Search Our Scientific Publications & Authors

Small 2019 Apr 24:e1900837. Epub 2019 Apr 24.

Laboratory of Advanced Materials, Department of Materials Science, Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200438, P. R. China.

Interfaces in semiconductor heterostructures is of continuously greater significance in the trend of scaling materials down to the atomic limit. Since atoms tend to behave more irregularly around interfaces than in internal materials, accurate energy band alignment becomes a major challenge, which determines the ultimate performance of devices. Therefore, a comprehensive understanding of the interplay between heterointerface, energy band, and macro-performance is desiderated. Read More

Small 2019 Apr 24:e1900131. Epub 2019 Apr 24.

Department of Materials Science and Engineering, National University of Singapore, Singapore, 117574, Singapore.

Transition metal dichalcogenides exhibit several different phases (e.g., semiconducting 2H, metallic 1T, 1T') arising from the collective and sluggish atomic displacements rooted in the charge-lattice interaction. Read More

J Chem Theory Comput 2019 Apr 24. Epub 2019 Apr 24.

In this work, we have examined the molecular mechanisms of allosteric regulation of the ABL tyrosine kinase at the atomic level. Atomistic modeling of the ABL complexes with a panel of allosteric modulators has been performed using a combination of molecular dynamics simulations, structural residue perturbation scanning and a novel community analysis of the residue interaction networks. Our results have indicated that allosteric inhibitors and activators may exert a differential control on allosteric signaling between the kinase binding sites and functional regions. Read More

J Am Chem Soc 2019 Apr 24. Epub 2019 Apr 24.

Center for Electrochemistry, Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States.

We report the catalytic activity of a single, isolated Pt deposit on Bi and Pb supports to probe the size and substrate effects on the electrochemical hydrogen evolution reaction (HER). Deposits were made electrolytically by an atom-by-atom method in a controlled plating; we prepared an individual Pt deposit on Bi and Pb ultramicroelectrodes (UMEs) such as a single isolated atom, clusters containing one to five Pt atoms, and nanoparticles to about 10 nm radius. A steady-state voltammogram on the single Pt deposits is observed by electrocatalytic amplification of the HER, with a negligible contribution by the HER at the substrate UME. Read More

J Am Chem Soc 2019 Apr 22. Epub 2019 Apr 22.

A major challenge which prohibits the practical application of single/double-transition metal (3d-M) oxides as oxygen evolution reaction (OER) catalysts is the high overpotentials during the electrochemical process. Herein, our theoretical calculation shows that Fe will be more energetically favorable in the tetrahedral site than Ni and Co, which can further regulate their electronic structure of binary NiCo spinel oxides for optimal adsorption energies of OER intermediates and improved electronic conductivity, and hence boost their OER performance. X-ray absorption spectroscopy study on the as-synthesized NiCoFe oxide catalysts indicates that Fe preferentially dopes into tetrahedral sites of the lattice, which induces high proportions of Ni and Co on the octahedral sites (the active sites in OER). Read More

Nanoscale 2019 Apr 24. Epub 2019 Apr 24.

Department of Materials Science and Engineering and Canadian Centre for Electron Microscopy, McMaster University, Main Street West, Hamilton, Ontario L8S 4M1, Canada.

Ternary III-nitride-based nanowires with highly efficient light-emitting properties are essential for a broad range of applications. By using the selective area molecular-beam epitaxy method, InGaN/AlGaN quantum disks (QDs) embedded in hexagonal GaN nanowires were successfully grown. With the help of atomic-scale-resolved transmission electron microscopy and atom probe tomography, atomic ordering and other related structural information, such as crystallography and local chemistry, have been unambiguously revealed to provide unique insights into the exceptionally strong photoluminescence enhancements. Read More

Nanoscale 2019 Apr 24. Epub 2019 Apr 24.

Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.

This paper reports on plastic recovery and self-healing behavior in longitudinally-twinned and [112] orientated SiGe nanowire (NW) beams when they are subjected to large bending strains. The NW alloys are comprised of lamellar nanotwin platelet(s) sandwiched between two semi-cylindrical twins. The loading curves, which are acquired from atomic force microscope (AFM) based three-point bending tests, reveal the onset of plastic deformation at a characteristic stress threshold, followed by further straining of the NWs. Read More

Nanoscale 2019 Apr 24. Epub 2019 Apr 24.

The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.

