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A Cascade FRET‐Mediated Ratiometric Sensor for Cu 2+ Ions Based on Dual Fluorescent Ligand‐Coated Polymer Nanoparticles
Author(s) -
Frigoli Michel,
Ouadahi Karima,
Larpent Chantal
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200900475
Subject(s) - förster resonance energy transfer , fluorescence , acceptor , photochemistry , copper , nanoparticle , chemistry , quenching (fluorescence) , anthracene , ion , materials science , analytical chemistry (journal) , nanotechnology , organic chemistry , optics , physics , condensed matter physics
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 ( R 0 ) 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 n M to 8.5 μ 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.