Metallic colloidal microscopy

A review of preparative methods for metal sols (colloidal metal particles) suspended in solution is given. The problems involved with the preparation and stabilization of non-aqueous metal colloidal particles are noted. A new method is described for preparing non-aqueous metal sols based on the clustering of solvated metal atoms (from metal vaporization) in cold organic solvents. Gold-acetone colloidal solutions are discussed in detail, especially their preparation, control of particle size (2-9 nm), electrophoresis measurements, electron microscopy, GC-MS, resistivity, and related studies. Particle stabilization involves both electrostatic and steric mechanisms and these are discussed in comparison with aqueous systems. 

Tsai DP, Kovacs J, Wang Z, Moskovits M, Shalaev VM, Suh JS, Botet R (1994) Photon scanning tunneling microscopy images of optical excitations of fractal metal colloid clusters. Phys Rev Lett 72(26) 4149... 

As for all catalysts, well-characterized samples are necessary to be able to relate the catalytic performance to physico-chemical properties. Transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAFS) were used in this study to characterize the stabilized metal colloid. The necessity of such extensive characterization of particle size has been outlined by Harada et al. [6,7] showing that the formation of aggregates may be overlooked and misinterpreted as large metal particles when using TEM alone. The actual availability of the polymer stabilized surface has been probed by hydrogen/oxygen titration adopted from the description of Bernard et al. [8]. 

Metal colloids in an aqueous solution are ideal markers for cell surfaces and intracellular components for microscopic observation (light and fluorescence microscopy, transmission and scanning electron microscopy) and for studying molecular organization and cell function It also has numerous medical uses as a drug and as a test for various diseases For more specific information about the interfacial behaviour... 

Several techniques are commonly used to measure the size distributions of metal colloid particles. Electron microscopy. X-ray diffi ction, and small angle X-ray scattering are the most commonly used, although dassical methods such as sedimentation rates are sometimes reported. The techniques whidi have been extensively applied to the sizing of polymer colloids and emulsions, [183] such as light scattering and neutron scattering, have been only rarely applied to the characterization of metal sols. [103, 151, 153, 184]... 

In this chapter we report some results for several nonionic polymers and cationic polyelectrolytes and their ability to stabilize platinum colloids. Both steric and electrostatic stabilization of the metal colloids can be combined by the use of polyelectrolytes (5). The materials have been examined by transmission electron microscopy (TEM) in order to determine the average particle size, size distribution and particle pe. The catalytic activity of these polymer-protected platinum nanoparticles has been tested by the hydrogenation of cyclohexene, d cyclooctene, and 1-hexene. 

Yamaguchi M, Kondo I. Immunoelectron microscopy of Proteus vulgaris by the plasma polymerization metal-extraction replica method differential staining of flagellar (H) and somatic (0) antigens by colloidal golds. J Electron Microsc 1989 38 382-388. 

Copper ions have been reduced in colloidal assemblies differing in their structures (55,56). In all cases, copper metal particles are obtained. Figure 9.3.1 shows the freeze-fracture electron microscopy (FFEM) for the various parts of the phase diagram. Their structures have been determined by SAXS, conductivity, FFEM, and by predictions of microstructures that require only notions of local curvature and local and global packing constraints. 

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