Cobalt-catalyzed hydrogen desorption from the LiNH2-LiBH4 system

A doping of 5 wt% CoCl2 considerably decreases the dehydrogenation temperature of a mixture of LiNH2 and LiBH4. More that 8 wt% of hydrogen can be released at ca. 155 degrees C. X-Ray absorption near edge structure (XANES) spectroscopy indicated the formation of metallic Co after ball milling CoCl2 with LiNH2 and LiBH4. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements revealed that Co particles have poor crystallinity and are finely dispersed in the sample, which could lead to a high catalytic efficiency.     

Clean synthesis of azo compounds using Magtrieve™ in the ionic liquid [<Emphasis Type="Italic">bmim</Emphasis>][Br]

A series of azo compounds, N-aryl-2-phenyldiazenecarboxamides, and 4-substituted-1,2,4-triazoline-3,5-diones, were synthesized using Magtrieve™, a magnetically retrievable and recyclable oxidant, in the ionic liquid [bmim][Br] under neutral condition. This procedure has several advantages, such as greenness, mild reactions, simple manipulation, and reusability of reagent and solvent. Correspondence: Yanqing Peng, Shanghai Key Laboratory of Chemical Biology, Institute of Pesticides and Pharmaceuticals, East China University of Science and Technology, Shanghai 200237, China.     

Evaluation of band broadening in chemiluminescence detection coupled to pressurized capillary electrochromatography with an off-column coaxial flow interface

A system of off-column coaxial flow chemiluminescence (CL) detection coupled to pressurized CEC (pCEC) was described. The interface utilized a reactor that introduced postcolumn CL reagent into the capillary effluents in a sheathing flow profile. To compare and evaluate band broadening of analytes caused by the detector, the typical CL compounds luminol and N-(4-aminobutyl)-N-ethylisoluminol (ABEI) were separated and detected by pCEC or capillary HPLC (cHPLC) coupled to CL and UV detector, respectively. The results demonstrated that the band broadening caused by off-column detection interface was minimized due to the fast kinetic nature of the CL reaction. With the proposed pCEC-CL system, the detection limits of luminol and ABEI were 1.0x10(-8) and 8.0x10(-8) mol/L, respectively, which were approximately 100-fold more sensitive than those obtained with UV absorption. In addition, separation and detection of the ABEI-labeled L-lysine (L-Lys) and L-arginine (L-Arg) were accomplished by pCEC-CL method based on the principle of ABEI-potassium ferricyanide-alkaline medium CL reaction system. Under the optimum conditions, good results could be achieved compared with pCEC-UV.     

A sweeping-micellar electrokinetic chromatography method for direct detection of some aromatic amines in water samples

A simple and rapid sweeping method for the online improvement of detection limit of some aromatic amines has been developed in this work. The optimum sweeping and separation conditions for 4-methylaniline, 3,4-dichloroaniline, 4-chloroaniline, and 4-aminophenyl were investigated in detail. Under the optimum conditions, the detection limits of these four aromatic amines ranged from 5.4 x 10(-10) to 4.6 x 10(-8)mol/L (S/N = 3), which was about 80-1090-folds lower than those of conventional sample injections. Linear response range were in the range of 2.5 x 10(-8)-2.0 x 10(-6)mol/L with the correlation coefficient between 0.9965 and 0.9994. Baseline separation was achieved within 10 min. After validation, the developed method was applied to determine 4-methylaniline, 3,4-dichloroaniline, 4-chloroaniline, and 4-aminophenyl in river water sample with average recoveries of 79.6-88.7%.     

Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flow

In this paper, we present the results of simultaneous screening of eight gibberellins (GAs) in coconut (Cocos nucifera L.) water by MEKC directly coupled to ESI-MS detection. During the development of MEKC-MS, partial filling (PF) was used to prevent the micelles from reaching the mass spectrometer as this is detrimental to the MS signal, and a cationic surfactant, cetyltrimethylammonium hydroxide, was added to the electrolyte to reverse the EOF. On the basis of the resolution of the neighboring peaks, different parameters (i.e., the pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation of eight GA standards. Under optimum conditions, a baseline separation of GA standards, including GA1, GA3, GA5, GA6, GA7, GA9, GA12, and GA13, was accomplished within 25 min. Satisfactory results were obtained in terms of precision (RSD of migration time below 0.9%), sensitivity (LODs in the range of 0.8-1.9 microM) and linearity (R2 between 0.981 and 0.997). MS/MS with multiple reaction monitoring (MRM) detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed the direct identification and confirmation of the GAs presented in coconut water (CW) sample after SPE, while, the quantitative analysis of GAs was performed by PF-MEKC-MS approach. GA1 and GA3 were successfully detected and quantified in CW. It is anticipated that the current PF-MEKC-MS method can be applicable to analyze GAs in a wide range of biological samples.     