We investigated a nanogap between a pair of palladium electrode tips with gas (nitrogen, hydrogen, and oxygen) and a biasing voltage using in situ atomic resolution environmental transmission electron microscopy (ETEM). We found an unexpected gas-solid (nitrogen-palladium) reaction that occurs on the surface of the positive electrode tip. A palladium nitride compound was synthesized with gaseous nitrogen at low pressure at room temperature. Read More

Phys Chem Chem Phys 2019 Apr 24. Epub 2019 Apr 24.

Department of Electronics Engineering and Computer Science, Fukuoka University, Fukuoka 814-0180, Japan.

Realization of future hybrid electronic devices combining organic and inorganic semiconductors requires a well-defined interface between both components. Such an interface can be formed generally by self-ordering of organic molecules on inorganic substrates, which is usually hindered by strong covalent bonds to the semiconductor surface. In this paper, the 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecules were unexpectedly found to form a locally self-ordered monolayer on a strongly interacting semiconductor surface of the Ge(001). Read More

Nanoscale 2019 Apr 24. Epub 2019 Apr 24.

Department of Civil and Environmental Engineering, The George Washington University, Washington, DC 20052, USA.

Biofilms are a cluster of bacteria embedded in extracellular polymeric substances (EPS) that contain a complex composition of polysaccharides, proteins, and extracellular DNA (eDNA). Desirable mechanical properties of the biofilms are critical for their survival, propagation, and dispersal, and the response of mechanical properties to different treatment conditions also sheds light on biofilm control and eradication in vivo and on engineering surfaces. However, it is challenging yet important to investigate mechanical behaviors of biofilms with a high spatial resolution because biofilms are very heterogeneous. Read More

Sheng Wu Yi Xue Gong Cheng Xue Za Zhi 2019 Apr;36(2):260-266

School of Chemical and Pharmaceutical Engineering, Huanghuai University, Zhumadian, Henan 463000, P.R.China.

A diblock copolymer, poly(ethylene glycol) methacrylate-block-glycidyl methacrylate (PEGMA-GMA), was prepared on glass substrate by surface-initiated atom transfer radical polymerization (SI-ATRP), and endothelial specific peptide Arg-Glu-Asp-Val (REDV) was immobilized at the end of the PEGMA-GMA polymer brush by ring opening reaction through the rich epoxy groups in the GMA. The structure and hydrophilicity of the polymer brushes were characterized by static water contact angle, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results showed that the REDV modified copolymer brushes were successfully constructed on the glass substrates. Read More

Chembiochem 2019 Apr 23. Epub 2019 Apr 23.

Academia Sinica, Institute of Atomic and Molecular Sciences, No.1, Sec. 4, Roosevelt, Rd., 10617, Taipei, TAIWAN.

Glycans have diverse functions and play vital roles in many biological systems such as influenza, vaccines, and cancer biomarkers. However, fully structural identification of glycans remains challenging. Glycan structure was conventionally determined by chemical methods or nuclear magnetic resonance spectroscopy which require a large amount of sample and are not readily applicable for glycans extracted from biological samples. Read More

J Am Soc Mass Spectrom 2019 Apr 16. Epub 2019 Apr 16.

Department of Chemistry, University of Utah, Salt Lake City, UT, 84112-0850, USA.

The reaction of atomic thorium cations with deuterated water as a function of kinetic energy from thermal to 10 eV was studied using guided ion beam tandem mass spectrometry. At thermal energies, both ThO + D and DThO + D are formed in barrierless exothermic processes and reproduce results in the literature obtained using ion cyclotron resonance mass spectrometry. As the energy is increased, the branching ratio between these two channels changes such that the dominant product changes from ThO to DThO and back to ThO, until ThD + OD is energetically available and is the dominant product channel. Read More

Faraday Discuss 2019 Apr 24. Epub 2019 Apr 24.

NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thompson Avenue, Cambridge, CB3 0HE, UK.

Hot electron photochemistry has made strong claims for improved control of chemical reactions. Here I discuss these claims in the light of a plethora of model experiments and theories, asking what are the key issues to solve. I particularly highlight the need to understand nanoscale thermal hot-spots, thermal gradients, and thermal transport, as well as the conventional optical confinement in plasmonics. Read More

Adv Sci (Weinh) 2019 Apr 30;6(8):1802131. Epub 2019 Jan 30.

