Fig. 3.

dSTORM imaging of dye-functionalized nanoparticles. a Schematic depiction of a spherical nanoparticle, functionalized with multiple Alexa647 fluorophores. The average density of the fluorophores can be adjusted by varying reaction conditions. b dSTORM image of multifunctional nanoparticles. Medium-density nanoparticles were immobilized on a glass coverslip and imaged using astigmatic 3D-dSTORM. c Probability mass function of the number of localizations per nanoparticle (grey bars), $N_{\mathrm{beads}}=379$. The probability mass function has been fit using a conditional compound Poisson distribution (solid magenta line), $\mathrm{Poisson}\left(\widehat{\lambda }=46.82\right),$ representing the functionalization reaction as a completely random arrival process. An alternative fit has been performed using a conditional compound negative binomial distribution (solid green line), $\mathrm{NBinomial}\left(\widehat{r}=6.54,\widehat{p}=0.12\right)$, indicating a functionalization process with increased dispersion. d Cumulative probability distribution of the number of localizations per bead (solid points). The plot shows an improved quality of the fit for a compound negative binomial function (solid green line) compared to a compound Poisson function (solid magenta line). Details of the distributions used in c and d can be found in the Supplementary Methods