Preparation of Inorganic Materials Using Ionic Liquids

Conventional synthesis of inorganic materials relies heavily on water and organic solvents. Alternatively, the synthesis of inorganic materials using, or in the presence of, ionic liquids represents a burgeoning direction in materials chemistry. Use of ionic liquids in solvent extraction and organic catalysis has been extensively studied, but their use in inorganic synthesis has just begun. Ionic liquids are a family of non‐conventional molten salts that can act as templates and precursors to inorganic materials, as well as solvents. They offer many advantages, such as negligible vapor pressures, wide liquidus ranges, good thermal stability, tunable solubility for both organic and inorganic molecules, and much synthetic flexibility. In this Review, the use of ionic liquids in the preparation of several categories of inorganic and hybrid materials (i.e., metal structures, non‐metal elements, silicas, organosilicas, metal oxides, metal chalcogenides, metal salts, open‐framework structures, ionic liquid‐functionalized materials, and supported ionic liquids) is summarized. The status quo of the research field is assessed, and some future perspectives are furnished.     

Nano-metal oxide: potential catalyst on thermal decomposition of ammonium perchlorate

In this review, an attempt to collect the summarised data of literature on catalytic effect of nano-oxides, such as mono oxides, mixed oxide, binary and ternary ferrites and rare earth metal oxides on the thermal decomposition of ammonium perchlorate (AP) is made. Influence of size effect of oxides on thermal decomposition of AP and comparison of bulk and nanosized oxides is also discussed here. Several experimental results revealed that due to small size and large surface area nanosized metal oxides are more potential catalysts on thermal decomposition of AP compared to their bulk size oxides.     

Thermal destruction of polymer-salt compositions containingd-metals in the form of oxygen-bearing anions

The behavior of polymer-salt compositions consisting of water-soluble nonionogenic polymers and salts containingd-metal-oxygen anions was studied in the range 20-700°C by thermal analysis, conductometry, optical microscopy, x-ray diffraction, and dilatometry. The salts used were ammonium heptamolybdate, ammonium B-paratungstate, and ammonium metavanActate and the polymers were poly(vinyl alcohol), polyvinylpyrrolidone, and methyl cellulose. The films prepared by drying the precursor compositions were found to retain, during heating, the polymer-salt molecular complexes formed at room temperature. The mechanism of the thermal destruction of the salts in the polymer-salt films was shown to differ from that in pure salts because, in the films, mutual stabilization of the polymer and salt took place. In the polymer-salt compositions, oxides were formed directly from amorphous precursors, without formation of intermediates, characteristic of the decomposition of pure salts. The oxides thus prepared consisted of fine particles and exhibited photochromic effect due to partial reduction of metal ions.     

A facile and general approach to polynary semiconductor nanocrystals via a modified two-phase method

Cu(2)ZnSnS(4) nanocrystals were synthesized through a modified two-phase method and characterized with transmission electron microscopy (TEM), powder x-ray diffraction (XRD) and UV-vis spectroscopy. Inorganic metal salts were dissolved in the polar solvent triethylene glycol (TEG) and then transferred into the non-polar solvent 1-octadecene (ODE) by forming metal complexes between metal ions and octadecylamine (ODA). Since nucleation and growth occur in the single phase of the ODE solution, nanocrystals could be produced with qualities similar to those obtained through the hot-injection route. Balancing the reactivity of the metal precursors is a key factor in producing nanocrystals of a single crystalline phase. We found that increasing the reaction temperature increases the reactivity of each of the metal precursors by differing amounts, thus providing the necessary flexibility for obtaining a balanced reactivity that produces the desired product. The versatility of this synthesis strategy was demonstrated by extending it to the production of other polynary nanocrystals such as binary (CuS), ternary (CuInS(2)) and pentanary (Cu(2 - x)Ag(x)ZnSnS(4)) nanocrystals. This method is considered as a green synthesis route due to the use of inorganic metal salts as precursors, smaller amounts of coordinating solvent, shorter reaction time and simpler post-reaction treatment.     