Nanostructured Materials Group Department of Advanced Electron Microscopy Imaging and Spectroscopy International Iberian Nanotechnology Laboratory (INL) Avenida Mestre Jose Veiga Braga 4715-330 Portugal.

Uncovering kinetics of sublimation atomically is critical to understanding both natural phenomena and advanced manufacturing technologies. Here, direct in situ atomic-scale observations to understand the effects of size, surface, and defects in the sublimation process of supported silver nanoparticles upon heating within an aberration-corrected transmission electron microscopy are conducted. Atomic-scale evidence to sublimation and atomic rearrangement in small Ag nanoparticles during heating is provided, and it is demonstrated that the sublimation-induced stable surfaces in the particles with a size smaller than ≈30 nm are {111} and {100} planes. Read More

Adv Sci (Weinh) 2019 Apr 19;6(8):1802104. Epub 2019 Feb 19.

Biotechnology Center Center for Molecular and Cellular Bioengineering TU Dresden Tatzberg 47-49 01307 Dresden Germany.

Human bone marrow mesenchymal stromal cells (MSCs) are used in clinical trials for the treatment of systemic inflammatory diseases due to their regenerative and immunomodulatory properties. However, intravenous administration of MSCs is hampered by cell trapping within the pulmonary capillary networks. Here, it is hypothesized that traditional 2D plastic-adherent cell expansion fails to result in appropriate morphorheological properties required for successful cell circulation. Read More

Chem Sci 2019 Apr 21;10(14):4038-4047. Epub 2019 Feb 21.

Instituto de Ciencia Molecular , Universitat de València , Catedrático José Beltrán 2 , 46980 Paterna , Spain . Email: ; Email: ; Email:

Mastering the nanostructuration of molecular materials onto solid surfaces and understanding how this process affects their properties are of utmost importance for their integration into solid-state electronic devices. This is even more important for spin crossover (SCO) systems, in which the spin transition is extremely sensitive to size reduction effects. These bi-stable materials have great potential for the development of nanotechnological applications provided their intrinsic properties can be successfully implemented in nanometric films, amenable to the fabrication of functional nanodevices. Read More

Chem Sci 2019 Apr 27;10(14):3976-3986. Epub 2019 Feb 27.

Biophysics and Department of Chemistry , University of Michigan , Ann Arbor , MI 48109-1055 , USA . Email:

In humans, β-amyloid and islet amyloid polypeptide (IAPP, also known as amylin) aggregations are linked to Alzheimer's disease and type-2 diabetes, respectively. There is significant interest in better understanding the aggregation process by using chemical tools. Here, we show the ability of a cationic polymethacrylate-copolymer (PMAQA) to quickly induce a β-hairpin structure and accelerate the formation of amorphous aggregates of β-amyloid-1-40, whereas it constrains the conformational plasticity of amylin for several days and slows down its aggregation at substoichiometric polymer concentrations. Read More

Sci Rep 2019 Apr 23;9(1):6465. Epub 2019 Apr 23.

Institut für Nanostruktur- und Festkörperphysik, Center for Free Electron Laser Science (CFEL), Universität Hamburg, Luruper Chaussee 149, 22761, Hamburg, Germany.

We investigated the fabrication and functional behaviour of conductive silver-nanowire-polymer composites for prospective use in printing applications. Silver-nanowires with an aspect ratio of up to 1000 were synthesized using the polyol route and embedded in a UV-curable and printable polymer matrix. Sheet resistances in the composites down to 13 Ω/sq at an optical transmission of about 90% were accomplished. Read More

Sci Rep 2019 Apr 23;9(1):6409. Epub 2019 Apr 23.

University of Bordeaux, CNRS UMR 5295, I2M, F-33400, Talence, France.

Cell morphological analysis has long been used in cell biology and physiology for abnormality identification, early cancer detection, and dynamic change analysis under specific environmental stresses. This work reports on the remote mapping of cell 3D morphology with an in-plane resolution limited by optics and an out-of-plane accuracy down to a tenth of the optical wavelength. For this, GHz coherent acoustic phonons and their resonance harmonics were tracked by means of an ultrafast opto-acoustic technique. Read More

Nat Commun 2019 Apr 23;10(1):1831. Epub 2019 Apr 23.

School of Physics, Georgia Institute of Technology, 837 State St, Atlanta, GA, 30332, USA.

