Opportunities for polymer-based nanowires in optoelectronics and nanophotonics

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Opportunities for polymer-based nanowires in optoelectronics and nanophotonics

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Synthesis and characterization of polymers for nonlinear optical applications

International audienceA difunctional NLO Azo-Dye chromophore has been synthesized and polymerization has been performed with a comonomer bearing a side-chain epoxy group. Deposition of the polymer on glass substrates was performed by spin-coating, resulting in uniform films up to 2 µm thickness. The orientation of the chromophore was performed under a " pin-to-plane " positive corona discharge followed by a heat-treatment in order to obtain reticulation of the films. Molecular orientation has been investigated using UV-Vis. and Raman spectroscopy. Poling of the films results in a decay of absorbency as well as in a blue shift of the spectrum. At the same time, the 1600 cm-1 band disappears from the Raman spectra, indicating orientation of the chromophores. Cross-linking has been studied by FTIR and all-optical poling and showed an improved stability of the electro-optic thin films

Gold Nanoparticles as Probes for Nano-Raman Spectroscopy: Preliminary Experimental Results and Modeling

This paper presents an effective Tip-Enhanced Raman Spectrometer (TERS) in backscattering reflection configuration. It combines a tip-probe nanopositioning system with Raman spectroscope. Specific tips were processed by anchoring gold nanoparticles on the apex of tapered optical fibers, prepared by an improved chemical etching method. Hence, it is possible to expose a very small area of the sample (~20 nm2) to the very strong local electromagnetic field generated by the lightning rod effect. This experimental configuration was modelled and optimised using the finite element method, which takes into account electromagnetic effects as well as the plasmon resonance. Finally, TERS measurements on single-wall carbon nanotubes were successfully performed. These results confirm the high Raman scattering enhancement predicted by the modelling, induced by our new nano-Raman device

Non-linear and resonance effects in carbon nanotube structures

International audienceIn this paper, we report on Raman scattering and Surface Enhanced Raman Scattering (SERS) studies of single walled carbon nanotubes (SWNTs) and carbon nanotube/conjugated polymers composites. We demonstrate that under SERS conditions we induce an abnormal anti-Stokes Raman emission, that can be interpreted as being due to a "single-beam pumped" Coherent Anti-Stokes Raman Scattering (CARS) effect. We also investigate in detail the anti-Stokes/Stokes (aS/S) intensity ratios of the radial breathing modes (RBMs) of SWNTs as a function of several parameters. From calculations, we show that resonance phenomena mostly explain the aS/S intensity ratio anomalies, but only at low frequencies. In addition, we describe results obtained with polymers like poly(bithiophene) (PBTh) polymerized on carbon nanotube thin films which exhibit also an amplification of its high frequency Raman modes in the anti-Stokes branch, generated by the plasmon excitation of metallic tubes. This phenomenon occurs in several other materials such as composites based on SWNTs and conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) and polyparaphenylene-vinylene (PPV) for modes located around 1500 cm−1

C-O-H species dissolution mechanisms under reducing conditions in a synthetic basaltic system : A spectroscopic study

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Facile route to gold-graphene electrodes by exfoliation of natural graphite under electrochemical conditions

International audienceAn original and practical procedure for preparing graphene-modified gold electrodes has been developed by careful control of the electrochemical exfoliation process of natural graphite. Pre-exfoliated (intercalated) graphite is first mechanically deposited onto a gold electrode. A cathodic treatment is then performed in N,N-dimethylformamide containing tetraalkylammonium salts at potential lower than −2 V vs. Ag/AgCl. This erodes the carbon coating through exfoliation of graphite particles. The result of this simple process, as identified by Raman spectroscopy, is a highly stable carbon surface made of graphene sheets, that gives well reproducible voltammetric responses (both in potential and intensity). Confocal Raman microspectrometry demonstrates that the bonded graphene phase consists of either 1 or 3 layers over micron-sized areas of the gold substrate. These layers can then subsequently be used as a trap to fix different organic groups. This easy and highly reproducible process could greatly simplify gold-graphene electrode production in the field of electrochemistry of graphite and its parent compounds. © 2016 Elsevier Lt

Polycristalline silicon deposited on glass by sub-atmospheric-pressure CVD at high rate

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