Towards brighter hybrid magnetic-luminescent nanoparticles: luminosity dependence on excited state properties of embedded dyes

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DOIResolve DOI: http://doi.org/10.1021/jp203239z
AuthorSearch for: ; Search for: ; Search for: ; Search for:
TypeArticle
Journal titleThe Journal of Physical Chemisty C
Volume115
Issue38
Pages1841218421; # of pages: 10
AbstractA series of hybrid, magnetic, and luminescent silica nanoparticles (SNP) have been synthesized and their photophysical properties characterized. The nanoparticles contain, on average, one iron oxide nanoparticle as a magnetic core. The embedded dyes include fluorescein, Alexa Fluor 546, tetramethylrhodamine (TMR), and 4,4-difluoro-5-(2-pyrrolyl)-4-bora-3a,4a-diaza-s-indacene (Bodipy), which are known to have a singlet excited state, and 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl), 7-(diethylamino)coumarin-3-carboxy (coumarin), and tris(bipyridine)ruthenium(II) dichloride (Rubipy) derivatives, which have a charge transfer excited state. In general, the photophysical properties of the magnetic-core dye-doped silica nanoparticles, SNPdye, where dye is one of the seven dyes studied in this project, are dictated by homogeneous energy transfer between dye molecules and by dye aggregation. Molecules with a small Stokes shift and affinity for aggregation upon silica encapsulation (TMR and Bodipy derivatives) can be only sparsely loaded (<50–60 molecules per a 60 nm in diameter nanoparticle) into the nanoparticle matrix before strong fluorescence quenching takes effect. These dyes yield the least bright nanoparticles whose luminosity strongly decreases as the intraparticle dye concentration increases above the rather low maximum brightness loading. Other common fluorophores (Alexa Fluor 546 and fluorescein) can be loaded into the silica matrix with little to no fluorescence quenching until the intermolecular separation becomes less than 5 nm (100–200 fluorophores per a 60 nm in diameter nanoparticle). Finally, significantly more (1200–4600) dye molecules with a charge transfer lowest excited state and large Stokes shift (Rubipy, dansyl, coumarin) can be loaded into the 60 nm in dameter nanoparticle with no indication of luminescence quenching. The results of this study suggest that the luminosity of a hybrid nanoparticle is highest when the embedded dye has a large Stokes shift and is not susceptible to aggregation, which both guarantee no or little intrananoparticle luminescence quenching. No luminescence quenching by the iron oxide magnetic core has been observed for any SNPdye series.
Publication date
LanguageEnglish
AffiliationNRC Steacie Institute for Molecular Sciences; National Research Council Canada
Peer reviewedYes
NPARC number19739633
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Record identifierdc8b8635-de57-4b2c-a1f0-56392e31c4cb
Record created2012-04-02
Record modified2017-03-23
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