Carbon nanotubes as SAW chemical sensors materials

We have designed, fabricated and characterized surface acoustic waves (SAWs) sensors coated by either single-wall carbon nanotubes (SWCNTs) or multi-wall carbon nanotubes (MWCNTs) for chemical detection of volatile organic compounds (VOCs), at room temperature. The carbon nanotubes (CNTs) were deposited by a spray-painting method onto STX-quartz substrates, coated by SiO2 films, used to implement the SAW sensors configured as 433.92 MHz two-port resonator-based oscillators. Upon individual exposure to tested VOCs such as ethanol, ethylacetate and toluene in nitrogen, the resonance frequency of the SAW oscillating sensor exhibits high downshift of a few hundreds (a few tens) of kHz for SWCNTs (MWCNTs) films dispersed into solvent of ethanol. High sensitivity of carbon nanotubes-coated SAW sensors has been achieved, at room temperature. The selectivity to VOCs under test can be controlled by the type of organic solvent used to disperse the carbon nanotubes as sensing materials onto SAW sensors. Preliminarily, some sensing mechanisms between chemical species to be detected and the carbon nanotubes will be discussed. (C) 2003 Elsevier B.V. All rights reserved.