Using three-dimensional finite-difference time-domain (FDTD) simulation, we described a systematic investigation on the electric field enhancement of the silver corrugated nanowires. The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) for corrugated nanowires can be markedly increased by 1 or 2 orders of magnitude as compared with the smooth nanowires. Moreover, the EF can be further increased with nanoparticle attachment on the corrugated Ag nanowires owing to the coupling between the discrete plasmon state of the nanoparticles and continuum plasmon states of the corrugated nanowire or the crossed corrugated nanowires. The surface plasmonic field distribution of Ag nanowires can be effectively controlled by the polarization of the incident light. Raman spectrum measurements show that the relatively dense corrugated nanowires exhibit a relatively high reproducibility and SERS enhancement attributed to the elimination of polarization-dependent SERS-anisotropic enhancement via the overlapping of randomly distributed Ag nanowires. Such nanostructures as potential nanoantennas offer a route to optimize plasmon coupling for designing miniaturization integration.

surface plasmon resonance. The plasmonic coupling effect at the nanometer gaps between metallic nanoparticles, i.e., the plasmonic hot spots, has also been utilized to further increase the SERS signals. [ 3 ] Extensive studies have been focused on creating hot spots spaced by small dielectric gaps of less than 10 nm. In addition to the original SERS platform made from electrochemically roughened surface, [ 4 ] a diverse novel SERS substrates have been developed, which include the well-ordered patterned arrays fabricated via lithographic techniques. [ 5 ] However, these techniques are limited by their low throughput, expensive operating cost, and small SERS active area. Importantly, it is still diffi cult to process small nanogaps down to sub-5 nm over large area. As such, size/shape controlled colloidal nanoparticles and their assemblies such as dimers, trimers, liner chains, core-satellite structures are attractive options due to the ability to synthesize through wet chemical approaches in bulk scale without the need of expensive instrumentation. [ 6 ] However, owing to the "coffee ring" effect, regulating the geometrical dimension, i.e., uniform nanoparticle gaps between colloidal nanoparticles via spontaneous aggregation or assembly are challenging. [ 7 ] With the assistance of surface ligands, nanoparticles can be assembled into superlattices, [ 8 ] but the introduction of polymer ligands unavoidably sacrifi ces the sensitivity of signals in a variety of applications, such as SERS, biosensors, plasmon-enhanced fl uorescence. Therefore, the central problem is to homogeneously produce well-defi ned plasmonic structures that can reproducibly fabricate sub-5 nm nanogaps with controllable gap distance and enhanced hot spot density within the plasmonic structure.In comparison with the nanoparticle superlattices obtained via self-assembly of metallic nanocrystals by means of the polymer ligands, [ 8 ] the ordered nanoparticle supercrystals may also be synthesized via replicating 3D colloidal (e.g., polymer or SiO 2 spheres) template [ 9 ] or ordered mesoporous silica (e.g., KIT-6, SBA-15, MCM-48) templates. [ 10 ] For example, 2D dimpled gold nanoplates were fabricated by vapor reduction using a 3D lattice of silica nanospheres (≈40 nm) as a template. [ 9 ] Unfortunately, the dimpled-type array is not suitable for the applications in SERS. Using ordered mesoporous silica (KIT-6 and SBA-15) template, Yamauchi's group has successfully fabricated polyhedral mesoporous Pt nanoparticles through a chemical reduction route. [ 10 ] However, the synthesis of highly Metallic periodic structures provide unique optical and photonic coupling effects. However, geometrically precise control of periodic structure is particularly challenging when studying scale at few nanometer. Here, a new class of highly ordered silver plasmonic supercrystals is successfully synthesized by means of a nanocasting process using ordered mesoporous silica as template. During the nanocasting via a chemical reduction, the diffusibility, viscosit...

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