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Hyperbolic paraboloid surfaces or saddle‐shaped materials can exist in two equilibrium shapes when the saddle shape reverses on itself and, therefore, can be used as structural elements of new stimuli‐responsive and shape‐changing materials. Here we propose a new fast and easy approach to the nanoarchitectonics of graphene oxide nanosheets to form curved interfaces. Our technology involves computer‐aid design, three dimensional (3D) printing, and casting curved templates for the assembly of two‐dimensional (2D) nanosheets. We demonstrate the feasibility of our approach for the nanoarchitectonics of graphene oxide flakes, though it can be expanded to include the whole family of 2D materials. The prepared free‐standing saddle‐shaped graphene oxide membranes show highly ordered nanostructure, typical for flat 2D multilayered materials. We optimize the preparation conditions to construct robust two‐dimensional membranes with nanostructured architecture and controllable thickness and curvature.

No abstract is provided for this article.

No abstract is provided for this article.

We observe a giant increase of the infrared intensity and a softening of the in-plane antisymmetric phonon mode Eu (~0.2 eV) in bilayer graphene as a function of the gate-induced doping. The phonon peak has a pronounced Fano-like asymmetry. We suggest that the intensity growth and the softening originate from the coupling of the phonon mode to the narrow electronic transition between parallel bands of the same character, while the asymmetry is due to the interaction with the continuum of transitions between the lowest hole and electron bands. The growth of the peak is a manifestation of the "charged-phonon" effect observed previously in organic chain conductors and doped fullerenes, which can now be tuned with the gate voltage.

Multilayer van der Waals (vdW) heterostructures have become an important platform in which to study novel fundamental effects emerging at the nanoscale. Standard nanopatterning techniques relying on electron-beam lithography and reactive ion etching, widely applied to pattern such heterostructures, however, impose some limitations on the edge accuracy and resolution, as revealed through numerous experiments with vdW quantum dots and point contacts. Here we present an alternative approach for electrode-free nanopatterning of thick multilayer vdW heterostructures based on atomic force microscopy (AFM). By applying an AC voltage of a relatively small frequency (1-10 kHz) between the sharp platinum tip and the substrate, we realize high-resolution ($\lesssim 100$ nm) etching of thick multicomponent heterostructures if the latter are deposited onto graphite slabs. Importantly, unlike more conventional electrode-free local anodic oxidation, our method does not require a special environment with excess humidity, can be applied at ambient conditions, and enables the patterning of multilayer heterostructures composed of graphene, graphite, hexagonal boron nitride (hBN), NbSe$_{2}$, WSe$_{2}$, and more.

The Mermin-Wagner theorem states that long-range magnetic order does not exist in one- or two-dimensional (2D) isotropic magnets with short-ranged interactions. The theorem has been a milestone in magnetism and has been driving the research of recently discovered 2D van der Waals (vdW) magnetic materials from fundamentals up to potential applications. In such systems, the existence of magnetic ordering is typically attributed to the presence of a significant magnetic anisotropy, which is known to introduce a spin-wave gap and circumvent the core assumption of the theorem. Here we show that in finite-size 2D vdW magnets typically found in lab setups (e.g., within millimetres), short-range interactions can be large enough to allow the stabilisation of magnetic order at finite temperatures without any magnetic anisotropy for practical implementations. We demonstrate that magnetic ordering can be created in flakes of 2D materials independent of the lattice symmetry due to the intrinsic nature of the spin exchange interactions and finite-size effects in two-dimensions. Surprisingly we find that the crossover temperature, where the intrinsic magnetisation changes from superparamagnetic to a completely disordered paramagnetic regime, is weakly dependent on the system length, requiring giant sizes (e.g., of the order of the observable universe ~10$^{26}$ m) in order to observe the vanishing of the magnetic order at cryogenic temperatures as expected from the Mermin-Wagner theorem. Our findings indicate exchange interactions as the main driving force behind the stabilisation of short-range order in 2D magnetism and broaden the horizons of possibilities for exploration of compounds with low anisotropy at an atomically thin level.

Journal Article Understanding 2D Crystal Vertical Heterostructures at the Atomic Scale Using Advanced Scanning Transmission Electron Microscopy Get access Sarah J Haigh, Sarah J Haigh School of Materials, University of Manchester, Manchester, M13 9PL, UKNational Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Aidan P Rooney, Aidan P Rooney School of Materials, University of Manchester, Manchester, M13 9PL, UKNational Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Tom JA Slater, Tom JA Slater School of Materials, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Eric Prestat, Eric Prestat School of Materials, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Ekaterina Khestanova, Ekaterina Khestanova National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Rob Dryfe, Rob Dryfe School of Chemistry, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Matej Velický, Matej Velický School of Chemistry, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Roman V Gorbachev, Roman V Gorbachev National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Rada Boya, Rada Boya National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Yang Cao, Yang Cao National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar ... Show more Irina Grigorieva, Irina Grigorieva National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Kostya Novoselov, Kostya Novoselov National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Fred Withers, Fred Withers National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Andre K Geim Andre K Geim National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 23, Issue S1, 1 July 2017, Pages 1714–1715, https://doi.org/10.1017/S1431927617009230 Published: 04 August 2017

