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Hao Zheng, Guang Bian, Guoqing Chang, Hong Lu, Su-Yang Xu, Guangqiang Wang, Tay-Rong Chang, Songtian Zhang, Ilya Belopolski, Nasser Alidoust, Daniel S Sanchez, Fengqi Song, Horng-Tay Jeng, Nan Yao, Arun Bansil, Shuang Jia, Hsin Lin, M Zahid Hasan
We combine quasiparticle interference simulation (theory) and atomic resolution scanning tunneling spectromicroscopy (experiment) to visualize the interference patterns on a type-II Weyl semimetal Mo_{x}W_{1-x}Te_{2} for the first time. Our simulation based on first-principles band topology theoretically reveals the surface electron scattering behavior. We identify the topological Fermi arc states and reveal the scattering properties of the surface states in Mo_{0.66}W_{0.34}Te_{2}. In addition, our result reveals an experimental signature of the topology via the interconnectivity of bulk and surface states, which is essential for understanding the unusual nature of this material...
December 23, 2016: Physical Review Letters
Waiz Karim, Clelia Spreafico, Armin Kleibert, Jens Gobrecht, Joost VandeVondele, Yasin Ekinci, Jeroen A van Bokhoven
Hydrogen spillover is the surface migration of activated hydrogen atoms from a metal catalyst particle, on which they are generated, onto the catalyst support. The phenomenon has been much studied and its occurrence on reducible supports such as titanium oxide is established, yet questions remain about whether hydrogen spillover can take place on nonreducible supports such as aluminium oxide. Here we use the enhanced precision of top-down nanofabrication to prepare controlled and precisely tunable model systems that allow us to quantify the efficiency and spatial extent of hydrogen spillover on both reducible and nonreducible supports...
January 4, 2017: Nature
K Yamamoto, A Klossek, R Flesch, F Rancan, M Weigand, I Bykova, M Bechtel, S Ahlberg, A Vogt, U Blume-Peytavi, P Schrade, S Bachmann, S Hedtrich, M Schäfer-Korting, E Rühl
The penetration of dexamethasone into human skin ex vivo is reported. X-ray microscopy is used for label-free probing of the drug and quantification of the local drug concentration with a spatial resolution reaching 70±5 nm. This is accomplished by selective probing the dexamethasone by X-ray absorption. Varying the penetration time between 10 min and 1000 min provides detailed information on the penetration process. In addition, the stratum corneum has been damaged by tape-stripping in order to determine the importance of this barrier regarding temporally resolved drug penetration profiles...
December 17, 2016: European Journal of Pharmaceutics and Biopharmaceutics
Fusheng Sun, Matthew L Polizzotto, Dongxing Guan, Jun Wu, Qirong Shen, Wei Ran, Boren Wang, Guanghui Yu
Understanding how heavy metals bind and interact in soils is essential for predicting their distributions, reactions and fates in the environment. Here we propose a novel strategy, i.e., combining two-dimensional correlation spectroscopy (2D COS) and synchrotron radiation based spectromicroscopies, for identifying heavy metal binding to functional groups in soils. The results showed that although long-term (23 yrs) organic fertilization treatment caused the accumulation of Cd (over 3 times) in soils when compared to no fertilization and chemical fertilization treatments, it significantly (p<0...
December 12, 2016: Journal of Hazardous Materials
Suhas Kumar, Ziwen Wang, Xiaopeng Huang, Niru Kumari, Noraica Davila, John Paul Strachan, David Vine, A L David Kilcoyne, Yoshio Nishi, R Stanley Williams
Transition-metal-oxide memristors, or resistive random-access memory (RRAM) switches, are under intense development for storage-class memory because of their favorable operating power, endurance, speed, and density. Their commercial deployment critically depends on predictive compact models based on understanding nanoscale physicochemical forces, which remains elusive and controversial owing to the difficulties in directly observing atomic motions during resistive switching, Here, using scanning transmission synchrotron X-ray spectromicroscopy to study in situ switching of hafnium oxide memristors, we directly observed the formation of a localized oxygen-deficiency-derived conductive channel surrounded by a low-conductivity ring of excess oxygen...
December 27, 2016: ACS Nano
Suhas Kumar, Noraica Davila, Ziwen Wang, Xiaopeng Huang, John Paul Strachan, David Vine, A L David Kilcoyne, Yoshio Nishi, R Stanley Williams
We analyzed micrometer-scale titanium-niobium-oxide prototype memristors, which exhibited low write-power (<3 μW) and energy (<200 fJ per bit per μm(2)), low read-power (∼nW), and high endurance (>millions of cycles). To understand their physico-chemical operating mechanisms, we performed in operando synchrotron X-ray transmission nanoscale spectromicroscopy using an ultra-sensitive time-multiplexed technique. We observed only spatially uniform material changes during cell operation, in sharp contrast to the frequently detected formation of a localized conduction channel in transition-metal-oxide memristors...
