We study numerically the measurement of distances and distance fluctuations by photothermal correlation spectroscopy and coupled plasmon resonances. Gold nanoparticle dimers form a coupled longitudinal plasmon resonance in the absorption cross section, which strongly depends on distance. This new plasmon resonance can be advantageously used to heat the particles in a photothermal microscope. We calculate the distance dependence of the photothermal signal as a function of particle size and distance. The results demonstrate that the photothermal signal autocorrelation function stay single exponential even for large amplitude fluctuations and thus directly reveals the dynamics of the distance fluctuations without any corrections as required for fluorescence resonance energy transfer (FRET). Further, we show, that this type of distance detection provides distance measures beyond the accessible range of a few nanometers as in FRET.

Date Published: 27 February 2009
PDF: 8 pages
Proc. SPIE 7185, Single Molecule Spectroscopy and Imaging II, 71850V (27 February 2009); doi: 10.1117/12.817847

Published in SPIE Proceedings Vol. 7185:
Single Molecule Spectroscopy and Imaging II
Jörg Enderlein; Zygmunt Karol Gryczynski; Rainer Erdmann, Editor(s)