Percolation in Carbon Nanotube Networks

Carbon nanotubes (CNTs) have become increasingly useful in different applications since they were discovered in 1991 by Sumio Iijima [1]. One of their many useful qualities is their electronic properties [2]. These CNTs, when formed into a network, can be used as transistors [3] or biosensors [4]. Transistors are devices that regulate either current flow or voltage and act as a switch; they are a crucial component of computers. Biosensors detect the presence of biomolecules. Efficient transistors and biosensors already exist; however, they are expensive to manufacture compared to these CNT networks. The ability of the CNT networks to be transistors or biosensors relies on the percolation properties of the networks. As long as these networks percolate, current can pass through the network from a source electrode to a drain electrode, which can then be modulated by an electrical or biological signal to make devices such as transistors useful

Multiply Folded Graphene

The folding of paper, hide, and woven fabric has been used for millennia to achieve enhanced articulation, curvature, and visual appeal for intrinsically flat, two-dimensional materials. For graphene, an ideal two-dimensional material, folding may transform it to complex shapes with new and distinct properties. Here, we present experimental results that folded structures in graphene, termed grafold, exist, and their formations can be controlled by introducing anisotropic surface curvature during graphene synthesis or transfer processes. Using pseudopotential-density functional theory calculations, we also show that double folding modifies the electronic band structure of graphene. Furthermore, we demonstrate the intercalation of C60 into the grafolds. Intercalation or functionalization of the chemically reactive folds further expands grafold's mechanical, chemical, optical, and electronic diversity.Comment: 29 pages, 10 figures (accepted in Phys. Rev. B

Scaling Resistance with Channel Length for Carbon Nanotube Networks

To inform the applicability of carbon nanotube networks for use as field effect transistors or as biosensors, we have run computer simulations in order to characterize the electrical properties of these networks, and specifically, how the resistance of these networks scales with the channel length for various amounts of metallic wires present in the networks. We find a trend that as the channel length increases, the resistance of the network increases as well. In addition, as the probability of metallic wires present in the network increases, the scaling factor of the resistance, m, increases at a larger constant rate with increasing channel length.https://digitalcommons.humboldt.edu/ideafest_posters/1293/thumbnail.jp

Graphene as a Long-Term Metal Oxidation Barrier: Worse Than Nothing

Anticorrosion and antioxidation surface treatments such as paint or anodization are a foundational component in nearly all industries. Graphene, a single-atom-thick sheet of carbon with impressive impermeability to gases, seems to hold promise as an effective anticorrosion barrier, and recent work supports this hope. We perform a complete study of the short- and long-term performance of graphene coatings for Cu and Si substrates. Our work reveals that although graphene indeed offers effective short-term oxidation protection, over long time scales it promotes more extensive wet corrosion than that seen for an initially bare, unprotected Cu surface. This surprising result has important implications for future scientific studies and industrial applications. In addition to informing any future work on graphene as a protective coating, the results presented here have implications for graphene’s performance in a wide range of applications

Subnanometer Vacancy Defects Introduced on Graphene by Oxygen Gas

The basal plane of graphene has been known to be less reactive than the edges, but some studies observed vacancies in the basal plane after reaction with oxygen gas. Observation of these vacancies has typically been limited to nanometer-scale resolution using microscopic techniques. This work demonstrates the introduction and observation of subnanometer vacancies in the basal plane of graphene by heat treatment in a flow of oxygen gas at low temperature such as 533 K or lower. High-resolution transmission electron microscopy was used to directly observe vacancy structures, which were compared with image simulations. These proposed structures contain C = O, pyran-like ether, and lactone-like groups.close