Metallic nanoparticles electronics applications

The most intensive development of the nanoparticle area concerns the synthesis of metal particles for applications in physics or in micro/nano-electronics generally. Besides the use of physical techniques such as atom evaporation, synthetic techniques based on salt reduction or compound precipitation (oxides, sulfides, selenides, etc.) have been developed, and associated, in general, to a kinetic control of the reaction using high temperatures, slow addition of reactants, or use of micelles as nanoreactors [15-20]. Organometallic compounds have also previously been used as material precursors in high temperature decomposition processes, for example in chemical vapor deposition [21]. Metal carbonyls have been widely used as precursors of metals either in the gas phase (OMCVD for the deposition of films or nanoparticles) or in solution for the synthesis after thermal treatment [22], UV irradiation or sonolysis [23,24] of fine powders or metal nanoparticles. 

The identification of structure sensitivity would be both impossible and useless if there did not exist reproducible recipes able to generate metal nanoparticles on a small scale and under controlled conditions, that is, with narrow size and/or shape distribution onto supports. Metal nanoparticles of controlled size, shape, and structure are attractive not only for catalytic applications, but are important, for example in optics, data storage, or electronics (c.f. Chapter 5). In order not to anticipate other chapters of this book (esp. Chapter 2), remarks will therefore be confined to few examples. 

The chapters of the book having been put forward to the reader are related to all practically important fields of interest, discussing a wide frame of points starting from application of nanoparticles in the field of manufacture, the devices for informatics and electronics and ending with self-assembly of metal nanoparticles, their characterization and relevance to biosystems. 

Willner and coworkers demonstrated three-dimensional networks of Au, Ag, and mixed composites of Au and Ag nanoparticles assembled on a conductive (indium-doped tin oxide) glass support by stepwise LbL assembly with A,A -bis(2-aminoethyl)-4,4 -bipyridinium as a redox-active cross-linker.8 37 The electrostatic attraction between the amino-bifunctional cross-linker and the citrate-protected metal particles led to the assembly of a multilayered composite nanoparticle network. The surface coverage of the metal nanoparticles and bipyridinium units associated with the Au nanoparticle assembly increased almost linearly upon the formation of the three-dimensional (3D) network. A coulometric analysis indicated an electroactive 3D nanoparticle array, implying that electron transport through the nanoparticles is feasible. A similar multilayered nanoparticle network was later used in a study on a sensor application by using bis-bipyridinium cyclophane as a cross-linker for Au nanoparticles and as a molecular receptor for rr-donor substrates.8... 

Metal nanoparticles have been used for many applications because of their unique characteristics, even before they were visualized as small particles of nano-meter order by using a transmission electron microscope [118]. For example, colored glasses, which gained in popularity in medieval times, contain nanoparticles of noble metals. These colors originate from the SPR of metal nanoparticles, which is the resonance phenomenon of surface electron density wave with incident light wave at the metal surface [119]. Since this resonance is sensitive to the dielectric constant of surrounding media, the phenomenon has... 

Nanoparticles consisting of noble metals have recently attracted much attention because such particles exhibit properties differing strongly from the properties of the bulk metal [1,2], Thus, such nanoparticles are interesting for their application as catalysts [3-5], sensors [6, 7], and in electronics. However, the metallic nanoparticles must be stabilized in solution to prevent aggregation. In principle, suitable carrier systems, such as microgels [8-11], dendrimers [12, 13], block copolymer micelles [14], and latex particles [15, 16], may be used as a nanoreactors in which the metal nanoparticles can be immobilized and used for the purpose at hand. 

Sintering is defined as a process in which distinct particles in a powder weld together and interdiffuse with each other at temperatures below their melting point. The concept has been employed in the fields of powder metallurgy and ceramics for hundreds of years. Sintering allows metal particles, whether nanoparticles for inkjet applications or larger particles for other printed electronics applications, to join together at a temperature below the melt phase in order to form the conductive path. 

This is probably one of the most important results with respect to applications of metal nanoparticles in future electronic nanodevices it impressively demonstrates Au55(PPh3)i2Cl6 to work as single electron switch at room temperature. From this knowledge, a series of consequences are following with respect to future electronic applications of this quantum dot. 

The formation of junctions in carbon nanotubes is important for use in electronic application. The SWNTs have been shown to react with silicon and transition metals and form metal carbide nanorods and nanoparticles at high temperature under high vacuum. A heterojunction interface with metal carbide at the tips of SWNTs is possible. Silicon and metal substrates such as Ti and Nb have been used with SWNTs to form long SiC, TiC, and NbC nanorods respectively. A small number of SWNTs with partial reaction are found to have coimected to SiC nanorods (Figure 15). The formation of such a carbide heterojunctions in carbon nanotubes with... 

Actually, one of the most important applications of metal nanoparticles is in the field of catalysis. Catalysts should offer large specific area in order to accelerate the access of reactants to the active sites. Nanoparticles, such as those synthesized by radiolysis, are thus particularly efficient in a number of reactions. However, catalyzed reactions are controlled not only by the kinetics, but also by the thermodynamics. Thus, due to their redox properties, nanoparticles with small sizes and low polydispersities are able to play a role as intermediate electron relays in an overall electron transfer between a donor and an acceptor. 

Surface plasmons (SPs) are collective electronic excitations near the surfaces of metallic structures. They can usually be described well with classical electromagnetic theory and correspond to electromagnetic fields that are localized and relatively intense near the metallic surfaces [1, 2]. These properties make them potentially useful for a variety of applications in optoelectronics, chemical and biological sensing, and other areas. Metallic nanostructures such as metal nanoparticles and nanostructured thin metal films, particularly those composed of noble metals such as silver or gold, are of special interest because often their SPs can be excited with visible-UV light and are relatively robust. 

Metal nanoparticles have attracted considerable interest due to their properties and applications related to size effects, which can be appropriately studied in the framework of nanophotonics [1]. Metal nanoparticles such as silver, gold and copper can scatter light elastically with remarkable efficiency because of a collective resonance of the conduction electrons in the metal (i.e., the Dipole Plasmon Resonance or Localized Surface Plasmon Resonance). Plasmonics is quickly becoming a dominant science-based technology for the twenty-first century, with enormous potential in the fields of optical computing, novel optical devices, and more recently, biological and medical research [2]. In particular, silver nanoparticles have attracted particular interest due to their applications in fluorescence enhancement [3-5]. 

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