Publications by authors named "Johanna Rosen"

51 Publications

Boridene: Two-dimensional MoB with ordered metal vacancies obtained by chemical exfoliation.

Science 2021 08;373(6556):801-805

Materials Design, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.

Extensive research has been invested in two-dimensional (2D) materials, typically synthesized by exfoliation of van der Waals solids. One exception is MXenes, derived from the etching of constituent layers in transition metal carbides and nitrides. We report the experimental realization of boridene in the form of single-layer 2D molybdenum boride sheets with ordered metal vacancies, MoBT (where T is fluorine, oxygen, or hydroxide surface terminations), produced by selective etching of aluminum and yttrium or scandium atoms from 3D in-plane chemically ordered (MoY)AlB and (MoSc)AlB in aqueous hydrofluoric acid. The discovery of a 2D transition metal boride suggests a wealth of future 2D materials that can be obtained through the chemical exfoliation of laminated compounds.
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http://dx.doi.org/10.1126/science.abf6239DOI Listing
August 2021

Out-Of-Plane Ordered Laminate Borides and Their 2D Ti-Based Derivative from Chemical Exfoliation.

Adv Mater 2021 Sep 5;33(38):e2008361. Epub 2021 Aug 5.

Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, SE-581 83, Sweden.

Exploratory theoretical predictions in uncharted structural and compositional space are integral to materials discoveries. Inspired by M SiB (T2) phases, the finding of a family of laminated quaternary metal borides, M' M″SiB , with out-of-plane chemical order is reported here. 11 chemically ordered phases as well as 40 solid solutions, introducing four elements previously not observed in these borides are predicted. The predictions are experimentally verified for Ti MoSiB , establishing Ti as part of the T2 boride compositional space. Chemical exfoliation of Ti MoSiB and select removal of Si and MoB sub-layers is validated by derivation of a 2D material, TiO Cl , of high yield and in the form of delaminated sheets. These sheets have an experimentally determined direct band gap of ≈4.1 eV, and display characteristics suitable for supercapacitor applications. The results take the concept of chemical exfoliation beyond currently available 2D materials, and expands the envelope of 3D and 2D candidates, and their applications.
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http://dx.doi.org/10.1002/adma.202008361DOI Listing
September 2021

Replacing Computed Tomography with "Rapid" Magnetic Resonance Imaging for Ventricular Shunt Imaging.

Pediatr Qual Saf 2021 Jul-Aug;6(4):e441. Epub 2021 Jul 28.

Division of Pediatric Emergency Medicine, UPMC Children's Hospital of Pittsburgh, Pittsburgh, Pa.

Introduction: Children with ventricular shunts undergo frequent neuroimaging, and therefore, radiation exposures, to evaluate shunt malfunctions. The objective of this study was to safely reduce radiation exposure in this population by reducing computed tomography (CT) and increasing "rapid" magnetic resonance imaging (rMRI-shunt) among patients warranting neuroimaging for possible shunt malfunction.

Methods: This was a single-center quality improvement study in a tertiary care pediatric emergency department (ED). We implemented a multidisciplinary guideline for ED shunt evaluation, which promoted the use of rMRI-shunt over CT. We included patients younger than 18 years undergoing an ED shunt evaluation during 11 months of the preintervention and 25 months of the intervention study periods. The primary outcome was the CT rate, and we evaluated the relevant process and balancing measures.

Results: There were 266 encounters preintervention and 488 during the intervention periods with similar neuroimaging rates (80.7% versus 81.5%, = 0.8.) CT decreased from 90.1% to 34.8% (difference -55.3%, 95% confidence interval [CI]: -71.1, -25.8), and rMRI-shunt increased from 9.9% to 65.2% (difference 55.3%, 95% CI: 25.8, 71.1) during the preintervention and intervention periods, respectively. There were increases in the mean time to neuroimaging (53.1 min; [95% CI: 41.6, 64.6]) and ED length of stay (LOS) (52.3 min; [95% CI: 36.8, 67.6]), without changes in total neuroimaging, 72-hour revisits, or follow-up neuroimaging.

Conclusions: Multidisciplinary implementation of a standardized guideline reduced CT and increased rMRI-shunt use in a pediatric ED setting. Clinicians should balance the reduction in radiation exposure with ED rMRI-shunt for patients with ventricular shunts against the increased time of obtaining imaging and LOS.
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http://dx.doi.org/10.1097/pq9.0000000000000441DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8322500PMC
July 2021

Acoustomicrofluidic Synthesis of Pristine Ultrathin TiCT MXene Nanosheets and Quantum Dots.

ACS Nano 2021 Jun 29. Epub 2021 Jun 29.

Micro/Nanophysics Research Laboratory, RMIT University, Melbourne, VIC 3000, Australia.

