Mixed lithium amide-lithium halide compounds: unusual halide-deficient amido metal anionic crowns

Molecular salt cellars: The addition of substoichiometric quantities of lithium halides to the lithium hexamethyldisilazide was studied. Surprisingly, a novel class of mixed amido-halide macrocyclic complexes, namely metal anionic crowns (MACs) was revealed (see picture: Li?pink, N?yellow, Cl?green, Si?orange, C?black).     

高能量超声辅助制备负载型贵金属纳米催化材料

介绍了一种利用高能量超声作用制备负载型纳米催化材料的方法.通过高能量超声作用下发生的还原反应,使原位生成的贵金属或双金属纳米颗粒负载于各种载体的表面,制备了一系列石墨烯基-、碳纳米管基-、金属氧化物(二氧化铈、α-三氧化二铁、二氧化钛)基-负载型贵金属纳米催化材料,并利用光电子能谱、透射电子显微镜、元素分析、电子衍射等方法表征了材料的结构和形貌.结果表明:贵金属纳米颗粒在载体的表面均匀地分布,颗粒的尺寸较小,分布较窄;颗粒的尺寸可以通过金属在载体中的负载量、金属前驱体的浓度和超声强度容易地进行调控.这种方法为负载型贵金属纳米催化剂的制备提供了一种有效的途径.     

Bacterial synthesized metal and metal salt nanoparticles in biomedical applications: An up and coming approach

In the present scenario, metal nanoparticles have elicited a great deal of interest in biomedical applications because of their unique properties and antimicrobial potentials. Over the past few years, the green nanotechnology has materialized as a momentous approach for the synthesis and fabrication of noble metal salt and metal nanoparticles. The green route synthesis exploits diverse reducing and stabilizing agents from bacterial resources for the successful synthesis of metal nanoparticles. This review mainly focuses on the biosynthesis of the most commonly studied metal and metal salt nanoparticles such as gold, silver, platinum, palladium, copper, cadmium, titanium oxide, zinc oxide, zinc sulphate, cadmium sulphide and many more. These noble nanoparticles can be exploited in pharmaceutical industry as antimicrobial and anti-biofilm agents, targeted delivery of anticancer drugs, biosensors, etc.     

Delving noble metal and semiconductor nanomaterials into enantioselective analysis

With growing interests paid to the enantioselective analysis of chiral molecules, roles played by noble metal and semiconductor nanomaterials surface gradually. Given the unique physicochemical properties of noble metal and semiconductor nanomaterials, the enantioselective analyses are classified into three categories: ?uorescence-based, colorimetry-based, and circular dichroism-based ones. In this paper, we review the existing progresses on enantioselective analysis, thanks to noble metal and semiconductor nanomaterials. Finally, the prospect of enantioselective analysis based on noble metal and semiconductor are discussed.     

Ionic‐Liquid‐Grafted Rigid Poly(p‐Phenylene) Microspheres: Efficient Heterogeneous Media for Metal Scavenging and Catalysis

Novel guanidinium ionic liquid‐grafted rigid poly(p‐phenylene) (PPPIL) microspheres have been developed for metal scavenging and catalysis. The noble‐metal nanoparticles supported on the microspheres surface can be used as efficient heterogeneous catalysts. The combination of nanoparticles and ionic liquid fragments on the microsphere surfaces enhance the activity and durability of the catalyst. The PPPIL ? Pd⁰ catalyst has been tested in the Suzuki cross‐coupling reaction, and exhibits much higher catalytic activity than Pd catalysts supported on porous polymer matrices. The PPPIL ? Pd⁰ catalyst can be recycled at least for nine runs without any significant loss of activity. The present approach may, therefore, have potential applications in transition‐metal‐nanocatalyzed reactions.     