Micro- and increasingly, nano-fabrication have enabled the miniaturization of atomic devices, from vapor cells to atom chips for Bose-Einstein condensation. Here we present microfabricated planar devices for thermal atomic beams. Etched microchannels were used to create highly collimated, continuous rubidium atom beams traveling parallel to a silicon wafer surface. Read More

Nat Commun 2019 Apr 23;10(1):1820. Epub 2019 Apr 23.

Department of Physics and Astronomy, MSN 3F3, George Mason University, Fairfax, VA, 22030, USA.

Tetradymite-structured chalcogenides such as bismuth telluride (BiTe) are of significant interest for thermoelectric energy conversion and as topological insulators. Dislocations play a critical role during synthesis and processing of such materials and can strongly affect their functional properties. The dislocations between quintuple layers present special interest since their core structure is controlled by the van der Waals interactions between the layers. Read More

Nat Commun 2019 Apr 23;10(1):1875. Epub 2019 Apr 23.

Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.

Converting carbon dioxide (CO) into liquid fuels and synthesis gas is a world-wide priority. But there is no experimental information on the initial atomic level events for CO electroreduction on the metal catalysts to provide the basis for developing improved catalysts. Here we combine ambient pressure X-ray photoelectron spectroscopy with quantum mechanics to examine the processes as Ag is exposed to CO both alone and in the presence of HO at 298 K. Read More

Nat Commun 2019 Apr 23;10(1):1825. Epub 2019 Apr 23.

Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO, 80309, USA.

Achieving and exceeding diversity of colloidal analogs of chemical elements and molecules as building blocks of matter has been the central goal and challenge of colloidal science ever since Einstein introduced the colloidal atom paradigm. Recent advances in colloids assembly have been achieved by exploiting the machinery of DNA hybridization but robust physical means of defining colloidal elements remain limited. Here we introduce physical design principles allowing us to define high-order elastic multipoles emerging when colloids with controlled shapes and surface alignment are introduced into a nematic host fluid. Read More

Radiother Oncol 2019 Mar 20;135:120-129. Epub 2019 Mar 20.

UK S-H, Campus Kiel, Klinik für Strahlentherapie (Radioonkologie), Kiel, Germany.

Prostate brachytherapy treatment using permanent implantation of low-energy (LE) low-dose rate (LDR) sources is successfully and widely applied in Europe. In addition, seeds are used in other tumour sites, such as ophthalmic tumours, implanted temporarily. The calibration issues for LE-LDR photon emitting sources are specific and different from other sources used in brachytherapy. Read More

Nanomaterials (Basel) 2019 Apr 12;9(4). Epub 2019 Apr 12.

University of Trento, Department of Civil, Environmental and Mechanical Engineering, via Mesiano 77, 38123 Trento, Italy.

The atomic disorder and the vibrational properties of Pd nanocubes have been studied through a combined use of X-ray diffraction and molecular dynamics simulations. The latter show that the trend of the mean square relative displacement as a function of the radius of the coordination shells is characteristic of the nanoparticle shape and can be described by a combined model: A correlated Debye model for the thermal displacement and a parametric expression for the static disorder. This combined model, supplemented by results of line profile analysis of the diffraction patterns collected at different temperatures (100, 200, and 300 K) can explain the observed increase in the Debye-Waller coefficient, and shed light on the effect of the finite domain size and of the atomic disorder on the vibrational properties of metal nanocrystals. Read More

Sensors (Basel) 2019 Apr 12;19(8). Epub 2019 Apr 12.

Nuclear Materials Research Division, Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 34057, Korea.

Pipe wall thinning and leakage due to flow accelerated corrosion (FAC) are important safety concerns for nuclear power plants. A shear horizontal ultrasonic pitch/catch technique was developed for the accurate monitoring of the pipe wall-thickness. A solid couplant should be used to ensure high quality ultrasonic signals for a long operation time at an elevated temperature. Read More

Polymers (Basel) 2019 Apr 12;11(4). Epub 2019 Apr 12.

Biobased Colloids and Materials, Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Espoo P.O. Box 11000, Finland.

