Length‐Selective Chemical Assembly of Vertically Aligned Carbon Nanotubes

Abstract

Many potential applications of carbon nanotubes (CNTs), ranging from electronics and optoelectronics to biology and medicine, require length‐controlled and well‐aligned CNTs on surfaces. In this work, the length selectivity behavior of wet‐dispersed CNTs on gold functionalized surfaces is investigated, providing new mechanistic insights into the length‐selective process that occurs upon chemical assembly. A combination of experimental evidence derived from atomic force microscopy and plane and cross‐sectional transmission electron microscopy implies a length‐selective deposition of CNTs on the functionalized gold surface. All the solutions containing either a high distribution of longer or shorter CNTs lead to the selective formation of vertically aligned carbon nanotubes with average lengths of 10.6 ± 3.1 nm. It is postulated that such length‐selective phenomenon is not only driven by diffusion mechanisms but also is governed by the interactions between the CNTs and the chemically functionalized surfaces. The orientation of the initial attached nanotubes, which act as nucleation sites in the CNT assembly process, is proposed to dictate the CNT length distribution on the surface and be dependent on the packing and ordering of the molecules on the functionalized surface.

Real-Time Visualization and Dynamics of Boron Nitride Nanotubes Undergoing Brownian Motion

“…These remarkable properties make BNNTs well-suited for a variety of applications, ranging from electronics to material engineering to biomedical applications. − A fundamental understanding of BNNT dynamics in solution would accelerate research in neat BNNT macroscopic materials, BNNT–polymer composites, and BNNTs in biological systems, as was the case for CNTs. − In fact, dilute rotational and translational diffusivities are the bases for understanding behavior in crowded systems, such as liquid crystals, gels, and polymer networks, and for understanding shear alignment in flow processes, which are key in material processing, biology, composites, and manufacturing, respectively. For example, liquid-phase processing would enable the large-scale production of BNNT films, fibers, and composites. − Understanding how BNNTs diffuse in solution is paramount to producing aligned films and fibers, as it provides a time scale for relaxation and reorientation. − Additionally, knowing how BNNT diffusion compares to that of other materials, such as polymers, can allow us to design composites that maximize BNNTs’ desired properties. , Finally, the study of how BNNTs behave in aqueous solution will allow us to more accurately predict their response to changes in environmental parameters, such as viscosity or temperature. This is particularly pertinent to biological studies where changes in environment are quite common. − Moreover, the ability to visualize BNNTs in real time could aid the study of interactions between BNNTs and biomolecules, which is crucial for the application of BNNTs in drug delivery or biological sensors. − Despite these important applications, real-time visualization of BNNTs in solution has been extremely limited, and the investigation of BNNT dynamics has never been reported.…”

Brownian Diffusion of Hexagonal Boron Nitride Nanosheets and Graphene in Two Dimensions

“…Still, we believe that all of the insights in this report provide a significant step toward understanding the hydrodynamics of 2D nanomaterials. As was realized with rigid rods, − this knowledge could be central for manipulating liquid-phase processing techniques to produce macroscopic materials. Additionally, this would be important in understanding the dynamics of 2D nanomaterials after introduction into biological systems, such as in drug nanocarriers …”

“…Theoretical predictions have been proposed for disk-like particle diffusion through a bulk solution; , however, to the best of our knowledge, little experimental work has been done at the single sheet level, with most work performed using bulk techniques such as dynamic light scattering (DLS). − On the other hand, for rigid rods, experimental studies on model rods, such as actin filaments, carbon nanotubes (CNTs), germanium nanowires, and boron nitride nanotubes (BNNTs), were utilized to determine and confirm a model of Brownian rod-like particle diffusion through a confined solution. These results were utilized to accelerate the understanding of the behavior and diffusion of rod-like particles in biological systems and in the production of materials from rigid rod building blocks, such as CNTs. − In each of these systems, the rigid rod particles were studied on the single-molecule level to understand how changes in rod length impact diffusivity. Additionally, each system was studied under confinement, as a confinement model is more applicable to both biological systems and materials processing .…”

Electrochemical communication with the inside of cells using micro-patterned vertical carbon nanofibre electrodes

“…Other examples include the intracellular insertion of DNA nanowires, which could electrochemically communicate with a cell12. We have recently modified surfaces with chemically self-assembled vertical aligned singled walled carbon nanotubes418 which were capable of communicating with the intracellular environment4 and further developed and used to delineate the immune cell function5. Others have used a single platinum nanoelectrode and inserted this in to a cell.…”