Amelia H. C. Hart

Chemical Vapor Deposition of Monolayer Rhenium Disulfide (ReS2)

The direct synthesis of monolayer and multilayer ReS2 by chemical vapor deposition at a low temperature of 450 °C is reported. Detailed characterization of this material is performed using various spectroscopy and microscopy methods. Furthermore initial field-effect transistor characteristics are evaluated, which highlight the potential in being used as an n-type semiconductor.

Field Emission with Ultralow Turn On Voltage from Metal Decorated Carbon Nanotubes

A simple and scalable method of decorating 3D-carbon nanotube (CNT) forest with metal particles has been developed. The results observed in aluminum (Al) decorated CNTs and copper (Cu) decorated CNTs on silicon (Si) and Inconel are compared with undecorated samples. A significant improvement in the field emission characteristics of the cold cathode was observed with ultralow turn on voltage (Eto ∼ 0.1 V/μm) due to decoration of CNTs with metal nanoparticles. Contact resistance between the CNTs and the substrate has also been reduced to a large extent, allowing us to get stable emission for longer duration without any current degradation, thereby providing a possibility of their use in vacuum microelectronic devices.

Enhanced field emission properties from CNT arrays synthesized on Inconel superalloy.

One of the most promising materials for fabricating cold cathodes for next generation high-performance flat panel devices is carbon nanotubes (CNTs). For this purpose, CNTs grown on metallic substrates are used to minimize contact resistance. In this report, we compare properties and field emission performance of CNTs grown via water assisted chemical vapor deposition using Inconel vs silicon (Si) substrates. Carbon nanotube forests grown on Inconel substrates are superior to the ones grown on silicon; low turn-on fields (∼1.5 V/μm), high current operation (∼100 mA/cm(2)) and very high local field amplification factors (up to ∼7300) were demonstrated, and these parameters are most beneficial for use in vacuum microelectronic applications.

Density Variant Carbon Nanotube Interconnected Solids

DOI: 10.1002/adma.201404995 from the individual dimensions of the CNTs, the interconnection also affects the density. Detailed microscopy and spectroscopy studies have been performed to explain the structure, properties, and other functional properties. In order to understand the structure, the top, bottom, and lateral sides of the 3D nanotube blocks were imaged using scanning electron microscopy (SEM). Figure 1 b,c shows the top and side view of the 3D-CNT solid blocks. SEM images show uniformly fl at top surfaces as well as the vertical alignment of the nanotubes. The top surface reveals the aligned CNTs are nicely spaced and form a microporous structure giving rise to the solid block. The side view shows aligned millimeter length CNTs exhibiting both buckling and bending due to their large height and network structure. In order to understand the in-depth morphology of the blocks, we sectioned the block at different planes and imaged using SEM as shown in Figure 2 . The 3D architectures entirely consist of entangled CNTs with different orientations producing spatially varying morphologies (Figure 2 a,e). The morphology for the intermolecular junctions reveals junctions of Y-type, X-type, multibranched, and ring-like confi gurations (Figure 2 b,c,d,f, respectively). Highly branched 3D-CNT network junctions are shown in Figure 2 d. Recent reports have shown that these kinds of multiterminal junctions are formed due to the presence of topological defects in the hexagonal carbon lattice within the junction region. [ 2,16,18 ] Solid blocks also contain solder-like junctions between CNT bundles (Figure 2 g,h). The nanoscale and solder-like junctions could be expected to improve mechanical and physical properties of the material. [ 2,19–21 ]

3D Macroporous Solids from Chemically Cross‐linked Carbon Nanotubes

Suzuki reaction for covalently interconnected 3D carbon nanotube (CNT) architectures is reported. The synthesis of 3D macroscopic solids made of CNTs covalently connected via Suzuki cross-coupling, a well-known carbon-carbon covalent bond forming reaction in organic chemistry, is scalable. The resulting solid has a highly porous, interconnected structure of chemically cross-linked CNTs. Its use for the removal of oil from contaminated water is demonstrated.

Anisotropically functionalized carbon nanotube array based hygroscopic scaffolds.

Creating ordered microstructures with hydrophobic and hydrophilic moieties that enable the collection and storage of small water droplets from the atmosphere, mimicking structures that exist in insects, such as the Stenocara beetle, which live in environments with limited amounts of water. Inspired by this approach, vertically aligned multiwalled carbon nanotube forests (NTFs) are asymmetrically end-functionalized to create hygroscopic scaffolds for water harvesting and storage from atmospheric air. One side of the NTF is made hydrophilic, which captures water from the atmosphere, and the other side is made superhydrophobic, which prevents water from escaping and the forest from collapsing. To understand how water penetrates into the NTF, the fundamentals of water/NTF surface interaction are discussed.

Spiers Memorial Lecture. Advances of carbon nanomaterials.

During the last two decades the exciting properties of carbon nanomaterials, i.e. fullerene, carbon nanotubes and graphene, have drawn pronounced attention. This brief review will discuss the recent advances in the science and applications of nanocarbons, mainly of nanotubes and graphene, and the opportunities and challenges that exist in future technologies based on these emerging materials. The review will discuss the growth and selection, chemical modifications, substitutional doping, and engineering three-dimensional structures, and demonstrations of possible applications. This is a perspective on how the advent of nanocarbons will enable the development of the next generation of carbon materials and technologies relevant for a broad range of applications.

Synthesis and photocurrent of amorphous boron nanowires

Although theoretically feasible, synthesis of boron nanostructures is challenging due to the highly reactive nature, high melting and boiling points of boron. We have developed a thermal vapor transfer approach to synthesizing amorphous boron nanowire using a solid boron source. The amorphous nature and chemical composition of boron nanowires were characterized by high resolution transmission electron microscopy, selected area electron diffraction, and electron energy loss spectroscopy. Optical properties and photoconduction of boron nanowires have not yet been reported. In our investigation, the amorphous boron nanowire showed much better optical and electrical properties than previously reported photo-response of crystalline boron nanobelts. When excited by a blue LED, the photo/dark current ratio (I/I₀) is 1.5 and time constants in the order of tens of seconds. I/I₀ is 1.17 using a green light.

Carbon nanotube core graphitic shell hybrid fibers.

A carbon nanotube yarn core graphitic shell hybrid fiber was fabricated via facile heat treatment of epoxy-based negative photoresist (SU-8) on carbon nanotube yarn. The effective encapsulation of carbon nanotube yarn in carbon fiber and a glassy carbon outer shell determines their physical properties. The higher electrical conductivity (than carbon fiber) of the carbon nanotube yarn overcomes the drawbacks of carbon fiber/glassy carbon, and the better properties (than carbon nanotubes) of the carbon fiber/glassy carbon make up for the lower thermal and mechanical properties of the carbon nanotube yarn via synergistic hybridization without any chemical doping and additional processes.