PhD defence of Tonnishtha Dasgupta

Colloidal crystallization in bulk, gravity and spherical confinement

This thesis investigates various aspects of colloidal crystallization with a particular focus on photonic crystals. Photonic crystals show a photonic bang gap as a consequence of alternating regions of high and low dielectric contrasts, and are promising for applications such as optical wave guides, optical sensors, energy storage and conversion. In Chapter 1, we introduce the ideas, challenges and motivation behind this thesis. In Chapter 2, we show that that monodisperse hard spheres sedimenting at high velocities onto a face-centered-cubic FCC (100) template form single large FCC crystals with very few defects, which is desirable for photonics. In Chapter 3, we study a colloidal self-assembly route for the binary MgCu2 Laves phase (LP) via templated sedimentation. The two sublattices of the MgCu2 LP can then be employed to make materials with wide photonic bandgaps. In Chapter 4, we discuss how to avoid a random stacking of the FCC and of its thermodynamically competing structure by adding polymer chains to the colloidal system. In Chapter 5, we investigate the role of attractions, on the formation of crystalline structures, from nanoparticle self-assembly inside a spherical confinement. In Chapter 6, we show that by introducing a degree of softness into the hard-sphere potential one can spontaneously nucleate binary LPs, a process which is otherwise hampered by glassy dynamics typical for such high densities. Finally, in Chapter 7, we show that the same binary mixture, inside a spherical confinement, self-assembles into an icosahedral quasicrystal, which possesses a photonic band gap.

Start date and time
End date and time
University Hall
PhD candidate
T. Dasgupta
Colloidal crystallization in bulk, gravity and spherical confinement
PhD supervisor(s)
prof. dr. M. Dijkstra