Magic carpet chemistry

A crystalline two-dimensional colloid that hangs several micrometres above a surface has been created by UK chemists. Erika Eiser and Nienke Geerts of the University of Cambridge were trying to make 3D photonic crystals when they noticed that one of their colloids was floating above the surface. Colloids that are coated with very short DNA strands bind strongly to a surface forming an amorphous substrate, but here they assembled into a two dimensional "carpet" due to weaker adsorption of the longer DNA molecules on to the surface. Magically, the team says the system may have applications as defect-free photonic crystals.