Luminescence techniques have increasingly found promising applications in biological research including single molecule detection, cellular imaging, gene profiling, proteomics, drug discovery and disease diagnostic. Fluorescent markers are extensively being used for labeling for cell imaging. Signal weakness due to low concentration of fluorophores attached with molecules and low photostability of molecular fluorophores are two major concerns for this technique⁽¹⁾.  Nearby conducting metallic particles, colloids, or surfaces are known to significantly influence the emission of vicinal luminophores ⁽²⁾. Using nanoparticles platforms, it is possible to increase the quantum yield and photostability of weakly luminescent probes by increasing their emission efficiency by modifying radiative decay rate or by coupling the emission with far field through scattering. Metal enhanced luminescence (MEL) has been studied mostly using silver and gold nanoparticles due to their intense, narrow SPR peaks. For large nanoparticles (>100nm) with high aspect ratios, MEL occurs mainly due to increase of the coupling efficiency of the fluorescence emission to the far field through nanoparticle scattering. In this case, as effect of ohmic losses on MEL is reduced, less expensive  metals such as Al and Cu, which are more lossy than Ag and Au, can be considered as promising candidates for enhancing luminescence⁽³⁾.

         This talk will focus on the MEL observed from aluminum and copper nanostructures.  Ordered arrays of metallic nano-islands with high aspect ratio have been fabricated using nanosphere lithography⁽⁴⁾ combined with e-beam evaporation. Enhanced luminescence emission from two thiol-reactive dyes Alexa Fluor 594 and Alexa Fluor 488 at the vicinity of these Al and Cu nanostructures is studied. The study of luminescence intensity as a function of the thickness of nanostructured metal surface will also be presented.  Preliminary results obtained so far are very encouraging with enhanced luminescence observed from the dyes at the proximity of aluminum nanostructures.

 Reference:

1.         E. L. Moal et. al., Biophys. J . 92, 2150–2161 (2007).

2.         C. D. Geddes, J. R. Lakowicz, J. Fluoresc. 12, 121-129 (2002).

3.         H. Mertens, A. Polman, in ArXiv e-prints. (2007), vol. 711.

4.         J. C. Hulteen, R. P. V. Duynea, J. Vac. Sci. Technol. A 13, 1553-1557 (1995).