Nano-sized metal particles physical properties

PHYSICAL AND CHEMICAL PROPERTIES OF NANO-SIZED METAL PARTICLES... 

Rao CNR, Kulkami GU, Thomas PJ, Agrawal W, Gautam UK, Ghosh M (2003b) Nanocrystals of metals, semiconductors and oxides novel synthesis and applications. Curr Sci 85 1041-1045 Rao CNR, Kulkami GU, Thomas PJ (2005) Physical and chemical properties of nano-sized metal particles. In Nicolais L, Carotenuto G (eds) Metal-polymer nanocomposites. WUey, Hoboken, New Jersey, pp 1-36... 

The investigation of the chemistry that occurs on the surface of colloidal metal particles is important for our imderstanding of many properties of nano-particles, such as their catalytic effects, their growth, and their electrochemical and photochemical behaviour. The electronics of nano-sized metal particles are changed when chemical events occur on the surface, and, consequently, certain physical properties such as their optical absorption are affected. On the other hand, optical measurements can often be used to trace the chemical modifications on the surface. 

Nano-sized metal fluorides have a promising perspective as inorganic component of organic polymers. Due to their small size the particles are invisible even in transparent polymers but may, in possibly decisive ways, change physical properties such as dielectric constant, index of refraction or mechanical properties. However, preventing agglomeration of these nano particles is a challenging task, but one that is not easy to accomplish and that needs to be further developed. 

As it is known [13, 14], the scale effects are often found at the study of different materials mechanical properties. The dependence of failure stress on grain size for metals (Holl-Petsch formula) [15] or of effective filling degree on filler particles size in case of polymer composites [16] are examples of such effect. The strong dependence of elasticity modulus on nanofiller particles diameter is observed for particulate-filled elastomeric nanocomposites [5], Therefore, it is necessary to elucidate the physical grounds of nano- and micromechanical behavior scale effect for polymer nanocomposites. 

Metal colloids are assemblies of atoms with unique physical and chemical properties. These colloidal particles are nano-crystals or nano-amorphous lumps composed out of 2 to 10 atoms. which are bound together by crystal energy. Within the state of matter described by cluster-type behavior we define a nano-particle, nano-cluster, nano island, precipitate or- whatever name is used for these assemblies as a colloidal particle not specifying the size, shape or property of this assembly (Figure 1). 

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