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Fluorescence et Diffusion Raman exaltée de surface (SERS) de molécules individuelles

Abstract : Two independent studies, both involving detection and analysis of optical spectroscopic signals at the single molecule level have been conducted.
By mean of wide-field fluorescence spectroscopy, the emission of single perylene orange dyes embedded in a thin solgel film has been monitored. It consists of recording movies of a large area of the sample, with a hundred or more of single emitters in focus whose signal report as much on the species photo-properties as on the matrix. The films have been harvested thanks to a specially devoted tailored software. The photobleaching processes, spatial mobility and an aggregation-like phenomenon are pointed out and discussed. The molecules also exhibit a rich variety of temporal dynamics, and spectral characteristics reflecting most notably the proposed excited state reconformation of perylene orange.
Scanning confocal microscopy is the second setup used. Here, we focus on the surface-enhanced Raman scattering of single organic molecules adsorbed on silver nano-cluster with complex shape. Some of them exhibit giant enhancement, estimated to be at least of 14 orders of magnitude, offering the possibility to record nicely resolved spectra with a collection time of one second. The associated chemical analysis give evidence that different chemical species are present, and permits to highlight the presence of Ag+ at the hot spot. At last, a cross characterization of the active aggregates by electronic microscopy shows up that a specific class of cluster morphology, with nano-bumps, seems to be preferentially required for the hot spot to exist.
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Contributor : Carine Julien <>
Submitted on : Wednesday, February 8, 2006 - 3:24:40 PM
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Carine Julien. Fluorescence et Diffusion Raman exaltée de surface (SERS) de molécules individuelles. Physique [physics]. Université Paris Sud - Paris XI, 2004. Français. ⟨tel-00011564⟩

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