Mechanism of Ammonia Detection by Chemically Functionalized Single-Walled Carbon Nanotubes: InSituElectrical and Optical Study of Gas Analyte Detection

Abstract

We provide definitive evidence for the mechanism of electronic detection of ammonia by monitoring in situ changes in the electrical resistance and optical spectra of films of poly(m-aminobenzenesulfonic acid)-functionalized SWNTs (SWNT-PABS). The increase of resistance during exposure to ammonia is associated with deprotonation of the PABS side chain that in turn induces electron transfer between the oligomer and the valence band of the semiconducting SWNTs. Near IR spectroscopy is used to demonstrate that the charge transfer is a weakly driven process, and this accounts for the high reversibility of the sensor. We show that the sensitivity of the chemiresistors increases as the film thickness is reduced to the percolation threshold and that the SWNT-PABS film thickness provides a simple means to enhance the electronic response.

Carbon-Nanotube Loaded Antenna-Based Ammonia Gas Sensor

“…The molecular structure and the interaction mechanism of PABS-SWNT with NH , proposed by Bekyarova et al [22], is shown in Fig. 1.…”

“…The well-defined composition and properties of covalently functionalized SWNTs provide an opportunity to dynamically characterize the nanotube electronic structure and electrical conductivity in the presence of analyte molecules [22].…”

Inkjet Printed, Self Powered, Wireless Sensors for Environmental, Gas, and Authentication-Based Sensing

“…The polymer attracts NH3 and creates a NH4 bonding, where the ammonia gas particle is physically attached to the SWNT. This is also hydrophilic, which allows it stay well suspended in water solution for inkjet printing purposes [13].…”

Organic Chemistry of Polyanilines: Tailoring Properties to Technological Applications~!2008-08-19~!2008-09-11~!2008-11-28~!

“…Multiwall carbon nanotubes (MWNTs) were solubilized by interaction with sulfonated polyaniline (SPAN), which was prepared by in situ polymerization of aniline onto the nanotubes, followed by sulfonation with chlorosulfonic acid in an inert solvent and hydrolysis in water [128]. In a related work, single wall carbon nanotubes (SWNT) were made soluble by covalent linking of poly(m-aminobenzene sulfonic acid) [129,130]. The solubility of functionalized polyanilines in various solvents, obtained by combinatorial functionalization (see above), could be then extended to the dispersion/solubilization of carbon nanotubes by polymer wrapping.…”