High photocurrent in silicon photoanodes catalyzed by iron oxide thin films for water oxidation

Silicon splits: The application of silicon to water oxidation is limited due to unfavorable interface properties. However, these can be circumvented by using a high-performance silicon photoanode with a catalytically active iron oxide thin film (see picture). This approach results in photocurrents as high as 17?mA?cm(-2) under 1?sun and zero overpotential conditions.     

A series of isoreticular, highly stable, porous zirconium oxide based metal-organic frameworks

Brolly good MOFs: A new series of hydrophobic isoreticular porous Zr oxide dicarboxylate MOFs have been prepared (see picture, Zr?blue polyhedra, O?red, C?black). They have a one-dimensional pore system, a rare combination of Lewis acidity and hydrophobic character, and a higher hydrothermal and mechanical stability than their UiO MOF polymorph counterparts.     

Use of carbonaceous polysaccharide microspheres as templates for fabricating metal oxide hollow spheres

A general method for the synthesis of metal oxide hollow spheres has been developed by using carbonaceous polysaccharide microspheres prepared from saccharide solution as templates. Hollow spheres of a series of metal oxides (SnO2, Al2O3, Ga2O3, CoO, NiO, Mn3O4, Cr2O3, La2O3, Y2O3, Lu2O3, CeO2, TiO2, and ZrO2) have been prepared in this way. The method involves the initial absorption of metal ions from solution into the functional surface layer of carbonaceous saccharide microspheres; these are then densified and cross-linked in a subsequent calcination and oxidation procedure to form metal oxide hollow spheres. Metal salts are used as starting materials, which widens the accessible field of metal oxide hollow spheres. The carbonaceous colloids used as templates have integral and uniform surface functional layers, which makes surface modification unnecessary and ensures homogeneity of the shell. Macroporous films or cheese-like nanostructures of oxides can also be prepared by slightly modified procedures. XRD, TEM, HRTEM, and SAED have been used to characterize the structures. In a preliminary study on the gas sensitivity of SnO2 hollow spheres, considerably reduced "recovery times" were noted, exemplifying the distinct properties imparted by the hollow structure. These hollow or porous nanostructures have the potential for diverse applications, such as in gas sensitivity or catalysis, or as advanced ceramic materials.     

Challenges in the understanding oxygen reduction electrocatalysis on transition metal oxides

Transition metal oxides are attractive noble metal-free catalysts of the oxygen reduction for application at the cathode of alkaline membrane fuel cells or metal-air batteries. However, despite of a rapidly increasing number of publications devoted to the oxygen electrocatalysis on transition metal oxides, a clear picture regarding the relations between their structure and composition on the one hand and electrocatalytic activity on the other hand is lacking. This short review discusses challenges facing researchers seeking to understand electrocatalysis of the oxygen reduction reaction on transition metal oxides.     

Selectively deposited noble metal nanoparticles on Fe3O4/graphene composites: stable, recyclable, and magnetically separable catalysts

A simple, efficient, and general approach was developed to selectively deposit noble metal (Pt, Pd, or PtPd) nanoparticles 3-5?nm in size on magnetite/graphene composites. The biomolecule L-lysine with two kinds of functional groups (NH(2) and COOH) played the key role of connecter between noble metals and Fe(3)O(4)/graphene composites. These composites were characterized by TEM, XRD, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the noble metals are mostly dispersed on the magnetite surfaces of the composites. The as-obtained composites are ideal recyclable catalysts for liquid-phase reactions owing to their stability and efficient magnetic separation. Among these catalysts, the PtPd-based composites exhibited the highest activity and resistance to poisoning during the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH(4). Such hybrid catalysts obtained by this simple, efficient method are expected to find use in industrial applications, where separation and recycling are critically required to reduce cost and waste production.     

Are Particulate Noble‐Metal Catalysts Metals,Metal Oxides,or Something In‐Between?