The conversion of layered transition metal carbides and/or nitrides (MXenes) into zero-dimensional structures with thicknesses and lateral dimensions of a few nanometers allows these recently discovered materials with exceptional electronic properties to exploit the additional benefits of quantum confinement, edge effects, and large surface area. Conventional methods for the conversion of MXene nanosheets and quantum dots, however, involve extreme conditions such as high temperatures and/or harsh chemicals that, among other disadvantages, lead to significant degradation of the material as a consequence of their oxidation. Herein, we show that the large surface acceleration-on the order of 10 million 's-produced by high-frequency (10 MHz) nanometer-order electromechanical vibrations on a chip-scale piezoelectric substrate is capable of efficiently nebulizing, and consequently dimensionally reducing, a suspension of multilayer TiCT (MXene) into predominantly monolayer nanosheets and quantum dots while, importantly, preserving the material from any appreciable oxidation. As an example application, we show that the high-purity MXene quantum dots produced using this room-temperature chemical-free synthesis method exhibit superior performance as electrode materials for electrochemical sensing of hydrogen peroxide compared to the highly oxidized samples obtained through conventional hydrothermal synthesis. The ability to detect concentrations as low as 5 nM is a 10-fold improvement to the best reported performance of TiCT MXene electrochemical sensors to date.
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http://dx.doi.org/10.1021/acsnano.1c03428DOI Listing
June 2021

The world of two-dimensional carbides and nitrides (MXenes).

Science 2021 06;372(6547)

A.J. Drexel Nanomaterials Institute and Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, USA.

A decade after the first report, the family of two-dimensional (2D) carbides and nitrides (MXenes) includes structures with three, five, seven, or nine layers of atoms in an ordered or solid solution form. Dozens of MXene compositions have been produced, resulting in MXenes with mixed surface terminations. MXenes have shown useful and tunable electronic, optical, mechanical, and electrochemical properties, leading to applications ranging from optoelectronics, electromagnetic interference shielding, and wireless antennas to energy storage, catalysis, sensing, and medicine. Here we present a forward-looking review of the field of MXenes. We discuss the challenges to be addressed and outline research directions that will deepen the fundamental understanding of the properties of MXenes and enable their hybridization with other 2D materials in various emerging technologies.
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http://dx.doi.org/10.1126/science.abf1581DOI Listing
June 2021

On-surface photopolymerization of two-dimensional polymers ordered on the mesoscale.

Nat Chem 2021 Aug 3;13(8):730-736. Epub 2021 Jun 3.

Deutsches Museum, Munich, Germany.

The use of solid supports and ultra-high vacuum conditions for the synthesis of two-dimensional polymers is attractive, as it can enable thorough characterization, often with submolecular resolution, and prevent contamination. However, most on-surface polymerizations are thermally activated, which often leads to high defect densities and relatively small domain sizes. Here, we have obtained a porous two-dimensional polymer that is ordered on the mesoscale by the two-staged topochemical photopolymerization of fluorinated anthracene triptycene (fantrip) monomers on alkane-passivated graphite surfaces under ultra-high vacuum. First, the fantrip monomers self-assemble into highly ordered monolayer structures, where all anthracene moieties adopt a suitable arrangement for photopolymerization. Irradiation with violet light then induces complete covalent crosslinking by [4+4] photocycloaddition to form a two-dimensional polymer, while fully preserving the long-range order of the self-assembled structure. The extent of the polymerization is confirmed by local infrared spectroscopy and scanning tunnelling microscopy characterization, in agreement with density functional theory calculations, which also gives mechanistic insights.
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http://dx.doi.org/10.1038/s41557-021-00709-yDOI Listing
August 2021

In-plane ordered quaternaryM4/3'M2/3″AlB2phases (-MAB): electronic structure and mechanical properties from first-principles calculations.

J Phys Condens Matter 2021 May 21;33(25). Epub 2021 May 21.

Thin Films Physics, Department of Physics, Chemistry, and Biology, Linköping University, SE-581-83 Linköping, Sweden.

We have by means of first principles density functional theory calculations studied the mechanical and electronic properties of the so called-MAB phases,'″AlB, where' = Cr, Mo, W and″ = Sc, Y. These phases, experimentally verified for MoScAlBand MoYAlB, display an atomically laminated structure with in-plane chemical order between the' and″ elements. Structural properties, along with elastic constants and moduli, are predicted for different structural symmetries, including the reportedR3̄m(#166) space group. We find all considered-MAB phases to be metallic with a significant peak in the electronic structure at the Fermi level and no significant anisotropy in the electronic band structure. The simulations also indicate that they are rather hard and stiff, in particular the Cr-based ones, with a Young's modulusof 325 GPa for″ = Sc. The Mo-based phases are similar, with= 299 GPa for″ = Sc, which is higher than the corresponding laminated carbides (-MAX phases).
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http://dx.doi.org/10.1088/1361-648X/abf9bcDOI Listing
May 2021

Ultrafast, One-Step, Salt-Solution-Based Acoustic Synthesis of TiC MXene.

ACS Nano 2021 Mar 26;15(3):4287-4293. Epub 2021 Feb 26.

Department of Physics, Chemistry, and Biology (IFM) Linköping University, SE-581 83 Linköping, Sweden.

