Hamburg 2009 – scientific programme
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SYSM: Single Molecule Spectroscopy of Nanoobjects
SYSM 1: Single Molecule Spectroscopy of Nanoobjects I
SYSM 1.3: Invited Talk
Thursday, March 5, 2009, 11:50–12:30, VMP 8 HS
Hot Brownian Motion and Photothermal Correlation Spectroscopy — •Romy Radünz1, Daniel Rings2, Klaus Kroy2, and Frank Cichos1 — 1Molecular Nanophotonics Group, Institute of Experimental Physics I, University Leipzig, Linnestra\sse 5, 04107 Leipzig, GERMANY — 2Soft Condensed Matter Theory, Institute of Theoretical Physics, University Leipzig, Vor dem Hospitaltore 1, 04103 Leipzig, GERMANY
We introduce a new technique for the measurement of tracer dynamics, called photothermal correlation spectroscopy, which is sensitive to single metal nanoparticles down to a radius of 2.5 nm with a time resolution of a few microseconds. The method is based on a fluctuation analysis of a heterodyne photothermal scattering signal, which is recorded in a simple confocal microscopy setup. It exploits the same principles as fluorescence correlation spectroscopy but targets the use of extremely photostable, non-fluorescent, nano-sized tracers as a replacement of fluorescent probes. To validate our approach, we verify that the Stokes-Einstein relation holds for heated diffusing gold nanoparticles, with an effective viscosity and temperature predicted by a semi-quantitative analytical model. This example of hot Brownian motion promises to shine new light into diffusion problems under thermal non-equilibrium as it is important for the heat conduction in nano-fluids. In summary, the presented method together with the photostability and the low size dispersion of gold nanoparticles provides large potential for broad applications especially in the field of high throughput biological screening.