We report on a simple, universal,
and large-scale self-assembly method for generation of spherical superclusters
from nanoscopic building blocks. The fundamentals of this approach
rely on the ultrahigh preconcentration of nanoparticles (NP) followed
by using either emulsification strategies or alternatively multiphase
microfluidic microdroplets. In both cases drying of the NP droplets
yields highly spherical self-assembled superclusters with unique optical
properties. We demonstrate that the behavior of these spheres can
be controlled by surface functionalization before and after the self-assembly
process. These structures show unique plasmonic collective response
both on the surface and within the supercluster in the visible and
infrared regions. Furthermore, we demonstrate that these strong, tunable
optical modes can be used toward ultrasensitive, reproducible, surface-enhanced
spectroscopies
