Plasmon resonance optical tuning based on photosensitive composite structures

This paper reports a numerical investigation of a periodic metallic structure sandwiched between two quartz plates. The volume comprised between the quartz plates and the metallic structure is infiltrated by a mixture of azo-dye-doped liquid crystal. The exposure to a low power visible light beam modifies the azo dye molecular configuration, thus allowing the wavelength shift of the resonance of the system. The wavelength shift depends on the geometry of the periodic structure and it also depends on the intensity of the visible light beam

In-situ 3D Micro-sensor Model using Embedded Plasmonic Island for Biosensors

The design of the microsensor system for biosensors using the plasmonic island is proposed. The sensor head is formed by the stacked layers of silicon-graphene-gold materials. The dual-mode operations of the sensor can be performed using the relationship of the changes between the electron mobility and optical phase, where the exciting environment can be light intensity (phase), electrical transient, heat, pressure, flavour and smoke, The change in light phase (intensity) in silicon and conductivity (mobility) in gold layers cause change in the output measurands. The design and simulation interpretation of the sensor is presented. The sensor manipulation using the MCM arrangement is simulated and interpreted for biosensor applications 3D imaging can also be applied to the MCM function, where the 3D in situ sensor function is possible. The sensor sensitivity of 2.0 × 10−21 cm2 V−1 s−1 (mW)−1 via simulation is obtained

Raman Characterization of Phenyl-Derivatives: From Primary Amine to Diazonium Salts

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Charge stability on thin insulators studied by atomic force microscopy

Charge diffusion in thin ${\rm Al}_2{\rm O}_3$ layers has been investigated by Atomic Force Microscopy (AFM). The layers were made by anodic oxidation of Al plates, in order to obtain plane and homogeneous amorphous oxides of known thicknesses. Under dry-nitrogen atmosphere, the charges are deposited by contact electrification: a deposit voltage is applied between the Al substrate of the layer and the metallized AFM tip brought to contact with the oxide. This process is perfectly controllable and reproducible, the quantity of charges deposited being proportional to the deposit voltage. Afterwards the tip is lifted up and scans the surface of the oxide in order to observe the diffusion of the deposited charges. Two behaviors were observed for the diffusion process depending on the thickness and on the deposit voltage. These results are interpreted by introducing an inhomogeneous trap distribution in the layer, the diffusion process being considered mainly as diffusion by hopping transport in the bulk

New electrochemical procedure for obtaining surface enhanced Raman scattering active polythiophene films on platinum

A new electrochemical procedure for obtaining Surface Enhanced Raman Scattering (SERS) spectra of silver islands polybithiophene composite films is described. During the electropolymerization process which consists to use silver dodecylsulfate micellar aqueous solution mixed with bithiophene and LiClO4, silver cations are reduced, thus giving metallic silver particles embedded within the polybithiophene (PbT) film. Both doped and undoped PbT species display SERS spectra with exaltation factors varying between 40 and 200 with respect to the film prepared in sodium dodecylsulfate. Vibrational characterization of both doped and undoped species show that the amount of the polymer structural defects are more important in the oxidized species than in the reduced ones. This general method allows to synthesize various polymeric films displaying SERS effect and appears very promising for the structural study of these materials

Gold nanoparticles in a cholesteric liquid crystal matrix: self-organization and localized surface plasmon properties

International audienceBy combining experimental and calculated optical extinction spectra, scanning electron microscopy and optical microscopy, we investigate the optical properties of a hybrid system consisting of a cholesteric liquid crystal and gold nanoparticles. Close to the air-exposed surface, the liquid crystal film exhibits a structural modulation. In this article, we explore how to use this modulation to drive the formation of gold nanoparticle assemblies and thus to control their localized surface plasmon properties. We found that the penetration of the gold nanoparticles within the liquid crystal modulation depends on the initial concentration of nanoparticles in the colloidal solution. Two distinct regimes are pointed out: (i) at low concentration the nanoparticles are weakly interacting and embedded in a homeotropic environment at the film surface (ii) at high concentration the penetration of the NPs occurs within the modulation, and their localized surface plasmon resonance is strongly red-shifted due to nanoparticles packing and electromagnetic interactions between the nanoparticles. This surface plasmon resonance shows sensitivity to the light polarization attributed to the formation of anisotropic aggregates oriented by the structural modulation of the liquid crystal