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NEWS

Michel Orrit

Molecular Nano-Optics and Spins, Leiden Institute of Physics, Leiden University

Friday, December 19th, 2014 at 11:30:00 AM

Conference Room Querzoli LENS

Enrico Fermi Colloquium

Published on-line at 02:26:38 PM on Friday, December 12th, 2014

Plasmonic gold nanorods as antennas for single-molecule dete

Optical signals provide unique insights into the dynamics of nano-objects and of their surroundings. I shall illustrate some optical experiments with single met

ABSTRACT

Optical signals provide unique insights into the dynamics of nano-objects and of their surroundings. I shall illustrate some optical experiments with single metal nanoparticles done in our group in the last few years.

i) We study single gold nanoparticles by photothermal and pump-probe microscopy.

We detect their acoustic oscillations launched by a pump pulse. These experiments can be done in an optical trap, where a single nanorod orients along the polarization of the trapping laser. We could thus clarify the origin of the damping of  

mechanical vibrations in gold nanoparticles.

ii) Photothermal microscopy opens the study of non-fluorescent absorbers, down to single-molecule sensitivity. Combining photothermal contrast with photoluminescence, we can measure the luminescence quantum yield on a single-particle basis and gain insight into the complex relaxation phenomena leading to emission by metal particles. Moreover, the high signal-to-noise ratio of this contrast mechanism opens up uses of individual gold nanoparticles for local plasmonic and chemical probing. Binding and unbinding events of single protein molecules can be detected in this way].

 iii) Gold nanorods generate strong field enhancements near their tips. By matching the rods' aspect ratio to a dye's fluorescence and excitation spectra, we could observe enhancements in excess of thousand-fold for the fluorescence of single Crystal Violet molecules. Such high enhancements have been observed before with bow-tie nanoantennas. Gold nanorods can produce equally high local fields thanks to their narrow plasmon resonance, but they are much easier to synthesize, functionalize and disperse in solution than lithographically-made nanostructures.

Acknowledgement :The work presented was done over the last 7 years by F. Kulzer, M. Lippitz, A. Tchebotareva, A. Gaiduk, P. Zijlstra, S. Khatua, M. A. van Dijk, P. V. Ruijgrok, M. Yorulmaz, HF. Yuan, L. Hou and N. Verhart in the author's group

For further informations, please contact Mario Agio.