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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...
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
J Li, D Gu, S S-Y Lee, B Song, S Bandyopadhyay, S Chen, S F Konieczny, T L Ratliff, X Liu, J Xie, J-X Cheng
Cancer cells are known to execute reprogramed metabolism of glucose, amino acids and lipids. Here, we report a significant role of cholesterol metabolism in cancer metastasis. By using label-free Raman spectromicroscopy, we found an aberrant accumulation of cholesteryl ester in human pancreatic cancer specimens and cell lines, mediated by acyl-CoA cholesterol acyltransferase-1 (ACAT-1) enzyme. Expression of ACAT-1 showed a correlation with poor patient survival. Abrogation of cholesterol esterification, either by an ACAT-1 inhibitor or by shRNA knockdown, significantly suppressed tumor growth and metastasis in an orthotopic mouse model of pancreatic cancer...
May 2, 2016: Oncogene
Suhas Kumar, Catherine E Graves, John Paul Strachan, Emmanuelle Merced Grafals, Arthur L David Kilcoyne, Tolek Tyliszczak, Johanna Nelson Weker, Yoshio Nishi, R Stanley Williams
As information bits of 0's and 1's are stored in crosspoint tantalum oxide memristors, or resistive random access memory (RRAM) cells, nanoscale-resolution in operando X-ray transmission spectromicroscopy is used by J. P. Strachan and co-workers, as reported on page 2772, to directly observe oxygen migration and clustering, revealing an important operation and failure mechanism of RRAM, a frontrunner technology for next-generation computer memory.
April 2016: Advanced Materials
Rachel Mak, Stefan M Wild, Chris Jacobsen
In x-ray spectromicroscopy, a set of images can be acquired across an absorption edge to reveal chemical speciation. We previously described the use of non-negative matrix approximation methods for improved classification and analysis of these types of data. We present here an approach to find appropriate values of regularization parameters for this optimization approach.
January 28, 2016: AIP Conference Proceedings
G Birarda, A Ravasio, M Suryana, S Maniam, H-Y N Holman, G Grenci
Water is a strong mid-infrared absorber, which has hindered the full exploitation of label-free and non-invasive infrared (IR) spectromicroscopy techniques for the study of living biological samples. To overcome this barrier, many researchers have built sophisticated fluidic chambers or microfluidic chips wherein the depth of the liquid medium in the sample compartment is limited to 10 μm or less. Here we report an innovative and simple way to fabricate plastic devices with infrared transparent view-ports enabling infrared spectromicroscopy of living biological samples; therefore the device is named "IR-Live"...
April 26, 2016: Lab on a Chip
Lorella Pascolo, Diana E Bedolla, Lisa Vaccari, Irene Venturin, Francesca Cammisuli, Alessandra Gianoncelli, Elisa Mitri, Elena Giolo, Stefania Luppi, Monica Martinelli, Marina Zweyer, Giuseppe Ricci
Many drugs, chemicals, and environmental factors can impair sperm functionality by inducing DNA damage, one of the important causes of reduced fertility potential. The use of vibrational spectromicroscopy represents a promising approach for monitoring DNA integrity in sperm, although some limitations exist, depending from the experimental conditions. Here, we report that when using FTIR spectromicroscopy to reveal oxidative stress mediated by Fenton's reaction on hydrated sperm samples, DNA damage interpretation is partially compromised by unexpected cell surface precipitates...
June 2016: Reproductive Toxicology
Paul M Donaldson, Chris S Kelley, Mark D Frogley, Jacob Filik, Katia Wehbe, Gianfelice Cinque
In this paper, we experimentally demonstrate the use of infrared synchrotron radiation (IR-SR) as a broadband source for photothermal near-field infrared spectroscopy. We assess two methods of signal transduction; cantilever resonant thermal expansion and scanning thermal microscopy. By means of rapid mechanical chopping (50-150 kHz), we modulate the IR-SR at rates matching the contact resonance frequencies of atomic force microscope (AFM) cantilevers, allowing us to record interferograms yielding Fourier transform infrared (FT-IR) photothermal absorption spectra of polystyrene and cyanoacrylate films...
February 8, 2016: Optics Express
D Carta, A P Hitchcock, P Guttmann, A Regoutz, A Khiat, A Serb, I Gupta, T Prodromakis
Reduction in metal-oxide thin films has been suggested as the key mechanism responsible for forming conductive phases within solid-state memory devices, enabling their resistive switching capacity. The quantitative spatial identification of such conductive regions is a daunting task, particularly for metal-oxides capable of exhibiting multiple phases as in the case of TiOx. Here, we spatially resolve and chemically characterize distinct TiOx phases in localized regions of a TiOx-based memristive device by combining full-field transmission X-ray microscopy with soft X-ray spectroscopic analysis that is performed on lamella samples...
2016: Scientific Reports
J R Lawrence, M J Waiser, G D W Swerhone, J Roy, V Tumber, A Paule, A P Hitchcock, J J Dynes, D R Korber
Commercial production of nanoparticles (NP) has created a need for research to support regulation of nanotechnology. In the current study, microbial biofilm communities were developed in rotating annular reactors during continuous exposure to 500 μg L(-1) of each nanomaterial and subjected to multimetric analyses. Scanning transmission X-ray spectromicroscopy (STXM) was used to detect and estimate the presence of the carbon nanomaterials in the biofilm communities. Microscopy observations indicated that the communities were visibly different in appearance with changes in abundance of filamentous cyanobacteria in particular...
May 2016: Environmental Science and Pollution Research International
Suhas Kumar, Catherine E Graves, John Paul Strachan, Emmanuelle Merced Grafals, Arthur L David Kilcoyne, Tolek Tyliszczak, Johanna Nelson Weker, Yoshio Nishi, R Stanley Williams
Oxygen migration in tantalum oxide, a promising next-generation storage material, is studied using in operando X-ray absorption spectromicroscopy. This approach allows a physical description of the evolution of conduction channel and eventual device failure. The observed ring-like patterns of oxygen concentration are modeled using thermophoretic forces and Fick diffusion, establishing the critical role of temperature-driven oxygen migration.
April 13, 2016: Advanced Materials
R Chakraborty, J Serdy, B West, M Stuckelberger, B Lai, J Maser, M I Bertoni, M L Culpepper, T Buonassisi
In situ characterization of micro- and nanoscale defects in polycrystalline thin-film materials is required to elucidate the physics governing defect formation and evolution during photovoltaic device fabrication and operation. X-ray fluorescence spectromicroscopy is particularly well-suited to study defects in compound semiconductors, as it has a large information depth appropriate to study thick and complex materials, is sensitive to trace amounts of atomic species, and provides quantitative elemental information, non-destructively...
November 2015: Review of Scientific Instruments
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