Determination of the two-dimensional distributions of gold nanorods by multiwavelength analytical ultracentrifugation

Simon E Wawra,Thaseem Thajudeen,Wolfgang Peukert,Michael Stingl,Lukas Pflug,Carola Kryschi

doi:10.1038/s41467-018-07366-9

Abstract

Properties of nanoparticles are influenced by various parameters like size, shape or composition. Comprehensive high throughput characterization techniques are urgently needed to improve synthesis, scale up to production and make way for new applications of multidimensional particulate systems. In this study, we present a method for measuring two-dimensional size distributions of plasmonic nanorods in a single experiment. Analytical ultracentrifuge equipped with a multiwavelength extinction detector is used to record the optical and sedimentation properties of gold nanorods simultaneously. A combination of sedimentation and extinction properties, both depending on diameter and length of the dispersed nanorods, is used to measure two-dimensional distributions of gold nanorod samples. The length, diameter, aspect ratio, volume, surface and cross-sectional distributions can be readily obtained from these results. As the technique can be extended to other non-spherical plasmonic particles and can be used for determining relative amounts of particles of different shapes it provides complete and quantitative insights into particulate systems.

Highlights

Properties of nanoparticles are influenced by various parameters like size, shape or composition
Dynamic light scattering (DLS), which is commonly used for the characterization of colloidal nanoparticles, does not allow the measurement of size and aspect ratio as the effects of both translational and rotational diffusion of the nanoparticles need to be taken into account[16]
It was used for the study of rod-like nanoparticles[4,28,29]. Other methods such as the discrete dipole approximation or the finite element method (FEM) allow calculating the spectra of individual true rod-like particles. This high flexibility and precision comes at the cost of high computational effort and requires the full structural information including the influence of the crystalline structure of the gold nanorods, the end cap geometry[34,35,36,37,38], the used optical constants of the material[30] and the optical properties of the host medium

Summary

Introduction

Properties of nanoparticles are influenced by various parameters like size, shape or composition. A combination of sedimentation and extinction properties, both depending on diameter and length of the dispersed nanorods, is used to measure two-dimensional distributions of gold nanorod samples. Dynamic light scattering (DLS), which is commonly used for the characterization of colloidal nanoparticles, does not allow the measurement of size and aspect ratio as the effects of both translational and rotational diffusion of the nanoparticles need to be taken into account[16]. Small angle X-ray scattering (SAXS) has been used to study the growth mechanism of gold nanorods during synthesis[18] allowing an in situ determination of mean lengths and diameters with high temporal resolution. Thajudeen et al showed that the mean length and diameter of nanorods can be accurately measured using a combination of electrospray scanning mobility particle sizer and AUC21

Methods

Results

Conclusion