Title page for ETD etd-09142007-164724

Type of Document Master's Thesis
Author Dorcéna, Cassandre Jenny
Author's Email Address cdorcena75@hotmail.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
  • surface enhanced fluorescence
  • surface plasmon resonance
  • metallic nanoparticles
  • fluorescence quenching
Date of Defense 2007-09-05
Availability unrestricted
Metallic 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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