Background-Suppression in the Detection of Gold Nanoparticles in Cells through Anti-Stokes Photoluminescence

In microscopy one of the fundamental limitations for particle imaging, localization and tracking is the signal-to-background ratio. Many techniques have been proposed to lower the background, including two-photon excitation, lifetime measurements, photothermal signal, etc., but they are usually hard to implement and require a dedicated setup. We present a simple solution that is readily achievable in any confocal microscope by detecting the anti-Stokes photoluminescence of single gold particles. We apply this technique to the imaging of gold nanorods in living cells. We show a high background rejection, lowering the effect of the cell self-fluorescence. This proves to have a great impact in the case of stained cells, where the background arises also from dye molecules. This new technique provides a simple detection scheme of smaller nano objects with standard setups, and will be an ideal approach for cellular biology.