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1.
An important challenge facing K-ion batteries lies in exploring earth-abundant and safe cathode materials that can provide high capacity with high migration rate of K ions.Here,we propose a simple and efficient method for searching potential K cathode materials with first principles calculations.Our screening is based on combinations of weight capacity,K ion occupation ratio,volume change per K,and valence limit.With this screening method we predicted a series of potential K ions cathodes with favorable electrochemical performance,such as K2VPO4CO3-like structures with 1 D diffusion channels,3 D channel structures K2CoSiO4,layered materials KCoO2,KCrO2,KVF4 and K5V3F14,and others.These potential cathodes have small volume changes,suitable voltage,and high capacity,with small diffusion barriers.They may be useful in K-ion batteries with high energy density and rate performance.  相似文献   

2.
Artificial base pairs,from the perspective of synthetic biology,are designed to contain the features of modularity,orthogonality,and manipulability.And the development of artificial base pairs has beat endowed with responsibility to understand the biological process,improve the recognition capacity and stability of aptamers,and develop the nucleoside drugs,diagnosis,and drag delivery.In this review,we first gave a concise introduction of artificial base pairs based on their interaction modes including alternative hydrogen bonding,hydrophobic interaction,and metal coordination.Then we displayed the detailed information of artificial base pairs with hydrogen bonding interaction,and analyzed how the changes of their structures affect their functions.Subsequently,we highlighted the applications of functional artificial base pairs in aptamer discovery,diagnosis,and drug delivery.Finally,an insight into the remaining challenges and future perspective of the artificial bases was provided.  相似文献   

3.
Inefficient electrocatalysts and high-power consumption are two thorny problems for electrochemical hydrogen(H2)production from acidic water electrolysis.Herein we report the one-pot precise synthesis of ultrafine Au core-Pt Au alloy shell nanowires(Au@PtxAu UFNWs).Among them,Au@Pt0.077 Au UFNWs exhibit the best performance for formic acid oxidation reaction(FAOR)and hydrogen evolution reaction(HER),which only require applied potentials of 0.29 V and-22.6 m V to achieve a current density of 10 m A cm-2,respectively.The corresponding formic acid electrolyzer realizes the electrochemical H2 production at a voltage of only 0.51 V with 10 m A cm-2 current density.Density functional theory(DFT)calculations reveal that the Au-riched Pt Au alloy structure can facilitates the direct oxidation pathway of FAOR and consequently elevates the FAOR activity of Au@Pt0.077 Au UFNWs.This work provides meaningful insights into the electrochemical H2 production from both the construction of advanced bifunctional electrocatalysts and the replacement of OER.  相似文献   

4.
有中学化学参考资料题:0.10 mol/L的NH4Cl和(NH4)2SO4溶液哪个pH值高?这似乎是个中学生可做的简单题目,仔细考虑不是如此.如果简单地认为盐酸和硫酸都是强酸,而硫酸是二元酸,硫酸铵溶液中铵盐浓度为0.20 mol/L,那么NH4Cl溶液pH高,那是不妥的.硫酸是二元酸,第一个氢离子能完全电离,第二个氢离子部分电离,如此考虑情况怎么样呢?是不是答案发生变化?这要通过计算来说明.  相似文献   

5.
Layered Li-rich Mn-based oxides are promising cathode materials for Li-ion batteries due to their high capacity and high operation voltage.However,their commercial applications are hindered by irreversible capacity loss in the first charge-discharge process,voltage decay during cycling,inefficient cyclability and rate capability.Many attempts have been performed to solve such issues,including the mechanism study and strategies to improve the electrochemical performance.This article provides a brief review and future perspective on the main challenges of the high-capacity Li-rich Mn-based cathodes for Li-ion batteries.  相似文献   

