes were characterized via Transmission Electron Microscopy (TEM) and selected area electron diffraction. The electro-oxidation behavior of CO and methanol on Pt-CNTs/GC electrodes were studied with cyclic voltommograms or chronoamperometry. Three oxidation peaks were observed for CO absorbed on Pt-CNTs/GC electrodes. Methanol was found to be dissociated spontaneously on the electrode to produce a strong absorbed intermediate CO. Among the three oxidation peaks, peak I was presumed to be due to the bridged CO absorption while peaks II and III were attributed to the split in the linear CO which is absorbed on the Pt-CNTs/GC nanocluster with different particle size and Pt film. The oxidation current of methanol on the Pt-CNTs/GC electrode did not always increase with the increase in the amount of Pt loading. The result indicates that there is an optimal Pt loading for methanol oxidation. It is necessary to select the catalyst with proper Pt loading when the anode of a direct-methanol fuel cell is prepared. __________ Translated from Chemical Journal of Chinese Universities, 2007, 28(6): 1135–1138 [译自: 高等学校化学学报]     

Isolation of New Polyketide Synthase Gene Fragments and a Partial Gene Cluster from East China Sea and Function Analysis of a New Acyltransfrase

Using the consensus-degenerate hybrid oligonucleotide primer polymerase chain reaction method, 26 new ketoacyl synthase (KS) fragments were isolated from a marine sediment sample in the East China Sea (ECS) and analyzed by construction of a phylogenetic tree. With a digoxigenin-labeled KS gene fragment used as a probe, a partial polyketide synthase (PKS) gene cluster was isolated and identified by hybridization screening of a marine sediment sample metagenome fosmid library constructed for this study. A new acyltransferase (AT) gene was cloned from the PKS gene cluster and heterogeneously expressed as a protein fused to maltose-binding protein (MBP). Ultraviolet spectrophotometry was used to study the binding of the MBP–AT fusion protein and single AT domain to substrates using MBP and bovine serum albumin as control proteins. Binding constants (Ka, per micromolar) were calculated and used to analyze the substrate specificity of the acyltransferase. We concluded that there are many unrevealed new PKS gene clusters in marine sediments in the ECS. The acyltransferase is presumably an acetyltransferase from a new PKS gene cluster.     

Alkylation of 2-naphthol with long-chain olefins over zeolites

Alkylation of 2-naphthol with tripropylene in the presence of zeolite catalysts HBEA, H-Y and H-MFI was studied. Comparative studies on the catalytic properties of H-BEA, H-Y and H-MFI zeolites were carried out under identical reaction conditions. The results showed that the H-BEA catalyst exhibited outstanding catalytic performance; and the conversion and selectivity of 2-naphthol could be 52.1% and 86.3%, respectively. It was found that the structure and acid strength of zeolite catalysts were the major influencing factors for the conversion and selectivity of 2-naphthol alkylation.     

Identification and quantitation of iodotyrosines and iodothyronines in hydrolysate of iodinated casein by capillary electrophoresis

In this paper, a new method for separation, identification and quantitation of iodotyrosines and iodothyronines [3-monoiodo-L-tyrosine (MIT), 3,5-diiodo-L-tyrosine (DIT), L-thyronine (T₀), 3,5-diiodo-L-thyronine (T₂), 3,5,3′-triiodo-L-thyronine (T₃) and 3,3′,5,5′-tetraiodo-L-thyronine (T₄)] was described by using capillary electrophoresis with photodiode-array ultraviolet-visible detection (CE-UV). The certain influence factors were systematically investigated, including the type, concentration and pH of buffer, and additive. We found that 10 mM sodium borate running buffer (pH 8.5) containing 0.10 mM β-CD as additive reagent allowed the best instrumental conditions for the optimum separation of the iodotyrosines and iodothyronines. Under optimized conditions, the analytical time was within 6 min, using an uncoated fused-silica capillary of 75 μm inner diameter with an effective length of 30 cm. The reproducibility of the migration time and peak area was less than 0.6% and 6.8%, respectively. A linear range from 10-1000 μg/mL and low limits of detection from 1.3-3.4 μg/mL were obtained at the detection wavelength of 280 nm. Our preliminary results show that the method is well suitable for determination of the hydrolysate of iodinated casein.     

