Metallic nanoparticles surface plasmon resonance tuning

Similar to zero-dimensional metal nanoparticles, most of the work on one-dimensional metal nanostructures focuses almost exclusively on gold nanorods. The high interest in anisometric gold nanoclusters arises from their unique optical and electronic properties that can be easily tuned through small changes in size, structure (e.g., the position, width, and intensity of the absorption band due to the longitudinal surface plasmon resonance is strongly influenced by the shell as well as the aspect ratio of the nanorods), shape (e.g., needle, round capped cylinder, or dog bone), and the inter-particle distance [157]. 

Whereas the resonance frequency of delocalized surface plasmons is given by the adjacent medium, which for Ag at the electrolyte interface is located in the near-UV range (350 nm), localized excitations from noble metal nanoparticles occur in the visible spectral range [121] and their resonance frequency can be tuned by their size and shape [122]. 

By modification with gold or silver nanoparticles, the color of PEDOTPSS can be tuned associated with the surface plasmon absorption resonance of the metal nanoparticles and the excitation of the bipolaron band of the conducting polymer to green or violet. ° The mixtures can be used as hybrid electrochromic layers (Figure 10.48). ° ... 

The simplest way to prepare a plasmonic nanostructure is thermal and electron beam deposition in vacuum on a flat substrate that is either hydrophilic or hydrophobic. Even though the roughness of the structure depends on the contact angle between the metal and substrate, which is less controllable, the method can be well applied to some metals. DUV plasmonic nanostructures were readily formed by thermal deposition of indium onto a glass substrate. The size of indium nanostructures can be controlled from 15 to 50 nm by the evaporation speed, pressure, and the deposited thickness. The resulting extinction peaks due to the dipole resonance were tuned to between 260 and 600 nm, which were used for surface enhancement of Raman spectroscopy by DUV excitation [7]. Self-assembled arrays of hemispherical gallium nanoparticles were deposited by molecular beam epitaxy on a sapphire support as a substrate for UV plasmonics. The mean NanoParticle radii of 23, 26, and 70 nm were fabricated at LSPR frequencies... 

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