Carbon nanotube acoustic and optical sensors for volatile organic compounddetection

Abstract

Carbon nanotube coated acoustic and optical sensors have been successfully studied forvolatile organic compound (VOC) sensing applications, at room temperature. Here,Langmuir–Blodgett (LB) films consisting of tangled bundles of single-walled carbonnanotubes (SWCNTs) have been transferred onto different transducing sensors by using alinker–buffer LB multilayered material of cadmium arachidate pre-deposited on thesensor surface to promote adhesion of SWCNTs. Two different kinds of sensorshave been designed, fabricated and utilized: quartz crystal microbalance 10 MHzAT-cut quartz resonators and standard silica optical fibre sensors based on lightreflectometry at a wavelength of 1310 nm. The proposed detection techniques are focusedon two key parameters in gas sensing applications: mass and refractive index,and their changes induced by gas molecule absorption. The results indicate highsensitivity, good repeatability and reversibility. Signals from each sensor type havebeen analysed and processed by using pattern recognition techniques such asprincipal component analysis and use of artificial neural networks. The recognitionof the hybrid system is successfully performed, improving the data fusion fromacoustic and optical sensors with SWCNT-functionalized sensors that are highlydiscriminating. To our knowledge, this is the first reported study of combined hybridintegration of acoustic sensors with optical fibre sensors using nanostructuredmaterials as single-walled carbon nanotubes for VOC detection, at room temperature.