Surface diffusion at the liquid-solid interface: quenching of fluorescence from pyrene covalently bound to methylated silica

Wong, Andrew L.; Harris, J. M.

doi:10.1021/j100168a034

Cited by 45 publications

(42 citation statements)

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“…Second, fluoresence emission and resonance enhanced SHG experiments have shown that solvation at hydrophilic silica surfaces is dominated by strong hydrogen bond donating sites that do not have any conformational flexibility. 45,47,48 If the silica surface donates hydrogen bonds to C152 through the solute's nitrogen lone-pair, then the surface will restrict the C152's ability to form the TICT state following photoexcitation. Such specific, directional association can inhibit the ability of adsorbed solutes to undergo large amplitude structural changes and the time dependent emission will resemble that of monomers solvated in less polar solvents.…”

Section: Discussionmentioning

confidence: 99%

“…These two results imply that C152 and C461 adsorb to silica through similar mechanisms, with surface silanol groups likely donating hydrogen bonds to the coumarin amine and/or carbonyl groups. [45][46][47][48][49][50] Linear growth in the emission spectra of films formed from higher concentrations implies multilayer formation. The primary difference between the two solutes' behaviors at the silica interface is the new feature in the C152 emission spectra.…”

Section: Steady State Adsorption Spectra and Langmuir Isothermsmentioning

confidence: 99%

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Surface induced changes in coumarin solvation and photochemistry at polar solid/liquid interfaces

Roy

Piontek

Walker

2011

Phys. Chem. Chem. Phys.

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Steady state and time-resolved fluorescence measurements compare the photophysical properties of Coumarin 152 (C152) and Coumarin 461 (C461) in bulk methanol solution and adsorbed to silica/vapor and silica/methanol interfaces. C152 and C461 share the same structure except for a -CF(3) (C152) or -CH(3) (C461) group at the molecule's 4-position. This modest structural difference leads to markedly different emission behavior in bulk solution and different organization when adsorbed to silica surfaces. Steady state emission spectra of C152 and C461 adsorbed to silica surfaces from bulk methanol solutions show that the two solutes have similar surface activities (ΔG(ads) of -29.0 kJ/mol and -30.8 kJ/mol for C152 and C461, respectively) and that the interface itself has a polarity similar to that of short chain alcohols. Both solutes appear to form multilayers at higher bulk concentrations given observed linear growth in fluorescence emission intensities. At higher C152 surface concentrations a second emissive state appears at longer wavelengths, whereas the emission of C461 remains dominated by a single feature. Time dependent emission of C152 and C461 adsorbed to the silica/methanol interface shows that the silica surface inhibits C152's fast, nonradiative pathway inferred from bulk solution measurements but the fluorescence lifetime of adsorbed C461 remains unchanged from bulk solution limits. These findings are discussed in terms of the interface's ability to restrict C152 isomerization into a nonradiative, twisted intramolecular charge-transfer (TICT) state, despite the fact that this conformation represents an energetic minimum in polar solvation environments.

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Section: Discussionmentioning

confidence: 99%

Section: Steady State Adsorption Spectra and Langmuir Isothermsmentioning

confidence: 99%

Surface induced changes in coumarin solvation and photochemistry at polar solid/liquid interfaces

Roy

Piontek

Walker

2011

Phys. Chem. Chem. Phys.

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“…[27][28][29] A few other sets of experimental data on the surface and lateral diffusion of various solutes in RPLC and of macromolecules on other stationary phases are available and listed in Table 2. Results previously published [27][28][29][30][31][32][33][34][35] suggest that Ds is a few orders of magnitude 725 ANALYTICAL SCIENCES JULY 2000, VOL. 16 Fig.…”

Section: Derivation Of An Estimate Of Dsmentioning

confidence: 94%

Kinetic Study of the Concentration Dependence of the Mass Transfer Rate Coefficient in Enantiomeric Separation on a Polymeric Imprinted Stationary Phase

Miyabe

Guiochon

2000

ANAL. SCI.