A good model? Noble‐metal particulate catalysts often require small amounts of oxygen to obtain optimal activity. However, the structure and stoichiometry of the oxidized metal clusters involved remains obscure, even almost two hundred years after their discovery. A heteropolypalladate salt (see picture; Pd yellow, O red) now offers a view of how oxygen might be incorporated into small noble‐metal clusters.

     

Are matrix isolated species really “isolated”? Infrared spectroscopic and theoretical studies of noble gas-transition metal oxide complexes

In this review, we summarize our recent results on matrix isolation infrared spectroscopic studies and theoretical investigations of noble gas-transition metal oxide complexes. The results show that some transition metal oxide species trapped in solid noble gas matrices are chemically coordinated by one or multiple noble gas atoms forming noble gas complexes and, hence, cannot be regarded as isolated species. Noble gas coordination alters the vibrational frequencies as well as the geometric and electronic structures of transition metal oxide species trapped in solid noble gas matrixes. The interactions between noble gas atoms and transition metal oxides involve ion-induced dipole interactions as well as chemical bonding interactions. Periodic trends in the bonding in these noble gas-transition metal complexes are discussed.     

Sustainable Production of Chemicals via Hydrotreating of CO2 and Biomass Derived Molecules Using Heterogeneous Noble Metal Oxide Catalysts

The noble metals are widely used in heterogeneous catalysis and automobile industry. The limited natural sources and high cost of noble metals dictates improving the efficiency of modern industry. This review considers the applications of noble metal oxide as potential solutions to the sustainability issues, including biomass conversion, CO₂ capture and conversion, green fuel production, etc. Noble metal oxides with their different compositions (monometallic and bimetallic) and structures exhibit a wide range of properties in heterogeneous catalysis. Although platinum metals in an oxidized form may not be the most common choice in hydroprocesses; recently, there have been studies indicating that they were highly active and selective catalysts in hydrogenation and hydrogenolysis. This review outlines the most established noble metal oxide catalysts used in hydrogenation catalysis and shed the light on the relation of noble metal oxide species to catalyst selectivity based on state-of-the-art techniques. Finally, the perspectives on the application of noble metal oxide catalysts to produce value-added chemicals are discussed.     

Ultraviolet-ultraviolet hole burning spectroscopy in a quadrupole ion trap: dibenzo[18]crown-6 complexes with alkali metal cations

Conformation selective: A new technique of ultraviolet-ultraviolet hole burning spectroscopy that can be applied to ions stored in a quadrupole ion trap (QIT) is developed and used to obtain the conformation-selective electronic spectra of dibenzo[18]crown-6 complexes with alkali metal cations (M(+), see picture; F(+) = fragment).     

Surface-immobilized single-site iridium complexes for electrocatalytic water splitting

Water into oxygen: Mono-iridium complexes (see picture; L=PO(3) H(2) or COOH) were immobilized on an indium tin oxide (ITO) surface to form a molecular electrocatalytic water oxidation assembly that mimics photosystem?II in producing molecular oxygen with high turnover numbers (TONs). The catalyst shows TONs for O(2) higher than 210?000 and turnover frequencies higher than 6.7?s(-1) during electrochemical catalytic water splitting.     

Interfacial synthesis of hollow TiO2 microspheres in ionic liquids

An interfacial sol-gel synthesis of inorganic hollow microspheres in room-temperature ionic liquids is newly developed. When metal alkoxides such as titanium tetrabutoxide, Ti(OBu)4, are dissolved in anhydrous toluene and injected into 1-buthyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6) under vigorous stirring, hollow titania microspheres are formed. The present technique is widely applicable to the reactive metal alkoxides such as Zr(OBu)4, Hf(OBu)4, Nb(OBu)4, and InSn3(OR)x, giving a general route to the metal oxide microspheres. When gold nanoparicles and carboxylate-containing dyes such as fluorescein isothiocyanate (FITC) are dissolved in the toluene microdroplets, they are stably immobilized in the microsphere shells. Calcination of the titania gel microspheres gives anatase TiO2 microspheres. The present method provides the first example of inorganic hollow microspheres formed in ionic liquids, and the ability to modify microspheres with metal nanoparticles or functional organic molecules would be widely applied to the design of smart organic/inorganic hybrid materials.     

