石墨烯负载的金属氧化物纳米颗粒的可控制备及催化性能

采用直接浸渍法、过氧化氢均相氧化沉积法和氨水催化水解法制备了石墨烯负载的铁、钴、镍金属氧化物纳米颗粒.研究了三种沉积方法对颗粒尺寸分布的影响;采用透射电子显微镜、傅里叶变换红外光谱、X射线衍射和X射线光电子能谱表征了催化剂的形貌与结构.用过氧化氢均相氧化沉淀法可制得粒径分布最均匀的纳米颗粒.过氧化氢的氧化作用可使石墨烯表面的氧化基团含量最大化,为纳米颗粒提供了足够的吸附与成核点.氨水加速了金属离子的水解与成核,导致纳米颗粒的粒径增大与不均.以苯甲醇氧化为探针反应考察了催化剂的性能.催化剂的活性按以下顺序逐渐下降:过氧化氢辅助沉积法>直接浸渍法>氨水催化水解法,与纳米颗粒尺寸增长趋势一致.纳米催化剂颗粒尺寸与其活性的良好关联性显示,发展石墨烯负载尺寸可控的纳米催化剂的方法具有重要意义.     

Chiral-at-metal complexes and their catalytic applications in organic synthesis

This tutorial review provides an introduction to the synthesis and characterization of chiral-at-metal complexes and their catalytic application in organic transformations. The synthetic access to these architectures either via chiral resolution or by employment of chiral ligands is described, characterization techniques for the complexes are referenced and the application of the R/S nomenclature is explained. Racemization and epimerization processes are often observed for the title compounds; the article gives mechanistic insights to these processes and describes how to recognize and document them. Finally, key catalytic applications in organic synthesis are presented and how the molecular architectures of the chiral-at-metal complexes lead to stereodifferentiation and, thus to enantiomeric excesses in the products.     

Copper oxide nanostructures: Controlled synthesis and their catalytic performance

Oval-plate-like, sphere-like, bundle-like and plate-like copper oxide (CuO) nanostructures were prepared by hydrothermal method using Cu(CH₃COO)₂·H₂O and NaOH as the reagents in the absence of any surfactants or templates. The morphology and structure of CuO nanostructures could be easily tailored by adjusting the amount of NaOH. The catalytic activity of the as-prepared CuO nanostructures was demonstrated by catalytic oxidation of methylene blue (MB) in presence of hydrogen peroxide (H₂O₂). The oval-plate-like CuO exhibited better catalytic activity and which was mainly attributed to the larger specific surface area.     

Room-temperature synthesis of pompon-like ZnO hierarchical structures and their enhanced photocatalytic properties

In this paper, an efficient and simple route combined with a subsequent calcining process to synthesize pompon-like ZnO microstructures at room temperature (25 °C) has been developed. The samples were intensively investigated by SEM, TEM, HRTEM, and XRD. The results indicate that the well-crystallized pompon-like ZnO is assembled by interlaced nanoplates with uniform thickness of about 50 nm. The photocatalytic trials confirm that the pompon-like ZnO exhibits excellent degradation efficiency under UV light. Moreover, the as-prepared ZnO samples show superior durability and stability after six photodegradation cycling runs. Finally, a mechanism was proposed to elucidate the photodegradation reaction of the pompon-like ZnO.     

Direct synthesis of metal oxide incorporated mesoporous SBA-15, and their applications in non-enzymatic sensing of glucose

One-step direct synthetic route is reported for the preparation of M-SBA-15 materials (M=Cu, Ni, Co, Fe, and Mn) with nSi/nM ratios ranging from 100 to 10 under mild acidic condition than conventionally employed for the synthesis of Si-SBA-15. Materials were characterized by a complementary combination of X-ray diffraction, nitrogen sorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, and UV-visible spectroscopy. Experimental evidences show that metal oxides are incorporated in the pore wall of SBA-15 matrices. A non-enzymatic electrochemical sensor device was fabricated for glucose detection based on M-SBA-15 materials. Cyclic voltammetry and linear sweep voltammetry were used to evaluate the catalytic activity of the M-SBA-15 modified electrode toward glucose. It was found that the Cu-SBA-15 (Si/Cu=20) modified electrode showed enhanced electrocatalytic activity toward the oxidation of glucose in alkaline solution compared to that of the conventional CuO and other M-SBA-15 materials investigated in this study. Under the optimal detection conditions, the Cu-SBA-15 (Si/Cu=20) exhibited linear behavior in the concentration range from 10 μM to 20 mM for the quantification of glucose with a limit of detection of 10 μM. Moreover, the Cu-SBA-15 modified electrode was also relatively insensitive to commonly interfering species such as ascorbic acid, uric acid, and dopamine.     

