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Issue 27, 2017
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Colloidal diffusion over a quenched two-dimensional random potential

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A two-layer colloidal system is developed for the study of diffusion over a quenched two-dimensional random potential. A mixture of bidisperse silica spheres is used to form a randomly packed colloidal monolayer on the bottom substrate. The corrugated surface of the bottom colloidal monolayer provides a gravitational potential field for the dilute diffusing particles in the top layer. The population probability histogram P(x,y) of the diffusing particles is obtained to fully characterize the random potential landscape U(x,y) via the Boltzmann distribution. The dynamical properties of the top diffusing particles, such as their mean square displacement (MSD), histogram of the escape time, and long-time self-diffusion coefficient, are simultaneously measured from the particle trajectories. A quantitative relationship between the long-time diffusion coefficient and the random potential is obtained, which is in good agreement with the theoretical prediction. The measured MSD reveals a wide region of subdiffusion resulting from the structural disorders. The crossover from subdiffusion to normal diffusion is explained by the Lorentz model for tracer diffusion through a heterogeneous space filled with a set of randomly distributed obstacles.

Graphical abstract: Colloidal diffusion over a quenched two-dimensional random potential

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Publication details

The article was received on 27 May 2017, accepted on 04 Jun 2017 and first published on 07 Jun 2017

Article type: Paper
DOI: 10.1039/C7SM01056G
Soft Matter, 2017,13, 4773-4785

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    Colloidal diffusion over a quenched two-dimensional random potential

    Y. Su, X. Ma, P. Lai and P. Tong, Soft Matter, 2017, 13, 4773
    DOI: 10.1039/C7SM01056G

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