Nanoparticle Nano Crystal

Figure 6.7 presents the general rules of nano assembly and their relationship with nanoelements. As a nano assembly becomes more desired (moving toward the right hand direction on the horizontal arrow of attrae-tive interaction-repulsive interaction balance), the nano element that will be expressed is a nano structural element. Typical nano pores, nanoparticles, nano crystals, nano emulsions, and nano composites are more likely to be obtained on this side of the arrow. On the other hand, if a nano assembly moves toward the left-hand side, it is more likely to obtain nano assembled systems that usually need an aid of external foree for their assembly. Colloidal erystal is one good example, especially when the size of nano assembly building unit (colloidal particle) is increased. Many top-down operation-based nanoelements are other examples. 

Nanoparticles. When all the three dimensions of the particulates are in the nanometer range, they are isodimensional nano particles or nano granules or nano crystals. 

Colloid properties are intrinsic and extrinsic, the first being e.g. chemical behavior, ionization potential or crystallographic structure, the second collective phenomena such as electron gas and lattice resonance. The scheme of electron-energy-levels highly dependent on cluster size and cluster shape is often cited as based on a quantum-size effect. Still most of the behavior of isolated and assembled metal nanoparticles could be deduced from the classic electromagnetic theory without any use of quantum behavior or statistic (Figure 5). Only ultra-small or semi-conductor clusters are not readily described by collective phenomena due a the well-defined assembly of atoms in nano-crystals or due the low number of electrons respectively. 

Since nanoscale metal nanoparticles are applicable to a number of areas of technological importance, the nano-structured materials chemistry will occupy much attention of scientists. It is certain that controlling the primary structures of metal nanoparticles, that is, size, shape, crystal structure, composition, and phase-segregation manner is still most important, because these structures dominate the physical and chemical properties of metal nanoparticles. Now the liquid phase synthesis facilitates the precise control of the primary structures. 

Recently, the synthesis of nano-sized HA has been proposed via reverse-micro-emulsion preparation, which is reported to be effective for controlling the hydrolysis and polycondensation of the alkoxides of the constituents. Using this preparation route, the nanoparticles crystallize directly to the desired phase at the relatively low temperature of 1050 °C and maintain surface areas higher than 100 m g after calcination at 1300 °C for 2h [107-109]. 

Films of materials deposited at or near room temperature (and in this respect 100°C is considered to be near room temperature) tend to have a small crystal size. This is not surprising since high temperatures are normally required to impart sufficient mobility to a freshly deposited species in order for recrystallization to occur. This small crystal size, which at one time was almost universally considered to be a disadvantage, is increasingly considered to be an advantage as interest in nanocrystalline and nanoparticle materials grows. The term nano crystalline usually refers to materials with a crystal size from a nanometer up to hundreds of nanometers (at this upper limit, the term microcrystalline starts to take over). 

The discussed models of the carbon nanofilaments and nanotubes forma tion allow many other thermodynamic factors to be taken into consider ation, all of which affect the shape, texture, and growth rate of the nano objects under discussion (see, e.g.. Refs. [6, 7]). It is assumed that the forma tion of the fluidized active component of the catalyst nanoparticles due to its stationary oversaturation with the crystallizing component gives rise to the possibility to synthesize nanofilaments and nanotubes from not only carbon but also from different substances, such as silicon carbide (over catalysts capable of dissolving carbon and silicon simultaneously), germanium metal (over gold metal catalysts [8]), and so on. 

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