Delving noble metal and semiconductor nanomaterials into enantioselective analysis

The chiroplasmonic and chiroexcitonic platform constructed from noble metal and semiconductor nanomaterials have significantly advanced enantioselective analysis. In this paper, we summarized the exciting progresses and contributions by the peers in the field.     

Progress on the development of DNA-mediated metal nanomaterials for environmental and biological analysis

This review summarized the recent progress on the synthesis, morphologies and properties of DNA-mediated metal nanomaterials including nanoparticles and nanoclusters. Moreover, their applications to environmental and biological analysis were introduced with the developing prospect in analytical chemistry.     

Thioallenoates in catalytic enantioselective [2+2]-cycloadditions with unactivated alkenes

The application of thioallenoates to catalytic enantioselective [2+2]-cycloadditions with unactivated alkenes is reported. In many cases, the thioallenoates examined exhibit superior reactivity and selectivity compared to the allenic esters generally used in these cycloadditions.     

Synthesis of chiral titanium-containing phosphinoamide ligands for enantioselective heterobimetallic catalysis

The synthesis of six chiral titanium-containing phosphinoamide ligands is discussed. These ligands assemble chiral heterobimetallic Pd–Ti complexes, enable enantioselective intramolecular allylic aminations with hindered amine nucleophiles and achieve selectivity up to 53% ee. Mechanistic studies demonstrate the reversibility of the enantio-determining C–N bond forming step, which leads to a gradual increase in the % ee of the reaction over time. These results represent a rare example of enantioselective heterobimetallic catalysis and suggest that these new ligands could find broad application in enantioselective transition metal catalysis.     

Photo-responsive metal/semiconductor hybrid nanostructure:A promising electrocatalyst for solar light enhanced fuel cell reaction

Direct alcohol fuel cells(DAFCs) have received wide attention as a new type of clean energy device because of their high energy conversion efficiency,portability,non-toxicity and pollution-free.Anode catalysts are the key factors affecting the performance of DAFCs.Recently studies show that using the optical activity of semiconductor materials as the carriers of traditional precious metal electrocatalysts,under the illumination of light sources,can greatly improve the electrocatalytic activity and stability of electrodes.In this review,the research progress of photo-responsive metal/semiconductor hybrids as the electrocatalysts for DAFCs in recent years is summarized,including:(1) Mechanism and advantages of photo-assistant electrochemical alcohol oxidation reaction,(2) me tal/semiconductor electrocatalyst for the different type of fuel cell reactions,(3) different kind of metals in photo-responsive metal/semiconductor hybrid nanostructure,(4) the personal prospects of the photo-responsive metal/semiconductor electrode for future application in DAFCs.     

Catalytic enantioselective conjugate addition en route to paxilline indoloterpenoids

Development of enantioselective synthesis of precursor en route to paxilline indoloterpenoids is described. Evaluation of 25 diphosphine-based ligands has led to identification of JosiPhos derivative that allows for asymmetric conjugate addition of homoprenyl Grignard reagent to 2-methylcyclopent-2-en-1-one in excellent yield and with appreciable levels of enantioinduction. Application to the conjugate addition of other Grignard reagents is demonstrated.     

Recent advances in electrochemiluminescence imaging analysis based on nanomaterials and micro-/nanostructures

Electrochemiluminescence (ECL) is a kind of luminescent phenomenon caused by electrochemical reactions. Based on the advantages of ECL including low background, high sensitivity, strong spatiotemporal controllability and simple operation, ECL imaging is able to visualize the ECL process, which can additionally achieve high throughput, fast and visual analysis. With the development of optical imaging technique, ECL imaging at micro- or nanoscale has been successfully applied in immunoassay, cell imaging, biochemical analysis, single-nanoparticle detection and study of mechanisms and kinetics of reactions, which has attracted extensive attention. In this review, the basic principles and apparatus of ECL imaging were briefly introduced at first. Then several latest and representative applications of ECL imaging based on nanomaterials and micro-/nanostructures were overviewed. Finally, the superiorities and challenges in ECL imaging for further development were discussed.     

