Assembly of untreated single-walled carbon nanotubes at a liquid–liquid interface

Untreated single-walled carbon nanotubes (SWCNTs) were assembled at a liquid–liquid interface to form an ultrathin film. The SWCNTs were dispersed into water using sodium dodecyl sulfate (SDS) as a solubilizing agent. Then, hexane was added to the dispersion to create a liquid–liquid interface. The SWCNTs were assembled at the interface to form a smooth ultrathin film when ethanol was added to the SWCNT water dispersion/hexane solution. The assembly mechanism was considered to be caused by the decreased wettability of SDS-coated SWCNT during the addition of ethanol because of desorption of SDS from the SWCNT surface. The assembly was remarkably robust and easily transferable to substrates. An AFM image of the film transferred onto a silicon substrate shows a closely packed uniform film of 3–8 nm thickness. The SWCNT ultrathin film showed high transparency of ca. 97% with an electrical conductivity of 71.4 S/cm. Fabrication processing was carried out in ambient conditions, thereby making it an attractive application for use in flexible electric devices.