Morphology of single-wall carbon nanotube aggregates generated by electrospray of aqueous suspensions

Airborne single-wall carbon nanotubes (SWCNTs) have a high tendency to agglomerate due to strong interparticle attractive forces. The SWCNT agglomerates generally have complex morphologies with an intricate network of bundles of nanotubes and nanoropes, which limits their usefulness in many applications. It is thus desirable to produce SWCNT aerosol particles that have well-defined, unagglomerated fibrous morphologies. We present a method to generate unagglomerated, fibrous particles of SWCNT aerosols using capillary electrospray of aqueous suspensions. The effects of the operating parameters of capillary electrospray such as strength of buffer solution, capillary diameter, flow rate, and colloidal particle concentration on the size distributions of SWCNT aerosols were investigated. Results showed that electrospray from a suspension of higher nanotube concentration produced a bimodal distribution of SWCNT aerosols. Monodisperse SWCNT aerosols below 100 nm were mostly non-agglomerated single fibers, while polydisperse aerosols larger than 100 nm had two distinct morphologies: a ribbon shape and the long, straight fiber. Possible mechanisms are suggested to explain the formation of the different shapes, which could be used to produce SWCNT aerosols with different morphologies.