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Proceedings Paper

Use of aluminum films as substrates for enhanced fluorescence in the ultraviolet-blue spectral region
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Paper Abstract

Thermal evaporation was used to deposit particulate aluminum films of varied thicknesses on quartz substrates. These substrates were characterized by scanning electron microscopy (SEM), which reveal that with an increase in aluminum thickness, the films progress from particulate towards smooth surfaces. Until now, metal-enhanced fluorescence (MEF) has primarily been observed in the visible-NIR wavelength region using silver or gold island films and roughened surfaces. We now report that fluorescence can also be enhanced in the ultraviolet-blue region of the spectrum using nano-structured aluminum films. We used two probes, one in the ultraviolet (a DNA base analogue 2-aminopurine: 2- AP) and another one in blue spectral region (a coumarin derivative: 7-HC) for the present study. We observed increased emission, decrease in fluorescence lifetime and increase in photostability of the dyes in a 10 nm spin-casted polyvinyl alcohol film on the Al nanostructured surfaces. We observe that the fluorescence enhancement factor depends on the thickness of the Al films because the size of the nanostructures formed varies with Al thickness. These studies indicate that Al nano-structured substrates can potentially find widespread use in MEF applications particularly in the UV - blue spectral regime. Finite-Difference Time-Domain (FDTD) calculations were performed that revealed enhanced near-fields induced around aluminum nanoparticles by a radiating fluorophore emitting at the emission wavelength of 2-AP. The effect of such enhanced fields on the fluorescence enhancement observed is also discussed.

Paper Details

Date Published: 21 February 2008
PDF: 12 pages
Proc. SPIE 6869, Plasmonics in Biology and Medicine V, 68690E (21 February 2008); doi: 10.1117/12.760724
Show Author Affiliations
Mustafa H. Chowdhury, Univ. of Maryland at Baltimore (United States)
Krishanu Ray, Univ. of Maryland at Baltimore (United States)
Joseph R. Lakowicz, Univ. of Maryland at Baltimore (United States)

Published in SPIE Proceedings Vol. 6869:
Plasmonics in Biology and Medicine V
Tuan Vo-Dinh; Joseph R. Lakowicz, Editor(s)

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