Electric Field Effects on Self-Organization Processes during Droplet Evaporation of Multiwall Carbon Nanotube Aqueous Suspension

Abstract

The self-organization of COOH-functionalized multiwall carbon nanotubes (MWCNTs) during droplet evaporation of their aqueous suspension in a constant uniform electric field (E) was investigated. It was established that the COOH-functionalization polarizes the MWCNTs in the transverse direction to their axis. Depending on their size, MWCNTs tended to agglomerate into three different stable structures in different drop regions. There were linear, fractal and cluster structures (LS, FS, and CS). Sizes of the FSs decreased as 1/Е, whereas the rate of their growth increased as Е2. The single-walled carbon nanotubes (SWCNTs) were found inside the LSs and CSs. The chiral indices of the SWCNTs were determined, corresponding to metallic and semiconducting conductivities. An analysis showed that as a result of coagulation and amassment of the carbon nanotubes (CNTs) near electrodes, there were formed conductive regions. When the concentration of MWCNTs reached some value in part nearest to an electrode, this part became conductive. The positive and negative electrodes, formed now by MWCNTs, shifted towards each other. The observed effects show that considered self-organization is controllable by the electric field.