Studies on the Displacement Reaction of Trialkylaluminum with Ethylene Catalyzed by Nitrogen Chelate Cobalt Complexes

The catalytic properties of a series of cobalt complexes containing bidenated nitrogen ligand for displacement reaction of trialkylaluminum with ethylene is reported. Effect of different reaction time, temperature and cobalt complexes containing different ligand on catalyst performance has been investigated.

Toehold-mediated strand displacement reaction-propelled cascade DNAzyme amplifier for microRNA let-7a detection

DNAzyme amplifiers have been extensively explored as a useful sensing platform,but single DNAzyme amplifier is limited in biosensing applications by its low sensitivity.Herein,a cascade DNAzyme amplifier was designed by exploiting concurrent amplification cycle principles of toehold-mediated strand displacement reaction(TSDR)and Zn^(2+)-assisted DNAzyme cycle with lower cost and simpler procedures.Compared with single DNAzyme amplifier,the proposed TSDR-propelled cascade DNAzyme amplifier exhibited higher sensitivity by releasing more DNAzyme through TSDR to cleave substrate strand during the DNAzyme cycle.Base on this,let-7a could be sensitively detected in the range of 5-50 nmol/L with a detection limit of 64 pmol/L.Furthermore,the dual signal amplification strategy of the cascade DNAzyme amplifier exhibited excellent selectivity to distinguish single-base mismatched DNA strands,which has been successfully applied to the determination of let-7a in blood serum,showing high promise in early cancer diagnosis.

Effect of CuO Particle Size on the Microstructure Evolution of Al_2O_(3P)/Al Composites Prepared Via Displacement Reactions in the Al/CuO System

An A1203p/A1 composite was successfully synthesized using a displacement reaction between 80 wt% A1 and 20 wt% CuO powders at a heating rate of 5 ℃/min. Two different sizes CuO particles were used, and all the experiments were conducted under an argon atmosphere. To analyze the microstructural evolution during synthesis, the A1-20 wt% CuO samples were heated to the temperatures selected according to the differential scanning calorimetry curve and then immediately quenched with water. The phase composites and microstructure of the water-quenching samples were in- vestigated using X-ray diffraction, optical microscopy, scanning electron microscopy and energy-dispersive spectrometry. The results indicate that the CuO particle size has a significant effect on the microstructural evolution of the samples during the heating stage and on the microstructure of synthesized composites. Smaller CuO particles can decrease the reaction temperature, narrow the reaction temperature range at the different reaction stages during the heating stage and make the size and distribution of in situ A1203 particles more uniform. The reaction between A1 and CuO can be complete as the temperature rises to 900 ℃. The size of the in situ A1203 particles is approximately 5 μm when the size of the CuO particles is less than 6 μm. This sample has a relatively high Rockwell hardness of 60 HRB.

1,3-Dinitro-2-chloro-5-trifluorotoluene and its bridged derivatives Ⅰ.An investigation on the displacement reactions of bidentate nucleophiles towards aromatic rings

The reactions of 1,3-dinitro-2-chloro-5-trifluorotoluene(DNCTT)(1)and its bridged com- pounds with bidentate nucleophiles have been investigated.Primary or secondary diamines and diethylene glycol react with 1 and its bridged derivatives by replacing the substituent grouppara to CF_3, whereas ethanedithiol reacts either by replacing the substituent group para to CF_3 or by displacing both groups and a nitro group.The results have been rationalized in terms of electronic effects and nucleophilicity of the nucleophiles.

High area-capacity Mg batteries enabled by sulfur/copper integrated cathode design

Rechargeable Mg batteries potentially display lower cost and competitive energy density compared with their Li-ion counterparts.However,the practical implementation of high area-capacity cathodes still remains a formidably challenging task.This work presents the sulfur/copper integrated cathodes fabricated by the conventional blade-coating process and slurry-dipping method.The sulfur/copper foil integrated cathodes deliver a high area-capacity of 2.6 mAh cm^(-2)after 40 cycles,while the sulfur/copperfoam integrated cathode exhibits an ultrahigh area-capacity of 35.4 mAh cm^(-2),corresponding to 743.1 Wh L^(-1)at the electrode level(1.5 times higher than the LiCoO_(2)-graphite system).The in-situ formed copper sulfide intermediates with sufficient cation defects can act as functional intermediates to regulate the sulfur electrochemistry during the first discharge process.The subsequent cycles are operated by the reversible displacement reaction between Mg-ions and copper sulfide active substances.In particular,the copper ions prefer to extrude along the[001]direction in copper sulfides lattice and simultaneously the rock-salt MgS crystals are generated.Besides,the nonuniform surface topography of the cycled Mgmetal anode,caused by the spatial inhomogeneity in current distribution,is demonstrated to lead to the battery performance degradation for high area-capacity Mg batteries.

排代离子在分离稀土离子元素中的作用研究

本文研究了以 EDTA为螯合剂 ,用高压离子交换螯合剂排代法分离稀土元素时 ,排代离子对谱带的移速及延伸 ,阻滞离子区段的变化的影响。

一种以上转换和Fe_(3)O_(4)纳米粒子为基础的超灵敏ctDNA检测系统

ctDNA是重要的肿瘤标志物之一,在肿瘤疾病的早期诊断和临床监控方面发挥着重要作用.目前,常用的ct DNA检测方法通常都缺乏足够的灵敏性和特异性,不能满足实际诊疗的需要.因此,我们急需一种新型的、超灵敏的ct DNA检测方法.上转换纳米粒子是一种优异的发光材料,因其独特的发光特性在生物医学方面具有重要应用.因此,我们设计了一种以上转换和Fe_(3)O_(4)纳米粒子为基础的ct DNA检测方法.在该检测系统中,上转换和Fe_(3)O_(4)纳米粒子通过DNA碱基互补配对原则自组装在一起.目标序列可以通过熵驱动链置换(ESDR)反应将连着上转换纳米粒子的核酸链释放出来.经磁性分离后,上清液中上转换纳米粒子在980 nm激光器激发下的荧光强度与目标序列的浓度在1 nmol L^(-1)–100 amol L^(-1)的范围内具有非常好的线性关系,经计算,最低检出浓度为1.6 amol L^(-1).此外,该检测系统在识别单碱基突变、实际细胞和血清样本的检测中均有较好的应用.因此,该检测系统因为其灵敏性和特异性在肿瘤早期诊断、疾病进行过程监控、治疗方法评价和愈后风险评估等方面具有重大应用潜力.

Target Recycling Transcription of Lighting-Up RNA Aptamers for Highly Sensitive and Label-Free Detection of ATP

We describe here a target recycling transcription of lighting-up aptamer strategy for detecting ATP in human serums in a label-free means with high sensitivity.ATP molecules specifically recognize the binding aptamer and result in the structure switching of the DNA assembly probes to imitate the target ATP molecule recycling cycles through the toehold-mediated strand displacement reaction,which causes the formation of many dsDNAs containing the RNA promoter sequences for subsequent transcription generation of large amounts of lighting-up aptamers.The organic dye,malachite green,then associates with these lighting-up aptamers to produce significantly enhanced fluorescence signals,which can sensitively detect ATP within a dynamic range from 10 to 500 nM in a label-free way.The sensing approach shows a detection limit of 7.3 nM and also has an excellent selectivity for ATP analogue molecules.In addition,this method can detect ATP molecules in diluted human serum samples sensitively,which proves the promising potential to diagnose ATP-related diseases.