6.
The perovskite transition metal oxide(TMO) has been considered in electrocatalysis for the modern clean energy technologies as its high electrochemical activity and low cost. The atomic scale engineering to the local stoichiometry of single crystal TMO provides a clue of the relation between electronic structure and catalytic performance. Here we report a hydrogen evolution reaction(HER) activity enhancement ~ 1761% of Bi0.85Sr0.15FeO_3 compared to the pure BiFeO_3. By the systemic investigation of the Sr doping level of Bi1-xSr_xFeO_3(BSFO), it is found that the HER enhancement originates from the improvement of ferromagnetism of BSFO without obvious scarification of the ferroelectricity at the room temperature. The multiple ferroic orderings in BSFO are beneficial for HER activity, which offers the strengthen of hybridization of Fe 3d and O2 p orbitals from the view of ferromagnetism, and the assistance of electron drift by spontaneous electric polarization. Our study not only affords the strategy of developing multiple ferroic orderings in TMO, but also facilitates the atomic scale understanding of the improved HER activity.  相似文献   

7.
The aqueous rechargeable Zn-ion batteries based on the safe,low cost and environmental benignity aqueous electrolytes are one of the most compelling candidates for large scale energy storage applications.However,pursuing suitable insertion materials may be a great challenge due to the strong electrostatic interaction between Zn^(2+)and cathode materials.Hence,a novel NaV6O15/V2O5 skin-core heterostructure nanowire is reported via a one-step hydrothermal method and subsequent calcination for high-stable aqueous Zn-ion batteries(ZIBs).The NaV6O15/V2O5 cathode delivers high specific capacity of 390 m Ah/g at 0.3 A/g and outstanding cycling stability of 267 m Ah/g at 5 A/g with high capacity retention over 92.3%after 3000 cycles.The superior electrochemical performances are attributed to the synergistic effect of skin-core heterostructured NaV6O15/V2O5,in which the sheath of NaV6O15 possesses high stability and conductivity,and the V2O5 endows high specific capacity.Besides,the heterojunction structure not only accelerates intercalation kinetics of Zn2+transport but also further consolidates the stability of the layers of V2O5 during the cyclic process.This work provides a new perspective in developing feasible insertion materials for rechargeable aqueous ZIBs.  相似文献   

8.
杨周  张文华 《催化学报》2014,35(7):983-988
正1.Introduction We have recently witnessed a breakthrough in highly effi-cient solar cells, where the organolead halide perovskite, CH3NH3PbI3, was used as an absorber of sunlight. The perov-skite was used to sensitize mesoporous TiO2 films in a solid-state mesoscopic solar cell to deliver a power conversion  相似文献   

9.
李俊生 《化学教育》2007,28(7):61-62
长期以来人们一直认为金属钠保存在煤油中是因为金属钠的密度比煤油的密度大且金属钠和煤油不发生化学反应的缘故,因此在教学中形成一个教师都默认学生也认可的事实,这个事实就是金属钠能保存在煤油中有2点原因:  相似文献   

10.
The effect of electrolytes on the micellar behavior of an amphiphilic drug,chlorpromazine(CPZ)hydroehloride,was studied using cloud point(CP)and dye solubilization techniques.In the presence of KBr,increase because of deprotonation of drug molecules at high pH. The visible absorbance increased(due to dye solubilization)with the increase in pH from 6.5 to 6.9,which indicated micellar growth.At fixed pH(6.7),addition of inorganic salts(KF,KC1,effecfiveness being in the order:F-Na >K ,which Was explained by considering cognizance of their hydrated radii.Compared with anions,their effect was small.Increase in[CPZ]caused micellar growth and hence the CP as well as the visible absorbance increased.The overall behavior Was discussed in terms of electrostatic interactions and micellar growth.  相似文献   

