Reverse micelle technique

To control the formation of nanoparticles with desired size, composition, structure, dispersion, and stability, a multifunction nanoagent is used. The active metals (Pd and Pt) react with the functional groups of the nanoagent, i.e., a pol5mier template. The polymer template determines the size, monodisperity, composition, and morphology of the particles (which is somewhat reminiscent of the reversed micelles technique mentioned above). 

Novel and effective bioseparation techniques must be continuously researched and developed for profitable removal of proteins and other bioproducts of interest from very dilute solutions (A. Ramakrishnan and A. Sadana, personal communication, 1999). There appear to be two techniques that have tremendous potential for commercial applications the reverse micelle technique and aqueous two-phase extraction. Before these techniques achieve their potential, it will be necessary to further delineate the effect of mass transfer, interactions at the interfaces, and other parameters that affect both the quality and quantity of proteins separated by these techniques. It is also necessary to have a large data bank of a wide variety of proteins and bioproducts with regard to their characteristics and stability to assist future improvements in bioseparations. 

Enormous advances and growth in the use of ordered media (that is, surfactant normal and reversed micelles, surfactant vesicles, and cyclodextrins) have occurred in the past decade, particularly in their chromatographic applications. New techniques developed in this field include micellar liquid chromatography, micellar-enhanced ultrafiltration, micellar electrokinetic capillary chromatography, and extraction of bioproducts with reversed micelles techniques previously developed include cyclodextrins as stationary and mobile-phase components in chromatography. The symposium upon which this book was based was the first major symposium devoted to this topic and was organized to present the current state of the art in this rapidly expanding field. 

Among the synthetic methods, the reverse micelle technique shall only briefly be mentioned. It is based on the use of water droplets in an organic phase of a surfactant. bi Metal salts, dissolved in the water droplets, are reduced inside the nanometer-sized water volume, to result in nanoparticles trapped in the micelles. Alloy-like particles as well as bimetallic core-shell particles thus become available. Size distributions up to over 20% have to be put up with this technique. Another disadvantage of the reverse micelle procedure is the lack of crystallinity due to the low synthesis temperature (<100°C) requiring subsequent aimealing at 200-300 Fe, Co, and Ni... 

There have been fewer reports on the particle size dependence of catalysis by platinum-catalyzed redox reactions. A report by Sharma et al. [21] showed that platinum colloidal nanoparticles do not demonstrate the same dependence on particle size as gold nanoparticles do for the reduction of hexacyanoferrate (III) by thiosulfate [19]. Platinum nanoparticles protected by sodium di(2-ethylhexyl) sulfosuccinate (synthesized by a reverse micelle technique) exhibit an optimum size ( 38 nm) for the reduction of ferricyanide by thiosulfate (Fig. 18.2). The reason for an optimum particle size is not fully understood however, they proposed the following explanation a shift in the Fermi level occurs as the diameter is increased. 

Misra, R.D.K., Gubbala, S., Kale, A. and EgelhofF, W.F. (2004) A comparison of the magnetic characteristics of nanocrystalline nickel, zinc, and manganese ferrites synthesized by reverse micelle technique. /. Mater. Sci. Eng., Bill, 164—174. 

Preparation of hollow silica-Rh, -Ir, and -Rh/Ir-bimetallic nanocomposites by reverse micelle technique and their unique adsorption and catalytic behavior... 

Hu et al. showed the preparation of highly porous nanorod-PANI-gra-phene nanocomposite films deposited onto the ITO substrate by in-situ electrochemical polymerization [135]. They used a reverse micelle technique by mixing oil and water in an aqueous solution of TritonX-100. The electro-migration of the ionic species is improved by the addition of dilute HNOj to the oil-water-surfactant solution followed by the polymerization of aniline monomer in presence of graphene dispersion. Figure 4.12 shows the schematic for the preparation of nanorod-PANI-graphene nanocomposites by reverse micelle in-situ electropolymerization technique. 

A reverse-micelle technique k considered an efficient route to produce high quality, monodisperse magnetic and superparamagnetic nanoparticles. It has been shown that the basic magnetic properties such as coercivity (He), saturation magnetization (Ms), Curie temperature (Jc) as well as lattice constank can be tuned by varying the cation stoichiometry [109]. In thk method, cation occupancy, elemental composition. 

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