First, the group grows MWCNT arrays on thin layers of silicon dioxide grown on top of silicon substrates. These are then incorporated into hybrid sensor devices after functionalizing them with various conducting polymers.

Crucial by-product

The nanotubes were fabricated by a CVD process, during which a thin amorphous carbon (a-C) layer formed on the surface of MWCNTs. The team used a plasma etch technique to not only tailor the a-C layer thickness, but also create additional active sites for the bonding of functional groups. A simple solvent modification of the polymer resulted in a gas selective response from the nanocomposite sensors.

FTIR characterization results revealed that the conducting polymers are covalently bonded with the nanotube surface and are responsible for obtaining selectivity and enhanced sensitivities.

Simple method

Even though there are several reports on the fabrication of CNT–polymer nano-composite films and solvent effects on polymer conductivity, this work presents a uniquely simple method for fabricating CNT–polymer nanocomposites and integrating them into sensor devices that exhibit selectivity to analyte gases.

The fabrication technique allows for a wide range of control over device sensitivity and selectivity, thus constituting an important step toward the commercialization of CNT-based sensor technologies.

The group is now investigating new MWNT-polymer-solvent combinations and compositions for further improvements in sensitivity, detectability and selectivity.

Full details can be found in the journal Nanotechnology.