A. Reale

Carbon nanotubes for gas detection: materials preparation and device assembly

An efficient sensing device for NH3 and NOx detection has been realized using ordered arrays of single-walled C nanotubes deposited onto an interdigitated electrode platform operating at room temperature. The sensing material has been prepared using several chemical–physical techniques for purification and positioning of the nanotubes inside the electrode gaps. In particular, both DC and AC fields have been applied in order to move and to align the nanostructures by electrophoresis and dielectrophoresis processes. We investigated the effects of different voltages applied to a gate contact on the back side of the substrate on the performances of the device and found that for different gas species (NH3, NOx) a constant gate bias increases the sensitivity for gas detection. Moreover, in this paper we demonstrate that a pulsed bias applied to the gate contact facilitates the gas interaction with the nanotubes, either reducing the absorption times or accelerating the desorption times, thus providing a fast acceleration and a dramatic improvement of the time dependent behaviour of the device.

Near-infrared photoluminescence of erbium tris(8-hydroxyquinoline) spin-coated thin films induced by low coherence light sources

The authors present the characterization of spin-coated erbium tris(8-hydroxyquinoline) (ErQ3) solution on glass substrates under high temperature conditions. Absorption and infrared photoluminescence, induced by laser and light emitting diode sources, were measured and compared to cast and evaporated ErQ3 samples. A broad absorption band and 1.52μm luminescence were observed, suggesting spin coating as a valid deposition technique for processing of organic infrared emitting diodes.

Evaluation of the gauge factor for membranes assembled by single-walled carbon nanotubes

Samples of single-walled carbon nanotubes (SWCNTs) organized in the form of thin membranes have been investigated in order to correlate the mechanical deformation and conductivity behavior of such nanosized material. The nanotubes gauge factor of piezoresistivity has been evaluated by comparing the electrical responses induced by the deformation in SWCNT membranes and in Si substrates with the same electrical characteristics. The gauge factor of the SWCNT–Si systems was found to be a factor 2.3–2.5 larger than that of the Si substrates. We have also observed that temperature slightly enhances the piezoresistive response of the SWCNT.

Carbon nanotubes dispersions in polymer matrix for strain sensing applications

We have performed studies on the correlation between mechanical deformations and electrical conductance on a new interesting hybrid material, a Single Wall Carbon Nanotubes (SWCNTs)/Poly(3,4-ethylenedioxythiophene) (PEDOT) composite. Two are the synthesis techniques utilized to prepare the composite material in form of few hundreds of nm thick films: a spin coating deposition starting from an aqueous dispersion of SWCNTs and PEDOT, and an electrochemical de*position starting from a dispersion of SWCNTs and EDOT monomer. The composite conductance changes induced by a modulated periodic elongation via a coherent technique have been monitored by measuring the voltage variations of a Wheatstone bridge connected with the films. The measurements were performed on SWCNTs/PEDOT composites layered on a rigid substrate. The piezoresistivity gauge factor (GF) of the various samples was evaluated by comparing their responses to mechanical deformations to those of a commercial strain gauge, sticked on a substrate of the same kind. We found no significant piezoresistive effect in the hybrid material films deposited by means of spin coating while the effect is remarkable for the composites prepared by means of the electrochemical technique. In this case the gauge factor is found to be up to 3-4 times higher than that of the commercial strain gauge.

3R all optical regeneration

The authors investigate a possible technique, based on a three stage cascade configuration, in order to implement an all-optical 3R regenerator. A multiwave-mixing based unit is used to perform simultaneously reshaping, re-amplification and wavelength conversion of a propagated signal. A fiber ring based unit is used to perform the all-optical timing extraction while a classical four-wave-mixing process inside a dispersion-shifted fibre is adopted for the retiming process.

Realization of a carbon nanotube-based triode

We report the design and realization of a carbon nanotube-based integrated triode. Patterned Si/SiO2/Nb/Nb2O5multilayer was successfully realized by means of a photolithographic process. Such structure constitutes the patterned substrate of the successive Hot Filament Chemical Vapour Deposition (HFCVD) process. Selective growth of highly oriented SWCNT arrays was obtained in the predefined locations while survival of the entire structure was achieved. Field emission measurements of such materials were carried out both on a diode and in a triode configuration. Good and reproducible field emission behaviour has been observed in several realized structures. In order to validate the experimental data a first simulation of the behaviour of the integrated vacuum triode with a single field emission CNT was also simulated.

3R all-optical regeneration with re-timing stage based on a clock auxiliary carrier

The authors investigate the implementation of an all-optical regenerator. A multi-wave-mixing unit is used to perform simultaneously: re-amplification, re-shaping, wavelength conversion and re-sampling. The re-sampling stage utilizes the clock extracted from reshaped signal by a fiber ring laser based unit.

Laser sintering of photoelectrode layers for Dye Solar Cell technology

Scanning laser processing has become a useful and often used tool in thin film solar cell industries, since it enables precise, low cost, non-contact and highly automated fabrication processes such as scribing, patterning, marking, edge deletion, local melting and sintering. Dye Solar Cells (DSCs) are electrochemical photovoltaic devices representing an attractive technology for large area solar energy conversion since they utilize relatively cheap materials and simple manufacturing processes often “borrowed” from the printing industry. In this paper we show successful application of laser processing to this technology.

Triple C, L and U-band wide amplification system by means of Rayleigh backscattering control

In this work a system able to generate Raman gain in C, L and U-band using only one E-band pump and a set of fiber Bragg grattings is presented. This approach allows large bandwidth in line distributed amplification. Gain and noise figure were experimentally characterized and are presented.

Single and Multi-Channel 2R Regeneration: An Overview

Transparent all-optical regeneration and wavelength conversion in dense wavelength division multiplexing (DWDM) transmission systems are key issues to ensure the progress of the transparent networks and their actual implementation. In this paper recent progress of several all optical 2R experimental systems focused on single and multi-channel approaches will be reported. In particular will be analysed the implementation matters and the regeneration capabilities of several devices based on the exploitation of non-linear phenomena in several media: semiconductor optical amplifier (SOA) and optical fibres in non linear regimes