Reversibilities surface modifications

Surface modifications commonly involve phases that change the surface polarity such as attaching a long-chain hydrocarbon, usually 18 carbons in length. This would be called a reverse-phase C18... 

Spherical porous silica gel is the easiest stationary phase material to handle however, although it is physically strong it is chemically unstable. Surface modification can expand its capability for different modes of chromatography, such as normal-phase, reversed-phase, size-exclusion, and ion-exchange liquid chromatography. These stable modifications are performed by chemical deriva-tization of the surface silanol groups. 

However, there are still some drawbacks in the use of CNT that need to be solved for practical applications. Not only large reversible capacities but also large irreversible capacities have been reported on CNTs [179, 183]. Such irreversible capacity together with the lack of voltage plateau during lithium extraction (hysteresis) limits the use of nanotubes as electrode material in LI Bs. However, an active study (based on CNT treatments, surface modification, use of CNT nanocomposite matrices, etc.) is being carried out in order to overcome such difficulties [184]. 

Surface Modification Considerations for the Selection of Reversed-Phase Chromatography Sorbents for Peptide Isolation... 

All the above considerations allow to conclude that the electronic surface modifications created imder irradiation eventually induce photoadsorption both in gas-solid and in liquid-solid regimes, being the photoadsorption phenomenon strictly related with the photoactivity of the solid photocatalysts. When light is switched off, a reversal of the process could be observed, although rarely the reversibility is complete and the achievement of a new equilibrium depends mainly on kinetics rather than thermodynamic factors. 

Belfer, S. et al., Surface modification of commercial composite polyamide reverse osmosis membranes, J. Membr. Sci., 139, 175, 1998. 

Belfer, S., Purinson, Y., and Kedem, O., Surface modification of commercial polyamide reverse osmosis membranes by radical grafting An ATR-FT-IR study, Acta Polym., 49, 574, 1998. 

Figure 19.9 illustrates the principle of surface modification of oxide nanoparticles with dyes. Dyes that absorb in the visible and/or IR region become colorless (or change to another color) upon undergoing reduction (or oxidation) under the influence of an electrochemical bias. The feasibility of this concept has already been demonstrated in our laboratory by binding a thiazine dye to nanostructured Sn02 film [156]. Reverse electrochromism obtained using such dye systems provides an alternate approach to conventional oxide-based electrochromic devices. 

Chemical surface modification methods of gas-separation membranes include treatment with fluorine, chlorine, bromine, or ozone. These treatments result in an increase in membrane selectivity with a decrease in flux. Cross-linking of polymers is often applied to improve the chemical stability and selectivity of membranes for reverse osmosis, pervaporation, and gas-separation applications (41). Mosqueda-Jimenez and co-workers studied the addition of surface modifying macromolecules, and the use of the additive... 

Depending on the surface modification reversed phase silicas can be grouped into (a) monomeric reversed phase silicas chemically modified with monofunctional silanes and (b) polymeric reversed phase silicas with a polymeric layer made by surface reaction with trifunctional silanes. 

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