Colloids EXAFS

Duff, D.G. et al., Structural characterization of colloidal platinum by high resolution electron microscopy and EXAFS analysis, Angew. Chem. 101, 610, 1989 Angew. Chem. Int. Ed. Engl., 28, 590,1989. 

J. Colloid Interface Sd. 204 61—65 Dardenne, K. Schafer,T Deneke, M. Rothe, J. Kim, J.I. (2001) Identification and characterisation of sorbed lutetium species on 2-line ferrihydrite by sorption data modelling, TRLFS and EXAFS. Radiochem. Acta 89 469-479... 

Manceau, A. Lanson, B. Schlegel, M.L. Harge, J.C. Musso, M. Eybert-Berard, L. Haze-marm, J.-L. Chateigner, D. Lamble, G.M. (2000) Quantitative Zn speciation in smelter-contaminated soils by EXAFS spectroscopy. Am. J. Sd. 300 289-343 Manceau, A. Nagy, K.L. Spadini, L. Ragnars-dottir, K.V. (2000 a) Influence of anionic layer structure of Fe-oxyhydroxides on the structure of Cd surface complexes. J. Colloid Interface Sd. 228 306-316... 

Spadini, L. Manceau, A. Schindler, P.W. Charlet, L. (1994) Structure and stability of Cd surface complexes on ferric oxides. 1. Results from EXAFS spectroscopy. J. Colloid Interface Sd. 168 78—86... 

An alcohol reduction method has been applied to the synthesis of polymer-stabilized bimetallic nanoparticles. They have been prepared by simultaneous reduction of the two corresponding metal ions with refluxing alcohol. For example, colloidal dispersions of Pd/Pt bimetallic nanoparticles can be prepared by refluxing the alcohol-water (1 1 v/v) mixed solution of palladium(II) chloride and hexachloro-platinic(IV) acid in the presence of poly(/V-vinyl-2-pyrrolidone) (PVP) at about 90-95°C for 1 h (Scheme 9.1.5) (25). The resulting brownish colloidal dispersions are stable and neither precipitate nor flocculate over a period of several years. Pd/ Pt bimetallic nanoparticles thus obtained have a so-called core/shell structure, which is proved by an EXAFS technique (described in Section 9.1.3.3). 

Colloidal dispersions of fine metal particles have a long history. Metal nanoparticles are now in the spotlight because of recent developments in nanometer-scale science and technology. Especially the precise structure of the monodispersed bimetallic nanoparticles has become clear quite recently, thanks to the development of EXAFS technology. The mechanism of formation, growth, and structure control is not completely clear yet. In some parts, especially in Section 9.1.4, the discussion may be speculative but is based on the experience of the present author for over 20 years. 

Guo, X., Du, Y Chen, F. el al. (2007a) Mechanism of removal of arsenic by bead cellulose loaded with iron oxyhydroxide (f -FeOOH) EXAFS study. Journal of Colloid and Interface Science, 314(2), 427-33. 

Although this chapter focuses mainly on colloidal doped semiconductors, it is of interest to discuss briefly the use of EXAFS to monitor thermally induced... 

As an example, Fig. 5.6 depicts a typical diffraction spectrum. It is evident that long range order does not exist in our chalcogenide samples. However, the broad difffactrogram peak centered at 20 = 42.5° has the characteristic of a nanodivided ruthenium metal [22]. This points out that the active center in this chalcogenide materials is essentially of metallic nature. The material, either in powder or colloidal form, was analyzed by the EXAFS technique [11]. The local range order of this technique allowed for some structural determination of our samples. Thus, for example, the co-ordination distances for ruthenium-selenium and ruthenium-ruthenium are R(RU-se) = 2.43 A y R(ru.rU) = 2.64 A, respectively. The metal-metal co-ordination distance is of the same order of magnitude as that of well known cluster based materials such as the Chevrel phase [35, 37], cf. Fig. 5.2b. This testifies that the used chemical route leads to the formation of cluster-like materials. 

