• Increase font size
  • Default font size
  • Decrease font size
Home Projects 1st call (2008) 4. Single nanoparticle as intracellular flash light

4. Single nanoparticle as intracellular flash light

Dr. S. Jeney (EPFL), Dr. J. Vörös (ETHZ) - PhD student: Flavio Mor

Biology has benefited tremendously from the development of novel imaging tools. It was long thought that light microscopy could only be operated with resolution above the Rayleigh limit. This was first overcome by near-field techniques such as scanning near-field microscopy (SNOM) and more recently by advanced fluorescence techniques such as the Stimulated Emission Depletion microscopy. In addition, novel tools based on the utilization of field enhancement close to nanoparticles are expected to contribute to the further advancement of imaging technologies. Nanoparticles as probes for optical near-field enhancement. Geometrical field enhancement at surfaces of large curvature as well as electromagnetic field enhancement resulting from surface plasmon excitation in metal, is a well-known physical effect frequently exploited in surface enhanced Raman scattering [1] and apertureless SNOM. Particularly the latter technique, exploits the fact that the enhanced optical field is strongly confined to the vicinity of a metal tip [2]. It has been demonstrated that the enhanced electric field at a gold nanotip is strong enough to produce even non-linear effects, e.g. that it can create second harmonic generation [3] as well as provide a very local light source for two-photon excitation [4]. Energy transfer from a locally enhanced optical field around an optically trapped gold bead of 40 nm in size to a fluorophore was also shown [5]. Recently simultaneous laser trapping and two-photon absorption leading to morphology-dependent resonance within a polymeric 10 μm-sphere was reported [6]. The field enhancement can be then termed “localized”, since the effect decays exponentially with the distance from the surface of the nanoparticle. The nanoparticle provides hence a local excitation source and can be used for imaging purposes.

[1] S. Nie and S. R. Emory; “Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering” Science 275 (1997) 1102.
[2] F. Zenhäusern, M. P. O'Boyle and H. K. Wickramasinghe; “Apertureless near-field optical microscope” Appl. Phys. Lett. 65 (1994) 1623.
[3] Bouhelier A, Beversluis M, Hartschuh A, et al.; “Near-field second-harmonic generation induced by local field enhancement” Phys. Rev. Lett. 90 (2003) 013903.
[4] E. J. Sanchez, L. Novotny and X. Sunney; "Near-field fluorescence microscopy based on twophoton excitation with metal tips" Phys. Rev. Lett. 82 (1999) 4014.
[5] T. Sugiura, S. Kawata and T. Okada; "Fluorescence imaging with a laser trapping scanning near-field optical microscope" J. Microsc. 194 (1999) 291.
[6] Morrish D, Gan XS, Gu M. “Scanning particle trapped optical microscopy based on twophoton-induced morphology-dependent resonance in a trapped microsphere” Appl. Phys. Lett. 88 (2006) 141103.

Contact: Flavio Mor