Silanol functions surface density

Prepare a solution of the silanation agent. For trimethylchlorosilane, use toluene as the solvent. The minimum requirement of the silanation agent is calculated by assuming the surface density of silanol to be one functionality per 0.1 nm. ... 

In order to avoid tedious procedures required to prepare packed CEC columns, some groups are studying the use of empty capillaries. Since solute-stationary phase interactions are key to the CEC process, appropriate moieties must be bound to the capillary wall. However, the wall surface available for reaction is severely limited. For example, a 100 pm i.d. capillary only has a surface area of 3xl0 4m2 per meter of length, with a density of functional sites of approximately 3.1 xlO18 sites/m2, which equals 0.5 pmol sites/m2. Moreover, surface modification cannot involve all of the accessible silanol groups, since some must remain to support the EOF. As a result, the use of bare capillaries in CEC has been less successful. 

The surface silanol groups are the sites which provide the anchor point of the functional silanes to the surface. For conventional hydroxylated silica, the density of silanol groups is remarkably... 

For the post-functionalized materials, the silanols present within the channels provide a suitable anchoring site for chemical attachment. Although the wall composition contains random interatomic bond angles and atomic location, there exists an uncharacteristically large and uniform density of silanol groups (other than the silanols that exist due to incomplete condensation) within the channels due to surfactant packing requirements. NMR studies showed that up to 40% of the silicon atoms located on the surface of the walls could be associated with hydroxyls [62],... 

For the electrostatic boundary condition, in this work we use the Basic Stem (BS) model developed by Behrens and Grier [9] in which the silica surfaces acquire charges in contact with water by the dissociation of silanol groups, SiOH SiO + H, so that the zeta potential (0 on the interface can be expressed as a function of the surface charge density (cr) ... 

The contribution to this component from protons of residual silanol groups at the silica surface and from those of adsorbed water molecules is below a few percent, as follows from the H NMR spectra shown in Fig. 3, which is in agreement with the results of T2 experiments using hydrophilic fumed silica. The density of silica was taken to be equal to that in silylated silicas. The T2 decay of the hydrophilic silica can be described by a single exponential function with a characteristic decay time of 0.18 ms. The amplitude of the decay was smaller... 

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