DNA-Wrapped Single-Walled Carbon Nanotube Assemblies

Nanotube Functionalization: Investigation, Methods and Demonstrated Applications

This review presents an update on nanotube functionalization, including an investigation of their methods and applications. The review starts with the discussion of microscopy and spectroscopy investigations of functionalized carbon nanotubes (CNTs). The results of transmission electron microscopy and scanning tunnelling microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, Raman spectroscopy and resistivity measurements are summarized. The update on the methods of the functionalization of CNTs, such as covalent and non-covalent modification or the substitution of carbon atoms, is presented. The demonstrated applications of functionalized CNTs in nanoelectronics, composites, electrochemical energy storage, electrode materials, sensors and biomedicine are discussed.

Multifunctional Heterogeneous Carbon Nanotube Nanocomposites Assembled by DNA-Binding Peptide Anchors

Although carbon nanotubes (CNTs) are remarkable materials with many exceptional characteristics, their poor chemical functionality limits their potential applications. Herein, a strategy is proposed for functionalizing CNTs, which can be achieved with any functional group (FG) without degrading their intrinsic structure by using a deoxyribonucleic acid (DNA)-binding peptide (DBP) anchor. By employing a DBP tagged with a certain FG, such as thiol, biotin, and carboxyl acid, it is possible to introduce any FG with a controlled density on DNA-wrapped CNTs. Additionally, different types of FGs can be introduced on CNTs simultaneously, using DBPs tagged with different FGs. This method can be used to prepare CNT nanocomposites containing different types of nanoparticles (NPs), such as Au NPs, magnetic NPs, and quantum dots. The CNT nanocomposites decorated with these NPs can be used as reusable catalase-like nanocomposites with exceptional catalytic activities, owing to the synergistic effects of all the components. Additionally, the unique DBP-DNA interaction allows the on-demand detachment of the NPs attached to the CNT surface; further, it facilitates a CNT chirality-specific NP attachment and separation using the sequence-specific programmable characteristics of oligonucleotides. The proposed method provides a novel chemistry platform for constructing new functional CNTs suitable for diverse applications.

A One-Step Chemical Strategy for the Formation of Carbon Nanotube Junctions in Aqueous Solution: Reaction of DNA-Wrapped Carbon Nanotubes with Diazonium Salts

A single-step chemical strategy allows the formation of single-walled carbon nanotube (SWCNT) molecular junctions in aqueous solution. SWCNTs were first wrapped with DNA to be water soluble and solution processable. Diazonium salts, which have been shown to react spontaneously with carbon nanotubes in water at room temperature, were then employed to covalently link SWCNT segments. The DNA wrapping of the nanotubes acted as a protective layer that limits the functionalization predominantly to the nanotube terminal ends, therefore allowing the assembly of linear SWCNT junctions. Upon increasing the concentration of the linker, we observed first the formation of side-to-end junctions, and eventually the assembly, through side-to-side interactions, of SWCNTs into bundles. This approach demonstrates the possibility of tuning the formation of linear and branched carbon nanotube junctions that in turn is of importance for the sustainable fabrication of solution-processable CNT-based nanoscale systems and devices.

DNA Directed Self-Assembly of Single Walled Carbon Nanotubes into Three-Way Junction Nanostructures

Utilization of a self-assembled two-dimensional DNA nanostructure to arrange single-walled carbon nanotubes (SWNTs) into predetermined structures at controllable angles is presented. A specially designed DNA three-way junction (3WJ) composed of three double-stranded DNA arms containing single-stranded overhang sequences was prepared by annealing of partially complementary ssDNA sequences and ultrasonicated with SWNTs, resulting in DNA-3WJ/SWNT hybrid nanostructures. Utilization of DNA-3WJ not only allowed the precise dispersion of SWNTs but also acted as a rigid template for the self-assembly of SWNTs into three-armed junctions at an angle of approximately 120° to each other as visualized by scanning electron microscopy and atomic force microscopy. Prepared DNA-3WJ/SWNT nanostructures were also demonstrated to have the appropriate binding sites for fluorophores, providing a simple method for the fluorescent labeling of SWNTs. When ssDNA sequences forming the DNA-3WJ are ultrasonicated with SWNTs, followed by annealing of resulting ssDNA wrapped SWNTs, instead of hybrid junctions composed of three SWNT molecules, a web-like structure composed of interconnected SWNT junctions was obtained. The design approaches demonstrated here provide simple methods for the arrangement of SWNTs into desired nanostructures utilizing pre-assembled DNA nanostructures as linkers in aqueous solution through noncovalent interactions which can greatly contribute to efforts along the controlled assembly of SWNTs.