Bound pyrene excimer photophysics and the organization and distribution of reaction sites on silica

Fluorescence Probing of Solvent Accessibility and Micropolarity on Silica and Alkylated Silica Surfaces

“…From the regression a value of R ϭ 3.7 Å is calculated. This is a very acceptable value for excimer formation between two aromatic species [2] [23] and together with the linearity of the plot obtained therefore strongly indicates that our two-step covalent linking scheme leads to a fairly statistical distribution of probes over the available surface area. Table 3.…”

“…(1) can then be modified to Equation (2), in which p is the In order to obtain more information about the probe disfraction of the solvation shell accessible to the solvent and tribution, resulting from the present method of attachment, ∆f M is the effective polarity of the matrix that occupies the we prepared a number of samples in which the same surrest of the solvation shell.…”

“…Equation (2) implies that the solvent accessibility, as measured by p, of the FP probes in FP1 and RFP1 can This provided the samples P1, P2, and P3 with increasing surface loading of a fluorescent pyrene unit. The welldirectly be derived from the ratio of the slopes of the LM plots obtained for FP itself and each of these modified sil-known strong tendency of these units to form a fluorescent excimer [23] can now be employed to detect via fluorescence icaЈs and that this accessibility must be greatly reduced to explain the much smaller slopes of the LM plots for FP1 spectroscopy the presence of probes that are within close range.…”

“…In the latter system regions of high density. However, in that case the reagent some inter-probe interaction is detectable from the contrimolecules that react with the silica already contain the py-bution of excimer emission (see Figure 3) and because of rene units [2] , which might induce such clustering via their the similar probe sizes it is thus feasible that some inter-π-π interaction. In our case (see Scheme 2) a two-step pro-probe interaction could also occur in FP1.…”

A chromatographic approach to the determination of relative free energies of interaction between hydrophobic and amphiphilic amino acid side chains

“…This corresponds to roughly 80 A 2 per molecule of bound stationary phase precursor. It has been suggested that derivatization of silica surfaces may be patchy, that is, some regions exist with little or no bonded phase, while other regions are more heavily derivatized (Lochmuller et al, 1984). Recent evidence from solid-state *H NMR of CI8-modified silica gel indicates that the extent of loading affects the mobility of individual chains, which seems to argue against an "uneven patch" model (Ziegler & Maciel, 1991).…”