New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation

Abstract

Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions.Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles.

Dynamic range multiwavelength particle characterization using analytical ultracentrifugation

“…AUC in combination with HDR analysis is superior to the single wavelength approach or scattering techniques. 28 Our technique takes advantage out of the direct fractionation of different size classes in the measurement cell during sedimentation, while an optimum SNR is achieved by automatically tuning the wavelengths being used for data evaluation dependent upon the particle size. The comparably high level of experimental random noise limits data quality.…”

Analysis of Particle Size Distributions of Quantum Dots: From Theory to Application

“…At this point it should be briefly mentioned that the same holds true for analytical centrifugation (AC) which works with lower gravitational fields but extends the measurement range to larger particle sizes (Detloff T. and Lerche D., 2008;Jafarzadeh S. et al, 2011;Krause B. et al, 2010;Walter J. et al, 2015c). Noteworthy, offline information from AUC, like for instance the optical properties of discrete QD fractions, could be implemented in evaluation routines based on UV/Vis spectroscopy.…”

Synthesis of stable iron oxide nanoparticle dispersions in high ionic media

“…Analytical centrifugation as a direct and absolute technique, is a powerful technique for the characterisation of nanoparticles in colloidal systems [56]. For instance, Chiu et al showed that the results of LumiSizer were comparable with those obtained using dynamic light scattering, scanning electron microscope and zeta potential analysis [57].…”