Super-resolution optical imaging of binary colloidal assemblies

Evaporation induced self-assembly of micro- and nanospheres exhibits 2D and 3D ordered packing. When particles of two different sizes are used, binary colloidal assemblies (BCAs) form metastructures with novel physical properties. Imaging of BCAs with scanning electron microscopy (SEM) limits the view to a surface morphology only. When fluorescence is incorporated into the individual particles, imaging methods traditionally used in the biological sciences can be applied, such as 3D structured illumination microscopy (3D-SIM) which can image at twice the lateral resolution of a typical optical microscope and, therefore, improve resolution by a factor of ~8 in a 3D voxel. We demonstrate the application of 3D-SIM imaging to map individual positions of 200 nm particles in 3D mono- and binary colloidal assemblies. We also present time-resolved fluorescence lifetime images which inform localised chemical environments in the different packing structures.