Measuring carbon nanotube diffusion is complex in 3D liquid environments. Single molecule fluorescence microscopy commonly provides nanotube trajectories in the 2D imaging plane with nanometer precisions but assessing the third dimension is more challenging task. To this aim, We will present two strategies based on point-spread function (PSF) engineering [1] or self-interfering PSF [2]. Because nanotubes are not spherical objects, 3D angular diffusion of the nanotubes shall also be considered. We will show that using a high-frame rate imaging (kHz) of nanotube movements, the autocorrelation time of nanotube fluorescence intensity can be computed in order to measure the rotational diffusion coefficient of the nanotubes. This further allows to estimate the length of the nanotubes either from the rotational diffusion coefficients alone, or by combining translational and rotational diffusion coefficients which has the advantage to avoid the requirement of knowing the solution viscosity or the SWCNT hydrodynamic diameter [3].

References

[1] Gresil, Lee, et al. In preparation

[2] Caceido, Lee, et al. In preparation

[3] Lee & Cognet J. Appl. Phys. 128 (2020) 224301