Nanoscale Distance Fluctuations probed by Photothermal Correlation Spectroscopy

摘要

We study numerically the measurement, of distances and distance fluctuations by photothermal correlation spectroscopy and coupled plasmon resonances. Gold nanopaxticle 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.