5. Nanotransfer Printing for Synthesis of Vertically Aligned Carbon Nanotubes with Enhanced Atomic Penetration

Vertically aligned carbon nanotubes (VACNTs) exhibit outstanding mechanical strength, chemical stability, and electrical characteristics; however, their constrained mechanical elasticity and chemical responsiveness spurred research on atomic decoration techniques for enhancing their mechanochemical attributes. Nevertheless, achieving uniform atomic decoration on the VACNT surface is difficult because of the high density and large aspect ratio of VACNT. Herein, a strategy to design and apply nanopatterned VACNTs (nVACNTs) based on a nanotransfer printing process is proposed to improve atomic penetrability. Nanopatterns inherent to nVACNTs facilitate atomic penetration, allowing for the more consistent and higher quality deposition of functional materials such as zinc oxide and alumina by atomic layer deposition. Furthermore, physical vapor deposition provides an improved coating of metal catalysts such as gold. The uniform deposition of ceramic layers on the entire surface of nVACNTs strengthens its mechanical resilience, owing to the diminished van der Waals forces of CNTs. Surface-decorated nVACNTs display an increased sensitivity to NO2 gas, which is attributed to the enhanced quality of the reactive catalyst deposition and augmented permeability. This strategy achieves a larger decorated area while increasing a catalytically active reaction area. The obtained results promise that the enhanced nVACNTs will expand the industrial applications of carbon nanotubes.