The
self-assembly of plasmonic nanoparticles into highly ordered
superlattices could pave the way toward novel nanomaterials for surface-enhanced
Raman scattering (SERS). Here, we propose the formation of large-area
superlattices of elongated rhombic dodecahedra in a vertical orientation
via a controlled droplet evaporation process. Expectedly, the constant
humidity of the experimental condition could control the evaporation
speed of droplets and this procedure promotes the balance between
driven depletion attraction and electrostatic repulsion in the system,
leading to the generation of well-organized three-dimensional (3D)
superlattices. The unique geometry of elongated rhombic dodecahedra
could establish the tetragonal superlattices, which breaks the conventional
hexagonal symmetry of gold nanorods. Specifically, the influence of
the type and concentration of surfactants, the concentration of nanoparticles,
and the amount of droplets on the preparation results were systematically
investigated to find the optimal assembly parameters. Remarkably,
such close-packed tetragonal arrays of vertically aligned elongated
rhombic dodecahedra exhibit more excellent SERS performance compared
with the traditional hexagonal superstructure of gold nanorods. Benefiting
from the high sensitivity and reproducibility of elongated rhombic
dodecahedron superlattices, their applications in the determination
of pesticide residues in apple and grape peels were successfully demonstrated.
As a result, this study may advance the production of innovative plasmonic
nanomaterials for a broad range of fields.