Colloidal stability hydrosols

Sodium salts of sulfonated triphenylphosphine P(m-C5H4S03Na)3 or alkyltriphenyl-methyltrisulfonates function as stabilizers for hydrosols of colloidal rhodium and (C6H5)2P-p-C6H5S03Na has been used by Schmid to prepare water soluble gold clusters which are isolable and redispersible without agglomeration [202]. 

A synthetic alternative to this is the chemical reduction of metal salts in the presence of extremely hydrophilic surfactants have yielded isolable nanometal colloids having at least 100 mg of metal per litre of water [105], The wide range of surfactants conveniently used to prepare hydrosols with very good redispersibility properties include amphiphilic betaines A1-A4, cationic, anionic, nonionic and even environmentally benign sugar soaps. Table 3.1 presents the list of hydrophilic stabilizers used for the preparation of nanostructured colloidal metal particles, and Table 3.2 shows the wide variety of transition metal mono- and bi-metallic hydrosols formed by this method [105,120],... 

Amhamdi, FI. Dumont, F. Buez-FIerman, C. (1997) Effect of urea on the stability of ferric oxide hydrosols. Colloids Surfaces 125 1-3 Amin, N. Arajs, S. (1987) Morin temperature of annealed submicronic a-Fe20j particles. Phys. Rev. B35 4810-4811 Amonette, J.E. Workman, D.J. Kennedy, D.W Fruchter, J.S. Gorby Y.A. (2000) Dechlorination of carbon tetrachloride by Fe(II) associated with goethite. Environ. Sci. Techn. 34 4606-4613... 

Penners, N.H.G. Koopal, L.K. (1987) The effect of particle size on the stability of hematite (a-Fe203) hydrosols. Colloids Surfaces 28 67-83... 

With selenium sols prepared by means of hydrazine hydrate at the ordinary temperature, by pouring into a large volume of water it has been shown that the stability of the colloid depends mainly on the degree of dispersion. An optimum concentration of electrolyte is necessary for the stability of the hydrosols. In the absence of electrolytes the system is quite unstable towards freezing. 

Arsenious sulphide has been the subject of extensive researches owing to the fact that it may readily be obtained as a hydrosol of considerable stability. Investigation of the factors which influence this stability has greatly added to our knowledge of colloid chemistry. 

Colloidal nickelous hydroxide is reduced to colloidal nickel by hydrogen in the presence of colloidal palladium as catalyst. The freshly precipitated hydroxide may also be reduced in a similar manner. It is advantageous to add sodium protalbinate to the mixture before reduction in order to increase the stability of the hydrosols produced.4... 

Palladium Hydrosol or Colloidal Palladium is readily prepared by the reduction of the chloride with acrolein5 or with hydrazine hydrate, in either case in the presence of an extract of Iceland moss 6 or in contact with sodium lysalbinate or protalbinate,7gum acacia,8 or with lanolin9 in a precisely similar manner to platinum,10 the function of the organic additions, which are protective colloids, being to increase the stability of the colloidal phase. 

In some other cases, the noble metals were deposited onto ceria from colloidal suspensions. Tlius, a stabilized rhodium hydrosol with an average particles size of 5 nm was used in the preparation of a Rh(i%)/Ce02 catalyst (182). Likewise, a series of Pd/Ce02 catalysts with 0.5, 2.5 and 5 wt.% have been prepared from microemulsion of metallic palladium, further destabilized by addition of tetrahydrofiiran (78). 

Amhamdi, IL, Dumont, R, and Buess-Herman, C., Effect of urea on the stability of ferric oxide hydrosols, Colloids Suif. A, 125, 1,1997. 

Research of Soviet scientists is surveyed. Contributions to various aspects of the colloid chemistry of silica are examined preparation and stabilization of silica hydrosols preparation of silica gels structural characterization of silicas surface chemistry elucidation adsorption and ion-exchange property examination and geometric and chemical modification of silicas, silica coatings, and so forth. 

Churaev, Nikologorodskaya, and co-workers (33) investigated the Brownian and electrophoretic motion of silica hydrosol particles in aqueous solutions of an electrolyte at different concentrations of poly(ethylene oxide) (PEO) in the disperse medium. The adsorption isotherms of PEO on the surface of silica particles were obtained. The thickness of the adsorption layers of PEO was determined as a function of the electrolyte concentration and the pH of the dispersed medium. The results can be used in an analysis of the flocculation and stabilization conditions for colloidal dispersions of silica (with non-ionogenic water-soluble polymers of the PEO type). 

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