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Sensitized Emission (sensitized + emission)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Sensitized Emission from Lanthanide-Doped Nanoparticles Embedded in a Semiconductor Sol,Gel Thin Film,

CHEMPHYSCHEM, Issue 11 2007
Sri Sivakumar Dr.
Abstract In2O3 sol,gel thin films made with LaF3:Ln3+ (Ln=Er, Nd, and Eu) nanoparticles were prepared and showed sensitized emission of the lanthanide ions after In2O3 matrix excitation. The excitation spectra showed an In2O3 absorption band in addition to the excitation peaks of the lanthanide ions, clearly demonstrating that there is energy transfer from the In2O3 matrix to Ln3+ (Er3+, Nd3+, and Eu3+). Similarly, HfO2 and ZrO2 sol,gel thin films made with LaF3:Ln3+ nanoparticles also showed energy transfer from the semiconductor matrix to the lanthanide ions. [source]

Imaging FRET standards by steady-state fluorescence and lifetime methods

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 12 2007
Beatriz Domingo
Abstract Imaging fluorescence resonance energy transfer (FRET) between molecules labeled with fluorescent proteins is emerging as a powerful tool to study changes in ions, ligands, and molecular interactions in their physiological cellular environment. Different methods use either steady-state fluorescence properties or lifetime to quantify the FRET rate. In addition, some provide the absolute FRET efficiency whereas others are simply a relative index very much influenced by the actual settings and instrumentation used, which makes the interpretation of a given FRET rate very difficult. The use and exchange of FRET standards in laboratories using these techniques would help to overcome this drawback. We report here the construction and systematic evaluation of FRET standard probes of varying FRET efficiencies. The standards for intramolecular FRET were protein fusions of the cyan and yellow variants of A. victoria green fluorescent protein (ECFP and citrine) joined by short linkers or larger protein spacers, or ECFP tagged with a tetracysteine motif and labeled with the biarsenical fluorochrome, FlAsH. Negative and positive controls of intermolecular FRET were also used. We compared these FRET standards with up to four FRET quantification methods: ratioing of acceptor to donor emission, donor intensity recovery upon acceptor photobleach, sensitized emission after spectral unmixing of raw images, and fluorescence lifetime imaging (FLIM). The latter was obtained with a frequency-domain setup able to provide high quality lifetime images in less than a second, and is thus very well suited for live cell studies. The FRET rates or indexes of the standards were in good agreement regardless of the method used. For the CFP-tetraCys/FlAsH pair, the rate calculated from CFP quenching was faster than that obtained by FLIM. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source]

A Cascade FRET-Mediated Ratiometric Sensor for Cu2+Ions Based on Dual Fluorescent Ligand-Coated Polymer Nanoparticles

CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2009
Michel Frigoli Dr.
Abstract Core-shell type dual fluorescent nanoparticles (NPs) in the 16,nm diameter range with a selective ligand (cyclam) attached to the surface and two fluorophores,9,10-diphenyl-anthracene (donor, D) and pyrromethene PM,567 (acceptor, A),embedded within the polymer core were synthesized and their fluorescent and copper-sensing properties were studied and compared to single D -doped and A -doped NPs. The acceptor (A) and donor (D) dyes were chosen to allow two sequential Förster resonance energy transfer (FRET) processes from D to A and from the encapsulated dyes to copper complexes that form at the surface and act as quenchers. NPs with different D/A loads were readily obtained by two consecutive entrapments of the dyes. Dual NPs present tunable fluorescence emission that is dependent on the doping ratio. FRET from D to A results in sensitized emission from A upon excitation of D, with FRET efficiencies reaching 80,% at high acceptor loads. A 9-fold amplification of the signal of A is observed at high D -to- A ratios. Single- and dual-dye-doped NPs were used to detect the presence of cupric ions in water by using the quenching of fluorescence as a transduction signal. In accordance with the spectral overlaps and the values of the critical distance (R0) of D, and A,copper complex pairs, the acceptor is much more sensitive than the donor. In dual fluorescent NPs, the sensitized emission of A is efficiently attenuated whereas the remaining emission of D is much less affected, allowing the detection of copper in a ratiometric manner upon excitation at a single (D) wavelength. Dual-dye-doped NPs with the highest acceptor loads (23,A -per-NP) were found to be the most sensitive for the detection of copper over a wide range of concentrations (20,nM to 8.5,,M). Owing to its great convenience and modularity, the cascade FRET strategy based on dual fluorescent NPs holds great promise for the design of various sensing nanodevices. [source]