Dominique Porterat

Optimized network of multi-walled carbon nanotubes for chemical sensing

This work reports the design of a resistive gas sensor based on 2D mats of multi-walled carbon nanotubes (MWCNTs) grown by aerosol-assisted chemical vapour deposition. The sensor sensitivity was optimized using chlorine as analyte by tuning both CNT network morphology and CNT electronic properties. Optimized devices, operating at room temperature, have been calibrated over a large range of concentration and are shown to be sensitive down to 27 ppb of chlorine. The as-grown MWCNT response is compared with responses of 2000 °C annealed CNTs, as well as of nitrogen-doped CNTs and CNTs functionalized with polyethyleneimine (PEI). Under chlorine exposure, the resistance decrease of as-grown and annealed CNTs is attributed to charge transfer from chlorine to CNTs and demonstrates their p-type semiconductor behaviour. XPS analysis of CNTs exposed to chlorine shows the presence of chloride species that confirms electron charge transfer from chlorine to CNTs. By contrast, the resistance of nitrogen-doped and PEI functionalized CNTs exposed to chlorine increases, in agreement with their n-type semiconductor nature. The best response is obtained using annealed CNTs and is attributed to their higher degree of crystallinity.

Influence of light intensity on the photoluminescence of silicon nanostructures

The strong visible photoluminescence (PL) of nanostructured silicon, such as porous Silicon and silicon nanocrystals, is studied as a function of the power and the wavelength of the excitation laser source. The position of the PL peak is a function of the fluence: when the incident fluence is increased, the PL peak is blueshifted, and it is redshifted to its initial position when the fluence is decreased back. The PL yield is strongly attenuated with the increasing fluence and this decrease is partially irreversible. The behavior is also found to be a function of the wavelength of excitation: the shorter the excitation wavelength, the stronger the fluence effect. The PL temporal behavior has also been studied and appears to be weakly sensitive to the fluence. Fluence effects are compared to temperature effects and both are noticeably different, proving the absence of heating effects in our experiment for a wide range of incident power. Auger effect and state filling are discussed in order to understand th...

Multi-Walled Carbon Nanotube Based Sensors for Selective Detection of Chemical Pollutants

This work reports the design of a resistive gas sensor based on 2D mats of multi-walled carbon nanotubes (MWCNT). The sensor sensitivity was optimised using chlorine by tuning both MWCNT network morphology and MWCNT electronic properties. Raw CNT were compared with annealed CNT. Besides, with the aim to enhance the sensor sensitivity and selectivity for detection of several gases, MWCNT were functionalized with poly (phenylene)-like or vinyl polymers using a process based on the diazonium chemistry. In this paper, we will mention the preparation of such sensors and we will demonstrate that the optimized devices are operating at room temperature, for the detection of pollutants such as chlorine, hydrogen chloride and ammonia. Such sensors are able to detect down to 30 ppb of pollutant, in particular for chlorine.