Photothermal Imaging of Nanometer-Sized Metal Particles Among Scatterers

Science  16 Aug 2002:
Vol. 297, Issue 5584, pp. 1160-1163
DOI: 10.1126/science.1073765

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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.

  • * These authors contributed equally to this work.

  • To whom correspondence should be addressed. E-mail: lounis{at}

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