Figure 3: Resolution increase in STED nanoscopy of fluorescent QDs.
(a) Qdot705 imaged in STED nanoscopy with λexc=628 nm excitation (Exc.) and λSTED=775 nm STED wavelength. Scale bar, 1 μm. (b) The same sample position as in a imaged only with the doughnut-shaped STED laser. Images in a and b were acquired by line-wise multiplexing to avoid drift between both images. (c) The image acquired with illumination by the STED laser beam only (b) was subtracted from the STED image (a) to result in a background-free final image (3 × 3 median filter). (d) Confocal image of the same sample region for comparison. (e) Inset from c, white square, with distinct QDs that could not be separated by confocal imaging (f). Scale bar, 300 nm. (g,h) Averaged line profile of 10 QDs in raw images (a,b) in subtracted image (c) and confocal image (d). (i) The full-width at half-maximum (FWHM) of single QDs (n=10) as function of the STED laser power can be well approximated by the STED resolution formula shown. Error bars represent±1 s.d.
