Unique Properties of Nanoparticles

Synthesis of polymer/nanoparticles composite materials is very important for the advanced material science. Materials of this type combine unique properties of nanoparticles with properties of polymers, and even reveal new properties not specific for their components. Moreover, a polymer also plays a role of stabilizer for extremely active nanoparticles. Metal oxides are an interesting class of inorganic nanoparticles due to optical, magnetic and electronic features [1-3],... 

Nanoparticles have been widely used in optical, resonant, electrical, and magnetic fields. The small size effect, large surface effect, and quantum tunnel effect demonstrate the unique properties of nanoparticles. It is necessary to study the techniques of nanoparticle preparation to meet the developments in nanotechnology and nanomaterials. In this section, we describe work carried out in our laboratory on the syntheses of several nanoparticles and nanocomposites and the study of their properties. 

The unique property of nanoparticles that is most widely utilized in the applications of rare earth oxides and sulphides is their high specific surface area. Specific surface area is defined as the surface area per unit weight. As the particle size is reduced, more atoms are exposed on the particle surface and hence the specific surface area increases drastically (Table 2). For example, when the particle diameter is reduced to 1 nm, only 1 g of Ce02 nanoparticles can have a surface area of 800 m, three times larger than the official tennis court. On the other hand, if the particles have a diameter of 100 pm, then 1 g of the powder has only 0.008 m of surface... 

Nanoparticles are finding application in many areas of technology due to their unique properties. The very high ratio of surface atoms to bulk atoms is the primary reason for the unique properties of nanoparticles. Due to the large surface area and quantum effects related to very small nanoparticles, the optical, electronic, and other properties are quite different than for larger particles of the same materials. Because of the unusual properties of nanoparticles, there are numerous emerging applications and processes where nanoparticles will be used. Examples of applications of nanoparticles include such diverse topics as ... 

It has been proposed that these nanometer- and micrometer-sized particles may have applications in biology in sensing and imaging applications or as delivery vehicles (De et al, 2008). The unique properties of nanoparticles such as their similar size to biomolecules such as proteins and polynucleic acids, as well as their ability to be tuned to contain a range of functional materials such as metal centers, dye molecules, etc. make them attractive candidates for biological and materials applications. The applicable of these nanoparticle platforms for therapeutic and diagnostic activities relies on the functionalization and also encapsulation potential of these materials. 

The utilization of large surface areas and, to a certain extent, controllable surface properties make carbon materials an ideal support for finely dispersed catalyst nanoparticles, as discussed in Section 15.2. The special features of nanocarbons for this purpose will be highlighted in the following section. Starting with the controlled synthesis of a variety of nanocarbon-inorganic hybrids, some examples will be discussed, where the superior catalytic performance arises from the unique properties of the nanostructured support. 

A number of experiments were devoted to semiconductors (104), and semiconductor nanoparticles (38, 105-109). Some of the experiments were devoted to the synthesis or growth process of the nanoparticles (105, 106, 109), while others were devoted to the unique properties of the particles (107, 108, 109). 

The foregoing discussion has focused on self-assembled monolayers formed on essentially flat electrode surfaces whose areas are vastly larger than those occupied by a single adsorbate. This field has now achieved a significant level of sophistication in terms of their structural characterization as well as their rational design for specific functions, e.g. chemically modulated switches. Although somewhat outside the scope of this book, another important area that exploits the unique properties of self-assembled monolayers is monolayer-protected metal clusters or nanoparticles. 

The properties of nanoparticles may often be significantly different from those of the smaller nanoclusters discussed above, which may have unique catalytic sites, different from those on nanoparticles (Argo and Gates, forthcoming). 

In conclusion, semiconductor quantum dots play the role of mechanical supports, photonic antennae, and fluorophores. Such versatility results from unique properties of semiconductor nanoparticles. 

Industrial interest in nanomaterials derives from the novel properties they exhibit. These are defined for this entry as materials having engineered discrete particulate domains with diameters in the range of 1 nm to a few hundred nanometers. These domains may appear in many forms, such as dispersions of nanoparticles in a liquid, on surfaces, or embedded in a continuous matrix. The unique properties of nanomaterials are a consequence of the small size and extremely large interfacial areas. In this regime, dramatic variations in the chemical and physical properties of a material may be effected. Representative examples of size-critical properties, enabling new industrial applications, reviewed in this entry include surface and interfacial, catalytic, optical, and mechanical. 

By the way, these days nanoscientists are trying to develop a different kind of magic bullet. They are exploiting the unique properties of nanotechnology for self-replication and self-assembly in a living cell, by planning nanoscale robots, nanobots, or nanoparticles to selectively destroy bacteria, cancer cells, and viruses. 

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