Size, Diffusion, and Sedimentation of Gold Nanorods

Abstract

We have used four different analytical techniques (electron microscopy (TEM), dynamic light scattering (DLS), analytical ultracentrifugation (AUC), and small angle X-ray scattering (SAXS) to measure the length and width as well as the diffusion coefficients of gold nanorods of different aspect ratio. All four methods could reproduce the trends in aspect ratio, and both length and width could be extracted once the ligand shell was accounted for. The CTAB bilayer coating was determined to have a thickness of 3.34, 3.02, and 3.26 nm by SAXS, DLS, and AUC, respectively. TEM nevertheless yielded the best predictions for the nanorod ensemble surface plasmon resonance by using COMSOL simulations. All four methods yielded better fits when the rods were treated as spherically capped cylinders.

Determination of Translational and Rotational Diffusivities of Anisotropic Nanoparticles by Heterodyne Polarized and Depolarized Dynamic Light Scattering

“…In connection with the determination of the L and d of the NRs, Seibt et al recently performed a comprehensive study using four analytical techniques, namely, TEM, DLS, analytical ultracentrifugation, and small-angle X-ray scattering. 28 In light of their work, some of the identified disadvantages of DLS found in the present work are briefly summarized. Since the determination of the L and d of the NR by DLS is based on models which correlate the diffusivities and the shape, the resulting values for L and d depend strongly on the chosen model and its applicability to different systems.…”

“…It is again related to the presence of impurities, as described in Section , that the experimental D T value is falsified for this system. In connection with the determination of the L and d of the NRs, Seibt et al recently performed a comprehensive study using four analytical techniques, namely, TEM, DLS, analytical ultracentrifugation, and small-angle X-ray scattering . In light of their work, some of the identified disadvantages of DLS found in the present work are briefly summarized.…”

“…Among the diverse types of anisotropic nanoparticles, nanorods are the most studied system. Many established optical techniques, including, e.g., single particle tracking, dark-field microscopy, , differential dynamic microscopy, and dynamic light scattering (DLS), − were applied for the determination of the D T and D R of nanorods. The DLS method is the most widely used method because of its measuring principle in macroscopic thermodynamic equilibrium without the need for any calibration procedure.…”

Mesoscale simulations of diffusion and sedimentation in shape-anisotropic nanoparticle suspensions

“…This degree of anisotropy is much smaller than that of many rod-like particles, such as those of biological origin like the fd virus 65,66 and tobacco mosaic virus, 13 that is often in the range λ ⪆ 10. Nanorods with smaller aspect ratios can be synthesized, 67–69 but we found surprisingly little data on their transport coefficients. Hence, we chose to study spherocylinders with these smaller aspect ratios to begin to bridge the knowledge gap between spheres and long rod-like NPs.…”