Time-varied synthesis of hierarchical ZnO microspheres and their applications in dye-sensitized solar cells

Journal of Solid State Electrochemistry - Hierarchically nano-structured ZnO microspheres have been synthesized solvothermally at variable reaction times (6, 12, 36, and 48 h) by using...     

Green synthesis of Copper oxide nanoparticles decorated with graphene oxide for anticancer activity and catalytic applications

Nanotechnology is an embryonic field that grips countless impacts on the drug delivery system. Nanoparticles as haulers increase the capability of target-specific drug delivery to many folds hence are used in the treatment of dreadful diseases such as cancer, diabetes, etc. This boom has aimed at, to synthesize Copper oxide nanoparticles (CuO-NPs) using Acalypha Indica leaf extract and then incorporated with graphene oxide (GO) to form GO-CuO nanocomposites. Secondly, to sightsee the photocatalytic activity of CuO-NPs and GO-CuO nanocomposites towards the decolorization of methylene blue-dye and to test its activity against HCT-116 Human colon cancer cell lines. Synthesized nanocomposites were characterized using FTIR, UV–vis, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray Photoelectron Spectroscopy (XPS) and transmission electron microscopy (TEM) analysis. The photocatalytic studies revealed that synthesized nanocomposites have the efficiency to degrade methylene blue dye by 83.20% and cytotoxic activity was found to be 70% against HCT-116 Human colon cancer cell lines at 100 μg/ml. GO-CuO nanocomposites have appreciable activity towards cancer cell lines and photocatalytic activity when compared to nanoparticles as such.     

Controlled fabrication of flower-like nickel oxide hierarchical structures and their application in water treatment

Flower-like NiO hierarchical structures with 2-5 μm diameter assembled from nanosheet building blocks have been successfully fabricated via a wet-chemical method combined with thermodecomposition technology. The template-free method is facile and effective in preparing flower-like NiO superstructures in high yield. The intermediate product and final hierarchical structures are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform IR (FTIR), and thermogravimetric analysis (TGA). The effects of growth temperature and reaction time on the morphologies of the as-prepared structures were investigated by SEM characterization and a possible mechanism for the formation of flower-like NiO is proposed. Based on the nitrogen adsorption and desorption measurements, the BET surface area of the as-obtained sample is 55.7 m2/g and the pore-size distribution plot indicates a bimodal mesopore distribution, with pore sizes of ca. 2.6 nm and 7.4 nm, respectively. In comparison with sphere-like and rod-like structures, the flower-like NiO hierarchical structures show an excellent ability to rapidly remove various pollutants when used as adsorbent and photocatalyst in waste-water treatment, which may be attributed to its unique hierarchical and porous surface structures.     

MTO Schiff-base complexes: synthesis, structures and catalytic applications in olefin epoxidation

Several Schiff-base ligands readily form complexes with methyltrioxorhenium(VII) (MTO) by undergoing a hydrogen transfer from a ligand-bound OH group to a ligand N atom. The resulting complexes are stable at room temperature and can be handled and stored in air without problems. Due to the steric demands of the ligands they display distorted trigonal-bipyramidal structures in the solid state, as shown by X-ray crystallography, with the O(-) moiety binding to the Lewis acidic Re atom and the Re-bound methyl group being located either in cis or trans position to the Schiff base. In solution, however, the steric differences seem not to be maintained, as can be deduced from (17)O NMR spectroscopy. Furthermore, the Schiff-base ligands exchange with donor ligands. Nevertheless, the catalytic behaviour is influenced significantly by the Schiff bases coordinated to the MTO moiety, which lead either to high selectivities and good activities or to catalyst decomposition. A large excess of ligand, in contrast to the observations with aromatic N-donor ligands, is detrimental to the catalytic performance as it leads to catalyst decomposition.     