Synthesis of ordered mesoporous crystalline carbon-anatase composites with high titania contents

A direct-triblock-copolymer templating method is demonstrated to synthesize ordered mesoporous crystalline C-TiO(2) (MCT) composites using phenolic resins and acid-base pairs [acidic TiCl(4) and basic counterpart Ti(OC(4)H(7))(4)] as carbon and titanium sources, respectively. The composites possess highly crystalline anatase pore walls that are "glued" by amorphous carbon, ordered mesostructure, high surface areas (approximately 200 m(2)/g), and large pore volumes (approximately 0.15 cm(3)/g). The titania content is as high as 87 wt%. MCT composite favors the immobilization of proteins and enhances the electrocatalytic properties in relation to the reduction of hydrogen peroxide.     

Aggregation of Electrochemically Active Conjugated Organic Molecules and Its Impact on Aqueous Organic Redox Flow Batteries

Molecule aggregation in solution is acknowledged to be universal and can regulate the molecule's physiochemical properties, which however has been rarely investigated in electrochemistry. Herein, an electrochemical method is developed to quantitatively study the aggregation behavior of the target molecule methyl viologen dichloride. It is found that the oxidation state dicationic ions stay discrete, while the singly-reduced state monoradicals yield a concentration-dependent aggregation behavior. As a result, the molecule's energy level and its redox potential can be effectively regulated. This work does not only provide a method to investigate the molecular aggregation, but also demonstrates the feasibility to tune redox flow battery's performance by regulating the aggregation behavior.     

CoFe2O4/CuO活化过氧乙酸高效降解磺胺甲恶唑(英文)

利用化学沉淀法和溶胶凝胶法,通过两步法成功制备出含有尖晶石钴铁氧体和氧化铜的复合催化剂CoFe₂O₄/CuO,通过扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和X射线衍射(XRD)对制备出的CoFe₂O₄/CuO进行表征,探究不同高级氧化体系对磺胺甲恶唑(SMX)去除能力,考察过氧乙酸(PAA)浓度、催化剂投加量、水体中常见干扰物质(Cl^-,HCO-3,SO₄^2-,HA)和不同自由基捕获剂对SMX去除的影响。分析结果表明CoFe₂O₄/CuO同时具有CoFe₂O₄与CuO的特征,对比单独CoFe₂O₄与CuO,CoFe₂O₄/CuO对PAA展现出极高的活化性能,在最佳反应条件下(催化剂投加量=20mg·L^-1,c(PAA)=200μ...     

An Arbitrarily Regulated Monomer Sequence in Multi-Block Copolymer Synthesis by Frustrated Lewis Pairs

Rapid access to sequence-controlled multi-block copolymers (multi-BCPs) remains as a challenging task in the polymer synthesis. Here we employ a Lewis pair (LP) composed of organophosphorus superbase and bulky organoaluminum to effectively copolymerize the mixture of methacrylate, cyclic acrylate, and two acrylates, into well-defined di-, tri-, tetra- and even a hepta-BCP in one-pot one-step manner. The combined livingness, dual-initiation and CSC feature of Lewis pair polymerization enable us to achieve not only a trihexaconta-BCP with the highest record in 8 steps by using four-component monomer mixture as building blocks, but also the arbitrarily-regulated monomer sequence in multi-BCP, simply by changing the composition and adding order of the monomer mixtures, thus demonstrating the powerful capability of our strategy in improving the efficiency and enriching the composition of multi-BCP synthesis.     

Acidic Media Impedes Tandem Catalysis Reaction Pathways in Electrochemical CO2 Reduction

Electrochemical CO₂ reduction (CO₂R) in acidic media with Cu-based catalysts tends to suffer from lowered selectivity towards multicarbon products. This could in principle be mitigated using tandem catalysis, whereby the *CO coverage on Cu is increased by introducing a CO generating catalyst (e.g. Ag) in close proximity. Although this has seen significant success in neutral/alkaline media, here we report that such a strategy becomes impeded in acidic electrolyte. This was investigated through the co-reduction of ¹³CO₂/¹²CO mixtures using a series of Cu and CuAg catalysts. These experiments provide strong evidence for the occurrence of tandem catalysis in neutral media and its curtailment under acidic conditions. Density functional theory simulations suggest that the presence of H₃O⁺ weakens the *CO binding energy of Cu, preventing effective utilization of tandem-supplied CO. Our findings also provide other unanticipated insights into the tandem catalysis reaction pathway and important design considerations for effective CO₂R in acidic media.