Nanomaterials defined

Figure 1.4. Catalysts are nanomaterials and catalysis is nanotechnology. If we define nanotechnology as the branch of materials science aiming to control material properties on the nanometer scale, then catalysis represents a field where nanomaterials have been applied commercially for about a century. Many synthetic techniques are available to...

There is no doubt that metallic nanoparticles that have defined sizes and shapes will become key components of a number of novel, highly sophisticated products, the prototypes of which are currently emerging from the industrial R D departments. The outlook is promising for the industrial production of defined 1.4nm metal clusters for use as single electron switches or transistors, for the cost-effective fabrication of ultrapure metallic nanomaterials needed for dye solar cells or sensors, and for the reproducible production of (particularly) efficient and durable... 

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... 

N anomaterials have been around for hundreds of years and are typically defined as particles of size ranging from 1 to 100 nm in at least one dimension. The inorganic nanomaterial catalysts discussed here are manganese oxides and titanium dioxide. Outside the scope of this chapter are polymers, pillared clays, coordination compounds, and inorganic-organic hybrid materials such as metal-organic frameworks. 

As the analytical, synthetic, and physical characterization techniques of the chemical sciences have advanced, the scale of material control moves to smaller sizes. Nanoscience is the examination of objects—particles, liquid droplets, crystals, fibers—with sizes that are larger than molecules but smaller than structures commonly prepared by photolithographic microfabrication. The definition of nanomaterials is neither sharp nor easy, nor need it be. Single molecules can be considered components of nanosystems (and are considered as such in fields such as molecular electronics and molecular motors). So can objects that have dimensions of >100 nm, even though such objects can be fabricated—albeit with substantial technical difficulty—by photolithography. We will define (somewhat arbitrarily) nanoscience as the study of the preparation, characterization, and use of substances having dimensions in the range of 1 to 100 nm. Many types of chemical systems, such as self-assembled monolayers (with only one dimension small) or carbon nanotubes (buckytubes) (with two dimensions small), are considered nanosystems. 

Well-defined Quantum Dots and Morphological Control of Nanomaterials... 

Nanomaterials are commonly defined as materials with morphological features on the nanoscale (commonly below 100 nm in one, two, or all three dimensions), but a more precise definition would limit the scope to only those materials showing unique properties different from individual atoms or molecules as well as the bulk as a result of their nanoscale dimensions. 

If one accepts the premise that self-assembly will be an important component of the formation of nanomaterials, it is clearly important to understand it as a process (or, better, class of processes). The fundamental thermodynamics, kinetics, and mechanisms of self-assembly are surprisingly poorly understood. The basic thermodynamic principles derived for molecules may be significantly different for those that apply (or do not apply) to nanostructures the numbers of particles involved may be small the relative influence of thermal motion, gravity, and capillary interactions may be different the time required to reach equilibrium may be sufficiently long that equilibrium is not easily achieved (or never reached) the processes that determine the rates of processes influencing many nanosystems are not defined. 

A group of nanomaterials, as the only criterion of membership becomes particle size, is very diversified. Particular members of the group differ from each other by molecular geometry (i.e., nanotubes, fullerenes, crystal structures, clusters, etc.) and physicochemical characteristics (i.e., organic, inorganic, semiconductors, isolators, metals, nonmetals, etc.). Thus, it may and should be assumed that they also differ by the mechanism of action and - in consequence - defining one common applicability domain and QSAR model for all of them is impossible. 

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... 

In contrast to many other nanomaterials, silica nanoparticles do not acquire any peculiar property from their submicrometric size, except for the corresponding increase of the surface area. As a matter of fact, they can simply be regarded as extremely small and highly porous glass spheres. What makes silica nanoparticles very interesting from the supramolecular point of view is the presence of a well-defined structure with compartments (bulk, surface, pores, shells, etc.) that can be rather... 

The goal of this chapter is to illustrate supported catalytic nanomaterials, with an emphasis on those that are simple and well-defined structurally (and thus relatively well understood), and to summarize generally important conclusions about their structure, bonding, reactivity, and catalytic properties. This summary is not exhaustive, and references to related reviews are cited. 

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