Send to:

Choose Destination
See comment in PubMed Commons below
Phys Chem Chem Phys. 2011 Aug 28;13(32):14758-66. doi: 10.1039/c1cp20254e. Epub 2011 Jul 13.

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

Author information

  • 1Chemical Physics Program, University of Maryland, College Park, College Park, MD 20742, USA.


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.

PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Royal Society of Chemistry
    Loading ...
    Write to the Help Desk