Two-dimensional materials provide with ability to control their properties with a number of methods. One of such methods is using strain and compression. In this work, we investigated the influence of locally induced strain through bubbles in thin ferromagnetic CrBr 3 using low-temperature magnetic force microscopy. As a result, domain pinning and higher coercive and saturation fields were observed in the bubble. In addition, nontrivial spin arrangements are allowed to take place in a non-homogeneously strained area, leading to different responses to the external magnetic field in comparison to a non-strained region. Finally, Raman spectroscopy and magneto-photoluminescence spectroscopy were performed to show alternation of the magnetic properties of the sample under mechanical deformation.

The electrochemical activity of the basal plane and edge plane of graphite has long been a subject of an extensive debate. While significant advances have been made, several gaps still exist in our understanding of this issue, namely, the relative differences in the electrochemical activity of the perfect basal plane and perfect edge plane and the dependence of measurable electrochemical quantities on the edge/defect density of the basal plane. In this work, we employ a microdroplet electrochemical cell technique and atomic force microscopy to measure localized electrochemical properties of the graphitic surface with known edge coverage. The electron transfer rate, capacitance, and density of electronic states of the perfect basal plane and perfect edge plane are estimated, and a qualitative model is proposed for the dependence of the electrochemical quantities on the defect density of the basal plane.

Graphene-based printable inks are advanced and promising candidates for flexible printed electronic devices. To develop large-scale graphene-based highly conductive electronics on the basis of existing printing approaches of the material, it is imperative to scale up its ink production methods and optimize the electrical properties of the printed films. Here, a sustainable approach for preparing high-conductive screen-printing graphene ink by recycling cellulose solvent is reported. The ink uses Cyrene solvent in circulation and produces highly concentrated and conductive graphene ink to conquer the limitation of graphene inks in massive industrial production brought by the high cost of the cellulose solvents. A systematic study of the sheet resistance variation with the number of cycles has been carried out. The average conductivity of the ink can exceed 3×104 S m−1, with only 2-hour shear exfoliation process, which exhibits about the same conductivity of recent works (using toxic NMP solvent, complex centrifugation, ultrasonication, etc.), but with much simpler and cost- effective fabrication process. The formulation of graphene inks allows flexible metal-free far- field tag antenna to be screen printed and integrated with off-the-shelf sensory chip to achieve battery-free wireless UHF RFID far field temperature sensing. The high responsiveness, accuracy and sensitivity of the RFID sensing tag were observed with instantaneous detection, accurate and reliable wireless data transmission.

The realization of extreme optical anisotropy is foundational for nanoscale light manipulation. The van der Waals (vdW) crystal MoOCl₂ has emerged as a promising candidate for this quest, hosting hyperbolic plasmon polaritons in the visible and near-infrared wavelengths. However, the fundamental anisotropic dielectric tensor governing this behavior has remained elusive. Here, we resolve this problem by providing the first experimental determination of the full dielectric tensor of hyperbolic vdW MoOCl₂. Via spectroscopic ellipsometry, Mueller matrix, and reflectance measurements, we quantify the material's optical duality: a metallic optical response (<i>ε</i>₁ < 0) along the crystallographic <i>a</i>-axis and a dielectric response (<i>ε</i>₁ > 0) along the orthogonal directions. This dichotomy drives an epsilon-near-zero (ENZ) condition at ≈512 nm and results in a giant in-plane birefringence of Δ<i>n</i> ≈ 2.2 for MoOCl₂. As a result, our work provides the critical missing experimental parameters for MoOCl₂, establishing it as a benchmark hyperbolic and ENZ material.

No abstract is provided for this article.

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Photoelectrochemistry of Pristine Mono- and Few-Layer MoS2Matěj Velický*, Mark A. Bissett, Colin R. Woods, Peter S. Toth, Thanasis Georgiou, Ian A. Kinloch, Kostya S. Novoselov, and Robert A. W. Dryfe*Cite this: Nano Lett. 2016, 16, 12, 8035Publication Date (Web):November 14, 2016Publication History Published online14 November 2016Published inissue 14 December 2016https://doi.org/10.1021/acs.nanolett.6b04704Copyright © 2016 American Chemical SocietyRIGHTS & PERMISSIONSACS AuthorChoicewith CC-BYlicenseArticle Views857Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (161 KB) Get e-Alerts Get e-Alerts