Experimental and theoretical investigations of the molecular structure,the spectroscopic properties and TD-DFT analysis of a new semiconductor hybrid based iron(III)

In this work, a new hybrid material (C₅H₆N₂Cl)₂[FeCl₄].Cl abbreviated (CAP)₂[FeCl₄].Cl was prepared using room temperature slow evaporation technique. The X-ray diffraction analysis revealed that the compound is crystallized in the centrosymmetric space group P2₁/c of the monoclinic system. The crystallographic network consists of an Fe(III) ion located on an inversion center and coordinated by four chlorine, isolated Cl^– and two (CAP)⁺ protonated cations linked by N–H...Cl and C–H...Cl hydrogen bonds to form a zero-dimensional network. Hirshfeld surface analysis was used to analyze intermolecular interactions present in the crystal structure. The vibrational properties were inspected by means of Infra-Red absorption and Raman diffusion spectroscopy techniques. In addition, theoretical calculations based on the DFT/B3LYP/LanL2DZ method and the time-dependent density functional theory (TD–DFT) were performed in order to gain more information and help in the examination of over-all properties of the title compound. Good and interesting experimental findings were presented and good consistency was found with the calculated results.     

Chemoselective and enantioselective analysis of proteinogenic amino acids utilizing N-derivatization and 1-D enantioselective anion-exchange chromatography in combination with tandem mass spectrometric detection

D-Amino acid analysis in biological samples still poses a challenge to analytical chemists. In higher developed species trace amounts of d-amino acids have to be detected in vast excesses of the corresponding L-enantiomers. This method utilizes an easy-to-carry-out derivatization step on the amino group with an iron ferrocenyl propionate hydroxy succinimide ester followed by one-dimensional enantioselective anion exchange chromatography with cinchona alkaloid based chiral stationary phases (CSPs). MS detection is carried out in the highly sensitive SRM (selected reaction monitoring) mode, which allows a chemoselective differentiation of amino acid derivatives as well as their enantioselective separation in one step. Application of this method allows LOD (limits of detection) in the low μmol L(-1) range and baseline enantioseparation for all proteinogenic amino acids except for Pro, Arg and His. The D-enantiomers of isomeric Leu and Ile were separated chromatographically and pose an example for the complementary selectivities of LC and MS. A successful application of this procedure to unprocessed human urine indicated the eligibility to analyse biological samples.     

Controlled growth of uniform noble metal nanocrystals: aqueous-based synthesis and some applications in biomedicine

Aqueous-dispersed single and binary noble metal nanocrystals have attracted much attention as key materials in many fields, especially in biomedicine, catalysis, etc. Controlled growth of the metal nuclei allow for the manipulation of uniform morphology of final products. This behavior would tailor their unique physiochemical and electronic properties and follows by their practical applications. This review presents an overall picture of kinetic formation of a particle and then summarizes an overview of recent progress in many research groups concerning aqueous- and/or polyol-based syntheses of many types of aqueous-dispersed single metallic and bimetallic nanocrystals with controlled shape. The main advantages in these synthetic approaches for the shape-controlled metal nanocrystals are simple, versatile, environmentally friendly, low cost, pure and single-crystalline products, and high yield. The formed products can be easily dispersed in water medium and compatible for biotechnological field. Particularly the biomolecule (antibody including protein and/or DNA)-conjugated gold nanocrystals have been utilized as an active agent for a broad range of biomedical applications. We expect that this review will have a high potential towards novel materials fabrication and nanotechnological fields.     

Electrochemiluminescence bioassays based on carbon nitride nanomaterials and 2D transition metal carbides

Electrochemiluminescence (ECL) is a powerful technique for bioassays. To meet the growing demand for bioassays, it is necessary to develop new ECL emitters and co-reaction acceleration strategies to improve detection sensitivity and expand the application scope. Carbon nitride nanomaterials and 2D transition metal carbides, as newly emerging carbon-based nanomaterials, have been increasingly used for ECL bioassays due to their attractive optical and electrochemical properties as well as diversity. In this minireview, we summarized the latest advances in ECL bioassays using carbon nitride nanomaterials and 2D transition metal carbides in the past two years. Finally, we briefly discuss the future trends and challenges of carbon-based nanomaterials for ECL bioanalysis.     

