Characterization of contact resistances in ceramic-coated vertically aligned carbon nanotube arrays

Chemically Bonded Carbon Nanotubes to Au Films for Robust High-Performance Electrochemical Double-Layer Supercapacitors

As energy storage devices, electrochemical double-layer capacitors (EDLCs) are a potential alternative to traditional batteries owing to their higher charge-discharge capability, higher power density, and longer life span; however, EDLCs typically lack energy density. Carbon nanotubes (CNTs), which have a high surface area and excellent conductivity, are promising for improving the energy density in EDLCs. In this study, an innovative approach was adopted to fabricate CNT-metal electrodes, in which chemical bonds between vertically aligned carbon nanotubes (VACNTs) and Au metal were formed via a linker molecule, resulting in robust, highly electrically conductive CNT-Au bonds without compromising the free-standing nature and quality of the VACNT array. Specifically, VACNT arrays prepared through chemical vapor deposition on an Al2O3/Si substrate were transferred onto Au metal while maintaining their free-standing arrangement. The average resistance at the CNT-Au interface was 0.5 kΩ over an area of 1 nm2, as measured using an atomic force microscopy-based technique. Supercapacitors fabricated using the prepared VACNT-Au electrodes had a specific capacitance of 50 mF cm-2 (9.5 F g-1), thereby outperforming most pure VACNT-based EDLCs. Moreover, these devices exhibited outstanding stability, with 74% capacitance retention after 100,000 charge-discharge cycles.

Nanoporous Membranes of Densely Packed Carbon Nanotubes Formed by Lipid-Mediated Self-Assembly

Nanofiltration technology faces the competing challenges of achieving high fluid flux through uniformly narrow pores of a mechanically and chemically stable filter. Supported dense-packed 2D-crystals of single-walled carbon nanotube (CNT) porins with ∼1 nm wide pores could, in principle, meet these challenges. However, such CNT membranes cannot currently be synthesized at high pore density. Here, we use computer simulations to explore lipid-mediated self-assembly as a route toward densely packed CNT membranes, motivated by the analogy to membrane-protein 2D crystallization. In large-scale coarse-grained molecular dynamics (MD) simulations, we find that CNTs in lipid membranes readily self-assemble into large clusters. Lipids trapped between the CNTs lubricate CNT repacking upon collisions of diffusing clusters, thereby facilitating the formation of large ordered structures. Cluster diffusion follows the Saffman-Delbrück law and its generalization by Hughes, Pailthorpe, and White. On longer time scales, we expect the formation of close-packed CNT structures by depletion of the intervening shared annular lipid shell, depending on the relative strength of CNT-CNT and CNT-lipid interactions. Our simulations identify CNT length, diameter, and end functionalization as major factors for the self-assembly of CNT membranes.