Deposition and Functionalization of Thin Films of Carbon Nanotubes Using Corona Based Electrostatic Charge Technique and Their Applications for Gas Detection

A new technique based on an electrostatic-force-directed-self-assembly has been developed to deposit thin films of multi-walled carbon nanotubes (MWCNTs) on thin dielectric wires of 8-10 mm length and 500 mu m diameter using corona-charging technique. The same technique has also been developed to self-functionalize the nanotubes via acid-free dry route. Functionalization of the film was achieved in a few seconds. Infrared and Raman spectroscopic measurements confirmed grafting of the films with oxygenated functional groups. The electrostatically self-assembled films were used as sensors to detect gases such as NO2 and NH3 with high sensitivity and repeatability up to 100 ppm (parts per million). It was observed that resistance of the deposited films increased tip to 9% when sensors were successively exposed to NH3 and decreased up to 6% with NO2 at room temperature. Recovery for (lie sensors was within few hours when exposed to NH3 and several hours for NO2 gas. The recovery was enhanced with UV exposure. It was realized that the corona based electrostatic self-assembly (CESA) pattering technique for batch fabrication of the sensors is fast., simple, low-cost, and required no specialized equipment. The technique also offers many technical advantages such as deposition at room temperature and self-functionalized CNT films for specific molecule detection.