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Preparation of europium complex-conjugated carbon dots for ratiometric fluorescence detection of copper(II) ions

Abstract:

In this work, by conjugating a europium complex, 4,4′-bis(1″,1″,1″,2″,2″,3″,3″-heptafluoro-4″,6″-hexanedion-6″-yl)chlorosulfo-o-terphenyl-Eu3+ (BHHCT-Eu3+), onto the surface of carbon dots (C-dots), a new type of dual-fluorophore nanoparticle, C-dots-BHHCT-Eu3+, has been successfully prepared for the ratiometric fluorescence detection of Cu2+ ions in aqueous media. The results of transmission electron microscopy (TEM) and fluorescence spectroscopy characterization indicate that the nanoparticles are monodisperse, spherical and uniform in size (∼8.6 nm in diameter), and have stable and well-resolved dual-wavelength emission properties. Under excitation at 337 nm, the composite nanoparticles of C-dots-BHHCT-Eu3+ exhibit two emission peaks at 410 nm and 615 nm, respectively. Upon the addition of Cu2+ ions, the emission intensity of the nanoparticles at 615 nm is significantly decreased, while that at 410 nm shows no response to the addition of Cu2+ ions. Correspondingly, the emission intensity ratio, I615/I410, shows a good linearity against the concentration of Cu2+ ions. In addition, the investigation results of fluorescence responses of the nanoparticles to different metal ions reveal that the fluorescence response of C-dots-BHHCT-Eu3+ to Cu2+ ions is highly specific without interference from other metal ions. All of the results suggest that the new dual-fluorophore composite nanoparticles could be used as a ratiometric fluorescence probe for the detection of Cu2+ ions in aqueous media with high selectivity and sensitivity.