Forestry industries in Chile are facing an important challenge-diversifying their products using green technologies. In this study, the potential use of Ionic Liquids (ILs) to dissolve and hydrolyze eucalyptus wood (mix of and ) kraft pulp was studied. The Bleached Hardwood Kraft Pulp (BHKP) from a Chilean pulp mill was used together with five different ILs: 1-butyl-3-methylimidazolium chloride [bmim][Cl], 1-butyl-3-methylimidazolium acetate [bmim][Ac], 1-butyl-3-methylimidazolium hydrogen sulfate [bmim][HSO], 1-ethyl-3-methylimidazolium chloride [emim][Cl], 1-ethyl-3-methylimidazolium acetate [emim][Ac]. Read More

Nanomaterials (Basel) 2019 Apr 12;9(4). Epub 2019 Apr 12.

Department of Pharmacy, University "G. d'Annunzio", Via dei Vestini, 66100 Chieti, Italy.

(1) Background: The aim of this study was to optimize, through a cheap and facile protocol, the covalent functionalization of graphene oxide (GO)-decorated cortical membrane (Lamina) in order to promote the adhesion, the growth and the osteogenic differentiation of DPSCs (Dental Pulp Stem Cells); (2) Methods: GO-coated Laminas were fully characterized by Scannsion Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses. In vitro analyses of viability, membrane integrity and calcium phosphate deposition were performed; (3) Results: The GO-decorated Laminas demonstrated an increase in the roughness of Laminas, a reduction in toxicity and did not affect membrane integrity of DPSCs; and (4) Conclusions: The GO covalent functionalization of Laminas was effective and relatively easy to obtain. The homogeneous GO coating obtained favored the proliferation rate of DPSCs and the deposition of calcium phosphate. Read More

Materials (Basel) 2019 Apr 22;12(8). Epub 2019 Apr 22.

Nano and Heterogeneous Material Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.

Twinning structures and their interfacial segregation play a key role in strengthening of magnesium alloys. Micro-steps are frequently existed in the incoherent twin boundaries, while the effect of them on interface and interfacial segregation is still not clear. In this work, we performed an atomic-scale microstructure analysis using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) to explore the effect of micro-steps on twin and its interfacial segregation in Mg-Ag alloy. Read More

Iran J Pharm Res 2018 ;17(Suppl2):87-97

Department of Pharmaceutical Biotechnology, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Production of nanoparticles has been attractive by biological based fabrication as an alternative to physical and chemical approaches due to exceeding need to develop safe, reliable, clean and eco-friendly methods for the preparation of nanoparticle for pharmaceutical and biomedical applications. In the present study, biogenic tellurium nanoparticles (TeNPs) were successfully prepared using potassium tellurite (KTeO, 3HO) via an eco-friendly and simple green approach by exploiting extracellular enzymes and biomolecules secreted from PTCC 5031 at room temperature for the first time. The biofabricated TeNPs were characterized by Atomic Force Microscope (AFM), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), Energy Dispersive X-ray spectroscopy (EDX), and Fourier Transform Infrared (FT-IR) spectrum. Read More

J Phys Condens Matter 2019 Apr 23. Epub 2019 Apr 23.

Department of Energy Conversion and Storage, Danmarks Tekniske Universitet, Fysikvej, Building 309, Lyngby, 2800, DENMARK.

Materials exhibiting a substitutional disorder such as multicomponent alloys and mixed metal oxides/oxyfluorides are of great importance in many scientific and technological sectors. Disordered materials constitute an overwhelmingly large configurational space, which makes it practically impossible to be explored manually using first-principles calculations such as density functional theory (DFT) due to the high computational costs. Consequently, the use of methods such as cluster expansion (CE) is vital in enhancing our understanding of the disordered materials. Read More

Nanotechnology 2019 Apr 23. Epub 2019 Apr 23.

School of Chemistry Physics and Mechanical Engineering and Institute for Future Environments, Queensland University of Technology Faculty of Science and Engineering, Brisbane, Queensland, AUSTRALIA.

Recent advances in helium ion microscopy (HIM) have enabled the use of fine-focused He+ beams to image and shape materials at the nanoscale. In addition to traditional ion milling, the beam can also be used to induce reactions, such as cross-linking, in films of organic molecules. Here, we compare the use of focused ion and electron beams to fabricate spatially-defined cross-linked features in nanometre-thick films of tetracene. Read More

ACS Appl Mater Interfaces 2019 Apr 23. Epub 2019 Apr 23.

