Chemical Alignment of Oxidatively Shortened Single-Walled Carbon Nanotubes on Silver Surface

Patterning of Single-Wall Carbon Nanotubes via a Combined Technique (Chemical Anchoring and Photolithography) on Patterned Substrates

Single-walled carbon nanotubes (SWNTs) have been chemically attached with high density onto a patterned substrate. To form the SWNT pattern, the substrate was treated with acid-labile group protected amine, and an amine prepattern was formed using a photolithographic process with a novel polymeric photoacid generator (PAG). The polymeric PAG contains a triphenylsulfonium salt on its backbone and was synthesized to obtain a PAG with enhanced efficiency and ease of spin-coating onto the amine-modified glass substrate. The SWNT monolayer pattern was then formed through the amidation reaction between the carboxylic acid groups of carboxylated SWNTs (ca-SWNTs) and the prepatterned amino groups. A high-density multilayer was fabricated via further repeated reaction between the carboxylic acid groups of the ca-SWNTs and the amino groups of the linker with the aid of a condensation agent. The formation of covalent amide bonding was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Scanning electron microscopy and UV-vis-near-IR results show that the patterned SWNT films have uniform coverage with high surface density. Unlike previously reported patterned SWNT arrays, this ca-SWNT patterned layer has high surface density and excellent surface adhesion due to its direct chemical bonding to the substrate.

Covalent assembly of shortened multiwall carbon nanotubes on polyelectrolyte films and relevant electrochemistry study

A significant and versatile approach was developed for perpendicularly aligning multiwall carbon nanotubes on diverse substrates suitable for layer-by-layer self-assembly. The multiwall carbon nanotubes (s-MWNTs) used were shortened with oxidation under ultrasonic and functionalized with acyl chloride in thionyl chloride (SOCl2). The monolayer of s-MWNTs perpendicularly grafted to the substrate was obtained by dipping the polyelectrolyte modifying substrate into a tetrahydrofuran suspension of the functionalized s-MWNTs. The interaction proved to be stable and not liable to be affected by the ambience. Transmission electron microscopy and atomic force microscopy were used to examine the morphology of the MWNTs and s-MWNTs grafted on the substrates. Raman spectroscopy was applied to verify the existence of s-MWNTs for assembly, and Fourier transform infrared absorption spectra were used to investigate the interaction pattern between s-MWNTs and polyelectrolyte. The electrochemistry properties of the monolayer of s-MWNTs when the substrate was indium-tin oxide were studied.

Electric-Field-Enhanced Assembly of Single-Walled Carbon Nanotubes on a Solid Surface

We report a novel electric-field-enhanced chemical assembly approach for fabricating highly aligned SWNT arrays on a solid surface with remarkably improved efficiency and packing density, which is very important for the real applications of carbon nanotube arrays. With the enhancement of the electric field, the assembling kinetics of SWNTs is remarkably speeded up to effectively decrease the assembling time, and the packing density can even exceed the saturated density of conventional assembly method by four times within only half an hour. The molecular dynamics simulation results illustrated the alignment of SWNTs with their long axes along the electric flux in solution, leading to the increase of packing density and efficiency through overcoming the steric hindrance of the "giant" carbon nanotubes.

Thermochemical Hole Burning on a Triethylammonium Bis-7,7,8,8-tetracyanoquinodimethane Charge-Transfer Complex Using Single-Walled Carbon Nanotube Scanning Tunneling Microscopy Tips

The present article describes a thermochemical hole burning (THB) effect on a charge-transfer complex triethylammonium bis-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)(2)) using single-walled carbon nanotube (SWNT) scanning tunneling microscopy (STM) tips, which demonstrates the possibility of optimizing the THB storage materials and the writing tips for ultrahigh-density data storage. TEA(TCNQ)(2) is proven to be a high-performance THB storage material, which gives deeper holes and larger hole depth-to-diameter ratio as compared to the previous materials dipropylammonium bis-7,7,8,8-tetracyanoquinodimethane and N-methyl-N-ethylmorpholinium bis-7,7,8,8-tetracyanoquinodimethane. Instead of conventional Pt/Ir STM tips, SWNT tips made by a unique chemical assembly technique we developed have been shown to be excellent writing tips for greatly decreasing the hole sizes and increasing the storage density. Possible reasons for the improvements on the storage performance were discussed.

Aligned Nanotubes

Since the discovery of carbon nanotubes by lijima in 1991, various carbon nanotubes with either a single- or multilayered graphene cylinder(s) have been produced, along with their noncarbon counterparts (for example, inorganic and polymer nanotubes). These nanostructured materials often possess size-dependent properties and show new phenomena related to the nanosize confinement of the charge carriers inside, which leads to the possibility of developing new materials with useful properties and advanced devices with desirable features for a wide range of applications. In particular, carbon nanotubes have been shown to exhibit superior properties attractive for various potential applications, ranging from their use as novel electron emitters in flat-panel displays to electrodes in electrochemical sensors. For many of the applications, it is highly desirable to have aligned/patterned forms of carbon nanotubes so that their structure/property can be easily assessed and so that they can be effectively incorporated into devices. In this Review, we present an overview on the development of aligned and micropatterned nanotubes, with an emphasis on carbon nanotubes.