Investigation of polymer-protected noble metal nanoparticles by transmission electron microscopy: control of particle morphology and shape

 Noble metal nanoparticles were prepared by the in situ reduction of the respective metal salt precursors in the presence of various protective polymers. Transmission electron microscopy (TEM) has been used to determine the particle shapes and morphologies. These are strongly influenced by the reduction methods and conditions chosen, but the choice of the protective polymer is equally important for controlling the particle morphologies and for the stabilization of the colloids. A whole spectrum of nanoparticle morphologies and shapes was obtained, ranging from nanoagglomerates which are nevertheless well-defined and well-stabilized to nanosized single crystals with triangular shape. Received: 2 February 1998 Accepted: 29 May 1998     

A general,enantioselective synthesis of 2-substituted thiomorpholines and thiomorpholine 1,1-dioxides

In the course of our drug discovery programs, we had need to access chiral, 2-substituted thiomorpholines and their oxidized congeners, thiomorpholine 1,1-dioxides. Here, we disclose a high-yielding, general protocol for the enantioselective synthesis of C2-functionalized thiomorpholines and thiomorpholine 1,1-dioxides.     

过渡金属(Mo,Fe,Co和Ni)基催化剂在电催化还原二氧化碳还原中应用

近年来,全球二氧化碳排放量逐年增加, 对人们赖以生存的生态环境已造成严重威胁, 因此将二氧化碳转化成高附加值的化学品和燃料受到前所未有的广泛关注. 与目前已开发的转化技术(如热催化和光催化等)相比, 电催化二氧化碳转化技术具有稳定的效率?可控的选择性?简单的反应单元和巨大的工业应用潜力, 是一种更为理想的转化技术之一. 从反应动力学来看, 目前的催化剂仍难以克服反应过程中高的能量屏障以及迟缓的反应速度. 另一方面, 电催化二氧化碳转化包含多个质子和电子的耦合过程, 反应过程包含多种路径, 反应产物往往是混合物. 在此背景下, 如何发展高催化效率和高选择性电催化剂成为目前研究的焦点. 在众多的电催化剂中, 贵金属及其合金展现出较高的电催化二氧化碳还原活性, 但储量小的缺点限制了其大规模的工业应用. 铜基材料可以把二氧化碳转化为附加值更高的产品. 然而, 铜基材料仍难以克服选择性差?失活严重和效率低等缺点. 作为一种更廉价的材料, 碳基催化剂具有价廉?比表面积大?导电性好?化学性质稳定以及优异的机械性能等优点在电催化二氧化碳还原中得到了广泛的研究. 然而, 单纯的碳催化剂对于二氧化碳分子活化以及吸附反应中间体能力较低, 导致了碳基材料催化电催化二氧化碳还原活性以及选择性较低. 因此, 开发出可实际应用的高效率和高选择性非贵金属电极材料是当前该技术研究中亟待解决的关键科学问题.过渡金属基化合物在能源转化中展现出巨大的应用潜力. 过渡金属价电子在d轨道, 而d轨道邻近费米能级, d轨道电子填充的变化使得d轨道中心与费米能级相对位置发生变化, 进而展现出多种催化活性. 电催化二氧化碳还原是一个多电子和质子耦合过程, 催化剂的本征活性由其表面电子结构决定. 在此背景下, 过渡金属基化合物价层电子轨道的多变性使其成为提高电催化二氧化碳还原效率和选择性的理想催化剂. 对于电催化二氧化碳还原, 不同中间体的标度关系是制约反应总效率的关键因素. N?rskov等研究发现, MoS2, MoSe2和Ni掺杂 MoS2催化剂上存在不同种类的活性位点. 不同的活性位点可以分别吸附反应中间体并使中间体的吸附过程相对独立, 从而有效打断中间体的标度关系. 2014,Salehi-Khojin等成功把MoS2应用在高效电催化二氧化碳还原中. 边缘Mo原子d带电子靠近费米能级的特性使其具有更高的电催化活性. 其它研究工作者通过引入掺杂物质, 进一步提高了MoS2的电催化二氧化碳还原性能. Fe位点在理论上虽然具有很高的电催化二氧化碳转化活性, 然而目前铁基催化剂的研究相对较少. Co基材料也可用于电催化二氧化碳转化.2016年, Xie等首次制备无机Co基材料用于电催化二氧化碳还原. 部分氧化的钴可以促进速控步骤反应进程, 进而降低整体反应的过电势. 基于此, 制备了超薄的Co3O4片层, 发现价电子轨道中心更靠近费米能级时, 电极材料展现出更高的催化活性. 进一步研究发现氧空穴的存在也可以减小速控步骤的能量屏障. 此外, Ni基材料也被证明具有高的催化二氧化碳转化活性. 目前这些研究工作对如何构建高性能电极材料在理论上给出了指导方向, 并且联系实验证明了方法的可行性. 受到这些工作的启发, 未来可将有巨大潜力的过渡金属基化合物化合物, 例如过渡金属氮化物?过渡金属磷化物?过渡金属碳化物和过渡金属硼化物等, 作为电催化剂研究其二氧化碳还原催化性能. 另外, 就目前的研究来看, 将二氧化碳有效地还原到特定的产物仍存在巨大的挑战. 如何优化过渡金属(Mo, Fe, Co和Ni)基催化剂价层d轨道结构, 促进反应中间体吸附过程, 将是解决催化活性和选择性这一科学问题的关键.     