As high capacity cathodes, O3-type Na-based oxides always suffer from a series of monoclinic transitions upon sodiation/desodiation, mainly caused by Na/vacancy ordering and Jahn-Teller distortion, leading to rapid structural degradation and serious performance fading. Herein, a simple modulation strategy is proposed to address this issue based on refrainment of electron localization in expectation to alleviate the charge ordering and change of electronic structure, which always lead to Na/vacancy ordering and Jahn-Teller distortion respectively. According to density functional theory calculations, Fe with slightly larger radius is introduced into NaNiMnO with the intention of enlarging transition metal layers and facilitating electronic delocalization. Read More

J Phys Chem B 2019 Apr 23. Epub 2019 Apr 23.

Triosephosphate isomerase (TIM) catalyzes the interconversion between dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde 3-phosphate (GAP), via an enediol(ate) intermediate. The active site residue Glu165 serves as the catalytic base during catalysis. It abstracts a proton from C1 carbon of DHAP to form reaction intermediate and donates a proton to C2 carbon of the intermediate to form product GAP. Read More

Inorg Chem 2019 Apr 23. Epub 2019 Apr 23.

Center for Materials Crystallography, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry , Aarhus University , Langelandsgade 140 , 8000 Aarhus C , Denmark.

Synthesis, crystal structures, and thermal and magnetic properties of the complete series of halide-free rare-earth (RE) metal borohydrides are presented. A new synthesis method provides high yield and high purity products. Fifteen new metal borohydride structures are reported. Read More

ACS Nano 2019 Apr 23. Epub 2019 Apr 23.

A convenient covalent functionalization approach and nanopatterning method of graphite and graphene is developed. In contrast to expectations, electrochemically activated dediazotization of a mixture of two aryl diazonium compounds in aqueous media leads to a spatially inhomogeneous functionalization of graphitic surfaces, creating covalently modified surfaces with quasi-uniform spaced islands of pristine graphite or graphene, coined nanocorrals. Cyclic voltammetry (CV) and chronoamperometry (CA) approaches are compared. Read More

ACS Appl Mater Interfaces 2019 Apr 23. Epub 2019 Apr 23.

Photo atomic layer etching (photo-ALE) of GaAs and AlGaAs semiconductors was investigated in deionized H2O and aqueous solution of NH4OH under weak excitation conditions (P  20 mW/cm2). The process is based on digital photocorrosion in a processed solution and a negligible corrosion during the light-off phase employed for dissolution of the photocorrosion products. An inductively-coupled plasma mass spectroscopy (ICP-MS) analysis revealed that photo-ALE of GaAs in an aqueous solution of NH4OH proceeds linearly with the number of reaction cycles, typically at ~ 0. Read More

Phys Rev Lett 2019 Jan;122(1):016102

Department of Applied Physics, Sookmyung Women's University, Seoul 04310, Korea.

Recent studies on a quasi-one-dimensional (quasi-1D) charge-density-wave (CDW) system, In atomic wires on Si(111), have brought intriguing issues on topological solitons in quasi-1D systems: the existence of few-atom-sized solitons, chirality of solitons, and the realization of logic exploiting the chirality switching. Using scanning tunneling microscopy and first-principles calculations, we show that the previously reported "short" phase-flip defects are In adatoms and thus have nonsolitonic nature, resolving the controversy over the existence of highly localized solitons. The observed "long" phase-flip and phase-slip defects are genuine solitons with and without chirality, respectively. Read More

Phys Rev Lett 2019 Jan;122(1):013401

Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.

We employ collisions of individual atomic cesium (Cs) impurities with an ultracold rubidium (Rb) gas to probe atomic interaction with hyperfine- and Zeeman-state sensitivity. Controlling the Rb bath's internal state yields access to novel phenomena observed in interatomic spin exchange. These can be tailored at ultralow energies, owing to the excellent experimental control over all relevant energy scales. Read More

Phys Rev Lett 2019 Jan;122(1):015703

Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA.

We study the elastic energy landscape of two-dimensional tin oxide (SnO) monolayers and demonstrate a transition temperature of T_{c}=8.5±1.8  K using ab initio molecular dynamics (MD) that is close to the value of the elastic energy barrier J derived from T=0  K density functional theory calculations. Read More

Phys Rev Lett 2019 Jan;122(1):013203

Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China.

