Helping nano-entities discover their nano-identity

A. Castro, M. Leeman, J.R. Runyon, L. Nilsson, M. Ulmius Storm
SOLVE Research and Consultancy AB,

Keywords: field-flow fractionation, FFF, light scattering, MALS, size distribution, dynamic light scattering, DLS, separation, fractionation, chromatography


Nanoscale materials are becoming increasingly prevalent in our lives. The strategies required to characterize the properties and performance of nanoscale materials can be as unique as the material itself. We have experienced that separation of the sample components into narrow size fractions before analysis can provide much more information about the sample. A state-of-the-art technique for analyzing size and characterizing nanoscale materials is field-flow fractionation (FFF). Field-flow fractionation physically separates the sample according to size before characterization. This allows to obtain information on structure and size across the entire sample distribution from single nanoparticles to large micron-sized aggregates with the help of different on-line spectroscopic and scattering techniques. It is also possible to collect the resulting fractions for additional off-line analysis or to provide monodisperse nanoparticle samples. However, FFF is still not commonly used in the nanomaterial community. We are presenting a couple of examples to show the importance of introducing separation techniques as FFF in the characterization of nanoparticles. One example illustrates a polydisperse nanoparticle sample analyzed with dynamic light scattering (DLS) and FFF. What is shown as a broad population in DLS, is in fact a sample with three populations corresponding to nanoparticle cores (as measured with transmission electron microscopy prior to coating), the coated particles, as well as aggregated particles. This data illustrates the difficulties involved in detecting different size populations in a complex sample without sample fractionation. Another example shows the separation and detection of populations that are not part of the nanoparticles. It is possible to differentiate a first population that corresponds to free coating material still remaining after washing steps, from a second population corresponding to the coated nanoparticles. SOLVE Research and Consultancy performs contract analysis and consultation within material characterization. Our expertise lies in the comprehensive characterization of materials at the nanoscale and to explain their behavior in solution.