Functionalization of carbon nanotubes for nitroaromatic explosive detection

Carbon Nanotubes (CNT) are considered as promising materials for many type new electronic devices due to their unique electronic structure and electric properties. In particular CNTs with suitable functional groups bonded to CNT surface can be used to reveal different chemical compounds. CNT based chemiresistors show promising performances in explosive sensing [Schnorr et al]. CNT chemiresistors can be deposited between electrodes by evaporation or dispersions, or can be effectively drawn from compressed CNT solids. Both these systems demonstrated a very high sensitivity in detecting explosives, in particular molecules of trinitrotoluene (TNT), which is a common explosive used in improvised explosive devices (IED). Moreover in such nanostructures the signal detection is based on conductance changes of the nanostructures in air, with cycles of detection and sensor recovery that can be performed by simple systems and with very low electrical power requirement. In the present work we present the synthesis and functionalization of CNTs with amino groups to prepare sensors for detecting explosives, in particular nitroaromatic explosives such as TNT. Multiwalled carbon nanotubes are used for the realization of devices with improved detection limit and selectivity to different types of notroaromatic explosives. Two type of CNTs (in powder form or by direct deposition on the silicon substrates) have been grown by aerosol-chemical vapor deposition (A-CVD) technique from SCIDRE (Germany) and analyzed by X-Ray diffraction, SEM, TEM and Raman spectroscopy. Very smooth and long CNTs with good electrical conductive properties are obtained. Three step of functionalization process have been performed: Oxidation (carboxylation-COOH), amidation and amino functionalization. For amidation we used the relatively simple gas phase amidation method, treating carboxylated CNTs with ammonia gas at high (~2500C) temperatures References : Schnorr, J. M., van der Zwaag, D., Walish, J. J., Weizmann, Y. & Swager, T. M. Sensory Arrays of Covalently Functionalized Single-Walled Carbon Nanotubes for Explosive Detection. //Advanced Functional Materials 23, 5285-5291 (2013).