Removal of strongly-bound gases from single-walled carbon nanotubes without annealing or ultraviolet light exposure

Abstract

Annealing at high temperatures and exposure to strong ultra violet light are the approaches used in the past for affecting the desorption of strongly bound gases such as ammonia (NH3) and nitrogen dioxide (NO2) from single wall carbon nanotubes (SWCNTs) and graphene. These methods pose severe limitations in the development of devices which can operate in normal ambient conditions. The use of another gas which can influence the kinetics of desorption of gases already present on the SWCNTs has not been explored in detail. Here we show that the redistribution of substrate impurity states near Fermi Level, caused by the electrostatic forces of polar molecules like water, accelerates the desorption of gases bound on SWCNT. This phenomenon can be used to facilitate complete, rapid and non-destructive desorption of NO2 and NH3 molecules from SWCNT chemiresistors at room temperature. Complete desorption of these gases were achieved within minutes instead of many hours as reported previously in the literature. The method provides a practical alternative for achieving recovery in CNT-based molecule detectors in air without the risk of degradation of the SWCNTs and their sensitive polymer composites which are used to achieve high sensitivity and selectivity.