title: Fluorescent DNA probes at liquid/liquid interfaces studied by surface second harmonic generation.
abstract: The properties of a series of oxazole yellow dyes, including the dicationic YOPRO-1 and its homodimeric parent YOYO-1 and two monocationic dyes (YOSAC-1 and YOSAC-3), have been investigated at the dodecane/water interface using stationary and time-resolved surface second harmonic generation (SSHG) combined with quantum chemical calculations. Whereas YOYO-1 exists predominantly as a H-dimer in aqueous solution, the stationary SSHG spectra reveal that such dimers are not formed at the interface. No significant H-aggregation was observed with YOPRO-1, neither in solution nor at the interface. In the case of the monocationic YOSAC dyes, a distinct SSHG band due to H-aggregates was measured at the interface, whereas only weak aggregation was found in solution. These distinct aggregation behaviors can be explained by the different orientations of the dyes at the interface, as revealed from the analysis of polarization-resolved experiments, the doubly-charged dyes lying more flat on the interface than the singly charged ones. Although YOYO-1 and YOPRO-1 do not form H-dimer/aggregates at the interface, time-resolved SSHG measurements point to the occurrence of intra- and intermolecular interactions, respectively, which inhibit the ultrafast non-radiative decay of the excited dyes via large amplitude motion, and lead to a nanosecond excited-state lifetime. The distinct behavior evidenced here for YOYO-1 and YOSAC dyes points to their potential use as fluorescent or SHG interfacial probes.
authors.affiliation: Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland. eric.vauthey@unige.ch.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Licari
authors.affiliation: Institut Lumière Matière, UMR CNRS 5306, Université Claude Bernard, Lyon 1, Campus LyonTech - La Doua, 10 Rue Ada Byron, 69622 Villeurbanne cedex, France.
authors.forename: Pierre-François
authors.initials: PF
authors.lastname: Brevet
authors.affiliation: Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland. eric.vauthey@unige.ch.
authors.forename: Eric
authors.initials: E
authors.lastname: Vauthey
mesh_terms: D015342:DNA Probes; D005456:Fluorescent Dyes; D013057:Spectrum Analysis; D013499:Surface Properties
chemical_list: D015342:DNA Probes; D005456:Fluorescent Dyes