Electrons aqueous clusters

Luther GW, Theberge SM, Rickard DT (1999) Evidence for aqueous clusters as intermediates during zinc sulfide formation. Geochim Cosmochim Acta 64 579-579 MacKenzie KJD (1975) The calcination of titania, V. Kinetics and mechanism of the anatase-ratile transformation in the presence of additives. Trans J British Ceram Soc 74 77-87 Malek J, Mitsuhashi T, Ramirez-Castellanos J, Matsui Y (1999) Calorimetric and high-resolution transmission electron microscopy study of nanocrystallization in zirconia gel. J Mater Res 14 1834-1843... 

The structures of aqueous clusters formed by the interaction of a cation, an electron, or an anion, with various sizes of water clusters bear no structural resemblance to the parent neutral water clusters because of the dominance of electrostatic interactions. However, things are very different in the case of interactions involving ir-systems with varying sizes of water clusters. This is because of the fact that the interactions existing between... 

Initial studies on the redox properties of the M6Yi2 " clusters were reported on poorly defined complexes simply noted as [TaeCli2] or [Nb(jCli2] (122). Aqueous cluster solutions were prepared from the sulfate salts TaeCli2S04 and Nb6Cli2S04 with various electrolytes. Some combination of water molecules and anions fills the coordination sphere of the MeY " cluster. Despite these ambiguities, the oxidized compounds M6Yi2 were obtained with various chemical oxidants by a two-electron transfer process (123) ... 

A review of preparative methods for metal sols (colloidal metal particles) suspended in solution is given. The problems involved with the preparation and stabilization of non-aqueous metal colloidal particles are noted. A new method is described for preparing non-aqueous metal sols based on the clustering of solvated metal atoms (from metal vaporization) in cold organic solvents. Gold-acetone colloidal solutions are discussed in detail, especially their preparation, control of particle size (2-9 nm), electrophoresis measurements, electron microscopy, GC-MS, resistivity, and related studies. Particle stabilization involves both electrostatic and steric mechanisms and these are discussed in comparison with aqueous systems. 

Furthermore, it has been demonstrated that the successful electrocatalytic reduction of C02 with [Ru(bpy)2(CO)2]2+ in aqueous MeCN is mainly due to the formation of a polymeric electroactive film, which occurs during the reduction of the complex.91 This film is composed of an open cluster polymer [Ru(bpy)(CO)2]ra (Scheme 6) based upon extended Ru°—Ru° bonds. Electropolymerization of [Ru(bpy)2(CO)2]2+ results from the overall addition of two electrons per mole of [Ru(bpy)2(CO)2]2+ and is associated with the decoordination of one bpy ligand (Equation (33)). 

The separation of a reactant system (solute) from its environment with the consequent concept of solvent or surrounding medium effect on the electronic properties of a given subsystem of interest as general as the quantum separability theorem can be. With its intrinsic limitations, the approach applies to the description of specific reacting subsystems in their particular active sites as they can be found in condensed phase and in media including the rather specific environments provided by enzymes, catalytic antibodies, zeolites, clusters or the less structured ones found in non-aqueous and mixed solvents [1,3,6,8,11,12,14-30],... 

In a more simple and cheap way, silver clusters can be prepared in aqueous solutions of commercially available polyelectrolytes, such as poly(methacrylic acid) (PM A A) by photo activation using visible light [20] or UV light [29]. Ras et al. found that photoactivation with visible light results in fluorescent silver cluster solutions without any noticeable silver nanoparticle impurities, as seen in electron microscopy and from the absence of plasmon absorption bands near 400 nm (F = 5-6%). It was seen that using PMAA in its acidic form, different ratios Ag+ MAA (0.15 1-3 1) lead to different emission bands, as discussed in the next section (Fig. 12) [20]. When solutions of PMAA in its sodium form and silver salt were reduced with UV light (365 nm, 8 W), silver nanoclusters were obtained with emission band centered at 620 nm and [Pg.322]

Finally in this section, we refer to classic studies on gas phase interactions carried out with a pulsed electron beam high ion source mass spectrometer, which have yielded details of hydrogen bonding of substituted pyridinium ions to water in the gas phase (79JA1675). These measurements afford thermodynamic data for the stepwise hydration of pyridinium ions XC6H4NH(OH2)n for values of n varying between 0 and 4. The attenuation of substituent effects is much less than for aqueous solution, because although the water molecules cluster round NH in the gas phase, they cannot provide an overall solvation network, the dielectric constant of which in the liquid phase serves to reduce the influence of the substituent dipole. 

The detection of sharp plasmon absorption signifies the onset of metallic character. This phenomenon occurs in the presence of a conduction band intersected by the Fermi level, which enables electron-hole pairs of all energies, no matter how small, to be excited. A metal, of course, conducts current electrically and its resistivity has a positive temperature coefficient. On the basis of these definitions, aqueous 5-10 nm colloidal silver particles, in the millimolar concentration range, can be considered to be metallic. Smaller particles in the 100-A > D > 20-A size domain, which exhibit absorption spectra blue-shifted from the plasmon band (Fig. 80), have been suggested to be quasi-metallic [513] these particles are size-quantized [8-11]. Still smaller particles, having distinct absorption bands in the ultraviolet region, are non-metallic silver clusters. 

---