多壳层中空金属氧化物的制备及其电化学应用研究进展

多壳层中空金属氧化物具有优异的物理和化学特性。其内部空腔及多壳层结构使其具有大的比表面积,为电化学反应提供了更多的活性位点,因此多壳层中空金属氧化物在电化学领域得到了广泛的应用。本文主要介绍了多壳层中空金属氧化物的合成进展,通过硬模板法、软模板法、选择性刻蚀法和热分解法为例,详细描述了制备得到的不同元素组成、不同壳层数的中空金属氧化物,总结了多壳层中空金属氧化物在超级电容器、锂离子电池和传感器领域表现出的优异性能,最后对多壳层中空金属氧化物的应用前景进行了展望。     

金属氧化物纳米线和纳米棒的制备及应用

本文综述了金属氧化物纳米线、纳米棒研究的新进展。重点评述了气相热化学合成法、热分解前驱物法、溶胶-凝胶电泳沉积法制备纳米线的过程及各自的生长机制，并对金属氧化物纳米线／棒的潜在应用作了介绍。     

有机凝胶法制备微细纤维的研究

以柠檬酸、乳酸及金属盐为原料,采用有机凝胶法制备了微细金属镍纤维、氧化铝纤维和氧化镁纤维.纤维的直径可以<1μm,组成纤维的晶粒在100nm以下.通过FTIR、XRD、DSC和SEM对纤维前驱体凝胶的结构、热分解过程及热处理产物的形貌进行了表征,并对其形貌的可控性进行了初步探索.试验结果表明有机凝胶法是一种很有前途的微细纳米结构纤维制备方法.     

Synthesis of Inorganic Nanotubes

Nanotubes constitute an exciting class of one‐dimensional nanomaterials of which carbon nanotubes are recognized widely as materials of importance. The possibility of having inorganic nanotubes was recognized early in the 1990s, accompanied by the report of nanotubes of MoS₂ and WS₂. Since then, nanotubes of several inorganic materials have been prepared and characterized. While nanotubes of metal chalcogenides and oxides form a high proportion of the inorganic nanotubes investigated hither to, nanotubes of many other materials have also been prepared and characterized. Several synthetic strategies including both physical and chemical methods have been employed, of which the use of templates, precursors, and hydro‐ or solvothermal methods are prominent. In this article, we shall present a brief account of the present status of the synthesis of nanotubes of elemental materials as well as binary and complex metal oxides, chalcogenides, pnictides and carbides.     

Nanosized Ni-Mn Oxides Prepared by the Citrate Gel Process and Performances for Electrochemical Capacitors

Nanosized Ni-Mn oxide powders have been successfully citrate gel precursors. The powder materials derived from prepared by thermal decomposition of the Ni-Mn calcination of the gel precursors with various molar ratios of nickel and manganese at different temperatures and time were characterized using thermal analysis （TG-DSC）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and Brunauer-Emmet-Teller （BET）. The optimized processing conditions of calcination at 400℃ for 1 h with Ni/Mn molar ratio 6 were proved to produce the nanosized Ni-Mn oxide powders with a high specific surface area of 109.62 m^2/g and nanometer particle sizes of 15-30 nm. The capacitance characteristics of the nanosized Ni-Mn oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） and exhibited both a doublelayer capacitance and a Faradaic capacitance which could be attributed to the electrode consisting of Ni-Mn oxides and residual carbons from the organic gel thermal decomposition. A specific capacitance of 194.8 F/g was obtained for the electrode at the sweep rate of 10 mV/s in 4 mol/L KOH electrolyte and the capacitor showed quite high cyclic stability and is promising for advanced electrochemical capacitors.     

Infrared spectra, Raman laser, XRD, DSC/TGA and SEM investigations on the preparations of selenium metal, (Sb2O3, Ga2O3, SnO and HgO) oxides and lead carbonate with pure grade using acetamide precursors

Ga₂O₃, Se metal, SnO, Sb₂O₃, HgO and PbCO₃ are formed upon the reaction of acetamide aqueous solutions with Ga(NO₃)₃, SeO₂, SnCl₂, SbCl₃, HgCl₂ and Pb(NO₃)₂, respectively, at 90°C. Different amorphous or crystalline phases can be obtained depending upon the experimental conditions (molar ratios, metal salts and temperature). The chemical mechanisms for the formations of this metal, oxides or carbonate are discussed and the X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscope (AFM) are described. The type of metal ions plays an important role in the decomposition of acetamide, leading to the formation of solid stable (metal, oxides or carbonate), soluble and gases species. These new precursors are more stable preventing the rapid precipitation of metal, oxides or carbonate. Furthermore, this route allows the formation of pure compounds in solutions.     

