Noncovalent Functionalization of Single-Wall Carbon Nanotubes for the Elaboration of Gas Sensor Dedicated to BTX Type Gases: The Case of Toluene

Abstract

Single-wall carbon nanotubes (SWNTs) have been noncovalently functionalized, using a dispersion technique, and the resulting hybrid materials are used for a gas sensing purpose. The functionalization entities are macrocycles (MCs) of phthalocyanines (Pc’s) and porphyrin (Por) derivatives. These MCs exhibit a highly delocalized π-system which can be used as a target for π–π interaction but also for monitoring of the functionalization process. Raman spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) analysis of the hybrid materials revealed the occurrence of the functionalization. The obtained hybrids are used as sensing layers for the detection of toluene. Two transduction modes (resistive and QCM (quartz crystal microbalance) type mass sensors) have been simultaneously used in order to understand the gas/material interaction. An improvement of the sensor responses due to the high surface area of the hybrid material has been observed. Desorption of the gas molecules from the free CNT surfaces sites happens faster than desorption from the MC-occupied CNT surface sites.