In recent years a variety of spectroscopic and other techniques have been employed to investigate and monitor hydrosilylation reactions. The techniques include multinuclear NMR, transmission electron microscopy, extended X-ray absorption fine structure (EXAFS), etc. Results from these experiments indicate that depending on the precatalyst, colloids and/or mononuclear complexes take part as catalytic intermediates. 

Bochatay, L. and Persson, P., Metal ion coordination at the water-manganite (g-MnOOH) interface II. An EXAFS study of zinc(II), J. Colloid Interface Sci., 229, 593, 2000. 

Roberts, D.R., Ford, R.G., and Sparks, D.L., Kinetics and mechanisms of Zn sorption on metal oxides using EXAFS, J. Colloid Interface Sci., in revision. 

Dent A. J., Ramsay J. D. F., and Swanton S. W. (1992) An EXAFS study of uranyl ion in solution and sorbed onto silica and montmorillonite clay colloids. Coll. Interface Sci. 150, 45-60. 

Redden G. B. and Bencheikh-Latmar J. R. (2001) Citrate enhanced uranyl adsorption on goethite an EXAFS analysis. J. Colloid Interface Sci. 244(1), 211—219. 

As mentioned above, EXAFS studies on nanoparticles synthesized in either powder form or nanoparticles from the colloidal solution were performed. The coordination distances for ruthenium-selenium and ruthenium-ruthenium are, respectively, R(Ru-se) = 2.43 A y R(Ru.ru) = 2.64 A. The metal-metal coordination distance is of... 

Spadini L, Manceau A, Schindler PW, Charlet L (1994) Structure and Stability of Cd Surface Complexes on Ferric Oxides. 1. Results from EXAFS Spectroscopy. J Colloid Interface Sci 168 73-86 Steefel Cl, van Cappellen P (1990) A new kinetic approach to modehng water-rock interaction Role of nucleation, precursors, and Ostwald ripening. Geochim Cosmochim Acta 54 2657-2677 Stem LA, Durham WB, Kirby SH (1997) Grain-size-induced weakening of H2O ices I and II and associated anisotropic recrystallization. J Geophys Res-Solid Earth 102 5313-5325 Suzuki A, Kotera Y (1962) The kinetics of the transition of titanium dioxide. Bull Chem Soc Japan 35 1353-1357... 

Schlegel ML, Manceau A, Chateigner D, Charlet L (1999) Sorption of metal ions on clay minerals 1. Polarized EXAFS evidence for the adsorption of Co on the edges of hectorite particles. J Colloid Interface Sci 215 140-158... 

Collins, C. R., Sherman, D. M., and Ragnarsddttir, K. V. (1999a). Surface complexation of Hg2+ on goethite mechanism from EXAFS spectroscopy and density functional calculations. J. Colloid Interface Sci. 219, 345-350. 

Sheals, J. et al.. Coadsorption of Cu(II) and glyphosate at the water-goethite (a-FeOOH) interface Molecular structures from FUR and EXAFS measurements, J. Colloid Inteif. Sci., 262, 38, 2003. 

Spadini, L. et al., Hydrous ferric oxide Evaluation of Cd-HFO surface complexation models combining Cd EXAFS data, potentiometric titration results and surface site structures identified from mineralogical knowledge, J. Colloid Interf. Sci., 266, 1, 2003. 

Osthols, E. et al.. Adsorption of thorium on amorphous silica An EXAFS study, 7. Colloid Intetf. Sci., 194, 10, 1997. 

Most recently, they have developed a cell configuration for the study of modified electrodes that employs, as a working electrode, colloidal graphite deposited onto kapton tape (typical window material). Such an arrangement minimizes attenuation due to the electrolyte solution. They coated the working electrode with a thin film of Nafion (a perfluoro sulfonate ionomer from E. I. DuPont de Nemours, Inc.) and incorporated [Cu(2,9-dimethy-1,10-phenanthroline)2] by ion exchange. They were able to obtain the EXAFS spectra around the copper K edge for the complex in both the Cu(I) and Cu(II) oxidation states. 

---