CBM seminar: 23rd July - h 14.00 - BASOVIZZA

[Maria Teresa]

Dear All,

you are kindly invited at CBM seminar:

Plasmonics for bio-sensing

Monday, July 23rd 2007

Conference Hall, Auditorium T Building AREA Science Park

Basovizza - Trieste

Moderator: prof. Giacinto Scoles, CBM/ELETTRA



2 pm: Fluorescence enhancement in hot spots of laterally arranged  
single gold nanoparticle dimers

Alpan Bek - Photonics and Optoelectronics Group, Physics Department  
and CeNS, Ludwig-Maximilians-Univesitat - Munich, Germany

Spontaneous emission can be modified by resonant coupling to the  
external electromagnetic environment. Resonant cavities, planar metal  
surfaces or metallic nanoparticles are examples of modified  
electromagnetic environment. Rough metal film surfaces are observed  
to enhance Raman scattering, resonance Raman scattering, and  
fluorescence from adsorbed molecules. Plasmonic metal nanoparticles  
also enhance local electromagnetic fields.The luminescence of  
fluorophores change when they are positioned in the close vicinity of  
gold nanoparticles (AuNPs). Nanoscale gaps between two spherical  
metal nanoparticles produce significant field enhancement and the  
enhancement factor is maximized if the excitation polarization lies  
in the center-to-center direction.

In this talk Alpan Bek reports on the enhancement of fluorescence  
from a single fluorescent sphere, which is sandwiched in the hot spot  
of strong field enhancement in between two individual gold  
nanoparticles. The fluorescence enhancing hot spot is produced by  
assembling a plasmonic gold nanoparticle pair with an atomic force  
microscope cantilever. The fluorescence intensity is monitored while  
the separation between the two gold nanoparticles is reduced by  
gradually pushing the gold nanoparticles closer to the fluorescent  
sphere. The enhancement factor is maximal when the distance between  
the two gold nanoparticles is smallest, the excitation polarization  
is parallel to the axis of the sandwich, and when the fluorescent  
sphere is positioned exactly on the axis connecting the two gold  
nanoparticles.



3 pm: Azimuthal rotation effects on plasmonic gratings dispersion  
curve and their application for DNA sensing

Filippo Romanato - CNR-INFM Laboratorio TASC - Trieste, Italy and  
NanYang Technological University – Singapore

In this present study the excitation of grating coupled surface  
plasmon is described as a function of groove azimuthal rotation.  
Ellipsometry and reflectrometry data analysis show that two plasmons  
with different directions can be excited with the same wavelength. A  
kinematical model can explain the phenomena in terms of light  
polarization conversion. Part of the incoming light that is groove  
perpendicular polarized is converted in groove parallel plasmons.  
This effects have been applied for surface DNA density detection.  
Scatterometry spectra for a wavelength range between 600nm and 750nm  
show a signal to noise ratio an order of magnitude better than  
conventional surface plasmon resonance spectroscopy. The improvement  
is due to the possibility to collect at the same time amplitude and  
phase of the groove parallel plasmons.


For information: CBM  tel. 040 375 7711 - info at cbm.fvg.it


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