21 February 2008 Fluorescence enhancement and focal volume reduction observed in c-shaped nano-apertures
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We evaluate the potential ability of c-shaped apertures milled in aluminum thin films to reduce the effective measurement volume and to enhance the fluorescence signal for fluorescence correlation spectroscopy of ATTO655 dye dissolved in a HEPES buffer solution. Previous studies have shown that by morphing a square aperture into a rectangular aperture while holding the cross-sectional area constant will yield strong polarization dependence in the reduction of the effective volume and about a factor of 2-3 enhancement in the fluorescence count rate per molecule. By morphing the rectangular aperture into a c-shaped aperture we gain further reduction in focal volume while maintaining the count rate enhancements. In particular, we compare c-shaped apertures to squares with the same cross-sectional area and show that one can achieve one molecule per focal volume at ~3µM (about a 1000 times reduction in effective volume compared to confocal FCS) while maintaining a fluorescence count rate per molecule of about an order of magnitude higher than for bulk diffusing dyes. Two orthogonal polarizations for the incident field have been studied to explore the effects on the focal volume reduction and fluorescence count rate enhancements.
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Yin Yuen, Yin Yuen, Samantha Fore, Samantha Fore, Thomas Huser, Thomas Huser, Lambertus Hesselink, Lambertus Hesselink, "Fluorescence enhancement and focal volume reduction observed in c-shaped nano-apertures", Proc. SPIE 6869, Plasmonics in Biology and Medicine V, 68690U (21 February 2008); doi: 10.1117/12.764053; https://doi.org/10.1117/12.764053

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