Thin films of carbon nanotubes via ultrasonic spraying of suspensions in N-methyl-2-pyrrolidone and N-cyclohexyl-2-pyrrolidone

Described is a method for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-methyl-2-pyrrolidone or N-cyclohexyl-2-pyrrolidone (CHP) and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent was quickly evaporated, leaving a thin film of randomly oriented nanotubes. Unlike other methods of spraying nanotube films, this does not require removal of surfactant after spraying and is compatible with creating films of functionalized nanotubes. Film thickness was controlled by the spray time and films were sprayed with thicknesses between 10 and 500 nm. Single-walled, multiwalled, and functionalized multiwalled nanotubes were sprayed. Transparent conducting thin films prepared by spraying single-walled carbon nanotubes dispersed in CHP demonstrated similar sheet resistance (for a given optical transmittance) as those prepared by spraying aqueous polymer-based dispersions that required postdeposition polymer removal.