The current quest for two-dimensional transition metal carbides and nitrides (MXenes) has been to circumvent the slow, hazardous, and laborious multistep synthesis procedures associated with conventional chemical MAX phase exfoliation. Here, we demonstrate a one-step synthesis method with local TiAlC MAX to TiCT MXene conversion on the order of milliseconds, facilitated by proton production through solution dissociation under megahertz frequency acoustic excitation. These protons combined with fluorine ions from LiF to selectively etch the MAX phase into MXene, whose delamination is aided by the acoustic forcing. These results have important implications for the future applicability of MXenes, which crucially depend on the development of more efficient synthesis procedures. For proof-of-concept, we show that flexible electrodes fabricated by this method exhibit comparable electrochemical performance to that previously reported.
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http://dx.doi.org/10.1021/acsnano.0c07242DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8034768PMC
March 2021

Structure-activity correlation of TiCTMXenes for C-H activation.

J Phys Condens Matter 2021 May 10;33(23). Epub 2021 May 10.

Department of Physics, Chemistry and Biology, IFM, Linköping University, 581 83 Linköping, Sweden.

As a bourgeoning class of 2D materials, MXenes have recently attracted significant attention within heterogeneous catalysis for promoting reactions such as hydrogen evolution and C-H activation. However, the catalytic activity of MXenes is highly dependent on the structural configuration including termination groups and their distribution. Therefore, understanding the relation between the structure and the activity is desired for the rational design of MXenes as high-efficient catalysts. Here, we present that the correlation between the structure and activity of TiCT(T is a combination of O, OH and/or F) MXenes for C-H activation can be linked by a quantitative descriptor: the hydrogen affinity (). A linear correlation is observed between the mean hydrogen affinity and the overall ratio of O terminations () in TiCTMXenes, in which hydrogen affinity increases as thedecreases, regardless to the species of termination groups. In addition, the hydrogen affinity is more sensitive to the presence of OH termination than F terminations. Moreover, the linear correlation between the hydrogen affinity and the activity of TiCTMXenes for C-H activation of both -CHand -CH- groups can be extended to be valid for all three possible termination groups. Such a correlation provides fast prediction of the activity of general TiCTMXenes, avoiding tedious activation energy calculations. We anticipate that the findings have the potential to accelerate the development of MXenes for heterogeneous catalysis applications.
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http://dx.doi.org/10.1088/1361-648X/abe8a1DOI Listing
May 2021

Bioinspired multisensory neural network with crossmodal integration and recognition.

Nat Commun 2021 02 18;12(1):1120. Epub 2021 Feb 18.

NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076, Aalto, Finland.

The integration and interaction of vision, touch, hearing, smell, and taste in the human multisensory neural network facilitate high-level cognitive functionalities, such as crossmodal integration, recognition, and imagination for accurate evaluation and comprehensive understanding of the multimodal world. Here, we report a bioinspired multisensory neural network that integrates artificial optic, afferent, auditory, and simulated olfactory and gustatory sensory nerves. With distributed multiple sensors and biomimetic hierarchical architectures, our system can not only sense, process, and memorize multimodal information, but also fuse multisensory data at hardware and software level. Using crossmodal learning, the system is capable of crossmodally recognizing and imagining multimodal information, such as visualizing alphabet letters upon handwritten input, recognizing multimodal visual/smell/taste information or imagining a never-seen picture when hearing its description. Our multisensory neural network provides a promising approach towards robotic sensing and perception.
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http://dx.doi.org/10.1038/s41467-021-21404-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7893014PMC
February 2021

Flexible Free-Standing MoO/TiCT MXene Composite Films with High Gravimetric and Volumetric Capacities.

Adv Sci (Weinh) 2021 Feb 31;8(3):2003656. Epub 2020 Dec 31.

Department of Physics, Chemistry and Biology (IFM) Linköping University Linköping 581 83 Sweden.

Enhancing both the energy storage and power capabilities of electrochemical capacitors remains a challenge. Herein, TiCT MXene is mixed with MoO nanobelts in various mass ratios and the mixture is used to vacuum filter binder free, open, flexible, and free-standing films. The conductive TiCT flakes bridge the nanobelts, facilitating electron transfer; the randomly oriented, and interconnected, MoO nanobelts, in turn, prevent the restacking of the TiCT nanosheets. Benefitting from these advantages, a MoO/TiCT film with a 8:2 mass ratio exhibits high gravimetric/volumetric capacities with good cyclability, namely, 837 C g and 1836 C cm at 1 A g for an ≈ 10 µm thick film; and 767 C g and 1664 C cm at 1 A g for ≈ 50 µm thick film. To further increase the energy density, hybrid capacitors are fabricated with MoO/TiCT films as the negative electrodes and nitrogen-doped activated carbon as the positive electrodes. This device delivers maximum gravimetric/volumetric energy densities of 31.2 Wh kg and 39.2 Wh L, respectively. The cycling stability of 94.2% retention ratio after 10 000 continuous charge/discharge cycles is also noteworthy. The high energy density achieved in this work can pave the way for practical applications of MXene-containing materials in energy storage devices.
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http://dx.doi.org/10.1002/advs.202003656DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7856882PMC
February 2021

Tailored synthesis approach of (MoY)AlC i-MAX and its two-dimensional derivative MoCT MXene: enhancing the yield, quality, and performance in supercapacitor applications.