Past,present, and future developments in enantioselective analysis using capillary electromigration techniques

Enantioseparation of chiral products has become increasingly important in a large diversity of academic and industrial applications. The separation of chiral compounds is inherently challenging and thus requires a suitable analytical technique that can achieve high resolution and sensitivity. In this context, CE has shown remarkable results so far. Chiral CE offers an orthogonal enantioselectivity and is typically considered less costly than chromatographic techniques, since only minute amounts of chiral selectors are needed. Several CE approaches have been developed for chiral analysis, including chiral EKC and chiral CEC. Enantioseparations by EKC benefit from the wide variety of possible pseudostationary phases that can be employed. Chiral CEC, on the other hand, combines chromatographic separation principles with the bulk fluid movement of CE, benefitting from reduced band broadening as compared to pressure-driven systems. Although UV detection is conventionally used for these approaches, MS can also be considered. CE-MS represents a promising alternative due to the increased sensitivity and selectivity, enabling the chiral analysis of complex samples. The potential contamination of the MS ion source in EKC-MS can be overcome using partial-filling and counter-migration techniques. However, chiral analysis using monolithic and open-tubular CEC-MS awaits additional method validation and a dedicated commercial interface. Further efforts in chiral CE are expected toward the improvement of existing techniques, the development of novel pseudostationary phases, and establishing the use of chiral ionic liquids, molecular imprinted polymers, and metal-organic frameworks. These developments will certainly foster the adoption of CE(-MS) as a well-established technique in routine chiral analysis.     

Dinickel catalyzed carbonylation reactions using metal carbonyl reagents as CO sources

Dinickel complexes promote stoichiometric Pauson–Khand reactions of enynes and CO (g). However, catalytic turnover is precluded by the strong binding of CO to the Ni₂ active site. This article describes the use of M(CO)_x reagents as stoichiometric CO precursors in Ni₂-catalyzed carbonylation reactions. As part of these studies, well-defined heterotrinuclear Ni₂Fe, Ni₂Co, and Ni₂Mn carbonyl clusters are synthesized using the [NDI]Ni₂ platform as a template (NDI = naphthyridine–diimine).     

