Reconstruction of the 3D structure of colloidosomes from a single SEM image

In this paper we show how the 3-dimensional structural arrangement of particles in a colloidosome is derived from a single scanning electron microscopy (SEM) image. We exploit the fact that particles are located on the surface of a sphere to directly quantify the 3-dimensional positions of all particles from a single 2-dimensional SEM image. The 3-dimensional particle positions are used to quantify the structural arrangement of the particles by performing both a Delaunay triangulation (DT) as well as a Voronoi tessellation (VT) of the colloidosome surface, which we use to validate the procedure for determining the 3-dimensional particle positions. In addition to the DT and the VT, we calculate the radial pair correlation function g(r). We explain how the pair-distribution is modified to suit a spherical surface and how the structural order relates to similar data on colloidal films. Our results illustrate that even for a colloidosome in its ground state, the resulting ordering is short-ranged (in our case 4 particle diameters), which is in contrast to densely packed colloidal films.