96 nanomaterials nanoporous material

Naturally occurring nanomaterials exist in a variety of complex forms. In this chapter a short set of definitions will be stated for clarity. Nanocrystals are single crystals with sizes from a few nm up to about 100 nm. They may be aggregated into larger units with a wide spectrum of microstructures. Nanoparticles are units of minerals, mineraloids or solids smaller in size than 100 nm, and composed of aggregated nanocrystals, nanoclusters or other molecular units, and combinations of these. Nanoclusters are individual molecular units that have well-defined structure, but too small to be true crystals. Al and ZnsSs solution complexes are types of nanoclusters with sizes from sub nanometer to a few nm. Nanoporous materials are substances with pores or voids of nanoscale dimensions. These materials can be single crystals, such as zeolites or... 

The field of nanoporous materials has emerged as one of the most exciting and diverse areas of nanomaterials. The discoveries of the last decade have demon-... 

Nanomaterials represent today s cutting edge in the development of novel advanced materials, which promise tailor-made functionality for unique applications in all important industrial sectors. Nanomaterials can be clusters of atoms, grains 100 nm in size, fibers that are less than 100 nm in diameter, films that are less than 100 nm in thickness, nanoholes, and composites that are a combination of these. In other words, it implies that the microstructures (crystallites, crystal boundaries) are nanoscale [1]. Nanomaterials include atom clusters, nanoparticles, nanotubes, nanorods, nanowires, nanobelts, nanofilms, compact nanostructured bulk materials, and nanoporous materials [2]. Materials in nanosize range exhibit... 

This article reviews the synthesis, characterization, and applications of rare earth oxide and snlphide nanomaterials. Special focus is placed on nanoparticulate materials and the description on nanoscale films and bulk nanoporous materials are intentionally excluded. In the first section, the synthesis methods of nanoparticles in general are reviewed, and examples of the production of rare earth oxides and sulphides are presented. The second section deals with the applications of rare earth oxides and sulphides, and they are discussed in relation to the unique properties of nanoscale particles. 

SBA-15 nanomaterial is described as a nanoporous material, which has maity appUcations in catalytic cases. Hexafluoroisopropanol dispersed into catalytical... 

Since the early talks of Richard Feynman in its There s Plenty of Room at the Bottom in 1959, there have been always a concern on what nano means and applies to. Recently, the Royal Society tried to make order between the definitions of nanoscience and nanotechnology, both referring to, respectively, the study or the preparation of materials from 100 nm down to the atomic level (approximately 0.2 nm) [1], Later, the British Standard Institution defined nanomaterial as material having one or more external dimensions in the nanoscale or which is nanostructured. [2] Accordingly, Murray makes a noticeable attempt to apply these concepts to nanoelectrochemistry of nanoparticles, nanoelectrodes, and nanopores, referring them as a dimensional scale of electrodes and electrochemical events [3]. 

In the past few decades, nanomaterials have received substantial attention and efforts from academic and industrial world, due to the distinct properties at the nanoscale. Nanoporous materials as a subset of nanomaterials... 

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

During past decades, a relatively new method attracted much of attention of experimentalists, namely, the sol-gel method widely implemented in numerous scientific and industrial applications. Actually, it caused a breakthrough in material science it is worth mentioning that sol-gel routes are cmcial for synthesis of nanomaterials, and one of methods of the 21st century namely, commercial nanoporous glasses are readily available on the market just thanks to sol-gel technologies. 

Relatively straightforward is the definition of nanoscopic voids. Nanopores and nanocavities are elongated voids or voids of any shape, and nanomaterials can incorporate especially nanopores in an ordered or disordered way. The former is of crucial importance for many of the hybrid materials discussed in the book (e.g., in Chapters 16 or 18). Nanochannel is also frequently used instead of nanopore, often in biological or biochemical contexts. Besides nanoporous, the term mesoporous is often found in hybrid materials research. Interestingly, the IUPAC has defined the terms mesoporous (pores with diameters between 2 and 50 nm), microporous (pores with diameters <2 nm) and macroporous (pores with diameters >50 nm), yet has not given a definition of nanoporous in the IUPAC Recommendations on the Nomenclature of Structural and Compositional Characteristics of Ordered Microporous and... 

Catalysts were some of the first nanostructured materials applied in industry, and many of the most important catalysts used today are nanomaterials. These are usually dispersed on the surfaces of supports (carriers), which are often nearly inert platforms for the catalytically active structures. These structures include metal complexes as well as clusters, particles, or layers of metal, metal oxide, or metal sulfide. The solid supports usually incorporate nanopores and a large number of catalytic nanoparticles per unit volume on a high-area internal surface (typically hundreds of square meters per cubic centimeter). A benefit of the high dispersion of a catalyst is that it is used effectively, because a large part of it is at a surface and accessible to reactants. There are other potential benefits of high dispersion as well— nanostructured catalysts have properties different from those of the bulk material, possibly including unique catalytic activities and selectivities. 

The template method is a general approach for preparing nanomaterials that entaU synthesis or deposition of the desired material within the cylindrical and monodisperse pores of a nanopore membrane or other solid [20-22]. Cylindrical nano-strucmres with monodisperse diameters and lengths are obtained, and depending on the membrane and synthetic method used, these may be solid nano wires or hollow nanombes. This method has been used to prepare nano wires and nanombes composed... 

The book starts with a brief introduction to nanomaterials followed by chapters dealing with the synthesis, structure and properties of various types of nanostructures. There are chapters devoted to oxomolybdates, porous silicon, polymers, electrochemistry, photochemistry, nanoporous solids and nanocatalysis. Nanomanipulation and lithography are covered in a separate chapter. In our attempt to make each contribution complete in itself, there is some unavoidable overlap amongst the chapters. Some chapters cover entire areas, while others expound on a single material or a technique. Our gratitude goes to S. Roy for his valuable support in preparing the index manuscript. 

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