PhD abstract

The asymmetrical flow field flow (AF4) is a technique used to measure the size of nanoparticles. It consists in  fractionating the different populations inside the sample as a function of their hydrodynamic diameter. In the 1960s, a model (thereafter called classical model) has been developed, relying the retention time of a nanoparticle with its hydrodynamic diameter. However, the model validity is based on work hypothesizes which are not always respected depending on the experimental conditions. The work of this PhD thesis has consisted firstly in the study of the mechanisms governing the nanoparticles retention inside the AF4 channel. Notably it has been shown that interactions between the nanoparticles and the accumulation wall of the AF4 biased the results predicted by the classical model. Another model (thereafter called p-w model), which takes electrostatic and Van de Walls interactions into account, has been developed. Tests realized with particle standards for size showed that the p-w model give results with a better trueness than the classical model and that it can be applied for a larger range of experimental conditions. A validation of this model has been conducted and an uncertainty budget has been developed by following the Monte Carlo method. The metrological traceability of the measurement results has also been demonstrated.

Key words

AF4, nanoparticles, FFF theory, method validation