NRET from naphthalene labels in multilayer shell wall on melamine formaldehyde microparticles fabricated with layer-by-layer self-assembly to pyrene-labeled polyelectrolyte in solution

Core-shell colloidal particles were prepared with the core of monodisperse melamine formaldehyde particles (MF) with a diameter of 3.5 μm. The shell deposited on the core by the layer-by-layer (LbL) self-assembly was made with a copolymer ANp3 of 2-acrylamido-2-methylpropanesulfonate sodium (AMPS) and 3 mol% naphthalene label monomer and poly(diallyldimethylammonium chloride) (PD). Nonradiative energy transfer (NRET) from the naphthalene labels deposited on the MF particles to pyrene labels at a polyelectrolyte APy3, a copolymer of AMPS and 3 mol% pyrene label monomer, or to an ionic pyrene probe 1-pyrenemethylamine hydrochloride (PyMeA · HCl) in water was observed. The NRET efficiency was expressed as the emission intensity ratio I/I₀ of naphthalene with and without existence of pyrene in the surrounding solution. With increasing pyrene concentration, I/I₀ decreased down to about 0.2 and the mechanism for this NRET from the inner naphthalene label to the pyrene labels in solution is still ambiguous.     

Modification of the halogen end groups of polystyrene prepared by ATRP

The stabilization modification of the halogen end groups of polystyrene prepared by atom transfer radical polymerization (ATRP) has been attempted. The reaction mechanism adopted is radical chain transfer reaction, and iso-propylbenzene is employed as not only the chain transfer agent but also the solvent. Moreover, Cu⁰ is used as the acceptor of the transformed halogen atom in some experiments. As evidenced by ¹H NMR analysis of the modified products, the halogen end group can really be converted into the much more stable carbon-hydrogen structure. When Cu⁰ is not used, the conversion of the halogen end groups rises rapidly during the early stage and the increase rate slows down after about 8 h reaction. In view of the influence of reaction temperature on the modification, the conversion increases almost exponentially with temperature in the range of 80-100 °C, and the increase rate slows down at higher temperature. ¹H NMR and SEC analyses prove that the modification reaction does not destroy the polymer backbone and the molecular weights remain almost the same as those of the unmodified samples. When Cu⁰ is introduced, the modification reaction proceeds much rapidly, the conversion of the halogen end groups rises almost linearly at the early stage and the nearly complete (>95%) dehalogenation of the polymeric chains is observed after only 12 h reaction. However, the molecular weights rise and the polydispersities become wider after the modification, which implies that the modification is accompanied with the couple termination of the polystyrene radicals besides chain transfer reaction. Furthermore, the couple termination can be restrained at some lower catalyst concentration. Indeed, the modified polymers show improved thermal stability, the initial weight loss temperatures is increased from 196 °C to 378 °C for the linear polystyrene and from 203 °C to 261 °C for the hyperbranched polystyrene.     

A fluorescent chemical sensor for Hg(II) based on a corrole derivative in a PVC matrix

A fluorescent chemical sensor for Hg(II) using 5,10,15-tris(pentafluorophenyl)corrole (H₃(tpfc)) as fluorophore is described in this paper. The response of the sensor is based on the fluorescence quenching of H₃(tpfc) by coordination with Hg(II). H₃(tpfc) based sensor shows a linear response towards Hg(II) in the concentration range from 1.2 × 10⁻⁷ to 1.0 × 10⁻⁴ M, with a working pH range from 5.0 to 8.0. The response time for Hg(II) concentration ≤1.0 × 10⁻⁵ M is less than 5 min. The sensor shows good selectivity for Hg(II) over alkali, and alkaline earth, and most of transition metal cations. The effect of the composition of the sensor membrane has been studied and the experimental conditions optimized. The corrole based sensor membrane can be easily regenerated just by washing with blank buffer solution after each measurement. The sensor has been used for determination of Hg(II) in water samples with satisfactory results.