Surface-active functional groups

Compound 20, Fig. 27(a), is representative of a large class of adsorbates which attach to the Pt surface in a single predominant orientation as a result of a surface-active functional group. 

To understand the structural requirements for a molecule to promote cytochrome c electrochemistry at gold electrodes, over 50 bifunctional organic compounds (X Y, where X is a surface-active functional group, Y is the protein-interactive ftmctionality, and is the linking structure) were investigated (21) to assess their ability to promote cytochrome c electrochemistry at a gold electrode. The results can be summarized as follows ... 

More interestingly, electron transfer reaction of cytochrome c and other redox proteins occurs with fast rates at modified electrodes. The most efficient electrode surface promoters tend to be bifunctional molecules containing surface-active functional groups (thiol, disulphide, or pyridyl) which bind the promoter to the electrode surface and weakly basic or anionic functional groups (such as pyridyl nitrogen, carboxy-late, sulphonate or phosphate) which can bind the positively charged cytochrome c [188-190,204-211]. For instance, if a gold electrode is modified with 4,4 -bipyridine, this promoter forms a monolayer at the... 

Bacterial cell walls contain different types of negatively charged (proton-active) functional groups, such as carboxyl, hydroxyl and phosphoryl that can adsorb metal cations, and retain them by mineral nucleation. Reversed titration studies on live, inactive Shewanella putrefaciens indicate that the pH-buffering properties of these bacteria arise from the equilibrium ionization of three discrete populations of carboxyl (pKa = 5.16 0.04), phosphoryl (oKa = 7.22 0.15), and amine (/ Ka = 10.04 0.67) groups (Haas et al. 2001). These functional groups control the sorption and binding of toxic metals on bacterial cell surfaces. 

It appears from the evolution of the adhesion index that a distinction has to be made between the interactions carbon blacks are able to have with unsaturated or with saturated (or near-to-saturated) elastomers. Thus, the adhesion index of butyl rubber is enhanced upon oxidation of the black, while the reverse is observed with polybutadiene 38). The improvement of the reinforcing ability of carbon black upon oxidation, in the former case, has been interpreted by Gessler 401 as due to chemical interactions of butyl rubber with active functional groups on the solid surface. Gessler, relating the reinforcing characteristics of the oxidized carbon black for butyl rubber to the presence of carboxyl groups on the surface of the filler, postulated a cationic... 

The surface area, the pore size, and the carbon yield are greatly influenced by oxidizing gas, heat-treatment temperature, and activation time. In addition, the oxidative activation introduced the surface acidic functional groups (SAFGs) on the pore surfaces of the carbon. The amounts of the SAFGs can be also controlled by... 

Types of inhibitor. The inhibitors used commercially generally consist of a mixture of the active component along with a surfactant and a solvent. Organic inhibitors contain active functional groups which bond to the metal surface and offer protection. The functional... 

Zero-length cross-linkers are reactive molecules that activate functional groups on surfaces without any chain elongation or incorporation in molecules that have to be attached. In this approach, all reactive surface modifications, for example aldehydes, epoxy-groups, and halogenated surfaces are also termed zero-length cross-linkers. 

Rebek and his co-workers have shown that replication - autocatalysis based on molecular recognition - best accommodates the facts observed in the reaction of 42 with 43, and that under the published conditions 44 is responsible for the autocatalysis. The results indicated template-catalyzed replication as the source of autocatalysis, where recognition surfaces and functional groups interact to form a productive termolecular complex. The mechanism demands that catalysis would be absent with esters that lack hydrogen-bonding sites. One complication of this system is that the initial product of this bimolecular preassociative mechanism is postulated to be a cw-amide, which isomerized to the frani-amide, the active form of template. This appears to be one major background reaction for product formation (Scheme 14). 

The pH of the material surrounding kaolin will determine whether or not its surface will have OH groups. When the pH is above 7, the deprotonation of hydroxyl groups occurs which eliminates the active functional groups from the surface. The chemical changes are consistent with the ability of kaolin to flocculate in suspensions. ... 

In order to improve the efficiency of activated carbon in organic compound removal, catalytic reactions are favored by modifications of the activated carbon surface. The functional groups are increased by oxidation treatment (see section on impregnation with metals or metal oxides). The metal coating the porous surface plays the role of catalyst or reacts with soluble organic compounds. 

In this approach, the use of the activated carbon surface, the functional groups or metal oxide on the surface and the presence of an oxidant, such as ozone or hydrogen peroxide, is combined to remove recalcitrant organic pollutants from water or wastewater. 

Figure 5.4, Hydrogen bonding of the active functional group of normal-phase bonded sorbents with the underlying silica surface.

Yoshida and co-workers [161] studied the relationship between the EDL properties in an organic electrolyte solution and the concentration of surface acidic groups of phenolic resins-based activated carbon fibres. The authors reported that EDL capacitors with high capacitance and low leakage current were obtained with ACF that showed an extremely low concentration of surface acidic functional groups per unit surface ar ... 

Deterioration proceeds inwards from the surface and the degree of deterioration varies with exposure time (t) and the depth from the surface (x). As the deterioration advances, deteriorated polymer molecules having infrared (IR) active functional groups as carbonyl (-CO) are created, and the degree of deterioration is reflected in... 

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