title: Plasmonic activation of a fluorescent carbazole-oxazine switch.
abstract: The covalent attachment of a carbazole fluorophore to an oxazine photochrome permits the reversible activation of fluorescence under optical control. Ultraviolet irradiation with a pulsed laser opens the oxazine ring to shift bathochromically the absorption of the carbazole component. Concomitant visible illumination excites selectively the carbazole fluorophore of the photochemical product to produce fluorescence. The photogenerated and fluorescent species reverts spontaneously on a submicrosecond timescale to the initial nonemissive state of the carbazole-oxazine dyad. The photochemical and photophysical properties engineered into this particular molecular switch allow the convenient monitoring of plasmonic effects on photochemical reactions with fluorescence measurements. In close proximity to silver nanoparticles, visible illumination with a continuous-wave laser also results in fluorescence activation. The metallic nanostructures enable the two-photon excitation of the oxazine component to induce the photochromic transformation and then facilitate the one-photon excitation of the photochemical product to generate fluorescence. Thus, these operating principles offer the opportunity to avoid altogether the need of pulsed ultraviolet irradiation to trigger the photochromic transformation and, instead, allow fluorescence activation with a single visible source operating at low illumination power.
authors: Laboratory for Molecular Photonics, Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida, 33146-0431 (USA), Fax: (+1) 305-284-4571.
authors: Jaume
authors: J
authors: Garcia-Amorós
authors: Subramani
authors: S
authors: Swaminathan
authors: Salvatore
authors: S
authors: Sortino
authors: Françisco M
authors: FM
authors: Raymo
mesh_terms: D002227:Carbazoles / Q000737:chemistry*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry; D010078:Oxazines / Q000737:chemistry*; D055668:Photochemical Processes; D017785:Photons; D011108:Polymers / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D020349:Surface Plasmon Resonance; D014466:Ultraviolet Rays
chemical_list: D002227:Carbazoles; D005456:Fluorescent Dyes; D010078:Oxazines; D011108:Polymers; C041514:carbazole; D012834:Silver
keywords: fluorescence; molecular switches; nanoparticles; photochromism; plasmonic effects