Nanomaterials liquid phase synthesis

The fundamental goal of nanoparticle research is to assemble atoms in a controllable way and design nanostructured materials with the desired physical and chemical properties. A major part of the research in the field of nanoscience is dedicated to the development of synthesis routes to nanoparticles and nanostructures. Conventionally, solid-state reactions between powders have successfully been employed for the low-cost production of bulk metal oxides. However, to obtain metal oxide nanoparticles with well-defined shape, size, and composition, these solid-state routes are unsuitable. In contrast to these high-temperature processes, liquid-phase synthesis routes, and in particular sol-gel routes, offer better possibility to control the variation of structural, compositional, and morphological features of the final nanomaterials [1,2]. 

Schur D.V., Dubovoy A.G., Lysenko E.A., Golovchenko T.N., Zaginaichenko S.Yu., Savenko A.F., et al. Synthesis of nanotubes in the liquid phase. Extended Abstracts, 8th International Conf. Hydrogen Materials Science and Chemistry of Carbon Nanomaterials (ICHMS 2003) Sudak (Crimea, Ukraine), 2003 399-402. 

Two distinct groups of experimental techniques were presented in COlL-2 to study the behaviour of different solutes in ionic liquids, spectroscopic and thermodynamic, giving access to different scales of the properties studied - one microscopic and the other macroscopic. It was possible to explain microscopically the phase behaviour of ionic liquid solutions by balancing the effects of the solute-solvent interactions and the dynamics of the solutions. Bases were established to assess the microscopic mechanisms responsible by the properties observed and so to open the way to the rapid advancement of the field contributing to the development of novel applications in a growing variety of disciplines including catalysis, synthesis, nanomaterial synthesis or pharmaceutics. 

The updated application of the ionic liquid in the synthesis of inorganic nanomaterials was briefly outlined. The main emphasis of the outline was a focus on the preorganized structure of the ionic liquid as template effect for inorganic nanomaterials. The particular strength of ionic liquids is their virtually unlimited flexibility of anions and cations combinations. As the cation or anion in the ionic liquid can be tailored by functional substitutes, the size and size distribution of the ionic liquid-stabilized metal nanopartides can be easily controlled too. In case ionic liquid phase behavior, chemical composition, and reactivity are also considered, ionic liquids provide a flexible toolbox for the fabrication of inorganics with various (and variable) properties simply by designing the appropriate precursor. These precursors are entities which are defined molecularly, which can be well characterized and studied as the transformation to the inorganic proceeds. 

The most important nanomaterial synthesis methods include nanolithography techniques, template-directed syntheses, vapor-phase methods, vapor-liquid-solid (VLS) methods, solution-liquid-solid (SLS) approaches, sol-gel processes, micelle, vapor deposition, solvothermal methods, and pyrolysis methods [1, 2]. For many of these procedures, the control of size and shape, the flexibility in the materials that can be synthesized, and the potential for scaling up, are the main limitations. In general, the understanding of the growth mechanism of any as-... 

At first, however, this review will provide the reader with a critical overview over the most commonly used nanomaterials. The emphasis here will be particularly on those aspects of their synthesis, manipulation, and characterization that are of significant importance for their use as dopants in liquid crystalline phases or as precursors for the formation of liquid crystalline superstructures including size and size-distribution, shape, chemical purity, post-synthesis surface modifications, stability of capping monolayers, and overall thermal as well as chemical stability. 

Prominent exceptions are studies on the liquid crystal phase formation and self-assembly of two-dimensional disc- or sheet-like nanomaterials such as the organization of nanodiscs or nanoplatelets into nematic, smectic, or columnar morphologies [263-270] (see Fig. 2 for an example of the self-assembly of nanoclay in aqueous suspensions) or the synthesis of CuCl nanoplatelets from ionic liquid crystal precursors as described by Taubert and co-workers [271-273]. 

Self-assembled microstructures of water and surfactant with or without oil have been the subject of intense research for several decades because of their rich structural variety. Microstructures ranging from spherical micelles, rod-like micelles, bicontinuous micro emulsions and liquid crystalline phases have broad commercial and scientific applications including nanomaterial synthesis, controlled delivery, coatings and detergents among many others. 

The use of ultrasonic irradiation for producing nanomaterials has been a research topic of great interest (Dhasn et al., 1999). This is due to the simplicity of sonochemical method, the cheap price of the equipment and that in many cases the as-prepared material is obtained in the crystalline phase. The ultrasonic-assisted aqueous room tempjerature ionic liquid method was applied to prepare zinc sulfide and zinc oxide nanomateiials (Zheng et al. 2010 Jia et al. 2010), among many other nanomatreials. Selection of the room temp>erature ionic liquid was mainly based on the fact that it can be obtained at a relatively low price and the method for its synthesis is simple. 

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