Search

We theoretically investigate the hybridization of the elemental surface plasmons in umbrella-shape plasmonic nanostructures and experimentally demonstrate the implementation of plasmonic multicolor metasurfaces as well as their application in colorimetric sensing. The three-dimension metallic umbrella arrays consist of a periodic canopy-capped-nanopillars with metal-coated sidewall and a backplane metal-film to form vertical nanocavity of canopy and film. Plasmonic coupling and energy confinement in nanocavity induce a noticeably resonance narrowing of multispectral reflection. The metasurfaced nanostructures appeared in vibrant and tunable colors with broad gamut derived from color blending mechanism due to multiple, narrow-band resonances. Vivid colors varied from red, yellow, green, blue to violet are easily achieved. It is also shown that such plasmonic metasurfaces can work as the feasible and real-time colorimetric refractive index sensor by measuring the distinct color variation to glucose concentration changes. Our sensor scheme shows its spectral sensitivity in the periodic umbrella array with respect to the refractive index change to be 242.5 nm/RIU with a figure of merit of 7.3. Furthermore, a refractive index resolution of colorimetric sensing up to 0.025 RIU has been accomplished.

We report a type of plasmonic palettes formed by an array of cross-shaped cavity nanostructures for multicolor image generation. And the nanocross-shaped antennas actually act as plasmonic cavity resonators and could realize surface plasmon excitation, resonating and coupling, which can impart intriguing optical properties. These features enable the nanotexted metasurfaces to implement full-gamut palettes through spatially color blending and continuously tunable coloration. We also employ the dark-field scattering and near-field scanning analysis to experimentally study the circularly nanoscale optical scattering in the new cavity-nanopin photonic metasurfaces resulting from aperiodic Fibonacci spiral arrangements.

This paper reports a simple and convenient method to fabricate a surface-enhanced Raman scattering substrate. It includes a green chemistry synthesis of Ag nanoparticles(NPs) and a process of coating a monolayer of the Ag NPs on a polydimethylsiloxane(PDMS) elastomer film. Ultra-low concentration of Ag+(10−8M) was used in Tollens method to synthesis monodisperse and relatively uniform Ag NPs. With recovery of the stretched PDMS film, the distribution of Ag NPs gets concentrated, resulting in an improvement of SERS detection sensitivity. Due to the transparent and flexible property of this highly sensitive SERS substrate, it exhibits great potential in in-situ detection of solid or irregular objects.

This paper presents an ultrasensitive and inexpensive method for ricin detection by surface enhanced Raman scattering (SERS) on shape-controlled gold nanocrystals substrates fabricated by integrating electrodeposition with dielectrophoresis (DEP). The ricin is captured by the rabbit anti-ricin polyclonal antibody which immobilized on the substrates. It was show that the limit of detection(LOD) could reach 0.1ng/ml in phosphate buffered saline (PBS), which is 2000 times less than the minimum lethal dose(with 500ml liquor).

In view of the toxic potential of a bioweapon threat, rapid visual recognition and sensing of ricin has been of considerable interest while remaining a challenging task up to date. In this study, a gold nanopin-based colorimetric sensor is developed realizing a multicolor variation for ricin qualitative recognition and analysis. It is revealed that such plasmonic metasurfaces based on nanopin-cavity resonator exhibit reflective color appearance, due to the excitation of standing-wave resonances of narrow bandwidth in visible region. This clear color variation is a consequence of the reflective color mixing defined by different resonant wavelengths. In addition, the colored metasurfaces appear sharp color difference in a narrow refractive index range, which makes them especially well-suited for sensing applications. Therefore, this antibody-functionalized nanopin-cavity biosensor features high sensitivity and fast response, allowing for visual quantitative ricin detection within the range of 10–120 ng mL−1 (0.15 × 10−9–1.8 × 10−9 m), a limit of detection of 10 ng mL−1, and the typical measurement time of less than 10 min. The on-chip integration of such nanopin metasurfaces to portable colorimetric microfluidic device may be envisaged for the quantitative studies of a variety of biochemical molecules.

We report a new arrayed plasmonic nanopixels capable of producing a continuum of colors. The pixels are nanohelm-shaped metal-dielectric-metal resonators and could efficiently cause surface-plasmon coupling, resonances and hybridization to propagate enhanced electromagnetic energy to far-field and thus achieve highly sophisticated color generation. Moreover, the surface-plasmon resonance frequency, intensity and related reflection spectrum line-width are significantly dependent upon incident angle of light, also resulting in a broad color tuning. Such plasmonic nanohelm pixels could map white light to splendid colors and be thus used to engineer vivid color display beyond the diffraction limit.