Self-assembly of single walled carbon nanotubes onto cotton to make conductive yarn

A simple, economical and scalable technique is demonstrated to make conductiveyarn. Singlewalledcarbonnanotubes (SWCNTs) are non-covalently functionalized with dye (Acid Red 91) and dispersed in water; while cottonyarn is treated with poly (ethylene imine). When the resulting yarn is immersed in the SWCNT dispersion, SWCNTs self-assemble onto the yarn due to electrostatic forces between the functionalized nanotubes and yarn. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy indicate the assembly of carbonnanotubes. The SWCNT functionalized yarn exhibits reasonable electrical conduction behaviour and are then used to make chemiresistors. The electrical resistance of the chemiresistors used as sensors increases on exposure to ammonia gas, which can be explained in terms of electron transfer between gas molecules and SWCNTs.