Surface chemistry, metal colloids

J1.3 Surface chemistry on colloidal metals spectroscopic study of adsorption of small molecules... 

J. S. Bradley, J. M. Millar, and E. W. HiU. Surface-chemistry on colloidal metals - a high-resolution nuclear-magnetic-resonance study of carbon-monoxide adsorbed on metallic palladium crystallites in colloidal suspension. J. Am. Chem. Soc., 113 4016 017, 1991... 

L/evelopment of sophisticated surface analytical techniques over the past two decades has revived interest in the study of phenomena that occur at the electrode-solution interface. As a consequence of this renewed activity, electrochemical surface science is experiencing a rapid growth in empirical information. The symposium on which this book was based brought together established and up-and-coming researchers from the three interrelated disciplines of electrochemistry, surface science, and metal-cluster chemistry to help provide a better focus on the current status and future directions of research in electrochemistry. The symposium was part of the continuing series on Photochemical and Electrochemical Surface Science sponsored by the Division of Colloid and Surface Chemistry of the American Chemical Society. 

Waite, T.D. (1986), "Photoredox Chemistry of Colloidal Metal Oxides", in J.A. Davis and K.F. Hayes, Eds., Geochemical Processes at Mineral Surfaces, Washington, ACS Symposium Ser. No. 323. 

D.T. Ray and R. Hogg, Bonding of Ceramics Using Polymers at Low Concentration Levels in Innovations in Materials Processing Using Aqueous, Colloid Surface Chemistry, F.M. Doyle, S. Raghavan, P. Somasundaran and G.W. Warren (eds.). The Minerals, Metals Materials Soeiety, Warrendale PA, 1989, pp. 165-180. 

SE Friberg, CC Yang. In FM Doyle, S Raghavan, P Soinasundaran, GW Warren, eds. Innovations in Materials Processing Using Aqueous, Colloid and Surface Chemistry. Warrendale, PA Minerals, Metals Materials Society, 1988, pp 181-191. 

It is likely that the unusual effectiveness of the silver preparations described herein is due to the relationship between the surface properties/inner properties (i.e., oxide/ metal) of the particles and the size distribution of the particles. The smaller the average particle size, the greater the surface area and the greater the contribution of the particular surface chemistry. However, if the particles are excessively small there can be a loss of stability and/or other interactions that negatively affect the product. The sifver compositions of the instant invention are remarkabie because they are stable in essentially pure water without surfactants, etc. Also, the materials are essentially colorless while other colloidal silver preparations (particularly with larger particle sizes) usually show colors. These properties are a result of the exact manufacturing conditions as discussed above. 

See, for example, pp. 403-406 in E. M. Thurman, Organic Geochemistry of Natural Waters, Martinus Nijhoff, Dordrecht, The Netherlands, 1986, and T. D. Waite, Photoredox chemistry of colloidal metal oxides, Chap. 20 in Geochemical Processes at Mineral Surfaces, ed. by J. A. Davis and K. F. Hayes, American Chemical Society, Washington, DC, 1986. 

This method is based on the chemical reduction of the metal salts in citrate solution. Metal-dye adsorbates will be formed if a dye in extremely diluted solution is added. The surface enhancement depends on the precipitation conditions, type and charge of the adsorbing dye molecule, the degree of colloidal aggregation, and many other factors [18-20], so that a full understanding of the chemistry at colloidal... 

Moreover, the described phenomena will bear relevance for the metal-promoter interaction in promoted supported transition or noble metal catalysts. Unless spillover effects play a decisive role, promotion can occur only if the active metal and promoter oxide are in contact. Obviously, in such complex systems the surface- and interface-free energies and the mobilities of individual components under preparation conditions critically will determine their morphology and distribution. For a deeper understanding of the detailed mechanisms of wetting and spreading in such complex systems as supported catalysts, additional fundamental studies are required, in which our basic knowledge in surface chemistry, surface spectroscopy, colloid and solid-state chemistry, and powder technology must be combined. 

There are many indications in the literature that surface chemistry plays an important role in photoelectrochemical reactions at extended electrodes and at particles. One example has already been given in Section 9.1.1, where it has been shown for CdS colloids that surface states could be blocked by adding Cd to the solution. There are, however, only a few quantitative investigations on this problem [5, 59, probably due to the lack of sufficiently sensitive methods. In the case of metal oxide particles, the adsorption of H2O plays an important role. Due to the amphoteric behavior of most metal hydroxides, two surface equilibria have to be considered [59] ... 

Friberg, S. E. Yang, C. C. In Innovations in Materials Processing Using Aqueous, Colloid and Surface Chemistry Doyle, F. M. Raghavan, S. Somasun-daran, P. Warren, G. W., Eds. Minerals, Metals, and Materials Society Warrendale, PA, 1988 p 181. 

The surface chemistry of the as-synthesized NCs has been exploited in order to develop methods for anchoring the semiconductor NCs directly to the sol-gel network. The approaches investigated are analogous to methods discussed in Section 2 with respect to organically modified gels, with one major exception - the colloidal NC, and not Just the starting metal salt, is directly tethered to the metal-oxide network ... 

General introduction/Electronic structure of metal clusters and cluster compounds/ Clusters in ligand shells/Clusters in cages/Discrete and condensed transition metal clusters in solids/Chemistry of transition metal colloids/Perspectives G.A. Somoijai, Introduction to Surface Chemistry and Catalysis, Wiley New York, 1994... 

Another aspect of this topic is the colloidal stability of nanoparticles, mainly in metal oxides. In water, the most common liquid medium, metal oxide surface chemistry is controlled by the surface hydroxyl groups [42-44]. The following surface equilibrium condition must therefore be considered ... 

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