The enantiomer-level isolation of single-walled carbon nanotubes (SWCNTs) in high concentration and with high purity for nanotubes greater than 1.1 nm in diameter is demonstrated using a two-stage aqueous two-phase extraction (ATPE) technique. In total, five different nanotube species of ∼1.41 nm diameter are isolated, including both metallics and semiconductors. We characterize these populations by absorbance spectroscopy, circular dichroism spectroscopy, resonance Raman spectroscopy, and photoluminescence mapping, revealing and substantiating mod-dependent optical dependencies. Using knowledge of the competitive adsorption of surfactants to the SWCNTs that controls partitioning within the ATPE separation, we describe an advanced acid addition methodology that enables the fine control of the separation of these select nanotubes. Furthermore, we show that endohedral filling is a previously unrecognized but important factor to ensure a homogeneous starting material and further enhance the separation yield, with the best results for alkane-filled SWCNTs, followed by empty SWCNTs, with the intrinsic inhomogeneity of water-filled SWCNTs causing them to be worse for separations. Lastly, we demonstrate the potential use of these nanotubes in field-effect transistors.
We have inkjet-printed in-plane 'metal-semiconductor-metal' type photodetectors on paper, one of the cheapest flexible substrates, which is also recyclable and foldable, in contrast to traditional plastic substrates. The photodetectors are made by using graphene as electrodes and various transition metal dichalcogenides (TMDs) as photoactive component. In particular, we have tested MoS 2 , WS 2 , MoSe 2 and MoTe 2 . Large differences in responsivity and sensitivity were observed for all of the TMDs measured, with MoS 2 showing the highest sensitivity and MoTe 2 producing the largest response. However, photodetectors made of MoTe 2 show a large decrease in responsivity after one week of exposure to air. The wavelength dependence of the responsivity in MoS 2 based devices was further analyzed using a supercontinuum photocurrent spectroscopy setup, with the results suggesting a bolometric or photoelectric origin of the signal. We also report some simple approaches to enhance the device performance and tune the energy range at which the maximum in responsivity or sensitivity is observed.
The Josephson effect is one of the most studied macroscopic quantum phenomena in condensed matter physics and has been an essential part of the quantum technologies development over the last decades. It is already used in many applications such as magnetometry, metrology, quantum computing, detectors or electronic refrigeration. However, developing devices in which the induced superconductivity can be monitored, both spatially and in its magnitude, remains a serious challenge. In this work, we have used local gates to control confinement, amplitude and density profile of the supercurrent induced in one-dimensional nanoscale constrictions, defined in bilayer graphene-hexagonal boron nitride van der Waals heterostructures. The combination of resistance gate maps, out-of-equilibrium transport, magnetic interferometry measurements, analytical and numerical modelling enables us to explore highly tunable superconducting weak links. Our study opens the path way to design more complex superconducting circuits based on this principle, such as electronic interferometers or transition-edge sensors.
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