Fig. 2: Super-resolution imaging of nanorods with different length.

a The pattern of the donut-shaped illumination of excitation point spread function (PSF) and the pattern of the resulted emission PSF after scanning across a single UCNPs. b Illustration of a process using a donut-shaped excitation beam to scan and resolve the heterogeneous structure of a single upconversion nanorod. c The corresponding luminescence intensities at the three typical positions to resolve the final negative-contrast super-resolution image of a nanorod. d The raw data of negative-contrast super-resolution images of five types of heterogeneous upconversion nanorods with tuneable lengths between the optically active components. e The average center-to-center distance and standard deviation of two actively doped segments of five types of heterogeneous upconversion nanorods measured from TEM and super-resolution imaging, data are shown as the mean ± SD. f Super-resolution image of the high concentration nanorods with an active segmental distance of 99.0 nm. g Super-resolution image of the mixture of two types of nanorods with active segmental distances of 90 nm and 122 nm, respectively. Pixel sizes in d, f, and g are 10 nm. Scale bars in a, d, f, and g are 500, 500, 400, and 250 nm, respectively.