Regioselective Plasmonic Coupling in Metamolecular Analogs of Benzene Derivatives

Abstract

In analogy with benzene-derived molecular structures, we construct plasmonic metamolecules by attaching Au nanospheres to specific sites on a hexagonal Au nanoplate. We employ a ligand exchange strategy that allows regioselective control of nanosphere attachment and study resulting structures using correlated electron microscopy/optical spectroscopy at the single-metamolecule level. We find that plasmonic coupling within the resulting assembly is strongly dependent on the structure of the metamolecule, in particular the site of attachment of the nanosphere(s). We also uncover a synergy in the polarizing effect of multiple nanospheres attached to the nanoplate. Regioselective control of plasmonic properties demonstrated here enables the design of novel structure-dependent electromagnetic modes and applications in three-dimensional spatial nanosensors.

Colloid‐Interface‐Assisted Laser Irradiation of Nanocrystals Superlattices to be Scalable Plasmonic Superstructures with Novel Activities

“…Such strategies include the interface‐assisted assemble superlattices (SLs), DNA‐based sequence‐specific bonding assemble structures, direct NC pattern optical lithography by photochemically active cation/anion groups, self‐assemblies by NC micelle to diamond‐like supercrystals, and so on . In as‐formed NC assembly SLs, the coupling interactions of constituent NCs are usually limited in the application of film‐scale devices as a result of the interparticle spacing produced by long‐chain organic ligands . For example, such insulating ligands at building block surfaces can generate a barrier for the electronic transport .…”

Optical and sensing properties of various shaped gold nanoplates and highly controlled asymmetric gold nanoplate/nanosphere coupled assemblies.

“…This leads to a similar red-shift for all light polarization directions, leading to one broad peak instead of multiple peaks. The unique synergistic effect in the shift in  max observed in the 4-ATP experiments described in Chapter 3 was also observed with Cys linkers 146. For example, the attachment of a single NS to a NP resulted in a 36 nm red-shift while the attachment of two NSs to the edge site of a Au NP resulted in a 82 nm red-shift, amounting to a shift of 41 nm per attached NS.…”

“…(75 nm vs 14 nm). In our previous studies,146 simulation of the electric field around the different regions of a hexagonal NP showed site-dependent electric field strengths in the order of the vertex > edge > terrace, which explains why the NS attached on the vertex site of a NP resulted in a bigger shift compared to attachment on the edge site for the triangular NP, which would show a similar electric field site dependence. Our results here agree well with the simulation of the polarization difference between the vertex and edge sites of a triangular NP.…”

“…The simulation of the near-field around a resonantly excited NP shows the polarizability of the NP. 146 Under in-plane excitation, a polarization map shows that the NP is most polarizable at its vertices, followed by the edges, and least polarizable at the terraces.…”

“…Using the darkfield microscope system and strategy we have developed to study individual NPs, 146 we first collected LSPR spectra of several individual NPs in air (RI=1.00) ( Figure 6.5A), and then covered those NPs with IPA (RI=1.37) and collected their spectra again. After application of the IPA we observed a significant color change in each of the NPs (Figure 6.5B).…”