The establishment of covalent junctions between carbon nanotubes (CNTs) and the modification of their straight tubular morphology are two strategies needed to successfully synthesize nanotube-based three-dimensional (3D) frameworks exhibiting superior material properties. Engineering such 3D structures in scalable synthetic processes still remains a challenge. This work pioneers the bulk synthesis of 3D macroscale nanotube elastic solids directly via a boron-doping strategy during chemical vapour deposition, which influences the formation of atomic-scale “elbow” junctions and nanotube covalent interconnections. Detailed elemental analysis revealed that the “elbow” junctions are preferred sites for excess boron atoms, indicating the role of boron and curvature in the junction formation mechanism, in agreement with our first principle theoretical calculations. Exploiting this material’s ultra-light weight, super-hydrophobicity, high porosity, thermal stability, and mechanical flexibility, the strongly oleophilic sponge-like solids are demonstrated as unique reusable sorbent scaffolds able to efficiently remove oil from contaminated seawater even after repeated use.

Although lithium ion batteries have gained commercial success owing to their high energy density, they lack suitable electrodes capable of rapid charging and discharging to enable a high power density critical for broad applications. Here, we demonstrate a simple bottom-up approach toward single crystalline vanadium oxide (VO2) ribbons with graphene layers. The unique structure of VO2-graphene ribbons thus provides the right combination of electrode properties and could enable the design of high-power lithium ion batteries. As a consequence, a high reversible capacity and ultrafast charging and discharging capability is achieved with these ribbons as cathodes for lithium storage. A full charge or discharge is capable in 20 s. More remarkably, the resulting electrodes retain more than 90% of the initial capacity after cycling more than 1000 times at an ultrahigh rate of 190C, providing the best reported rate performance for cathodes in lithium ion batteries to date.

Gold and silver nanoparticles and nanostructures exhibit plasmon resonances that result in strong scattering and absorption of light, as well as enhanced optical fi elds near the metal surface. The resonant fi eld enhancement dramatically enhances the weak Raman scattering signals from molecules near the metal surface. [ 1 ] This effect, called surface enhanced Raman scattering (SERS), has been widely pursued as a molecular sensing technology over the past decade. [ 2 , 3 ] SERS is non-destructive, suffi ciently sensitive for single molecule detection, and provides inherent molecular specifi city since it yields molecular vibrational spectra. While fi eld enhancement occurs over an entire nanostructure surface, SERS signals are strongest from small gaps between nanoparticles referred to as "hot spots" where the fi eld enhancement is maximal. [ 4 , 5 ] Most SERS work to date has focused on detection with substrates that are designed to maximize the density, sensitivity, and reproducibility of hot spots in order to give the strongest possible SERS signal. Many substrates have been developed which refl ect the variety of nanofabrication, synthesis, and assembly strategies that have emerged over the past decade. These include semiconducting nanowires, [ 6 ] aggregated colloids, [ 7 , 8 ] colloidal lithography, [ 9 , 10 ] soft lithography, [ 11 , 12 ] e-beam lithography, [ 13 ] and colloidal assembly. [ 14 , 15 ] Most of the substrates consist of nanostructured gold or silver on a fl at substrate. Some reports describe substrates with increased surface roughness to increase the number of hot spots, including aligned carbon nanotube substrates that support silver nanoparticles. [ 16 ] These substrates were found to provide highly sensitive detection. However, optical scattering and light collection occur in a three dimensional focal volume. Therefore, to maximize the quantity of scattered light generated and detected, SERS substrates should contain hot spots in a large three dimensional volume that is matched to the optics of the SERS instrumentation. Three dimensional substrates have been fabricated and tested based on porous silicon, microfabricated silicon, and porous gold. [17][18][19][20] These have indeed improved the detection limit for small molecules like trinitrotoluene (TNT). Therefore, it is desirable to create densely packed metal nanostructures with nanogaps to form plentiful hot spots for better SERS performance. [21][22][23] In the present study, we describe the fabrication of a structurally tunable 3D SERS substrate based on vertically aligned CNTs. Vertically aligned CNTs provide a new paradigm to realize three dimensional SERS substrates with high nanoparticle density. The vertically aligned CNTs were synthesized on a SiO 2 substrate by water-assisted chemical vapor deposition (CVD). The resulting vertically aligned CNTs were several millimeters long and were composed of a mixture of double-and triple-walled nanotubes. [ 24 , 25 ] A gold fi lm (50 nm thickness) was deposited on top of the CN...

Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs) were synthesized by a combination of anodization and chemical vapor deposition techniques. A 3-D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device.

We have created stable dispersions of single wall carbon nanotubes (SWNTs) in water by employing a noncovalent functionalization scheme that allows carboxylic acid moieties to be attached to the SWNT surface by a pi-pi stacking interaction. Pyrenecarboxylic acid (PCA) is noncovalently attached to the surface of SWNTs and affords highly uniform and stable aqueous dispersions. This method was developed to provide a noncovalent alternative to the commonly used oxidative acid treatment functionalization of carbon nanotubes. This alternative strategy avoids the damage to the carbon nanotube structure inherent to oxidative acid treatments. Carbon nanotubes are commonly functionalized with oxidative acid treatment schemes to create polymer-nanotube composites and improve the adhesion between the polymer and carbon nanotubes. Composites of SWNTs and polycarbonate were prepared and tested to determine the effect of PCA on the adhesion of the SWNTs to the polymer matrix. These tests confirmed that PCA improved the SWNT-polycarbonate adhesion and improved the dispersion of the SWNTs throughout the matrix. This study demonstrates that stable dispersions of SWNTs can be achieved without substantial cutting, introduction of defects, or covalent modification, by employing a simple and effective noncovalent functionalization with PCA.