Surface anchoring sites

Scheme 4 Cr(VI) anchoring reaction on silicon membered rings of increasing dimensions (and decreasing strain) and the successive CO-reduction. Surface anchoring sites are those reported in Scheme 2...

In principle, different surface sites can serve as anchoring sites but the surface OH groups are the most common anchoring groups on the oxide surfaces.225 These OH groups can take part in different reactions. For example, inorganic salts can react with the surface OH groups (Scheme 7.7).226... 

The insertion of the flexible chain between the anchoring site and the silica surface gives the PPh2 ligands a high degree of freedom, thereby permitting their easy coordination to the metal center and the ability to react as a free phosphine in solution. 

Prior to functionalization the carbon nanomaterials were washed in concentrated nitric acid (65% Fisher Scientific) for 8 h using a Soxhlet device in order to remove catalyst residues of the nanomaterial synthesis as well as to create anchor sites (surface oxides) for the Co on the surface of the nanomaterials. After acid treatment the feedstock was treated overnight with a sodium hydrogen carbonate solution (Gruessing) for neutralization reasons. For the functionalization of the support media with cobalt particles, a wet impregnation technique was applied. For this purpose 10 g of the respective nanomaterial and 10 g of cobalt(II)-nitrate hexahydrate (Co(N03)2-6 H20, Fluka) were suspended in ethanol (11) and stirred for 24 h. Thereafter, the suspension was filtered via a water jet pump and finally entirely dried using a high-vacuum pump (5 mbar). 

Thus, in this section we will present the various reactive sites that can be found on the surface of the more common substrates, i.e. the surface reactive functionahties, the surface defects and, in addition, the anchoring sites on the nanoparticles which can induce autocatalytic effects. Selected examples will illustrate the major role played by surface chemistry. 

Adherent, conformal LPD ceramic film either crystalline (Method 2) or amorphous (Method 1) can be obtained on polyimides. This is in contrast to silanol-bearing surfaces (good for Method 1 only) or sulfonated surfaces (good for Method 2 only). The fact that the polyimides accommodate both titania preparations may be due to the partial hydrolysis of the polymer surface under oxide deposition conditions. This provides a mix of carboxylic acid and amide sites that anchor the titania by a combination of coulombic and chelation-based effects.22 An important lesson of this work is that the interaction of the polymer surface with the deposition solution may create oxide film anchoring sites. This does not negate activating the polymer surface. It recognizes that the polymer surface can react further under the deposition conditions. 

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