吡咯基金属络合物的制备及其在有机合成中的应用

本文综述了近年来吡咯基金属络合物的研究进展, 详细讨论了σ~N-、σ~C-、π-型吡咯基金属络合物的制备方法, 以及各类吡咯基金属络合物在有机合成中的应用。     

Controlled synthesis of multi-shelled transition metal oxide hollow structures through one-pot solution route

As one type of promising candidates for environmental and energy-related systems,multi-shelled transition metal oxide hollow structures(MS-TMOHSs) have drawn great scientific and technical interest in the past few years.This article highlights recent advances in one-pot solution synthesis of MSTMOHSs. We begin it with an overview of synthetic strategies that have been exploited to achieve these peculiar structures.We then focus on one-pot solution approaches in the following four sections:i) soft templates directed growth;ii) Ostwald ripening;iii) controlled etching;and iv) gas bubble assisted growth.After giving a brief discussion on the unique properties and applications of these multi-shelled hollow structures,we conclude this review with the general challenges and the potential future directions of this exciting area of research.     

Enantioselective syntheses of trans-3,4-difluoropyrrolidines and investigation of their applications in catalytic asymmetric synthesis

[reaction: see text] Asymmetric syntheses of enantiopure trans-3,4-difluoropyrrolidines have been prepared by the introduction of fluorine at both centers in a single operation; asymmetric epoxidations and additions to benzaldehyde were conducted using catalysts whose chirality depends on organofluorine asymmetry.     

金属-氧化物超晶格纳米结构催化剂(英文)

正Supported metal catalysts such as Pt-Sn/Al2O3, Cu/ZnO/ Al2O3, and Pt-Rh/CeO2-Al2O3 have been industrially applied for petrochemical and environmental related reactions. The com-mon feature of these supported catalysts is that 1 to 10 nm metal nanoparticles are highly dispersed on high surface area porous oxides. The microstructure of the catalyst on the na-noscale in terms of size, morphology, and interface strongly     

Biomolecules as promising ligands in the synthesis of metal nanoclusters: Sensing,bioimaging and catalytic applications

The use of metal nanoclusters as sensing probes has recently attracted considerable interest from researchers. In particular, metallic nanoclusters (e.g., Au, Ag, Cu, Pt) have been noticed a wide range of applications in the field of fluorescence sensing and bioimaging. The stabilization of metal nanoclusters with organic molecules, proteins, and amino acids enhances their optical properties and analytical applications. In this review, synthetic routes for the fabrication of metal nanoclusters are summarized. This review also describes the metal nanoclusters properties including aggregation-induced emission, optical absorption, non-linear optical, and chiral properties. We discussed the analytical applications of metal nanoclusters for sensing of wide variety of analytes including drugs, biomolecules, biomarkers. Further, the catalytic applications of metal nanoclusters are also briefly summarized. Finally, we summarize the challenges and future perspectives of metal nanoclusters in analytical chemistry.     

Gelatin-immobilized metal complexes: synthesis and applications

Formation of p-, d- and f-metal complex gelatin-immobilized matrix systems using reactions of electrophilic, nucleophilic substitution and template synthesis, and employment of these materials in photographic processes, in spectroscopy and for absorption of metal ions, have been summarized and discussed. The review covers the period 1990–2005.     

Nanocast mesoporous mixed metal oxides for catalytic applications

Since the initial discovery of ordered mesoporous silica in early 1990s, considerable innovations were achieved regarding their synthesis, characterization and applications. One of the best outcomes of these intense research efforts is the development of a solid templating method called “nanocasting”, which is based on using mesoporous silica (or carbon) as a rigid template. This solid-to-solid replication method opened the pathway for synthesizing high surface area non-silica mesostructured materials that are challenging to obtain through conventional self-assembly processes which are based on amphiphilic soft structure-directing agents. In particular, the replicated metal oxide mesostructures obtained by this method were found to be highly versatile for a wide range of applications, especially in catalysis, owing to their large specific surface area. Furthermore, the nanocasting method is particularly suited for the synthesis of mixed metal compositions, favored by the possible confinement of mixed precursors in the nanopores of the template. In this account, we discuss some of the recent developments regarding the synthesis of nanocast mixed metal oxides and their perspectives of catalytic applications. It is here the choice of the authors to place emphasis on a few representative examples of compositions (e.g., non-noble metal-based catalysts, perovskites) and catalytic reactions (e.g., hydrogen production, gas-phase oxidation).     

