The Change in Gas Absorption Behavior for Oxygen-Doped Carbon Nanotubes

The Change in Gas Absorption Behavior for Oxygen-Doped Carbon Nanotubes

Carbon nanotubes (CNTs) have a unique one-dimensional nanostructure, along with various other useful properties. Recentlythey have attracted much attention for their possible application as gas sensors. Many existing CNT-based gas sensors focus onthe promotion of sensitivity, selectivity, and response time, but little research has been done on the change in gas absorptionbehavior. This study examined the effects of oxygen doped CNTs on gas absorption behavior; the improvements in gas sensingcapabilities were explored and recorded. The crystalline graphite structure of the pristine CNTs was improved via a 200°Cpost-treatment annealing process. After the annealing, the sensitivity of the CNTs was improved and this was attributed to theenriched oxygenated groups (C = O and O = C-O bonds) on CNT surface. Gas absorption behavior was found to change fromdominant physisorption to dominant chemisorption, resulting from the enriched oxygenated groups, especially the O = C-O bond.Using an enlarged bias of more than 5V, the magnified adsorption energy that arose from the enriched oxygenated groups couldbe overcome and the observed dominant chemisorption behavior returned to dominant physisorption. Oxygen doped CNTs is thusa valid area of further research and development for gas sensor designers to consider.