Evaporation-induced self-assembly of nanoparticles from a sphere-on-flat geometry

(Figure Presented) Nanoscience in coffee rings: Nanoparticles with easily tailored optical and electronic properties can be dynamically self-assembled into spatially ordered, 2D patterns (see SEM picture) simply by allowing a drop of a nanoparticle solution to evaporate in a confined, axially symmetric geometry. Utilizing the "coffee-ring" phenomenon, this approach, which dispenses with the need for lithography and external fields, is fast, cheap, and robust.