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Molecular Fluorescence in the Vicinity of a Nanoscopic Probe
Published
Author(s)
H F. Hamann, M Kuno, Alan Gallagher, David Nesbitt
Abstract
The dramatic modifications of molecular fluorescence in the proximity of a sharp nanoscopic probe is investigated by an apertureless or antenna-based near-field scanning optical microscope, which exploits the interactions between a fluorescent sample and a laser illuminated Si atomic force microscope probe. Specifically, luminescence is monitored from evanscently excited, dye-doped polystyrene nanospheres (Rs = 20-80 nm) on a fused silica prism surface as a function of probe-sample geometry. The incident laser is enhanced in the near-field of the probe tip, resulting in images with high sensitivity (ςminnearly equal to} 2 2 in a 1 Hz detection bandwidth) and strongly subdiffraction-limited spatial resolution. At probe-sample distances greater than nearly equal to}λ/2, the images are dominated by far-field interference between (i) direct fluorescence from the molecular sample and (ii) indirect fluorescence from image dipoles induced in the atomic force microscope probe. Near-field shadowing of the molecular fluorescence by the probe also occurs and is studied as a function of probe-sample detector geometry. Finally, effects of probe-sample proximity on the fluorescence emission spectrum are investigated. In summary, the data elucidate several novel near and far-field molecular fluorescence enhancement effects relevant to further development of molecular and nonostructural spectroscopic methods with spatial resolution well below the diffraction limit.
Hamann, H.
, Kuno, M.
, Gallagher, A.
and Nesbitt, D.
(2001),
Molecular Fluorescence in the Vicinity of a Nanoscopic Probe, Journal of Chemical Physics
(Accessed April 25, 2024)