Multi-modal probing of oxygen and water interaction with metallic and semiconducting carbon nanotube networks under ultraviolet irradiation

Abstract

Carbon nanotube (CNT) networks composed of semiconducting single wall nanotubes (s-SWNTs), metallic single wall nanotubes (m-SWNTs), and multiwall nanotubes (MWNTs) were exposed to O2 and H2O vapor in the dark and under UV irradiation. Changes in film resistance and mass were measured in situ. In the dark, resistance of metallic nanotube networks increases in the presence of O2 and H2O, whereas resistance of s-SWNT networks decreases. We find that UV irradiation increases the sensitivity of CNT networks to O2 and H2O by more than an order of magnitude. Under UV irradiation, the resistance of metallic nanotube networks decreases in the presence of O2 and H2O likely through the generation of free charge carriers. UV irradiation increases the gas/vapor sensitivity of s-SWNT networks by nearly a factor of 2 compared to metallic nanotube networks. Networks of s-SWNTs show evidence of delamination from the gold-plated QCM crystal, possibly due to preferential adsorption of O2 and H2O on gold.