Photothermal imaging of nanometer-sized metal particles among scatterers.
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.
Boyer
David
D
Physique Moléculaire Optique et Hertzienne, CNRS et Université Bordeaux I, 351 Cours de la Libération, 33405 Talence Cedex, France.
Tamarat
Philippe
P
Maali
Abdelhamid
A
Lounis
Brahim
B
Orrit
Michel
M