December 1, 2016: Nanoscale
A Klossek, S Thierbach, F Rancan, A Vogt, U Blume-Peytavi, E Rühl
Advanced Raman techniques, such as stimulated Raman spectroscopy (SRS), have become a valuable tool for investigations of distributions of substances in biological samples. However, these techniques lack spectral information and are therefore highly affected by cross-sensitivities, which are due to blended Raman bands. One typical example is the symmetric CH2 stretching vibration of lipids, which is blended with the more intense Raman band of proteins. We report in this work an approach to reduce such cross-sensitivities by a factor of 8 in human skin samples...
November 15, 2016: European Journal of Pharmaceutics and Biopharmaceutics
Michael Giulbudagian, Fiorenza Rancan, André Klossek, Kenji Yamamoto, Jana Jurisch, Victor Colombo Neto, Petra Schrade, Sebastian Bachmann, Eckart Rühl, Ulrike Blume-Peytavi, Annika Vogt, Marcelo Calderón
In this paper we present a comprehensive study for the ability of thermoresponsive nanogels (tNG) to act as cutaneous penetration enhancers. Given the unique properties of such molecular architectures with regard to their chemical composition and thermoresponsive properties, we propose a particular mode of penetration enhancement mechanism, i.e. hydration of the stratum corneum. Different tNG were fabricated using dendritic polyglycerol as a multifunctional crosslinker and three different kinds of thermoresponsive polymers as linear counterpart: poly(N-isopropylacrylamide) (pNIPAM), p(di(ethylene glycol) methyl ether methacrylate - co - oligo ethylene glycol methacrylate) (DEGMA-co-OEGMA475), and poly(glycidyl methyl ether - co - ethyl glycidyl ether) (tPG)...
December 10, 2016: Journal of Controlled Release: Official Journal of the Controlled Release Society
Paul M Dietrich, Wolfgang E S Unger, Sufal Swaraj
Soft x-ray spectromicroscopy techniques have seen great amount of development in the recent years, and with the development of new diffraction limited synchrotron source, many new nanoscale and mesoscale characterization opportunities of applied materials are foreseen. In this perspective, the authors present some examples that illustrate the capabilities of spectromicroscopy techniques, namely, 2D and 3D spatially resolved chemical quantification, surface and bulk sensitive measurements, and polarization dependent measurements as applied to iron oxide nanoparticulate materials of biological, geological, and other origins...
October 28, 2016: Biointerphases
Alessandra Gianoncelli, George Kourousias, Lucia Merolle, Matteo Altissimo, Anna Bianco
The current status of the TwinMic beamline at Elettra synchrotron light source, that hosts the European twin X-ray microscopy station, is reported. The X-ray source, provided by a short hybrid undulator with source size and divergence intermediate between bending magnets and conventional undulators, is energy-tailored using a collimated plane-grating monochromator. The TwinMic spectromicroscopy experimental station combines scanning and full-field imaging in a single instrument, with contrast modes such as absorption, differential phase, interference and darkfield...
November 1, 2016: Journal of Synchrotron Radiation
Dogan Erbahar, Toma Susi, Xavier Rocquefelte, Carla Bittencourt, Mattia Scardamaglia, Peter Blaha, Peter Guttmann, Georgios Rotas, Nikos Tagmatarchis, Xiaohui Zhu, Adam P Hitchcock, Chris P Ewels
C60 fullerene crystals may serve as important catalysts for interstellar organic chemistry. To explore this possibility, the electronic structures of free-standing powders of C60 and (C59N)2 azafullerenes are characterized using X-ray microscopy with near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy, closely coupled with density functional theory (DFT) calculations. This is supported with X-ray photoelectron spectroscopy (XPS) measurements and associated core-level shift DFT calculations. We compare the oxygen 1s spectra from oxygen impurities in C60 and C59N, and calculate a range of possible oxidized and hydroxylated structures and associated formation barriers...
October 17, 2016: Scientific Reports
Rita Tóth, Roché M Walliser, István Lagzi, Florent Boudoire, Marcel Düggelin, Artur Braun, Catherine E Housecroft, Edwin C Constable
Periodic precipitation processes in gels can result in impressive micro- and nanostructured patterns known as periodic precipitation (or Liesegang bands). Under certain conditions, the silver nitrate-chromium(vi) system exhibits the coexistence of two kinds of Liesegang bands with different frequencies. We now present that the two kinds of bands form independently on different time scales and the pH-dependent chromate(vi)-dichromate(vi) equilibrium controls the formation of the precipitates. We determined the spatial distribution and constitution of the particles in the bands using focused ion beam-scanning electron microscopy (FIB-SEM) and scanning transmission X-ray spectromicroscopy (STXM) measurements...
October 12, 2016: Soft Matter
Yang Li, Jing Wan, Detlef-M Smilgies, Nicole Bouffard, Richard Sun, Randall L Headrick
The nucleation mechanisms during solution deposition of organic semiconductor thin films determine the grain morphology and may influence the crystalline packing in some cases. Here, in-situ optical spectromicroscopy in reflection mode is used to study the growth mechanisms and thermal stability of 6,13-bis(trisopropylsilylethynyl)-pentacene thin films. The results show that the films form in a supersaturated state before transforming to a solid film. Molecular aggregates corresponding to subcritical nuclei in the crystallization process are inferred from optical spectroscopy measurements of the supersaturated region...
