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

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,mum X 60 mum X 3 mum. With the technique presented, the structure -mobility relationship of 216-nm latex particle in a porous polymer network was studied in three dimensions. (C) 2003 Optical Society of America.