Synthesis and characterization of elution behavior of nonspherical gold nanoparticles in asymmetrical flow field-flow fractionation (AsFlFFF)

Asymmetrical flow FFF (AsFlFFF) is a member of field-flow fractionation (FFF) and can provide the separation of particles with size from nano to microscale based on their hydrodynamic diameters with smaller particles being eluted earlier than larger ones. For spheres, if the AsFlFFF conditions are well optimized, the FFF theory allows prediction of the elution time for a given diameter. Herein, we aim to use the AsFlFFF channel to compare the elution behavior of the gold nanoparticles with three different morphologies and give a comprehensive depiction for the mechanism of their separation in AsFlFFF. Furthermore, the particles size obtained from AsFlFFF was compared with that obtained from other techniques such as transmission electron microscopy (TEM), and dynamic light scattering. In this study, gold nanospheres (GNS), gold nanotriangles (GNT), and gold nanorods (GNR) were synthesized. TEM data stated that the mean particle diameter and the edge length of GNS and GNT were 51 and 35 nm, respectively, and the length of GNR was 47 nm. Although, the diameter of GNS is close to the length of GNR, the elution time of GNS (4.45 min) was much longer than that of the GNR (3.70 min) at the same AsFlFFF conditions. Also, the elution time of GNT was longer than that of GNR, even though it has smaller size than GNR. This might be attributed to GNR reaching an equilibrium position that is farther away from the accumulation wall of the channel than GNS, resulting in earlier elution than GNS. The GNT particles are rather similar in shape to spheres, and may behave more closely to the spheres than GNR. It seem that AsFlFFF could be an analytical technique for particle size analysis and separation of nanoparticles of different shapes.