Nanoscale 2021 Jan 18;13(1):311-319. Epub 2020 Dec 18.

Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden.

A vacancy-ordered MXene, MoCT, obtained from the selective etching of Al and Sc from the parent i-MAX phase (MoSc)AlC has previously shown excellent properties for supercapacitor applications. Attempts to synthesize the same MXene from another precursor, (MoY)AlC, have not been able to match its forerunner. Herein, we show that the use of an AlY alloy instead of elemental Al and Y for the synthesis of (MoY)AlC i-MAX, results in a close to 70% increase in sample purity due to the suppression of the main secondary phase, MoAlC. Furthermore, through a modified etching procedure, we obtain a MoCT MXene of high structural quality and improve the yield by a factor of 6 compared to our previous efforts. Free-standing films show high volumetric (1308 F cm) and gravimetric (436 F g) capacitances and a high stability (98% retention) at the level of, or even beyond, those reported for the MoCT MXene produced from the Sc-based i-MAX. These results are of importance for the realization of high quality MXenes through use of more abundant elements (Y vs. Sc), while also reducing waste (impurity) material and facilitating the synthesis of a high-performance material for applications.
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http://dx.doi.org/10.1039/d0nr07045aDOI Listing
January 2021

Theoretical Prediction and Synthesis of a Family of Atomic Laminate Metal Borides with In-Plane Chemical Ordering.

J Am Chem Soc 2020 Oct 13;142(43):18583-18591. Epub 2020 Oct 13.

Thin Film Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.

All atomically laminated MAB phases (M = transition metal, A = A-group element, and B = boron) exhibit orthorhombic or tetragonal symmetry, with the only exception being hexagonal TiInB. Inspired by the recent discovery of chemically ordered hexagonal carbides, i-MAX phases, we perform an extensive first-principles study to explore chemical ordering upon metal alloying of MAlB (M from groups 3 to 9) in orthorhombic and hexagonal symmetry. Fifteen stable novel phases with in-plane chemical ordering are identified, coined i-MAB, along with 16 disordered stable alloys. The predictions are verified through the powder synthesis of MoYAlB and MoScAlB of space group 3̅ (no. 166), displaying the characteristic in-plane chemical order of Mo and Y/Sc and Kagomé ordering of the Al atoms, as evident from X-ray diffraction and electron microscopy. The discovery of i-MAB phases expands the elemental space of these borides with M = Sc, Y, Zr, Hf, and Nb, realizing an increased property tuning potential of these phases as well as their suggested potential two-dimensional derivatives.
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http://dx.doi.org/10.1021/jacs.0c08113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7596753PMC
October 2020

C-H activation of light alkanes on MXenes predicted by hydrogen affinity.

Phys Chem Chem Phys 2020 Sep 13;22(33):18622-18630. Epub 2020 Aug 13.

Department of Physics, Chemistry and Biology, IFM, Linköping University, 581 83 Linköping, Sweden.

C-H activation of light alkanes is one of the most important reactions for a plethora of applications but requires catalysts to operate at feasible conditions. MXenes, a new group of two-dimensional materials, have shown great promise as heterogeneous catalysts for several applications. However, the catalytic activity of MXenes depends on the type and distribution of termination groups. Theoretically, it is desired to search for a relation between the catalytic activity and the termination configuration by employing a simple descriptor in order to avoid tedious activation energy calculations. Here, we show that MXenes are promising for splitting C-H bonds of light alkanes. Furthermore, we present how a quantitative descriptor - the hydrogen affinity - can be used to characterize the termination configuration of TiCT (T = O, OH) MXenes, as well as the catalytic activity towards dehydrogenation reactions, using propane as model system. First-principles calculations reveal that the hydrogen affinity can be considered as an intrinsic property of O and OH terminated TiC MXenes, in which the mean hydrogen affinity for the terminated TiC MXenes is linearly correlated to the statistical average of their OH fraction. In addition, the C-H activation energies exhibit a strong scaling relationship to the hydrogen affinity. This quantity can therefore yield quick predictions of catalytic activity of terminated TiC MXenes towards C-H activations, and even predict their chemical selectivity toward scissoring different C-H bonds. We believe that the hydrogen affinity will accelerate the discovery of further applications of the broad family of MXenes in heterogeneous catalysis.
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http://dx.doi.org/10.1039/d0cp02471fDOI Listing
September 2020

Impact of strain, pressure, and electron correlation on magnetism and crystal structure of MnGaC from first-principles.

Sci Rep 2020 Jul 9;10(1):11384. Epub 2020 Jul 9.

Thin Film Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83, Linköping, Sweden.