11.
徐雪峰  郭志谋  梁鑫淼 《色谱》2012,30(11):1188-1193
研究了在反相高效液相色谱模式下,基于点击化学的β-环糊精手性固定相对苯并恶嗪类对映体的手性分离情况。考察了流动相中有机改性剂的类型和比例、缓冲盐的浓度和pH值对分离的影响。考察结果表明: 乙腈作为有机改性剂比甲醇更有利于苯并恶嗪对映体的分离;乙酸三乙胺缓冲盐体积分数从0.1%增大到1.0%时,苯并恶嗪对映体的保留时间和分离度都随之减小,在pH 4.1时苯并恶嗪对映体具有最大分离度。因此确定乙腈和体积分数为0.1%的乙酸三乙胺缓冲盐流动相(pH 4.1)为最佳分离条件。分离机理研究结果表明,固定相和样品之间的包容络合相互作用以及样品和固定相之间的氢键作用,是样品得以分离的基础。本研究为进一步深入研究β-环糊精固定相提供了实验基础,同时也证明了点击化学在手性环糊精固定相制备中具有极大潜力。  相似文献   

12.
Chiral separations by open tubular capillary electrokinetic chromatography.   总被引:2,自引:0,他引:2  
The inner walls of 50 microns fused-silica capillaries are etched by ammonium hydrogendifluoride and then modified by the silanization/hydrosilation method with a chiral selector. Three different types of selectors were evaluated: lactone, beta-cyclodextrin and naphthylethylamine. Each of the bonded chiral stationary phases provided at least partial separation for one type of racemic solute. These results confirm that bonded organic moieties on the etched inner wall of a capillary can provided sufficient solute-bonded phase interactions to influence the retention of molecules driven through a capillary by electroosmosis or a combination of electroosmosis and electrophoretic mobility.  相似文献   

13.
The enantiomeric separation of a set of 30 new chiral furan derivatives has been achieved on native and derivatized beta-cyclodextrin stationary phases using high performance liquid chromatography (HPLC). The hydroxypropyl-beta-cyclodextrin (Cyclobond RSP), the 2,3-dimethyl-beta-cyclodextrin (Cyclobond DM), and the acetyl-beta-cyclodextrin (Cyclobond AC) stationary phases are the most effective chiral stationary phases (CSPs) for the separation of these racemates in the reverse phase mode. No enantioseparations have been observed on the native beta-cyclodextrin chiral stationary phase (Cyclobond I 2000) and only a few separations have been attained on the S-naphthylethyl carbamate beta-cyclodextrin (Cyclobond SN) and 3,5-dimethylphenyl carbamate beta-cyclodextrin (Cyclobond DMP) chiral stationary phases in the reverse phase mode. The polar organic and the normal phase mode on these CSPs are not effective for separation of these compounds. The characteristics of the analytes, including steric bulk, hydrogen bonding ability, and geometry, play an important role in the chiral recognition process. The pH affects the enantioseparation of compounds with ionizable groups and the addition of 0.5% methyl tert-butyl ether to the mobile phase significantly enhances the separation efficiency for some highly retained compounds.  相似文献   

14.
 合成了2,6-二-O-戊基-β-环糊精键合硅胶固定相(PCDS)。利用傅里叶红外光谱、X射线光电子能谱、莫氏(Molisch)试验颜色反应对其进行了表征。以邻苯二甲酸二甲酯、甲苯和菲为测试溶质,评价该键合固定相的色谱性能,并考察了该固定相对一些位置异构体的色谱分离效果,讨论了可能的分离机理。  相似文献   

15.
Two bonded chiral stationary phases (CSPs), 8-aminoquinoline-2-ylmethyl- and 8-aminoquinoline-7-ylmethyl-diaza-18-crown-6-capped [3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl silica particles (non-porous, 1.5 microm), have been prepared and evaluated using capillary liquid chromatography at high pressures (> or = 8000 p.s.i.). High column efficiency (up to 400 000 plates m(-1)) was achieved for chiral separations. These CSPs with two recognition sites, i.e. substituted-diaza-18-crown-6 and beta-cyclodextrin combined with high chromatographic efficiency provide good resolution of a variety of enantiomers and positional isomers in relatively short times under reversed-phase conditions. After inclusion of a Ni (II) ion from the mobile phase, the positively charged crown ether-capped beta-cyclodextrin facilitates specific static, dipolar, and host-guest complexation interactions with solutes.  相似文献   

