Three-dimensional tracking of fluorescent nanoparticles with subnanometer precision by use of off-focus imaging

Abstract

We show that the position of a fluorescent nanoparticle can be measured in three dimensions with subnanometer precision and 100-ms temporal resolution by use of standard epifluorescence video imaging in off-focus mode. The particle can be tracked without feedback in a volume of at least $40 \mathit{\mu }\mathrm{m}\times 60 \mathit{\mu }\mathrm{m}\times 3 \mathit{\mu }\mathrm{m}$. With the technique presented, the structure–mobility relationship of 216-nm latex particle in a porous polymer network was studied in three dimensions.