Elliptically polarized laser pulses (EPLPs) are widely applied in many fields of ultrafast sciences, but the ellipticity (ϵ) has never been in situ measured in the interaction zone of the laser focus. In this Letter, we propose and realize a robust scheme to retrieve the ϵ by temporally overlapping two identical counterrotating EPLPs. The combined linearly electric field is coherently controlled to ionize Xe atoms by varying the phase delay between the two EPLPs. Read More

Phys Rev Lett 2019 Jan;122(1):010405

Department of Physics, Stanford University, Stanford, California 94305, USA.

We report direct observations of photon-mediated spin-exchange interactions in an atomic ensemble. Interactions extending over a distance of 500  μm are generated within a cloud of cold rubidium atoms coupled to a single mode of light in an optical resonator. We characterize the system via quench dynamics and imaging of the local magnetization, verifying the coherence of the interactions and demonstrating optical control of their strength and sign. Read More

Phys Rev Lett 2019 Jan;122(1):011803

University of Wisconsin - Madison, Madison, Wisconsin, USA.

A search is performed for dark matter particles produced in association with a top quark pair in proton-proton collisions at sqrt[s]=13  TeV. The data correspond to an integrated luminosity of 35.9  fb^{-1} recorded by the CMS detector at the LHC. Read More

Phys Rev Lett 2019 Jan;122(1):011801

J. Stefan Institute, 1000 Ljubljana.

We report on the first Belle search for a light CP-odd Higgs boson, A^{0}, that decays into low mass dark matter, χ, in final states with a single photon and missing energy. We search for events produced via the dipion transition ϒ(2S)→ϒ(1S)π^{+}π^{-}, followed by the on-shell process ϒ(1S)→γA^{0} with A^{0}→χχ, or by the off-shell process ϒ(1S)→γχχ. Utilizing a data sample of 157. Read More

Phys Rev Lett 2019 Jan;122(1):016103

School of Physics, University of Melbourne, Parkville, Victoria 3010, Australia.

Advances in source monochromation in transmission electron microscopy have opened up new possibilities for investigations of condensed matter using the phonon-loss sector of the energy-loss spectrum. Here, we explore the spatial variations of the spectrum as an atomic-sized probe is scanned across a thin flake of hexagonal boron nitride. We demonstrate that phonon spectral mapping of atomic structure is possible. Read More

Phys Rev Lett 2019 Jan;122(1):016802

MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, New South Wales 2109, Australia.

The surface of diamond is reported to undergo nonablative photochemical etching when exposed to ultraviolet (UV) radiation which allows controlled single and partial layer removal of lattice layers. Oxygen termination of surface dangling bonds is known to be crucial for the etching process; however, the exact mechanism of carbon ejection remains unclear. We investigate the interaction of UV laser pulses with oxygen-terminated diamond surfaces using atomic-scale surface characterization combined with first-principles time-dependent density functional theory calculations. Read More

Phys Rev Lett 2019 Jan;122(1):010408

School of Physics and Technology, Wuhan University, Wuhan, Hubei 430072, China.

Dynamical decoupling (DD) is an active and effective method for suppressing decoherence of a quantum system from its environment. In contrast to the nominal biaxial DD, this work presents a uniaxial decoupling protocol that requires a significantly reduced number of pulses and a much lower bias field satisfying the "magic" condition. We show this uniaxial DD protocol works effectively in a number of model systems of practical interest, e. Read More

Phys Rev Lett 2019 Jan;122(1):016805

University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna 1090, Austria.

Polaron formation plays a major role in determining the structural, electrical, and chemical properties of ionic crystals. Using a combination of first-principles calculations, scanning tunneling microscopy, and atomic force microscopy, we analyze the interaction of polarons with CO molecules adsorbed on the reduced rutile TiO_{2}(110) surface. Adsorbed CO shows attractive coupling with polarons in the surface layer, and repulsive interaction with polarons in the subsurface layer. Read More

Phys Rev Lett 2019 Apr;122(13):132001

University of Wisconsin-Madison, Madison, Wisconsin, USA.

Signals consistent with the B_{c}^{+}(2S) and B_{c}^{*+}(2S) states are observed in proton-proton collisions at sqrt[s]=13  TeV, in an event sample corresponding to an integrated luminosity of 143  fb^{-1}, collected by the CMS experiment during the 2015-2018 LHC running periods. These excited b[over ¯]c states are observed in the B_{c}^{+}π^{+}π^{-} invariant mass spectrum, with the ground state B_{c}^{+} reconstructed through its decay to J/ψπ^{+}. The two states are reconstructed as two well-resolved peaks, separated in mass by 29. Read More