Monolayer dispersion surface bond

In the case of an ionic compound such as oxide or salt dispersed on the surface of y-Al203 or TiO, the surface bond between the monolayer and the surface of support is usually strong enough to make the entropy effect... 

T Aizawa, Y Hwang, W Hayami, R Souda, S Otani, Y Ishizawa. Phonon dispersion of monolayer graphite on Pt(lll) and NbC surfaces Bond softening and interface structure. Surf Sci 260 311, 1992. 

Different methods were used to prepare well-dispersed or monolayer type materials on various carriers. A desirable dispersion can be obtained by the first method developed in our experiments as long as certain conditions are carefully chosen and controlled for the different systems. The location, coordination and M-O bond strength of those surface-dispersed ferric ions are strongly determined by the nature of the supports and the preparative methods. Significant changes in oxidation-reduction properties and catalytic performances for the most well-dispersed or monolayer dispersed samples suggest that there is a strong interaction between the support and supported component. 

Surfactants adsorb on solid surfaces due to hydrophobic bonding, electrostatic interaction, acid-base interaction, polarisation of rr electrons and dispersion forces. Hydrophobic bonding occurs between the hydrophobic surfactant tail and the hydrophobic solid surface (tail down adsorption with monolayer structure) or between the hydrophobic tails of the surfactant adsorbed on the hydrophilic solid surface and the hydrophobic tails of the surfactant from the liquid phase (head down adsorption with bilayer structure) [54, 55]. 

Electrostatic interactions occur between the ionic head groups of the surfactant and the oppositely charged solid surface (head down adsorption with monolayer structure) [56]. Acid-base interactions occur due to hydrogen bonding or Lewis acid-Lewis base reactions between solid surface and surfactant molecules (head down with monolayer structure) [57]. Polarisation of jt electrons occurs between the surfactant head group which has electron-rich aromatic nuclei and the positively charged solid surface (head down with monolayer structure) [58]. Dispersion forces occur due to London-van der Waals forces between the surfactant molecules and the solid surface (hydrophobic tail lies flat on the hydrophobic solid surface while hydrophilic head orients towards polar liquid) [59]. 

V—0-Support (930cm ) and V—O—V (625 cm ) bonds. Similar distributions of monomeric and polymeric surface VO4 species are found on other oxide supports with the exception of Si02 [30]. For the supported V20s/Si02 catalyst system, only isolated surface VO4 species are present below the maximum dispersion limit (<3 V atoms/nm ). For all supported vanadium oxide catalysts, crystalline V2O5 NPs are also present above the monolayer surface coverage or maximum dispersion limit [31]. 

The application of transition metal oxide monolayer/support systems as carriers for platinum allows the possibility of modification of the properties of platinum in a wide range [5]. According to our previous works we adopted an optimal loading of platinum (2 %w). The reaction of platinum compound with OH groups of the support proceeded to the formation of transition metal-O-Pt bond, according to the reaction (3) - a useful tool for obtaining well dispersed noble metal on the surface of inorganic support [6,7]. 

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