Stereospecific synthesis and catalytic activity of L-histidylidene metal complexes

We report on the synthesis, metal coordination, and catalytic impact of histidylidene, a histidine-derived N-heterocyclic carbene (NHC) ligand. The histidinium salt 3, comprising methyl substituents at both heterocyclic nitrogens and protected at the C- and N-terminus of the amino acid, was rhodated and iridated by a transmetallation protocol using Ag(2)O. Ambient temperature and short reaction times were pivotal for full retention of configuration at the α-carbon. The stereospecificity of the reaction was conveniently probed by (31)P NMR spectroscopy after transmetallation with rhodium(I) and coordination of enantiopure (S)-Ph-binepine. The histidylidene rhodium complexes are highly efficient catalysts for the mild hydrosilylation of ketones. For the cationic complexes [Rh(cod)(histidylidene)(phosphine)](+), lowering the temperature shifted the rate-limiting step of the catalytic reaction to an earlier stage that is not enantioselective. Hence the asymmetric induction-which is governed by the chiral phosphine-did not improve at low temperature.     

In2O3-based multicomponent metal oxide films and their prospects for thermoelectric applications

Thermoelectric properties of In₂O₃–SnO₂-based multi-component metal oxide films formed by spray pyrolysis method are studied. It is shown that the introduction of additional components such as gallium and zinc can control the parameters of the deposited layers. At that, the doping with gallium is more effective for optimization of the efficiency of the thermoelectric conversion. The explanation of the observed changes in the electro-physical and thermoelectric properties of the films at the composition change is given. It is found that the main changes in the properties of multicomponent metal oxide films take place at concentrations of dopants which correspond to their limit solubility in the dominant oxide.     

Tantallaaziridines: from synthesis to catalytic applications

Tantallaaziridines are a class of organometallic compounds containing three-membered rings that include a tantalum, carbon and nitrogen atom. Closely related complexes containing the related iminoacyl ligand can be used as starting materials for tantallaaziridine synthesis. Tantallaaziridines can also be synthesized by reduction of imines or β-hydrogen abstraction of amides to give stable, isolable complexes. Tantallaaziridines possess a reactive Ta-C bond that can undergo stoichiometric transformations with unsaturated organic molecules to give new organometallic products. Upon quenching of such reactions with aqueous workup, selectively substituted small molecule amines can be prepared. Tantallaaziridines have also been proposed as catalytic intermediates in the direct α-alkylation of amines, hydroaminoalkylation, by exploiting the β-hydrogen abstraction route to regenerate the catalytically active species. Recent progress and remaining challenges in the field will be discussed.     

Aromaticity in transition metal oxide structures.

The concept of aromaticity is useful for understanding the properties of some polyoxometalates containing transition metals such as vanadium, molybdenum, and tungsten having structures based on metal macropolygons and macropolyhedra with M-O-M edges. Thus, the aromatic macrocuboctahedral Keggin ions readily undergo one-electron reductions to highly colored mixed-valence "blues" (e.g., molybdenum blue), whereas the macroicosahedral Silverton ions, M(IV)Mo12O42(8-) (M(IV) = Ce, Th, U), which, like cyclohexane, do not have vertex valence orbitals available for delocalization, do not undergo analogous reduction reactions. A macrohexagon of d1 vanadium(IV) atoms as V-O-V units has been imbedded into an electronically inactive borate matrix in the ion [V6B20O50H8](8-). The small beta unit for the V-O-V interactions in this V6 macrohexagon leads to an unprecedented example of high spin aromaticity with a paramagnetism corresponding to four unpaired electrons per V6 unit in contrast to benzene, which is diamagnetic and hence exhibits low spin aromaticity. The M-O-M interactions in these aromatic metal oxides are closely related to the Cu-O-Cu interactions in the high critical temperature superconducting copper oxides which are essential to the electron transport in these systems.