Zinc-cobalt oxide spinels with precursor-controlled degree of inversion

Zinc-cobalt oxide spinels, ZnCo₂O₄, have been prepared by thermal decomposition of three different precursors: (I) coprecipitated zinc-cobalt hydroxide nitrate; (II) coprecipitated zinc-cobalt hydroxide, and (III) zinc-cobalt hydroxide nitrate prepared by isomorphous replacement of the tetrahedrally coordinated Co²⁺ ions in the double-layered parent cobalt hydroxide nitrate by Zn²⁺ ions. It has been shown that the cationic distribution in the oxide product is predetermined by the cationic distribution of the precursor. The coprecipitated precursors (I) and (II) decompose to statistical spinels, whereas precursor (III) decomposes to a normal Zn [Co₂]O₄ spinet.     

Microprobe speciation analysis of inorganic solids by fourier transform laser mass spectrometry

Fourier transform (FT) laser microprobe mass spectrometry (LMMS) aims at the characterization of local constituents at the surface of solids. Signals from structural fragments specify the main building blocks of the analyte while adduct ions, consisting of one or two intact analyte molecules and a stable ion, allow specific identification of the molecule. A series of inorganic reference compounds including binary salts, oxides, and oxy salts was analyzed to assess the FT LMMS capabilities for the determination of the inorganic molecular composition. Compounds from different classes can be tentatively identified by deductive reasoning while those with the same elements in different stoichiometries require comparison with reference spectra.     

2D molecular precursor for a one-pot synthesis of semiconducting metal sulphide nanocrystals

2D molecular materials, namely, metal alkyl thiolates, have been used as a single-source precursor for the synthesis of semiconducting metal sulphide nanocrystals (NCs) by thermal decomposition. These 2D molecular precursors have all the ingredients required for metal sulphide synthesis (metal source, sulphur source and protecting ligand). In this study, we demonstrate a simple and general ‘solvothermal decomposition’ approach for the synthesis of high-quality \(\hbox {Cu}_{2}\hbox {S}\), PbS, CdS, MnS and ZnS NCs. The size of the NC can also be controlled by changing the decomposition temperature. Furthermore, the optical properties of the NCs have also been studied.     

Sol-gel processing of titanium-containing thin coatings

Through X-ray photoelectron spectroscopy, chemical composition and the valency state of elements modified by SnO₂, Fe₂O₃ and SiO₂ titanium-based coatings has been studied. It has been established that metal alkoxides and salts used as precursors after a certain thermal treatment of the layer are transformed into the respective oxide stable state. At depth in the coatings, oxides of Ti(IV) and Sn(IV) are unstable and exhibit stoichiometrical disturbances. The phenomenon is discussed in relation to argon-ion sputtering conditions, the inhibition of the diffusion of sodium ions from the glass substrate, and the residual carbon from organic radicals. It has been proved that sol-gel processing, using (C₄H₉O)₄ Ti as precursor, may be successfully applied for the synthesis of good, highly reflective oxide coatings of compositions, correlating with those of the starting sol solution.     

Preparation and characterization of precursors of Y2O3 stabilized ZrO2 by metal-organic compounds

8 mol% Y₂O₃-stabilized ZrO₂ has been prepared by four routes which involve yttrium and zirconium metal organic compounds as starting materials. The thermal decomposition of the precursors has been investigated by means of thermal analysis, X-ray diffraction and SEM technique with regard to their chemical homogeneity and phase composition. The possible reactions during precursor preparations are discussed.     

