Preparation and Properties of Polymer-Wrapped Single-Walled Carbon Nanotubes

Intimate electrical contact occurs between a substituted poly(metaphenylenevinylene) (PmPV) and bundles of single‐walled nanotubes (SWNT) as evidenced by atomic force microscopy, optical, and electronic measurements carried out on single, isolated SWNT/PmPV structures (see picture). PmPV may provide a useful route toward “functionalizing” the SWNT without destroying their electrical character

Achieving a quantum smart workforce

Interest in building dedicated Quantum Information Science and Engineering (QISE) education programs has greatly expanded in recent years. These programs are inherently convergent, complex, often resource intensive and likely require collaboration with a broad variety of stakeholders. In order to address this combination of challenges, we have captured ideas from many members in the community. This manuscript not only addresses policy makers and funding agencies (both public and private and from the regional to the international level) but also contains needs identified by industry leaders and discusses the difficulties inherent in creating an inclusive QISE curriculum. We report on the status of eighteen post-secondary education programs in QISE and provide guidance for building new programs. Lastly, we encourage the development of a comprehensive strategic plan for quantum education and workforce development as a means to make the most of the ongoing substantial investments being made in QISE.Comment: 18 pages, 2 figures, 1 tabl

Starched Carbon Nanotubes

Common‐or‐garden starch can render single‐walled carbon nanotubes (SWNTs) readily soluble in water. The secret is to preorganize the linear amylose component in the starch into a helix with iodine prior to bringing the SWNTs on the scene. The SWNTs displace the iodine molecules in a “pea‐shooting” type of mechanism (see scheme). After some physical cajoling of the aqueous solution containing the starch–SWNT complex, a fine “bucky paper” is formed. Spitting in the aqueous solution, followed by sitting around for a few hours, also enables equally fine “bucky paper” to be harvested

Whence Molecular Electronics?

The drive toward yet further miniaturization of silicon-based electronics has led to a revival of efforts to build devices with molecular-scale components. The field of molecular electronics is teeming with results, rationalizations, and speculations [HN1]. Some claims may have been exaggerated, but news stories of a crisis in the field (1) are premature. Reports of passive molecular electronics devices, such as tunnel junctions and rectifiers, as well as of active devices, for example, single-molecule transistors and molecular switch tunnel junctions, have withstood scientific scrutiny. Simple molecular electronic devices usually consist of organic molecules sandwiched between conducting electrodes. According to early predictions, such devices could show electron tunneling (2) [HN2] or one-way flow of current (rectification) [HN3] through the molecule (3). In most tunneling junctions, linear alkanes are sandwiched between metal electrodes. Measurements over the past 25 years (4, 5) have largely validated McConnell's prediction (2) that the tunnel current depends exponentially on the length of the molecules between conducting electrodes [HN4]. In rectifiers, a molecule composed of an electron donor, a bridge, and an electron acceptor is extended between two electrodes (see the first figure, top panel). Experiments (6, 7) have again validated the early prediction by Aviram and Ratner (3) [HN5]

Whence Molecular Electronics?

The drive toward yet further miniaturization of silicon-based electronics has led to a revival of efforts to build devices with molecular-scale components. The field of molecular electronics is teeming with results, rationalizations, and speculations [HN1]. Some claims may have been exaggerated, but news stories of a crisis in the field (1) are premature. Reports of passive molecular electronics devices, such as tunnel junctions and rectifiers, as well as of active devices, for example, single-molecule transistors and molecular switch tunnel junctions, have withstood scientific scrutiny. Simple molecular electronic devices usually consist of organic molecules sandwiched between conducting electrodes. According to early predictions, such devices could show electron tunneling (2) [HN2] or one-way flow of current (rectification) [HN3] through the molecule (3). In most tunneling junctions, linear alkanes are sandwiched between metal electrodes. Measurements over the past 25 years (4, 5) have largely validated McConnell's prediction (2) that the tunnel current depends exponentially on the length of the molecules between conducting electrodes [HN4]. In rectifiers, a molecule composed of an electron donor, a bridge, and an electron acceptor is extended between two electrodes (see the first figure, top panel). Experiments (6, 7) have again validated the early prediction by Aviram and Ratner (3) [HN5]

Interactions between Conjugated Polymers and Single-Walled Carbon Nanotubes

The chemical interactions between single walled carbon nanotubes (SWNTs) and two structurally similar polymers, poly{(m-phenylenevinylene)-co-[(2,5-dioctyloxy-p-phenylene)vinylene]}, or PmPV, and poly{(2,6-pyridinylenevinylene)-co-[(2,5-dioctyloxy-p-phenylene)vinylene]}, or PPyPV, are investigated. The fundamental difference between these two polymers is that PPyPV is a base and is readily protonated via the addition of HCl. Both polymers promote chloroform solubilization of SWNTs. We find that the SWNT/PPyPV interaction lowers the pKa of PPyPV. Optoelectronic devices, fabricated from single polymer-wrapped SWNT structures, reveal a photogating effect on charge transport which can rectify or amplify current flow through the tubes. For PmPV wrapped tubes, the wavelength dependence of this effect correlates to the absorption spectrum of PmPV. For PPyPV, the wavelength dependence correlates with the absorption spectrum of protonated PPyPV, indicating that SWNTs assist in charge stabilization

Interactions between Conjugated Polymers and Single-Walled Carbon Nanotubes

The chemical interactions between single walled carbon nanotubes (SWNTs) and two structurally similar polymers, poly{(m-phenylenevinylene)-co-[(2,5-dioctyloxy-p-phenylene)vinylene]}, or PmPV, and poly{(2,6-pyridinylenevinylene)-co-[(2,5-dioctyloxy-p-phenylene)vinylene]}, or PPyPV, are investigated. The fundamental difference between these two polymers is that PPyPV is a base and is readily protonated via the addition of HCl. Both polymers promote chloroform solubilization of SWNTs. We find that the SWNT/PPyPV interaction lowers the pKa of PPyPV. Optoelectronic devices, fabricated from single polymer-wrapped SWNT structures, reveal a photogating effect on charge transport which can rectify or amplify current flow through the tubes. For PmPV wrapped tubes, the wavelength dependence of this effect correlates to the absorption spectrum of PmPV. For PPyPV, the wavelength dependence correlates with the absorption spectrum of protonated PPyPV, indicating that SWNTs assist in charge stabilization

Single-Walled Carbon Nanotube Based Molecular Switch Tunnel Junctions

This article describes two‐terminal molecular switch tunnel junctions (MSTJs) which incorporate a semiconducting, single‐walled carbon nanotube (SWNT) as the bottom electrode. The nanotube interacts noncovalently with a monolayer of bistable, nondegenerate [2]catenane tetracations, self‐organized by their supporting amphiphilic dimyristoylphosphatidyl anions which shield the mechanically switchable tetracations from a two‐micrometer wide metallic top electrode. The resulting 0.002 μm^2 area tunnel junction addresses a nanometer wide row of ≈2000 molecules. Active and remnant current–voltage measurements demonstrated that these devices can be reconfigurably switched and repeatedly cycled between high and low current states under ambient conditions. Control compounds, including a degenerate [2]catenane, were explored in support of the mechanical origin of the switching signature. These SWNT‐based MSTJs operate like previously reported silicon‐based MSTJs, but differently from similar devices incorporating bottom metal electrodes. The relevance of these results with respect to the choice of electrode materials for molecular electronics devices is discussed