Correlated absorption and photoluminescence of single gold nanoparticles.

We perform simultaneous absorption (photothermal) and fluorescence detection of gold nanospheres with diameters of 80, 60, 40, 20, 10, and 5 nm. We unambiguously identify the same individual nanoparticles (NPs) over large areas (>400 μm(2)) by means of atomic force microscopy (AFM) and optical absorption (photothermal) microscopy. We correlate the height of NPs measured with AFM with absorption and fluorescence signals from the same individual NPs. That allows us to compare their brightness and estimate their fluorescence quantum yield at the single NP level.