Type of Document Master's Thesis Author Dorcéna, Cassandre Jenny Author's Email Address email@example.com URN etd-09142007-164724 Title Effects of Metallic Nanoalloys on Dye Fluorescence Degree Master of Science Department Electrical and Computer Engineering Advisory Committee
Advisor Name Title Meehan, Kathleen Committee Chair Love, Brian J. Committee Member Raman, Sanjay Committee Member Xu, Yong Committee Member Keywords
- surface enhanced fluorescence
- surface plasmon resonance
- metallic nanoparticles
- fluorescence quenching
Date of Defense 2007-09-05 Availability unrestricted AbstractMetallic nanoparticles (NPs) are exploited for their ability to interact with organic
compounds and to increase significantly the fluorescence intensity and the photostability
of many fluorescent dye molecules. Metal enhanced fluorescence (MEF) is therefore
widely investigated for biosensing applications. When used in immunoassays, silver
island films (SIFs) could augment the fluorescence intensity of fluorescein by a factor of
seventeen; SIFs were also able to double or triple the emission intensity of cyanine dyes
which are commonly used in (deoxyribonucleic acid) DNA microarrays. The emission
intensity of indocyanine green – widely used as a contrast agent in medical imaging –
was about twenty times higher in the proximity of SIFs.
This enhancement phenomenon - due to the surface plasmon polaritons associated
with the metallic NPs – can be explained by energy transfer from the metal NPs to the
fluorescent dye molecules or by a modified local electromagnetic field experienced by
the fluorophores in the vicinity of metal surfaces.
Our research focused on the optical characterization of colloidal gold-silver alloy
NPs containing different ratios of gold and silver (Au1.00-Ag0.00, Au0.75-Ag0.25, Au0.50-
Ag0.50, and Au0.25-Ag0.75), as well as their interaction with three fluorophores: rose
bengal, rhodamine B, and fluorescein sodium. Depending upon the dye quantum yield
and its concentration in solution, enhancement or quenching of fluorescence was
obtained. Thus, a three to five times increase in fluorescence intensity was observed in a
2.0 mM solution of rose bengal with all nanoalloys, a slight enhancement of fluorescence
(1.2 – 1.6 times) was noticed in a 0.13 mM solution of rhodamine B with all four types of
NPs, and fluorescence quenching occurred in all the fluorescein-NP solutions regardless
of the dye concentration.
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