Nano-sized metal particles properties

Nano-sized metal particles are usually present in the supported metallic catalysts used industrially. The smaller the particle size, the larger the fraction of metal surface atoms exposed, which are therefore accessible to reactants. However, as the size of the metal particles decreases to the molecular range, their properties and, consequently, their catalytic behavior change. Both well-defined metal clusters and small metal aggregates can be generated by applying proper activation... 

The intense research interest to nano-sized metal particles and clusters is explained by their unique properties that differ significantly from properties of bulk metals. For example, luminescence from clusters has received an increasing attention, while the process is unlikely in case of bulk metals since they do not have band gaps. Luminescence of nano-sized transition metal particles can be of great practical importance in various fields of science, medicine and industry. 

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. 

The study of fluorescence of molecules situated near nano-sized metal particles has been the subject of considerable experimental interest in recent years, largely due to important biological applications and the emergence of nano-technology. The spectroscopic properties of molecules interacting with small solid-state particles was investigated theoretically and experimentally over two decades ago. The work pointed to a competition between enhanced radiative processes and additional non-radiative chaimels introduced by the presence of particles. It was found that the specific optical properties of the solid played an important role, as well as the geometric shape of the particle, and the location of the molecule relative to the particle. 

Surface-adsorbed polystyrene spheres as a template for nano-sized metal particle formation. Optical properties of nano-sized Au particle, H. Takei, J. Vac. Sci. Technol. B, 1999,17, 1906. 

Making uniform nano-sized metal oxide particles is also of interest. Such particles could have a higher specific surface area and a higher density of surface defects than those made by conventional preparation methods. This could be beneficial to their catalytic properties. If the oxide particle is multi-component, then such nano-sized particles, each containing the various components would provide more intimate contact or... 

Electric sparks arising between metal granules of A1 or Fe in electric fields can be used for producing micro- and nano-sized hydroxide particles. These hydroxides possess a unique structure, and properties that can be efficiently used for water treatment and disinfection.10,11... 

Nano-crystaUine metal particles have been developed more recently (Gleiter, 2000). The grain size is generally below 100 nm, and the range of 5-50 nm is more typical. These materials have better properties for hydrogen storage than their conventional counterparts. 

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. 

The rapid development of nanotechnology has revolutionized scientific developments in recent decades [1]. The synthesis, characterization, and application of functionalized nanoparticles are currently a very active field of research [2], Due to the size limitation of metal nanoparticles, they show very unique properties, which are called nano-size effect or quantum-size effect , which is different from those of both bulk metals and metal atoms. Such specific properties are usually dominated by the atoms located on the surface. In nanoparticles systems, the number of atoms located on the surface of the particles increases tremendously with decreasing of the particle diameter [3]. 

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