Plasmonic-Based Mechanochromic Microcapsules as Strain Sensors.

Efficiently detecting mechanical deformations within materials is critical in a wide range of devices, from micro-electromechanical systems to larger structures in the aerospace industry. This communication reports the fabrication of new mechanochromic micrometer-size capsules enabling the detection of strains. These microcapsules are synthesized using an emulsification approach.

Plasmon Resonances in Self-Assembled Two-Dimensional Au Nanocrystal Metamolecules.

We explore the evolution of plasmonic modes in two-dimensional nanocrystal oligomer "metamolecules" as the number of nanocrystals is systematically varied. Precise, hexagonally ordered Au nanocrystal oligomers with 1-31 members are assembled via capillary forces into polygonal topographic templates defined using electron-beam lithography. The visible and near-infrared scattering response of individual oligomers is measured by spatially resolved, polarized darkfield scattering spectroscopy.

Dendronization-induced phase-transfer, stabilization and self-assembly of large colloidal Au nanoparticles.

The phase-transfer of CTAB-coated aqueous, spherical gold nanoparticles, with metallic core diameters ranging from ca. 27 to 54 nm, into organic solvents by exchanging the primitive polar bilayer with lipophilic, disulfide dendritic ligands is reported. The presence of such a thick nonpolar organic shell around these large nanoparticles enhances their stabilization against aggregation, in addition to enabling their transfer into a variety of solvents such as chloroform, toluene or tetrahydrofuran.

Topological darkness in self-assembled plasmonic metamaterials.

Self-assembled plasmonic metamaterials are fabricated from silver nanoparticles covered with a silica shell. These metamaterials demonstrate topological darkness or selective suppression of reflection connected to global properties of the Fresnel coefficients. The optical properties of the studied structures are in good agreement with effective medium theory.

Bottom-up fabrication and optical characterization of dense films of meta-atoms made of core-shell plasmonic nanoparticles.

In an attempt to fabricate low index metamaterials by a bottom-up approach, meta-atoms constituted of silica-coated silver nanoparticles are assembled by a Langmuir-Schaefer technique into thin films of large area and well-controlled thickness. The silica shells ensure a constant distance between the silver cores, hence providing a constant coupling of the localized surface plasmon resonance (LSPR) of the nanoparticles in the assembled composite material. The optical response is studied by normal angle spectral reflectance measurements and by variable angle spectroscopic ellipsometry.