Nitrogen oxides removal by catalytic methods

 Nitrogen oxides are harmful compounds, dangerous to the natural environment. This review reports on progress in studies of catalytic processes to promote nitrogen oxide decomposition as well as catalytic NO reduction from mobile exhaust sources. The activities of catalysts receiving attention in the technical literature range from metallic ones to transition metal oxides supported on zeolites, metal oxides and magnesium fluoride. Also the current ideas on the mechanism of catalytic decomposition and reduction of nitrogen oxides are reviewed. Received: 11 February 1999 / Accepted: 1 June 1999     

Molten salts for rechargeable batteries

The growing demand of advanced electrochemical energy storage devices for various applications, including portable electronic products, electric vehicles, and large-scale energy storage grids, has triggered extensive research interests and efforts on various rechargeable batteries such as lithium/sodium-ion batteries (LIBs/NIBs), aluminium-ion batteries (AIBs), liquid metal batteries (LMBs), and molten-air batteries (MABs) in the past decades. A key issue to push forward the development of these batteries is the exploration of high-performance electrodes and electrolytes, which calls for efficient and versatile synthetic methods. Molten salts (MSs), liquid-phase ionic compounds or mixtures, provide an effective platform to widen the reaction temperatures and enrich the chemical environments for the synthesis of novel electrode materials and electrolytes. In this review, the general principles of molten salts and recent research progresses on molten salt-based battery materials are surveyed. Molten-salt synthesis of electrode materials, including sintering and electrolysis, are emerging as competitive substitutes for conventional synthesis techniques. These methods have shown their effectiveness and uniqueness in adjusting the crystal structure, morphology, and performance of electrode materials for LIBs/NIBs, as suggested by recent progresses and applications of diverse cathodes (layered oxides, spinel oxides, polyanions, etc.) and anodes (metal oxides, alloys, carbons, etc.). Furthermore, the applications of molten salts as effective electrolytes are demonstrated in representative new-type secondary batteries including AIBs, LMBs and MABs. Finally, the emerging opportunities, challenges, and interesting research trends are envisioned to promote the further development of molten-salt methodology for rechargeable batteries.     

Shaping Colloidal Rutile into Thermally Stable and Porous Mesoscopic Titania Balls

High crystallinity and controlled porosity are advantageous for many applications such as energy conversion and power generation. Despite many efforts in the last decades, the direct synthesis of organic–inorganic composite materials with crystalline transition metal oxides is still a major challenge. In general, molecules serve as inorganic precursors and heat treatment is required to convert as‐synthesized amorphous composites to stable crystalline materials. Herein, an alternative approach to the direct synthesis of crystalline polymer–metal oxide composites by using a spherical polyelectrolyte brush as the template system is presented. Pre‐synthesized electrostatically stabilized rutile nanocrystals that carry a positive surface charge are used as inorganic precursors. In this approach, the strong Coulomb interactions between anionic polyelectrolyte brush chains and cationic crystalline rutile colloids, whose surfaces are not capped and therefore reactive, are the key factors for the organic–inorganic crystalline composite formation. Stepwise calcination first under argon and followed with a second calcination in air lead to the complete removal of the polymer template without collapse and porous rutile balls are obtained. The results suggest that any colloids that carry a surface charge might serve as inorganic precursors when charged templates are used. It is expected that this hierarchical route for structuring oxides at the mesoscale is generally applicable.     

用冲击波合成法制备纳米铁酸镍粉体

用冲击波处理用共沉淀法制备的氧化铁氧化镍混合物,合成了铁酸镍,用ＸＲＤ１ＴＥＭ及电子衍射法对合成产物进行了表征。合成在本为具有较高的磁化强度的纳米级铁酸,主要原因可能是纳米前体有较高的反应活性,冲击波作用时间极短,冲击波处理可能成为制备复合金属化物纳米粉体的新方法。     

Metal Oxide Hollow Nanostructures for Lithium‐ion Batteries

Metal oxide hollow structures have received great attention because of their many promising applications in a wide range of fields. As electrode materials for lithium‐ion batteries (LIBs), metal oxide hollow structures provide high specific capacity, superior rate capability, and improved cycling performance. In this Research News, we summarize the recent research activities in the synthesis of metal oxide hollow nanostructures with controlled shape, size, composition, and structural complexity, as well as their applications in LIBs. By focusing on hollow structures of some binary metal oxides (such as SnO₂, TiO₂, Fe₂O₃, Co₃O₄) and complex metal oxides, we seek to provide some rational understanding on the effect of nanostructure engineering on the electrochemical performance of the active materials. It is thus anticipated that this article will shed some light on the development of advanced electrode materials for next‐generation LIBs.