Cobalt colloids

Pathmamanoharan C and Philipse A P 1998 Preparation and properties of monodisperse magnetic cobalt colloids grafted with polyisobutene J. Colloid Interface Sol. 205 304-53... 

Fig. 6.1. TEM micrographs of the cobalt colloidal solution (a) as prepared fresh, (b) after a week of aging, (c) after a month of aging (inset ED pattern).

As described at the end of the last section, we came upon the study of metal oxide nanoparticles in aqueous solution accidentally. Our only earlier experience with this class of nanoparticles, although in organic solvents such as THF, was the investigation of the controlled 02-mediated oxidation of tetraalkylammonium bromide stabilized cobalt colloids prepared size-selectively by the electrochemical method (Fig. 8.5) [53]. 

Palladium and cobalt colloids stabilized with iro-butylaluminoxane, (i o-BuAIO) , in methylcyclohexane catalyzed the hydrogenation of the activated double bond of acenaphthylene to acenaphthene at 25 °C, (Eqn. 6.6). In the case of the cobalt catalyst, heating to 80 °C resulted in the further hydrogenation of one of the aromatic rings in acenaphthene, a reaction which was poisoned by the addition of dibenzothiophene. 

Cobalt, sepn. of from nickel, (cm) 532 Codeine and morphine, D. of 740 Coefficient of variation 135 Colloidal state 418 See also Lyophilic, Lyophobic Colorimeters light filters for, 661 photoelectric, 645, 666 Colorimetric analysis 645 criteria for, 672 general remarks on, 645, 672 procedure, 675 solvent selection, 674 titration, 652... 

Late transition metal or 3d-transition metal irons, such as cobalt, nickel, and copper, are important for catalysis, magnetism, and optics. Reduction of 3d-transition metal ions to zero-valent metals is quite difficult because of their lower redox potentials than those of noble metal ions. A production of bimetallic nanoparticles between 3d-transi-tion metal and noble metal, however, is not so difficult. In 1993, we successfully established a new preparation method of PVP-protected CuPd bimetallic nanoparticles [71-73]. In this method, bimetallic hydroxide colloid forms in the first step by adjusting the pH value with a sodium hydroxide solution before the reduction process, which is designed to overcome the problems caused by the difference in redox potentials. Then, the bimetallic species... 

Later, Chung et al. successfully developed an intramolecular Pauson-Khand reaction in water without any cosolvent by using aqueous colloidal cobalt nanoparticles as catalysts. The catalyst was prepared by reducing an aqueous solution of cobalt acetate containing sodium dode-cyl sulfate (SDS) surfactant. The cobalt nanoparticle could be reused eight times without any loss of catalytic activity (Eq. 4.57).107... 

Balthis and Bailar6 obtained tris (ethylenediamine) chromium-(III) complexes by the oxidation of chromium(II) solutions, using a procedure somewhat similar to that used for the synthesis of cobalt (III) com plexes. Mori7 described the preparation of hexaamminechromium(III) salts from the oxidation of chromium (II) salts in the presence of ammonia. The results obtained in both syntheses have been erratic.8,9 Berman noted that the foregoing syntheses are rendered dependable by the use of a catalyst of activated platinum on asbestos. Schaeffer,100 in a subsequent study, independently used colloidal platinum as a catalyst but reported some difficulty in separating it from the product.106 The procedures recommended and described here are based on the use of platinized asbestos as the catalyst. 

Sugimoto T. and Matuevic E. 1979. Colloidal cobalt hydrous oxides. Preparation and properties of monodispersed Co304. J. Inorg. Nucl. Chem. 41 165-72. 

Sarellas A., Niakolas D., Bourikas K., Vakros J., and Kordulis C. 2006. The influence of the preparation method and the Co loading on the structure and activity of cobalt oxide/y-alumina catalysts for NO reduction by propene. J. Colloid. Interf. Sci. 295 165-72. 

Cobalamin, 25 803 folic acid and, 25 802 Cobalt (Co), 7 207-228. See also Co-base superalloys 60Co isotope 60Co nucleus Fe-Ni-Co alloys Dicobalt octacarbonyl Tetracobalt dodecacarbonyl analysis, 7 215-216 in ceramic-matrix composites, 5 554t coke formation on, 5 266 colloidal suspensions, 7 275 economic aspects, 7 214-215 effect on copper resistivity, 7 676t environmental concerns, 7 216 health and safety factors, 7 216-218 in M-type ferrites, 11 66, 69 occurrence, 7 208... 

Inks, 14 311-336 ball-point, 14 328 cellulose acetates, 5 438 cellulose ester applications, 5 403-404 cobalt applications, 7 244-245 as colloid, 7 272t, 273t color and coloring materials for, 14 316-318... 

Puntes, V.F., Krishnan, K.M., and Ahvisatos, A.P., Colloidal nanocrystal shape and size control the case of cobalt Science, 291, 2115,2001. 

S. Son, S. Lee, Y. Chung, S. Kim, and T Hyeon, The first intramolecular Pauson—Khand reaction in water using aqueous colloidal cobalt nanoparticles as catalysts. Organ. Lett. 4,277—279 (2002). 

V. F. Puntes, K. M. Krishnan, and A. P. Alivisatos, Colloidal nanocrystal shape and size control The case of cobalt. Science 291, 2115-2117 (2001). 

Blesa, M.A. Maroto, A.J.G. (1986) Dissolution of metal oxides. J. chim. phys. 83 757—764 Blesa, M.A. Matijevic, E. (1989) Phase transformation of iron oxides, oxyhydroxides, and hydrous oxides in aqueous media. Adv. Colloid Interface Sci. 29 173-221 Blesa, M.A. Borghi, E.B. Maroto, A.J.G. Re-gazzoni, A.E. (1984) Adsorption of EDTA and iron-EDTA complexes on magnetite and the mechanism of dissolution of magnetite by EDTA. J. Colloid Interface Sci. 98 295-305 Blesa, M.A. Larotonda, R.M. Maroto, A.J.G. Regazzoni, A.E. (1982) Behaviour of cobalt(l 1) in aqueous suspensions of magnetite. Colloid Surf. 5 197-208... 

Duran, J.D.G. Gonzallez-Caballero, E. (2000) Stability of cobalt-ferrite colloidal particles. Effect of pH and applied magnetic field. Langmuir 16 7954-7961 De Vitre, R. Belzile, N. Tessier, A. (1991) Spe-ciation and adsorption of arsenic on diage-netic iron oxyhydroxides. Limnol. Oceanogr. 36 1480-1485... 

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