Formation of Highly Pure and Patterned Carbon Nanotube Films on a Variety of Substrates by a Wet Process Based on Light-Induced Dispersibility Switching

A simple fabrication method for patterned carbon nanotube (CNT) films is presented, using the concept of light-induced dispersibility switching with a photoresponsive dispersant. A comparison with other dispersants highlights the important role played by an azobenzene-derived cationic molecule as a photoisomerizable dispersant in the successful manufacture of patterned CNT films. Upon UV irradiation for a short time (∼0.5 min), a dispersion composed of CNTs and photoresponsive dispersant exhibited a dispersibility change due to the photoisomerization of the photoresponsive dispersant, and then the dispersant detached-CNT deposited onto the substrate. Our method enables patterned CNT films to be obtained directly from CNT dispersions onto various substrates such as glass, polyethylene terephthalate, and silicone rubber, expanding the possible applications of CNT films. Furthermore, the process minimizes the amount of the residual dispersant in the fabricated CNT film, reducing the amount of impurities, and improving the quality of the patterned CNT film.