(306b) Experimental and Theoretical Comparison of Aspect-Ratio-Dependent Diffusion of CdSe Nanocrystals through Nanochannels

The use of nanofluidic devices as a means of separating biomolecules, nanoparticles, and other small species is of fundamental importance. Experimentally obtained transport properties can be compared to theory and computer simulations to further elucidate our understanding of their transport properties at the nanoscale. In particular, we have evaluated toluene suspensions of CdSe nanocrystals (NCs) to determine the effect of their aspect ratio on diffusion constant and eventual equilibrium concentration in nanochannels (100 nm w x 400 nm d). To quantitatively monitor NC diffusion, we measure spectrally resolved photoluminescence (PL) from these NCs as a function of time and distance from the nanochannel inlet, using laser scanning confocal microscopy. The PL intensity is compared to a diffusion model that allows NC-wall adsorption. The comparison reveals that the hindered NC diffusion constant is approximately two orders of magnitude lower than that observed in microchannels and that the NC-wall adsorption is negligible. The NC equilibrium concentration, approximated by the NC concentration near the nanochannel inlet, also reveals strong aspect ratio dependence that compares well with a theory that accounts for physical interactions of NCs with channel geometry.