Nanoscale definition

The definition above is a particularly restrictive description of a nanocrystal, and necessarily limits die focus of diis brief review to studies of nanocrystals which are of relevance to chemical physics. Many nanoparticles, particularly oxides, prepared dirough die sol-gel niediod are not included in diis discussion as dieir internal stmcture is amorjihous and hydrated. Neverdieless, diey are important nanoniaterials several textbooks deal widi dieir syndiesis and properties [4, 5]. The material science community has also contributed to die general area of nanocrystals however, for most of dieir applications it is not necessary to prepare fully isolated nanocrystals widi well defined surface chemistry. A good discussion of die goals and progress can be found in references [6, 7, 8 and 9]. Finally, diere is a rich history in gas-phase chemical physics of die study of clusters and size-dependent evaluations of dieir behaviour. This topic is not addressed here, but covered instead in chapter C1.1, Clusters and nanoscale stmctures, in diis same volume. 

For a flying height around 2 nm, collisions between the molecules and boundary have a strong influence on the gas behavior and lead to an invalidity of the customary definition of the gas mean free path. This influence is called a "nanoscale effect" [46] and will be discussed more specifically in Chapter 6. 

The correction of mean free path, hi by the nanoscale effect function results in a smaller mean free path, or a smaller Knudsen number in other word. As a matter of fact, a similar effect is able to be achieved even if we use the conventional definition of mean free path, / = irSn, and the Chapmann-Enskog viscosity equation, /r = (5/16)... 

These two examples show that regular patterns can evolve but, by definition, dissipative structures disappear once the thermodynamic equilibrium has been reached. When one wants to use dissipative structures for patterning of materials, the dissipative structure has to be fixed. Then, even though the thermodynamic instability that led to and supported the pattern has ceased, the structure would remain. Here, polymers play an important role. Since many polymers are amorphous, there is the possibility to freeze temporal patterns. Furthermore, polymer solutions are nonlinear with respect to viscosity and thus strong effects are expected to be seen in evaporating polymer solutions. Since a macromolecule is a nanoscale object, conformational entropy will also play a role in nanoscale ordered structures of polymers. 

Although the scope of this chapter is limited to catalyst nanoencapsulation for the purpose of process intensification, we take a broad view of the definition of nanoencapsulation. The capsule or catalyst, or both, may be on the nanoscale. Additionally, the various methods of nanoencapsulation may be of the order of up to a few microns. 

The examples cited in this chapter are but a rather small and arbitrary selection from the richly varied possibilities for supramolecular bonding. Recognition of the intrinsic chemical (partially covalent, exchange-type) character of supramolecular interactions leads inevitably to an extended definition of chemistry that includes many aspects of nanoscale aggregation, structure, and function in the biophysical and material-science domains. From this viewpoint, the molecule is seen to be... 

This review focuses on nanoparticles, namely objects that are roughly spherical. We use the commonly accepted definition for nanoscale objects of having a dimension below 100 nm, and so identify nanoparticles as objects with a diameter of 100 nm or smaller. The review does not focus on larger aspect ratio nanoscale materials such as nanotubes and nanorods, though they are mentioned in some cases. 

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. 

Definition of the nanoscale covers all species having at least one diameter of 100 nm or less. When nanoparticles are intentionally synthesized to be used in a range of consumer goods, they are called nanomaterials. Without doubt, one can say that we are now at the beginning of nanoindustrial revolution. Different types of nanomaterials are frequently applied in electronics, space technology, cosmetics and sunscreens production, medicine and pharmacy, solar energetics, textile industry, sport equipment, and many other areas [22, 23]. 

There is often a grey area concerning the best definition for small particulate matter. In particular, most structures are automatically referred to as nanoscale materials," fueled by the popularity of the nanotechnology revolution. However, the most precise use of the nano" prefix e.g., nanoparticles) is only for materials with architectural dimensions e.g., diameters, thicknesses, etc.) of less than 100 nm intermediate dimensions between 100 and 1,000 nm should instead be referred to as submicron." CRC Handbook of Chemistry and Physics, 84th ed., CRC Press New York, 2004. 

The results clearly demonstrate that cyclohexane in the nanoscale slit space between the carbonaceous solids freezes, e.g., when the distance comes down to 4 nm, even at 8.4 C, which is above the bulk freezing point of 6.4X3. Further, the degree of elevation was in good accord with the prediction by our model [3] based on the attractive potential energy of the wall. Though the extent of the elevation itself might look rather small, we believe that the finding of the definite existence of the elevation, and its accord with the prediction of our model would be of much importance in the research field of the phase behavior in nanopores. 

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... 

While the first two issues highlighted in the previous paragraph are clearly associated with multiscale simulation, the second two are associated with nanotechnology and nanoelectronics, which are widely perceived as the future of the semiconductor industry. The relationship between multiscale simulation and nanoscale science and technology, however, depends on one s perspective as there are different definitions of the word nanotechnology ... 

Nanoscale liquid chromatography (nano-LC) using RP separation materials is the default choice for LC-MS of peptides from proteome digests. Nano-LC has excellent sensitivity using 50-100 pm diameter columns and 200-300 nL/min flow rates (166). An all-inclusive definition for nano-LC is an LC that separates nanoliter amounts of sample, with nanoliter amounts of mobile phase, and yields detection limits in the range of nanograms per milliliter (167). 

Huge advances have been made over the last 15 years in the research, development, application, commercialization and understanding of the mechanisms of action of nanoscale drug delivery systems. Many of these advances have had a spectacular impact on the prevention, diagnosis and treatment of a wide range of diseases. This is especially trae in the treatment of many cancers, and it is in the oncology field that the majority of the formulation advances have been made. Pharmaceutically, the most important nanotechnologies are exemplified and discussed below (see Table 39.10 for definitions and descriptions). 

Lipospheres were first reported by Domb, who described them as water-dispersible solid microparticles of a particle size between 0.2 and 100 pm in diameter, composed of a solid hydrophobic fat core stabilized by a monolayer of phospholipid molecules embedded in the microparticles surface [1], Using this definition, lipo-sphere size is on the nanometer scale. Usually, nanoscale particles consisting of a solid lipid core are termed SLN [16], though sometimes inconsistent nomenclature can be found. Unlike SLN, lipospheres are restricted to the stabilizing material of a phospholipid layer because of their definition [1], This chapter focuses on research results obtained for peptide and protein formulations termed lipospheres, and it does not consider SLN literature at large. 

Microfluidics is also a cross-disciplinary subject that uses the methods and principles of microelectronics to construct very small analogs or models of such macroscopic fluidic elements as wind tunnels, valves, or fluidic amplifiers. The natural question that comes to mind is at what dimensional scale does fluid motion depart from the extremely well understood and well established laws of fluid dynamics There is no definitive answer to that question yet since the study of fluid motion in microscale and nanoscale structures is still at an early stage. 

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