Jump to main content
Jump to site search

Issue 32, 2011
Previous Article Next Article

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

Author affiliations

Abstract

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 −CF3 (C152) or −CH3 (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 (ΔGads 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.

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

Back to tab navigation

Supplementary files

Publication details

The article was received on 28 Jan 2011, accepted on 15 Jun 2011 and first published on 13 Jul 2011


Article type: Paper
DOI: 10.1039/C1CP20254E
Citation: Phys. Chem. Chem. Phys., 2011,13, 14758-14766
  •   Request permissions

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

    D. Roy, S. Piontek and R. A. Walker, Phys. Chem. Chem. Phys., 2011, 13, 14758
    DOI: 10.1039/C1CP20254E

Search articles by author

Spotlight

Advertisements