Design and synthesis of porous non-noble metal oxides for catalytic removal of VOCs

The design and synthesis of highly active non-noble metal oxide catalysts, such as transition- and rare-earth-metal oxides, have attracted significant attention because of their high efficiency and low cost and the resultant potential applications for the degradation of volatile organic compounds(VOCs). The structure-activity relationships have been well-studied and used to facilitate design of the structure and composition of highly active catalysts. Recently, non-noble metal oxides with porous structures have been used as catalysts for deep oxidation of VOCs, such as aromatic hydrocarbons, aliphatic compounds, aldehydes, and alcohols, with comparable activities to their noble metal counterparts. This review summarizes the growing literature regarding the use of porous metal oxides for the catalytic removal of VOCs, with emphasis on design of the composition and structure and typical synthetic technologies.     

Ligand‐Assisted Co‐Assembly Approach toward Mesoporous Hybrid Catalysts of Transition‐Metal Oxides and Noble Metals: Photochemical Water Splitting

A bottom‐up synthetic approach was developed for the preparation of mesoporous transition‐metal‐oxide/noble‐metal hybrid catalysts through ligand‐assisted co‐assembly of amphiphilic block‐copolymer micelles and polymer‐tethered noble‐metal nanoparticles (NPs). The synthetic approach offers a general and straightforward method to precisely tune the sizes and loadings of noble‐metal NPs in metal oxides. This system thus provides a solid platform to clearly understand the role of noble‐metal NPs in photochemical water splitting. The presence of trace amounts of metal NPs (≈0.1 wt %) can enhance the photocatalytic activity for water splitting up to a factor of four. The findings can conceivably be applied to other semiconductors/noble‐metal catalysts, which may stand out as a new methodology to build highly efficient solar energy conversion systems.     

Catalytic activity of noble metal ions for the degradation of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine in the presence of oxidizing agent, and its application to the determination of ultra trace amounts of ruthenium

Trace quantities of ruthenium(II) ion catalyze the oxidation of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (TPPS) by potassium bromate. This reaction can be used for the determination of ultra trace amounts of ruthenium using the water-soluble porphyrin with its high molar absorbance. The scope of the reaction was investigated in terms of the reaction conditions and selectivity with respect to other noble metal ions. The effect of pH, concentration of bromate, the reaction time, and the type of metalloporphyrin were studied so as to optimize the method for the determination of trace amounts of Ru(III). The apparent reaction rate constant for the disappearance of TPPS (or metal-TPPS) is proportional to the root of the concentration of bromate, and directly related to that of Ru(III). The limit of detection is 0.11?nM (equal to 10.7?pg?mL^?1) at pH?4.25, where the turnover number is 201. The reproducibility for five measurements at 2.7?nM of Ru(III) was 2.9%.

Seed-mediated growth method for high-quality noble metal nanocrystals

This review highlights work from the authors’ laboratory on the recent development of seed-mediated growth method for noble metal nanocrystals. The seed-mediated growth method has become one of the most efficient and versatile methods for synthe-sizing high-quality noble metal nanocrystals. The seed-mediated growth method can separate the nucleation and growth stages of metal nanocrystals, and thus provide better control over the size, size distribution, and crystallographic evolution of metal nanocrystals. Because of its high controllability, the seed-mediated growth method is especially promising in providing mechanistic insights into the growth mechanisms of noble metal nanocrystals. In this review, the thermodynamic and kinetic parameters for the nucleation and growth of noble metal nanocrystals are systematically summarized. Mechanistic understanding of these parameters is provided. These studies provide useful guidelines for the rational design and synthesis of novel noble metal nanocrystals with high quality.