Robust Assembly of Colloidal Nanoparticles for Controlled-Reflectance Surface Construction

Controlled placement of nanoscale particles with nanometer precision on substrates/surfaces is highly desired toward functional nanodevices. Herein, we report the robust assembly of colloidal nanoparticles onto nanostructured aluminum surfaces. The surfaces are configured by porous anodic alumina (PAA) membranes on top of textured aluminum substrates. Capillary force and geometry confinement enable rapid and precise transfer of colloidal nanoparticles from solutions into PAA templates. Such top-down control of bottom-up assembly demonstrates large-area (>1 × 1 cm2) integration of nanoscale particles with exceedingly high yield (>95%) and exceptionally high density (>1010 particles/cm2). The plasmonic coupling between gold nanoparticles and aluminum surfaces, as well as between adjacent nanoparticles, is responsible for the unique reflectance from the assembled surfaces. The reflectance minimum (resonant absorption) can be readily shifted from visible to near-infrared by simple structural variation. The ap...