Photothermal Imaging of Nanometer-Sized Metal Particles Among Scatterers
David Boyer,1
Philippe Tamarat,1
Abdelhamid Maali,1
Brahim Lounis,1*
Michel Orrit2*
Ambient optical detection of labeled molecules is limited for
fluorescent dyes by photobleaching and for semiconducting nanoparticles by "blinking" effects. Because nanometer-sized metal particles do
not optically bleach, they may be useful optical labels if suitable
detection signals can be found. We demonstrate far-field optical
detection of gold colloids down to diameters of 2.5 nanometers with a
photothermal method that combines high-frequency modulation and
polarization interference contrast. The photothermal image is immune to
the effects of scattering background, which limits particle imaging
through Rayleigh scattering to diameters larger than 40 nanometers.
1 Physique Moléculaire Optique et Hertzienne,
CNRS et Université Bordeaux I, 351 Cours de la Libération,
33405 Talence Cedex, France.
2 Huygens Laboratory,
Universiteit Leiden, Postbus 9504, 2300 RA Leiden, Netherlands.
*
These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail:
lounis{at}cpmoh.u-bordeaux.fr