16.
Two novel chiral stationary phases (CSPs) were prepared based upon the regioselective immobilizations of beta-cyclodextrin (beta-CD) at its C2 position to the silica support. The mono-2A-azido-2A-deoxyperphenylcarbamoylated beta-cyclodextrin and mono-2A-azido-2A-deoxyperacetylated beta-cyclodextrin were synthesized by selective tosylation and azidolysis followed by perfunctionalisation. The derivatised cyclodextrins were then immobilized onto the aminised silica gel via the Staudinger reaction to provide new chiral stationary phases. Their application to high-performance liquid chromatography (HPLC) enantioseparation of racemic compounds was demonstrated using beta-adrenergic blockers, flavonone compounds, benzodiazepinones, antihistamines and weakly protolytic compounds, of which good separations were achieved for some racemic compounds, for instance, bendroflumethiazide (Rs 6.26), oxazepam (Rs 5.99), temazepam (Rs 2.85) and althiazide (Rs 1.13) when compared with the corresponding CSPs where the beta-CD molecule was regioselectively immobilized at the C6 position. The enantiodiscriminatory properties of these CSPs were found to be affected by the orientation of the CD cavity under reversed-phase conditions, and also by the derivitising groups of the CD. The HPLC results inferred that the mono-6A-azido-6A-deoxyperphenylcarbamoylated CD CSP (CD bonded at C6 position to silica) exhibited slightly better chiral recognition ability than mono-2A-azido-2A-deoxyperphenylcarbamoylated CD CSP under the normal-phase and reversed-phase modes on the separation of 31 different racemic compounds and drugs. On the contrary, higher chiral recognition abilities were observed on the mono-2(A)-azido-2A-deoxyperacetylated CD CSP compared to mono-6A-azido-6A-deoxyperacetylated CD CSP.  相似文献   

17.
β-环糊精是以1,4-糖苷键首尾相连的环状低聚糖,具有手性识别功能,特别是衍生化的β-环糊精键合固定相,对手性化合物具有良好的拆分能力。本文介绍了β-环糊精的结构和性质,综述了各种衍生化的β-环糊精液相色谱键合固定相及其在手性化合物拆分中的应用。  相似文献   

18.
本文评述了气相色谱手性分离的发展过程,介绍了氨基酸、二肽、金属配合物、环糊精、多糖、手性离子液体、环肽、键合以及交联类气相色谱手性固定相以及各类型的拆分机理,展望了气相色谱手性固定相的研究前景。  相似文献   

19.
以3-氨基丙基三乙氧基硅烷、3-异氰酸丙基三乙氧基硅烷和3-缩水甘油醚氧基丙基三甲氧基硅烷作为键合臂,将葡萄糖和N-乙酰-D-氨基葡萄糖键合到硅胶上作为高效液相色谱手性固定相,对15种手性化合物进行拆分.研究结果表明:不同的键合臂对它们的手性分离能力有较大的影响,葡萄糖及其衍生物是一类具有良好实用前景的手性固定相.  相似文献   

20.
合成了海藻糖、龙胆二糖、蜜二糖三种二糖类键合硅胶高效液相色谱手性固定相,采用湿法装柱制备了色谱柱.在高效液相色谱正相条件下,该类固定相对醇类、胺类、氨基酸类对映异构体以及一些手性药物表现出了一定的拆分效果.特别是海藻糖固定相在所拆分的9种手性化合物中,有6种手性化合物能得到较好的分离,表现出较好的手性分离性能.并且手性固定相之间具有较好的互补性.  相似文献   

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