Shell Particles

Liz-Marzan L M, Giersig M and Mulvaney P 1996 Synthesis of nanosized gold-silica core-shell particles Langmuir 12 4329-35... 

When monomers of drastically different solubiUty (39) or hydrophobicity are used or when staged polymerizations (40,41) are carried out, core—shell morphologies are possible. A wide variety of core—shell latices have found appHcation ia paints, impact modifiers, and as carriers for biomolecules. In staged polymerizations, spherical core—shell particles are made when polymer made from the first monomer is more hydrophobic than polymer made from the second monomer (42). When the first polymer made is less hydrophobic then the second, complex morphologies are possible including voids and half-moons (43), although spherical particles stiU occur (44). 

Tamil S.S., Spatz, J.P., Klok H.A., and Martin M. Gold-polypyrrole core-shell particles in diblock copolymer micells, Aiiv. Mater., 10, 132, 1998. 

For the characterization of Langmuir films, Fulda and coworkers [75-77] used anionic and cationic core-shell particles prepared by emulsifier-free emulsion polymerization. These particles have several advantages over those used in early publications First, the particles do not contain any stabihzer or emulsifier, which is eventually desorbed upon spreading and disturbs the formation of a particle monolayer at the air-water interface. Second, the preparation is a one-step process leading directly to monodisperse particles 0.2-0.5 jim in diameter. Third, the nature of the shell can be easily varied by using different hydrophilic comonomers. In Table 1, the particles and their characteristic properties are hsted. Most of the studies were carried out using anionic particles with polystyrene as core material and polyacrylic acid in the shell. 

Engineering of Core-Shell Particles and Hollow Capsules... 

An important class of materials that originates from the precursor core-shell particles is hollow capsules. Hollow capsules (or shells ) can be routinely produced upon removal of the core material using chemical and physical methods. Much of the research conducted in the production of uniform-size hollow capsules arises from their scientific and technological interest. Hollow capsules are widely utilized for the encapsulation and controlled release of various substances (e.g., drugs, cosmetics, dyes, and inks), in catalysis and acoustic insulation, in the development of piezoelectric transducers and low-dielectric-constant materials, and for the manufacture of advanced materials [14],... 

Hollow gold spheres or core-shell particles consisting of a gold shell on a core of some other material have recently attracted attention. This is because they have interesting and tunable optical extinction properties [56]. These can be readily calculated using Mie theory [57], and there had been some scattered early interest in these shapes as a result [58, 59], but the versatility and properties of these particles only became widely... 

Figure 7. TEM images of Ag-core/Au-shell particles in molar ratio Ag Au of (a, b) 1 1 (c, d) 1 3. Note the enlargement of the particles as the Au-shell becomes thicker (panels (a) and (c)) as well as the resolution of the lattice planes (panels (b) and (d)). The power spectra indicate that Au grows epitaxially onto the Ag-seeds. (Reprinted from Ref. [153], 2000, with permission from American Chemical Society.)...

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