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April 2008 - Molecular quenching and relaxation in a plasmonic tunable system:

Molecular fluorescence decay is significantly modified when the emitting molecule is located near a plasmonic structure. When the lateral sizes of such structures are reduced to nanometer-scale cross-sections, they can be used to accurately control and amplify the emission rate. In this contribution, we extend the Green dyadic method, to quantitatively investigate both radiative and non-radiative decay channels experienced by a single fluorescent molecule confined in an adjustable dielectric-metal nanogap. The technique produces data in excellent agreement with current experimental work.

Recently, a team from the PND Network has developed a versatile scheme well-suited for describing and predicting new photophysical mechanisms triggered by the vicinity of complex plasmonic devices. When applied to an adjustable plasmonic nanogap geometry, this new framework successfully reproduces experimental signals. Consequently, this new numerical tool can be used to support current experimental work developed in the field of molecular plasmonics. In particular, it can be applied to any geometrical configuration, to the accurate computation of the dissipation losses, and to the research of strategies to minimize them. Finally, by introducing an appropriate model for the ex- citation rate, the method can be extended to the description of optical relaxation of single molecules located in an STM nanogap.

 
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Sequence of three maps of the fluorescence intensity scattered in the farfield zone (rainbow color scale increasing from blue to red). The tip-molecule distance is fixed at 2.5 nm and three orientations of the transition dipole moments (red arrows) are investigated: (A) parallel to the sample surface; (B) tilted with an angle of 45° and (C) perpendicular to the surface.


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Sixth Framework Programme Information Society Technologies
 
Plasmo-nano-devices is an IST Network of Excellence
in the 6th Framework Programme of the European Union.