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Two-Photon Excited Fluorescence Depolarisation and Electronic Energy Migration within Donor-Donor Pairs
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
2009 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 11, no 33, 7152-7160 p.Article in journal (Refereed) Published
Abstract [en]

A unified theoretical description is presented for one- and two-photon excited fluorescence depolarisation and electronic energy migration   within pairs of chromophores. Two weakly coupled donor groups are   linked via a rigid macromolecule with the ability to undergo restricted   reorienting motions. Describing these reorienting motions as well as   their influence on the coupling is rather complex, but can be accounted   for by using the extended Forster theory. Here explicit expressions  have been derived for chromophores belonging to the point groups D-2h,   D-2 and C-2v when residing in uniaxial potentials (i.e. C-infinity v   symmetry). From the given basic equations, it is possible however, to   derive the relevant equations for molecules of arbitrary symmetry in   any uniaxial orienting potential. The expected time-resolved   fluorescence anisotropy for different two-photon absorption tensors are   compared for reorienting fluorophores in liquids, as well as in   anisotropic systems. Simulated fluorescence depolarisation data are   also displayed that mimic energy migration within pairs of two-photon   excited donor molecules, which simultaneously undergo reorienting   motions within effectively isotropic and uniaxially anisotropic   environments. The obtained results demonstrate that the time-resolved   fluorescence anisotropy strongly depends on the properties of the   two-photon absorption tensor, as well as on using a linear or a circular polarisation of the excitation field.

Place, publisher, year, edition, pages
2009. Vol. 11, no 33, 7152-7160 p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97542DOI: 10.1039/b900650hISI: 000268974700009OAI: oai:DiVA.org:uu-97542DiVA: diva2:172530
Available from: 2008-09-18 Created: 2008-09-18 Last updated: 2010-07-09Bibliographically approved
In thesis
1. Two-Photon Excited Fluorescence Depolarisation: Experimental and Theoretical Development
Open this publication in new window or tab >>Two-Photon Excited Fluorescence Depolarisation: Experimental and Theoretical Development
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We have studied fundamental aspects of time-resolved two-photon excited fluorescence depolarisation. The thesis presents experimental as well as theoretical progress. We show that a multi-photon induced instrumental response function obtained from a suspension of gold nanoparticles is appropriate for the analysis of two-photon excited fluorescence decays obtained using time-correlated single photon counting detection. Theoretical expressions have been derived for the fluorescence anisotropy decay obtained upon two-photon excitation of various molecular systems in liquid solutions: a) an anisotropic rigid rotor that undergoes rotational diffusion in the presence of ultrafast unresolved restricted reorientations, e.g. librations. b) a molecular group covalently attached to a stationary macromolecule, and undergoing local reorientation in a uniaxial ordering potential. A new approach to the analysis of two-photon excited fluorescence depolarisation experiments was developed, which combines data obtained by using linearly and circularly polarised excitation light, in a global manner. In the analysis, knowledge about unresolved reorientations was obtained from one-photon excitation studies of the corresponding systems. By means of this procedure it has been possible to obtain quantitative information about the molecular two-photon absorption tensor for perylene and two of its derivatives. Thereby the symmetry of the final excited and intermediate vibronic states could be assigned. The analysis reveals that the two-photon transition studied with the 800 nm laser exhibits mixed character. An important finding from the experiments was that the two-photon absorption tensor appears to be solvent dependent. Furthermore, the thesis presents the first theoretical treatment of two-photon excited donor-donor energy migration in the presence of molecular reorientation and which applies the extended Förster theory. Explicit expressions for molecules that belong to the point groups D2h, D2 and C2v are given. Preliminary experiments are finally also reported on a two-photon excited donor-donor energy migration system consisting of a bisanthryl-bisteroid.

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket, 2008. 78 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 552
Keyword
Two-photon excitation, Fluorescence, Fluorescence depolarisation, Fluorescence anisotropy, Time-correlated single photon counting, Gold nanoparticles, Rotational diffusion, Excited state symmetry, Extended Förster theory, Orientation correlation functions, Donor-donor energy migration (DDEM)
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-9285 (URN)978-91-554-7282-5 (ISBN)
Public defence
2008-10-10, Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, 752 37 UPPSALA, Uppsala, 10:15
Opponent
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Available from: 2008-09-18 Created: 2008-09-18Bibliographically approved

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