Nanoparticle dynamics in simple fluids



Coglitore, D
(2016) Nanoparticle dynamics in simple fluids. Doctor of Engineering thesis, University of Liverpool.

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Abstract

The Stokes-Einstein relation is considered a benchmark in the transport of small particles in fluids, predicting an increase in diffusion with decreasing particle size. However, there is doubt about its validity at the nano-scale where some theoretical studies have predicted deviations from it. Experimental data from single nanoparticle tracking are presented in this thesis, collected using a recently-developed technique based on the optical phenomenon of caustics to detect the particle in a conventional inverted optical microscope. Experiments were performed on gold and polystyrene nanoparticles dispersed in water and glycerol-water mixtures, with viscosities ranging from 0.00008 to 0.15 Pa·s, to investigate the effect of nanoparticle size, density, concentration, and liquid viscosity on diffusion rates at a fixed temperature of 30°C. It is shown that below a critical concentration and critical size of particle diffusion falls orders of magnitude below the Stokes-Einstein prediction and it is better represented by the fractional Stokes-Einstein relation. At these experimental conditions, the diffusion coefficient was found to be constant with particle size and independent of material, but dependent on fluid viscosity. This thesis is aimed at enriching the knowledge on nanoparticle motion in simple fluid. The validity of the Stokes-Einstein diffusion at the nanoscale is addressed by experiments, within the context of simple, isotropic fluids.

Item Type: Thesis (Doctor of Engineering)
Divisions: Faculty of Science and Engineering > School of Engineering
Depositing User: Symplectic Admin
Date Deposited: 23 Aug 2017 09:37
Last Modified: 26 Apr 2022 12:21
DOI: 10.17638/03007090
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3007090