The atomically laminated MnGaC has previously been synthesized as a heteroepitaxial thin film and found to be magnetic with structural changes linked to the magnetic anisotropy. Related theoretical studies only considered bulk conditions and thus neglected the influence from possible strain linked to the choice of substrate. Here we employ first principles calculations considering different exchange-correlation functionals (PBE, PW91, PBEsol, AM05, LDA) and effect from use of + U methods (or not) combined with a magnetic ground-state search using Heisenberg Monte Carlo simulations, to study influence from biaxial in-plane strain and external pressure on the magnetic and crystal structure of MnGaC. We find that PBE and PBE + U, with U ≤ 0.25 eV, gives both structural and magnetic properties in quantitative agreement with available experimental data. Our results also indicate that strain related to choice of substrate or applied pressure is a route for accessing different spin configurations, including a ferromagnetic state. Moreover, the easy axis is parallel to the atomic planes and the magnetocrystalline anisotropy energy can be increased through strain engineering by expanding the in-plane lattice parameter a. Altogether, we show that a quantitative description of the structural and magnetic properties of MnGaC is possible using PBE, which opens the way for further computational studies of these and related materials.
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http://dx.doi.org/10.1038/s41598-020-68377-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7347948PMC
July 2020

Composition Tuning of Nanostructured Binary Copper Selenides through Rapid Chemical Synthesis and their Thermoelectric Property Evaluation.

Nanomaterials (Basel) 2020 Apr 28;10(5). Epub 2020 Apr 28.

Department of Applied Physics, KTH Royal Institute of Technology, SE-106 91 Stockholm, Sweden.

Reduced energy consumption and environmentally friendly, abundant constituents are gaining more attention for the synthesis of energy materials. A rapid, highly scalable, and process-temperature-sensitive solution synthesis route is demonstrated for the fabrication of thermoelectric CuSe. The process relies on readily available precursors and microwave-assisted thermolysis, which is sensitive to reaction conditions; yielding CuSe at 200 °C and CuSe at 250 °C within 6-8 min reaction time. Transmission electron microscopy (TEM) revealed crystalline nature of as-made particles with irregular truncated morphology, which exhibit a high phase purity as identified by X-ray powder diffraction (XRPD) analysis. Temperature-dependent transport properties were characterized via electrical conductivity, Seebeck coefficient, and thermal diffusivity measurements. Subsequent to spark plasma sintering, pure CuSe exhibited highly compacted and oriented grains that were similar in size in comparison to CuSe, which led to its high electrical and low thermal conductivity, reaching a very high power-factor (24 µW/Kcm). Density-of-states (DOS) calculations confirm the observed trends in electronic properties of the material, where Cu-deficient phase exhibits metallic character. The TE figure of merit () was estimated for the materials, demonstrating an unprecedentedly high at 875 K of 2.1 for CuSe sample, followed by 1.9 for CuSe. Synthetic and processing methods presented in this work enable large-scale production of TE materials and components for niche applications.
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http://dx.doi.org/10.3390/nano10050854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7712069PMC
April 2020

Ultrafast assembly of swordlike Cu(1,3,5-benzenetricarboxylate) metal-organic framework crystals with exposed active metal sites.

Nanoscale Horiz 2020 Jul 23;5(7):1050-1057. Epub 2020 Apr 23.

Micro/Nanophysics Research Laboratory, School of Engineering, RMIT University, Melbourne, VIC 3000, Australia.

Owing to their large surface area and high uptake capacity, metal-organic frameworks (MOFs) have attracted considerable attention as potential materials for gas storage, energy conversion, and electrocatalysis. Various strategies have recently been proposed to manipulate the MOF surface chemistry to facilitate exposure of the embedded metal centers at the crystal surface to allow more effective binding of target molecules to these active sites. Nevertheless, such strategies remain complex, often requiring strict control over the synthesis conditions to avoid blocking pore access, reduction in crystal quality, or even collapse of the entire crystal structure. In this work, we exploit the hydrodynamics and capillary resonance associated with acoustically-driven dynamically spreading and nebulizing thin films as a new method for ultrafast synthesis of swordlike Cu(1,3,5-benzenetricarboxylate) (Cu-BTC) MOFs with unique monoclinic crystal structures (P2/n) distinct to that obtained via conventional bulk solvothermal synthesis, with 'swordlike' morphologies whose lengths far exceed their thicknesses. Through pulse modulation and taking advantage of the rapid solvent evaporation associated with the high nebulisation rates, we are also able to control the thicknesses of these large aspect ratio (width and length with respect to the thickness) crystals by arresting their vertical growth, which, in turn, allows exposure of the metal active sites at the crystal surface. An upshot of such active site exposure on the crystal surface is the concomitant enhancement in the conductivity of the MOF, evident from the improvement in its current density by two orders of magnitude.
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http://dx.doi.org/10.1039/d0nh00171fDOI Listing
July 2020

Controlled-Atmosphere Flame Fusion Single-Crystal Growth of Non-Noble fcc, hcp, and bcc Metals Using Copper, Cobalt, and Iron.

Angew Chem Int Ed Engl 2020 Aug 8;59(32):13246-13252. Epub 2020 May 8.

Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081, Ulm, Germany.