2016: Scientific Reports
K Yamamoto, A Klossek, R Flesch, T Ohigashi, E Fleige, F Rancan, J Frombach, A Vogt, U Blume-Peytavi, P Schrade, S Bachmann, R Haag, S Hedtrich, M Schäfer-Korting, N Kosugi, E Rühl
Label-free detection of core-multishell (CMS) nanocarriers and the anti-inflammatory drug dexamethasone is reported. Selective excitation by tunable soft X-rays in the O 1s-regime is used for probing either the CMS nanocarrier or the drug. Furthermore, the drug loading efficiency into CMS nanocarriers is determined by X-ray spectroscopy. The drug-loaded nanocarriers were topically applied to human skin explants providing insights into the penetration and drug release processes. It is shown that the core-multishell nanocarriers remain in the stratum corneum when applied for 100min to 1000min...
August 24, 2016: Journal of Controlled Release: Official Journal of the Controlled Release Society
Justine Dionne, Thierry Lefèvre, Michèle Auger
To plentifully benefit from its properties (mechanical, optical, biological) and its potential to manufacture green materials, the structure of spider silk has to be known accurately. To this aim, the major ampullate (MA) silk of Araneus diadematus (AD) and Nephila clavipes (NC) has been compared quantitatively in the liquid and fiber states using Raman spectromicroscopy. The data show that the spidroin conformations of the two dopes are indistinguishable despite their specific amino acid composition. This result suggests that GlyGlyX and GlyProGlyXX amino acid motifs (X = Leu, Glu, Tyr, Ser, etc...
August 18, 2016: International Journal of Molecular Sciences
Christoph Baeumer, Christoph Schmitz, Astrid Marchewka, David N Mueller, Richard Valenta, Johanna Hackl, Nicolas Raab, Steven P Rogers, M Imtiaz Khan, Slavomir Nemsak, Moonsub Shim, Stephan Menzel, Claus Michael Schneider, Rainer Waser, Regina Dittmann
The continuing revolutionary success of mobile computing and smart devices calls for the development of novel, cost- and energy-efficient memories. Resistive switching is attractive because of, inter alia, increased switching speed and device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, is essential for further advances. Here we use in operando spectromicroscopy to verify that redox reactions drive the resistance change...
2016: Nature Communications
Bosheng Zhang, Dennis F Gardner, Matthew H Seaberg, Elisabeth R Shanblatt, Christina L Porter, Robert Karl, Christopher A Mancuso, Henry C Kapteyn, Margaret M Murnane, Daniel E Adams
We report a proof-of-principle demonstration of a new scheme of spectromicroscopy in the extreme ultraviolet (EUV) spectral range, where the spectral response of the sample at different wavelengths is imaged simultaneously. This scheme is enabled by combining ptychographic information multiplexing (PIM) with a tabletop EUV source based on high harmonic generation, where four spectrally narrow harmonics near 30 nm form a spectral comb structure. Extending PIM from previously demonstrated visible wavelengths to the EUV/X-ray wavelengths promises much higher spatial resolution and a more powerful spectral contrast mechanism, making PIM an attractive spectromicroscopy method in both microscopy and spectroscopy aspects...
August 8, 2016: Optics Express
Zenghui Wang, Hao Jia, Xu-Qian Zheng, Rui Yang, G J Ye, X H Chen, Philip X-L Feng
Black phosphorus (P) has emerged as a layered semiconductor with a unique crystal structure featuring corrugated atomic layers and strong in-plane anisotropy in its physical properties. Here, we demonstrate that the crystal orientation and mechanical anisotropy in free-standing black P thin layers can be precisely determined by spatially resolved multimode nanomechanical resonances. This offers a new means for resolving important crystal orientation and anisotropy in black P device platforms in situ beyond conventional optical and electrical calibration techniques...
September 14, 2016: Nano Letters
Sergey Kharintsev, Alexander Alekseev, Joachim Loos
In this paper, we gain insight into the design and optimization of plasmonic (metallic) tips prepared with dc-pulsed voltage electrochemical etching gold wires, provided that, a duty cycle is self-tuned. Physically, it means that etching electrolyte attacks the gold wire equally for all pulse lengths, regardless of its surface shape. Etchant effect on the reproducibility of a curvature radius of the tip apex is demonstrated. It means that the gold conical tips can be designed chemically with a choice of proper etchant electrolyte...
January 15, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
D Carta, P Guttmann, A Regoutz, A Khiat, A Serb, I Gupta, A Mehonic, M Buckwell, S Hudziak, A J Kenyon, T Prodromakis
Resistive random access memory (RRAM) is considered an attractive candidate for next generation memory devices due to its competitive scalability, low-power operation and high switching speed. The technology however, still faces several challenges that overall prohibit its industrial translation, such as low yields, large switching variability and ultimately hard breakdown due to long-term operation or high-voltage biasing. The latter issue is of particular interest, because it ultimately leads to device failure...
August 26, 2016: Nanotechnology
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