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Molecular imprinting is a most attractive method of preparation of dedicated stationary phases for chromatography. Its use for enantioseparations is attracting considerable interest. 1,2 Imprinted materials can provide a very high selectivity for the objective compound, i.e., the imprinted molecule. [1][2][3][4][5] Although analytical applications are rapidly developing, the situation on the preparative front is less rosy. 1 Columns packed with imprinted stationary phases exhibit a poor efficiency and elution peaks are often unsymmetrical, especially for the more retained enantiomer. Sellergren et al. 1,2 suggested that the nonlinear behavior of the adsorption isotherm was the main cause of the broad and unsymmetrical bands observed for L-phenylalanine anilide (PA) on an L-PA imprinted chiral stationary phase. Although the possibility of a slow mass transfer kinetics was also pointed out, no detailed study supported this assumption. Yet, information on the mass transfer characteristics of imprinted stationary phases is necessary to clarify strategies for the improvement of these materials.Most kinetic studies in chromatography assume that four mass transfer processes are involved in a column, (1) axial dispersion, (2) fluid-to-particle mass transfer, (3) intraparticle diffusion, and (4) adsorption/desorption. 6 The contributions of these four processes to peak spreading are evaluated separately. Axial dispersion and the fluid-to-particle mass transfer resistance are inherent to flow processes through packed beds. They are well understood, relatively easy to control, and their contributions are often small. By contrast, intraparticle diffusion and adsorption/desorption give often larger contributions to the mass transfer resistance in the column. Their properties are intrinsic to each packing material and they are still often poorly understood. In order to evaluate the actual performance of packing materials, the characteristics of the mass transfer kinetics inside stationary phase particles must be clarified.Sajonz et al. 7 measured the adsorption equilibrium isotherm and the mass transfer kinetics of L-and D-PA on a polymeric stationary phase imprinted with L-PA, using a staircase frontal analysis method. The isotherm was well represented by either the Bi-Langmuir or the Freundlich models, but not by the simple Langmuir isotherm. The equilibrium data suggested that the distribution of the adsorption energy on the surface of the imprinted stationary phase is heterogeneous and showed that this phase has a high selectivity for the imprinted L-enantiomer. The lumped mass transfer rate coefficient (km,L) was calculated from each single breakthrough curve by applying the transport model of chromatography. 6 The values of km,L increased with increasing concentration of the enantiomers. The extent of the positive concentration dependence of km,L was larger for L-PA than for D-PA. It is expected that a more detailed analysis of the overall mass transfer rate parameter, km,L, could provide new, useful information and all...

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“…D s was found to be a few orders of magnitude smaller than D m Guiochon, 1999a, 2000a). Other experimental data were also reported on surface and lateral diffusions in RPLC (Bogar et al, 1984;Hansen and Harris, 1995;Wong and Harris, 1991;Zulli et al, 1994) and in ion exchange separation of BSA (Tilton et al, 1990;Yoshida et al, 1994). However, despite the general conclusion that diffusivity varies with the temperature, no information was provided for the temperature conditions in many reports.…”

Section: Estimation Of K Adsmentioning

confidence: 99%

A Study of Mass Transfer Kinetics in an Enantiomeric Separation System Using a Polymeric Imprinted Stationary Phase

Miyabe

Guiochon

2000

Biotechnology Progress

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Chromatographic data pertaining to the enantioseparation of L- and D-phenylalanine anilide (PA) on a polymeric stationary phase imprinted with L-PA were studied from the viewpoints of phase equilibrium, mass transfer kinetics, and the thermodynamic properties of this enantiomeric separation system. The concentration dependence of the lumped mass transfer rate coefficient (k(m,L)) previously published was analyzed to obtain new information concerning the mass transfer characteristics in this chiral separation system. It was shown that intraparticle diffusion contributed much more to k(m,L) than adsorption/desorption. The positive concentration dependence of k(m,L) seemed to be interpreted by considering that of the surface diffusion coefficient, itself explained by the heterogeneous surface model. The characteristic features of the phase equilibrium, the mass transfer kinetics, and the thermodynamics of the enantiomeric separation system probably result from the adsorption energy distribution on the surface of the imprinted phase having an exponential decay.

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Surface diffusion at the liquid-solid interface: quenching of fluorescence from pyrene covalently bound to methylated silica

Cited by 45 publications

References 0 publications

Surface induced changes in coumarin solvation and photochemistry at polar solid/liquid interfaces

Surface induced changes in coumarin solvation and photochemistry at polar solid/liquid interfaces

Kinetic Study of the Concentration Dependence of the Mass Transfer Rate Coefficient in Enantiomeric Separation on a Polymeric Imprinted Stationary Phase

A Study of Mass Transfer Kinetics in an Enantiomeric Separation System Using a Polymeric Imprinted Stationary Phase

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