The growth of noble-metal single crystals via the flame fusion method was developed in the 1980s. Since then, there have been no major advancements to the technique until the recent development of the controlled-atmosphere flame fusion (CAFF) method to grow non-noble Ni single crystals. Herein, we demonstrate the generality of this method with the first preparation of fcc Cu as well as the first hcp and bcc single crystals of Co and Fe, respectively. The high quality of the single crystals was verified using scanning electron microscopy and Laue X-ray backscattering. Based on Wulff constructions, the equilibrium shapes of the single-crystal particles were studied, confirming the symmetry of the fcc, hcp, and bcc single-crystal lattices. The low cost of the CAFF method makes all kinds of high-quality non-noble single crystals independent of their lattice accessible for use in electrocatalysis, electrochemistry, surface science, and materials science.
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http://dx.doi.org/10.1002/anie.201915389DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496678PMC
August 2020

Tactile sensory coding and learning with bio-inspired optoelectronic spiking afferent nerves.

Nat Commun 2020 03 13;11(1):1369. Epub 2020 Mar 13.

NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076, Aalto, Finland.

The integration and cooperation of mechanoreceptors, neurons and synapses in somatosensory systems enable humans to efficiently sense and process tactile information. Inspired by biological somatosensory systems, we report an optoelectronic spiking afferent nerve with neural coding, perceptual learning and memorizing capabilities to mimic tactile sensing and processing. Our system senses pressure by MXene-based sensors, converts pressure information to light pulses by coupling light-emitting diodes to analog-to-digital circuits, then integrates light pulses using a synaptic photomemristor. With neural coding, our spiking nerve is capable of not only detecting simultaneous pressure inputs, but also recognizing Morse code, braille, and object movement. Furthermore, with dimensionality-reduced feature extraction and learning, our system can recognize and memorize handwritten alphabets and words, providing a promising approach towards e-skin, neurorobotics and human-machine interaction technologies.
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http://dx.doi.org/10.1038/s41467-020-15105-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7070032PMC
March 2020

Interrater Reliability of the New Sport-Specific Evidence-Based Classification System for Para Va'a.

Adapt Phys Activ Q 2020 Mar 6;37(3):241-252. Epub 2020 Mar 6.

The Swedish School of Sport and Health Sciences (GIH).

The purpose of this study was to examine the interrater reliability of a new evidence-based classification system for Para Va'a. Twelve Para Va'a athletes were classified by three classifier teams each consisting of a medical and a technical classifier. Interrater reliability was assessed by calculating intraclass correlation for the overall class allocation and total scores of trunk, leg, and on-water test batteries and by calculating Fleiss's kappa and percentage of total agreement in the individual tests of each test battery. All classifier teams agreed with the overall class allocation of all athletes, and all three test batteries exhibited excellent interrater reliability. At a test level, agreement between classifiers was almost perfect in 14 tests, substantial in four tests, moderate in four tests, and fair in one test. The results suggest that a Para Va'a athlete can expect to be allocated to the same class regardless of which classifier team conducts the classification.
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http://dx.doi.org/10.1123/apaq.2019-0141DOI Listing
March 2020

Utility of ECGs in the pediatric emergency department for patients presenting with a seizure.

Am J Emerg Med 2020 07 20;38(7):1362-1366. Epub 2019 Nov 20.

UPMC Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States. Electronic address:

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http://dx.doi.org/10.1016/j.ajem.2019.11.016DOI Listing
July 2020

Predictive theoretical screening of phase stability for chemical order and disorder in quaternary 312 and 413 MAX phases.

Nanoscale 2020 Jan;12(2):785-794

Thin Film Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.

In this work we systematically explore a class of atomically laminated materials, Mn+1AXn (MAX) phases upon alloying between two transition metals, M' and M'', from groups III to VI (Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W). The materials investigated focus on so called o-MAX phases with out-of-plane chemical ordering of M' and M'', and their disordered counterparts, for A = Al and X = C. Through use of predictive phase stability calculations, we confirm all experimentally known phases to date, and also suggest a range of stable ordered and disordered hypothetical elemental combinations. Ordered o-MAX is favoured when (i) M' next to the Al-layer does not form a corresponding binary rock-salt MC structure, (ii) the size difference between M' and M'' is small, and (iii) the difference in electronegativity between M' and Al is large. Preference for chemical disorder is favoured when the size and electronegativity of M' and M'' is similar, in combination with a minor difference in electronegativity of M' and Al. We also propose guidelines to use in the search for novel o-MAX; to combine M' from group 6 (Cr, Mo, W) with M'' from groups 3 to 5 (Sc only for 312, Ti, Zr, Hf, V, Nb, Ta). Correspondingly, we suggest formation of disordered MAX phases by combing M' and M'' within groups 3 to 5 (Sc, Ti, Zr, Hf, V, Nb, Ta). The addition of novel elemental combinations in MAX phases, and in turn in their potential two-dimensional MXene derivatives, allow for property tuning of functional materials.
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http://dx.doi.org/10.1039/c9nr08675gDOI Listing
January 2020

Flexible Freestanding MoO -Carbon Nanotubes-Nanocellulose Paper Electrodes for Charge-Storage Applications.

ChemSusChem 2019 Dec 8;12(23):5157-5163. Epub 2019 Nov 8.

Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183, Linköping, Sweden.