Theoretical and experimental insights into the electrochemical heavy metal ion sensing with nonconductive nanomaterials

Nonconductive nanomaterial is a type of modifiers widely used in electrochemical heavy metal ion detection. Despite a large number of studies devoted to the electrochemical stripping behaviors of modifiers, a clear picture regarding the structure–performance relationship is still lacking. Recently, benefiting from the development of fine-structure characterization techniques and density functional theory calculations, the atomic details on how the surface interaction between heavy metal ions and the modifiers leads to its high sensitivity have attracted much attention. This short review discusses the development and challenge of nanomaterial-based stripping behaviors in the determination of heavy metal ions and highlights the structure–performance relationship at the atomic level.     

Neomacrophorin and premacrophorin congeners from Trichoderma sp. 1212-03

Six novel neomacrophorin and four novel premacrophorin congeners were isolated from the fungus Trichoderma sp. 1212-03. Their planar structures and relative configurations were determined by conventional NMR and mass spectrometry techniques. The electronic circular dichroism (ECD) spectral comparisons with known neomacrophorins were effective for elucidating the structures of congeners carrying 2,3-epoxybenzoquinone (1, 2) and 2,3-epoxybenzosemiquinol substructures (3, 4, 5, 7, 8, and 9). The configuration of the 6-hydroxy-2-cyclohexene-1,4-dione moiety in 5′-deoxyneomacrophorin IV (6) was elucidated by NMR spectral comparison with those of known purpurogemutantidin (16) and mancrophorin F (17). This also resulted in the configurational revision of 16. The relative configuration of the 5,6-epoxy-2-cyclohexen-1,4-diol in premacrophorintriol-II (10) was determined by ¹³C chemical shift analysis using density functional theory calculations at the ωB97X-D/6-31G* level of theory. Compounds 1 and 6 exhibited potent cytotoxicity against human Caucasian colon adenocarcinoma cell line COLO 201.     

Novel bio compactable silver nanowires and nanocubes: An effective treatment against carbapenem and vancomycin resistant strains isolated from cancer patients

Blood stream infections in the cancer patients are a critical problem which leads to considerable rate of mortality and morbidity. In view of this herein, we account the response of Poly Vinyl Pyrrolidone (PVP) coated silver nanowires (Ag-NWs) and silver nano cubes (Ag-NCs) towards carbapenem (Escherichia coli) and vancomycin (Staphylococcus aureus) resistant strains as well as to human epithelial cells. The prepared PVP capped silver nanomaterials were in the range of 80 nm (Ag-NC) and 25 nm (Ag-NW) as observed from Transmission Electron Microscopy (TEM). Though the selected strains were resistant to carbapenem and vancomycin, PVP capped Ag-NWs and Ag-NCs could inhibit the growth of these strains. These nanomaterials could break the cell wall and damage the genetic material of these strains as observed by death rate assay and alkaline comet assay. Furthermore, we have shown that toxicity of Ag-NWs and Ag-NCs precisely follows the dose retort pattern. Even though the resistant strains were susceptible to a concentration of 10 µg ml^?1 of silver nanomaterials the epithelial cells were not affected by the same concentration. It is also confirmed with live dead staining assay and observed that metabolic activities of epithelial cells were not affected by a concentration of 10 µg ml^?1. Overall, this work suggests that these nanomaterials can be utilized to treat the multiple drug resistant strains from cancer patients.     

Synthesis of a new chiral organocatalyst derived from (S)-proline containing a 1,2,4-triazolyl moiety and its application in the asymmetric aldol reaction. Importance of one molecule of water generated in situ

A simple and efficient preparation of a novel chiral derivative of (S)-proline containing a 1,2,4-triazolyl moiety is described. The high-yielding synthetic protocol includes the use of microwave irradiation to afford new chiral pyrrolidine derivatives in high yield. Our triazolyl-containing heterocycle was evaluated as organocatalyst (10 mol% load, under neat reaction conditions) in the enantioselective aldol reaction between four different types of ketones and a variety of aryl aldehydes. Good results in terms of enantioselectivity and chemical yield were observed under solvent-free reaction conditions and in the absence of any additive. Evidence is provided for the involvement of the water molecule generated upon enamine formation in the transition state of the aldol reaction.