Differentiation of gas molecules using flexible and all-carbon nanotube devices

Carbon nanotubes (CNTs) are extremely sensitive to the electronic perturbations from environmental gases. However, the electrical detection of carbon monoxide (CO) is still a challenge. Here we show that 1 ppm of CO can be electrically detected at room temperature using a CNT resistor and the detection is proposed related to the sidewall functionalities (COOH). A simple all-CNT electronic nose composed of two resistors (or one resistor plus one transistor) is able to differentiate CO and other oxidative gases (for example NO and NO₂). The electronic nose is working on both conventional SiO ₂/Si and flexible substrates.