Herein, a one-step synthesis protocol was developed for synthesizing freestanding/flexible paper electrodes composed of nanostructured molybdenum oxide (MoO ) embedded in a carbon nanotube (CNT) and Cladophora cellulose (CC) matrix. The preparation method involved sonication of the precursors, nanostructured MoO , CNTs, and CC with weight ratios of 7:2:1, in a water/ethanol mixture, followed by vacuum filtration. The electrodes were straightforward to handle and possessed a thickness of approximately 12 μm and a mass loading of MoO -CNTs of approximately 0.9 mg cm . The elemental mapping showed that the nanostructured MoO was uniformly embedded inside the CNTs-CC matrix. The MoO -CNTs-CC paper electrodes featured a capacity of 30 C g , normalized to the mass of MoO -CNTs, at a current density of 78 A g (corresponding to a rate of approximately 210 C based on the MoO content, assuming a theoretical capacity of 1339 C g ), and exhibited a capacity retention of 91 % over 30 000 cycles. This study paves the way for the manufacturing of flexible/freestanding nanostructured MoO -based electrodes for use in charge-storage devices at high charge/discharge rates.
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http://dx.doi.org/10.1002/cssc.201902394DOI Listing
December 2019

Synthesis of (VSc)AlC i-MAX phase and VC MXene scrolls.

Nanoscale 2019 Aug;11(31):14720-14726

Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.

We report the synthesis and characterization of a new laminated i-MAX phase, (V2/3Sc1/3)2AlC, with in-plane chemical ordering between the M-elements. We also present evidence for the solid solution (V2-xScx)2AlC, where x ≤ 0.05. Chemical etching of the Al and Sc results in a two-dimensional (2D) MXene counterpart: V2-xC from the latter phase. Furthermore, etching with HF yields single-sheet MXene of flat morphology, while LiF + HCl gives MXene scrolls. We also show a 4× reduction in etching time for (V2-xScx)2AlC compared to V2AlC, suggesting that traces of Sc changes the phase stability, and make the material more susceptible to etching. The results show a path for improved control of MXene synthesis and morphology, which may be applicable also for other MAX/MXene systems.
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http://dx.doi.org/10.1039/c9nr02354bDOI Listing
August 2019

The impact of impairment on kinematic and kinetic variables in Va'a paddling: Towards a sport-specific evidence-based classification system for Para Va'a.

J Sports Sci 2019 Sep 22;37(17):1942-1950. Epub 2019 Apr 22.

a Department of Sport and Health Sciences , The Swedish School of Sport and Health Sciences (GIH) , Stockholm , Sweden.

Para Va'a is a new Paralympic sport in which athletes with trunk and/or leg impairment compete over 200 m. The purpose of this study was to examine the impact of impairment on kinematic and kinetic variables during Va'a ergometer paddling. Ten able-bodied and 44 Para Va'a athletes with impairments affecting: trunk and legs (TL), legs bilaterally (BL) or leg unilaterally (UL) participated. Differences in stroke frequency, mean paddling force, and joint angles and correlation of the joint angles with paddling force were examined. Able-bodied demonstrated significantly greater paddling force as well as knee and ankle flexion ranges of movement (ROM) on the top hand paddling side compared to TL, BL and UL. Able-bodied, BL and UL demonstrated greater paddling force and trunk flexion compared to TL, and UL demonstrated larger bottom hand paddling side knee and ankle flexion ROM compared to BL. Significant positive correlations were observed for both male and female athletes between paddling force and all trunk flexion angles and ROM in the trunk and pelvis rotation and bottom hand paddling side hip, knee and ankle flexion. The results of this study are important for creating an evidence-based classification system for Para Va'a.
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http://dx.doi.org/10.1080/02640414.2019.1606763DOI Listing
September 2019

Element Replacement Approach by Reaction with Lewis Acidic Molten Salts to Synthesize Nanolaminated MAX Phases and MXenes.

J Am Chem Soc 2019 Mar 7;141(11):4730-4737. Epub 2019 Mar 7.

Engineering Laboratory of Advanced Energy Materials , Ningbo Institute of Industrial Technology, Chinese Academy of Sciences , Ningbo , Zhejiang 315201 , China.

Nanolaminated materials are important because of their exceptional properties and wide range of applications. Here, we demonstrate a general approach to synthesizing a series of Zn-based MAX phases and Cl-terminated MXenes originating from the replacement reaction between the MAX phase and the late transition-metal halides. The approach is a top-down route that enables the late transitional element atom (Zn in the present case) to occupy the A site in the pre-existing MAX phase structure. Using this replacement reaction between the Zn element from molten ZnCl and the Al element in MAX phase precursors (TiAlC, TiAlC, TiAlN, and VAlC), novel MAX phases TiZnC, TiZnC, TiZnN, and VZnC were synthesized. When employing excess ZnCl, Cl-terminated MXenes (such as TiCCl and TiCCl) were derived by a subsequent exfoliation of TiZnC and TiZnC due to the strong Lewis acidity of molten ZnCl. These results indicate that A-site element replacement in traditional MAX phases by late transition-metal halides opens the door to explore MAX phases that are not thermodynamically stable at high temperature and would be difficult to synthesize through the commonly employed powder metallurgy approach. In addition, this is the first time that exclusively Cl-terminated MXenes were obtained, and the etching effect of Lewis acid in molten salts provides a green and viable route to preparing MXenes through an HF-free chemical approach.
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http://dx.doi.org/10.1021/jacs.9b00574DOI Listing
March 2019

On-Surface Synthesis of Ethynylene-Bridged Anthracene Polymers.

