Passivated metal particles Passive” polymer

Plasma is effective in the fabrication of nanocomposites, such as nanoparticles composed of one material and covered by a nanolayer of another. Relevant examples include, in particular, carbon-coated magnetic metal particles produced in thermal arc plasma (McHenry et al., 1994), as well as polymer-coated nanoparticles with improved adhesion, corrosion resistance, and surface passivation produced in RF plasma in a fluidized bed (Shi et al.,... 

Metal-polymer nanocomposites can be obtained by two different approaches, namely, in situ and ex situ techniques. In the in situ methods, metal particles are generated inside a polymer matrix by decomposition (e.g., thermolysis, photolysis, radiolysis, etc.) or chemical reduction of a metallic precursor dissolved into the polymer. In the ex situ approach, nanoparticles are first produced by soft-chemistry routes and then dispersed into polymeric matrices. Usually, the preparative scheme allows us to obtain metal nanoparticles whose surface has been passivated by a monolayer of -alkanethiol molecules (i.e., Crfiin+i-SH). Surface passivation has a fundamental role since it avoids aggregation and surface oxidation/contamination phenomena. In addition, passivated metal particles are hydrophobic and therefore can be easily mixed with polymers. The ex-situ techniques for the synthesis of metal/polymer nanocomposites are frequently preferred to the in situ methods because of the high optical quality that can be achieved in the final product. 

The fnnctionality present on the MNP surface also greatly impacts their assembly behavior. In most cases, the surface of the MNPs is passivated by an organic monolayer that protects them from aggregation and provides solubility in solvents. The particle surface also represents the interface at which the particle and polymer interact within the composite assembly. Self-assembly processes require favorable interactions between the MNP building blocks and the polymer, such that stable equilibrium (or near equilibrium) structures are formed. The types of intermolecular noncovalent interactions include hydrogen bonding, metal coordination, electrostatic, dipole-dipole, and hydrophobic interactions, as well as van der Waals forces, between MNPs and polymers. The successful self-assembly of MNPs into well-defined nanostructures not only depends on the ability to control precisely their composition, shape, and size but also on the modification of the MNP surface with the desired functionahty that mediates interactions with the polymer. 

Attachment of various layers to metals is an important process which permits protection of the metal from the environment, but also provides particular properties to the surface. Therefore, metal coating with paints, polymers, surfactants and so forth is an industrial process of wide application and there exists a large variety of methods for this purpose [12]. These properties of passivated product is a function of the interaction between particle surface and additives. The formation of weak and strong bonds between the metal particles and the organic layer depends on the mature of both components. For example, alkanesUanes form veiy stable monolayers on aluminum oxides. The headgroup of the molecule, a trichloro- or trialkoxysilane, forms a covalent bond with surface OH [13]. This process has found industrial applications as a possible substitute for chromate treatments [14]. One of the most... 

CuNPs) in Fig. 7 shows the monodisperse and uniformly distributed spherical particles of 10+5 nm diameter. The solution containing nanoparticles of silver was found to be transparent and stable for 6 months with no significant change in the surface plasmon and average particle size. However, in the absence of starch, the nanoparticles formed were observed to be immediately aggregated into black precipitate. The hydroxyl groups of the starch polymer act as passivation contacts for the stabilization of the metallic nanoparticles in the aqueous solution. The method can be extended for synthesis of various other metallic and bimetallic particles as well. 

Transition-metal nanopartides are of fundamental interest and technological importance because of their applications to catalysis [22,104-107]. Synthetic routes to metal nanopartides include evaporation and condensation, and chemical or electrochemical reduction of metal salts in the presence of stabilizers [104,105,108-110]. The purpose of the stabilizers, which include polymers, ligands, and surfactants, is to control particle size and prevent agglomeration. However, stabilizers also passivate cluster surfaces. For some applications, such as catalysis, it is desirable to prepare small, stable, but not-fully-passivated, particles so that substrates can access the encapsulated clusters. Another promising method for preparing clusters and colloids involves the use of templates, such as reverse micelles [111,112] and porous membranes [106,113,114]. However, even this approach results in at least partial passivation and mass transfer limitations unless the template is removed. Unfortunately, removal of the template may re-... 

In this chapter, two new approaches for the synthesis of metal-polymer nanocomposite materials have been described. The first method allows the preparation of contact-free dispersions of passivated gold clusters in polystyrene, and it is based on a traditional technique for the colloidal gold synthesis—that is, the alcoholic reduction of tetrachloroauric acid in presence of poly(vinyl pyrrolidone) as polymeric stabilizer. The primary function of the stabilizer is to avoid cluster sintering, but it also allows us to isolate clusters by co-precipitation. It has been found that the obtained polymer-protected nanometric gold particles can be dissolved in alkane-thiol alcoholic solutions to yield thiol-derivatized gold clusters by thiol absorbtion on the metal surface. Differently from other approaches for thioaurite synthesis available in the literature, this method allows complete control over the passivated gold cluster structure since a number of thiol molecules can be equivalently used and the... 

For all-printed thin film transistors (TFT), various organic and inorganic metal electrode materials, such as conductive polymer, carbon nanotube (CNT), organic metal compound, or metal nano-particles, have been used as gate and source/drain electrodes [6-11] in a combination with inkjet- and laser-based printing methods. One of the immediate applications for all-printed TFT would be flexible or rugged display backplane and disposable radio frequency identification (RFID) tags. In addition, printed metal electrodes and TFT have also been used to fabricate passive circuit components, power transmission sheets and sensors for ambient electronics and electronic skin [12-13]. 

Briefly, the process consists in the formation of metallic ultra-dispersed particle that are in situ simultaneously chemically passivate with a polymer matrix (reactions 1 and 2) [143] ... 

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