detecting/tracking nano particle
There are a few ways to do nanoparticle tracking, although I'm not sure they will exactly apply to your system.

Dynamic light scattering or DLS has been used to get the distribution of nanoparticle sizes in solution/suspension over time. Generally, the data gives information on the ensemble, not single-particle tracking.

Nanoparticle tracking analysis or NTA also relies on scattered light, but gives frame-to-frame analysis of each particle's trajectories.

There are other related techniques... Another approach is to create an Anti-Brownian ELectrokinetic (ABEL) trap - to monitor the particle or protein dynamics and apply forces to push it back. This technique was developed by the Moerner lab at Stanford, for example Acc. Chem. Res., 2012, 45 (11), pp 1955–1964