Angew Chem Int Ed Engl 2019 May 12;58(20):6559-6563. Epub 2019 Mar 12.

IMDEA Nanociencia, C/ Faraday 9, Ciudad Universitaria de Cantoblanco, 28049, Madrid, Spain.

Engineering low-band-gap π-conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on-surface synthesis protocol to overcome such difficulties and produce poly(p-anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr moieties is deposited and annealed to 400 K, resulting in anthracene-based polymers. High-resolution nc-AFM measurements confirm the nature of the ethynylene-bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface-stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design π-conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on-surface synthesis.
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http://dx.doi.org/10.1002/anie.201814154DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563096PMC
May 2019

Electronic and optical characterization of 2D TiC and NbC (MXene) thin films.

J Phys Condens Matter 2019 Apr 22;31(16):165301. Epub 2019 Jan 22.

Department of Physics, Chemistry and Biology (IFM), Thin Film Physics Division, Linköping University, SE-58183 Linköping, Sweden.

Two-dimensional (2D) transition metal carbides and/or nitrides (MXenes) are a new class of 2D materials, with extensive opportunities for property tailoring due to the numerous possibilities for varying chemistries and surface terminations. Here, TiAlC and NbAlC MAX phase epitaxial thin films were deposited on sapphire substrates by physical vapor deposition. The films were then etched in LiF/HCl solutions, yielding Li-intercalated, 2D TiCT and NbCT films, whose terminations, transport and optical properties were characterized. The former exhibits metallic conductivity, with weak localization below 50 K. In contrast, the Nb-based film exhibits an increase in resistivity with decreasing temperature from RT down to 40 K consistent with variable range hopping transport. The optical properties of both films were determined from spectroscopic ellipsometry in the 0.75 to 3.50 eV range. The results for TiCT films confirm the metallic behavior. In contrast, no evidence of metallic behavior is observed for the NbCT film. The present work therefore demonstrates that one fruitful approach to alter the electronic and optical properties of MXenes is to change the nature of the transition metal.
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http://dx.doi.org/10.1088/1361-648X/ab00a2DOI Listing
April 2019

A Tungsten-Based Nanolaminated Ternary Carbide: (W,Ti)C.

Inorg Chem 2019 Jan 4;58(2):1100-1106. Epub 2019 Jan 4.

Department of Materials Science and Engineering , Drexel University , Philadelphia , Pennsylvania 19104 , United States.

Nanolamellar transition metal carbides are gaining increasing interests because of the recent developments of their two-dimensional (2D) derivatives and promising performance for a variety of applications from energy storage, catalysis to transparent conductive coatings, and medicine. To develop more novel 2D materials, new nanolaminated structures are needed. Here we report on a tungsten-based nanolaminated ternary phase, (W,Ti)C, synthesized by an Al-catalyzed reaction of W, Ti, and C powders at 1600 °C for 4 h, under flowing argon. X-ray and neutron diffraction, along with Z-contrast scanning transmission electron microscopy, were used to determine the atomic structure, ordering, and occupancies. This phase has a layered hexagonal structure ( P6 /mmc) with lattice parameters, a = 3.00880(7) Å, and c = 19.5633(6) Å and a nominal chemistry of (W,Ti)C (actual chemistry, WTiC). The structure is comprised of layers of pure W that are also twin planes with two adjacent atomic layers of mixed W and Ti, on either side. The use of Al as a catalyst for synthesizing otherwise difficult to make phases, could in turn lead to the discovery of a large family of nonstoichiometric ternary transition metal carbides, synthesized at relatively low temperatures and shorter times.
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http://dx.doi.org/10.1021/acs.inorgchem.8b02226DOI Listing
January 2019

2D Transition Metal Carbides (MXenes) for Carbon Capture.

Adv Mater 2019 Jan 4;31(2):e1805472. Epub 2018 Nov 4.

Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83, Linköping, Sweden.

Global warming caused by burning of fossil fuels is indisputably one of mankind's greatest challenges in the 21st century. To reduce the ever-increasing CO emissions released into the atmosphere, dry solid adsorbents with large surface-to-volume ratio such as carbonaceous materials, zeolites, and metal-organic frameworks have emerged as promising material candidates for capturing CO . However, challenges remain because of limited CO /N selectivity and long-term stability. The effective adsorption of CO gas (≈12 mol kg ) on individual sheets of 2D transition metal carbides (referred to as MXenes) is reported here. It is shown that exposure to N gas results in no adsorption, consistent with first-principles calculations. The adsorption efficiency combined with the CO /N selectivity, together with a chemical and thermal stability, identifies the archetype Ti C MXene as a new material for carbon capture (CC) applications.
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http://dx.doi.org/10.1002/adma.201805472DOI Listing
January 2019
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