Elimination of D-band in Raman spectra of double-wall carbon nanotubes by oxidation

In this Letter, we present an in situ Raman spectroscopy study of oxidation-induced changes in the structure and composition of double-wall carbon nanotubes (DWCNTs). Above 480 °C, the intensity of the D band decreases to less than 0.01% of the G band intensity, when measured using the 780 nm laser excitation. The D band was absent from the Raman spectra recorded with the 514.5 nm excitation. Thermogravimetric analysis and high-resolution transmission electron microscopy are used to explain the observed results. We conclude that oxidation provides a purification method for the DWCNT which leads to a sample containing tubes having nearly clean surfaces without disordered carbon

Die Auswirkung des Multikinase-Inhibitors Sorafenib in einem murinen in vivo Hypertrophiemodel

Die Herzinsuffizienz, die unter anderem infolge einer Herzmuskelhypertrophie auftritt, ist eine der weltweit führenden Todesursachen und eine Behandlung dieser Erkrankung ist bis heute nur symptomatisch möglich. In dieser Arbeit wurde die Auswirkung des Multikinase Inhibitors Sorafenib der Firma Bayer hinsichtlich seiner Wirkung auf die Entwicklung einer Herzmuskelhypertrophie getestet. Bei diesem Medikament handelt es sich um einen bei der Behandlung des fortgeschrittenen Nierenzellkarzinoms eingesetzten Wirkstoff, der die sog. MAP-Kinase- Signalkaskade der Zelle blockiert. Dieser Signalweg ist an einer Vielzahl von Zellfunktionen beteiligt und sorgt für die Übertragung eines ankommenden extrazellulären Signals durch das Zytosol in den Zellkern. Vermittelt werden so unter anderem die Differenzierung, die Proliferation oder die Apoptose der Zelle. Die Wirksamkeit der Substanz wurde an einem murinen in vivo Hypertrophiemodell getestet. Dazu wurde das Medikament Mäusen, die zuvor einer transversalen aortalen Konstriktion (TAC) zur Induzierung einer myokardialen Hypertrophie unterzogen wurden, in einer tägliche Dosis von 10 mg/kg KG mittels einer Magensonde verabreicht. Zudem wurde eine TAC-Kontrollgruppe und zwei Sham Gruppen gebildet. In diesen beiden Gruppen wurden die Tiere derselben Operation unterzogen, mit dem Unterschied, dass der Aortenbogen nicht ligiert wurde und somit keine Obstruktion im Ausflusstrakt des linken Ventrikels erzeugt wurde. Eine der Sham Gruppen wurde ebenfalls mit Sorafenib behandelt, die andere erhielt, ebenso wie die TAC-Kontrollgruppe, die für das Medikament notwendige Trägersubstanz zur Kontrolle. Verabreicht wurde das Medikament über einen Zeitraum von zwölf Tagen. Nach diesem Zeitraum wurden die Tiere einer invasiven hämodynamischen Messung unterzogen. Dabei wurde über die rechte A. carotis interna eine Messsonde eingeführt mit welcher zunächst die peripheren und nach einem adäquaten Messintervall durch Vorschieben der Sonde in den linken Ventrikel die zentralen hämodynamischen Daten aufgezeichnet. Im Ergebnis konnte keine wesentliche, statistisch relevante Besserung der Hypertrophie durch das Medikament nachgewiesen werden. Auch auf den Blutdruck oder andere hämodynamische Parameter zeigten sich nach zwölf tägigem Behandlungsintervall keine signifikanten Auswirkungen. Tendenziell erscheint indes die Hypertrophie nach der Applikation von Sorafenib geringer ausgeprägt zu sein als im Vergleich mit der Kontrollgruppe. Bei fehlendem statistischen Nachweis dieser Beobachtung ist zu diskutieren, in wie weit ein verändertes Studiendesign hinsichtlich der Therapiedauer oder der zu applizierenden Dosis ein signifikante Änderung herbeiführen könnte

In situ raman spectroscopy study of oxidation of nanostructured carbons

The ability to synthesize carbon nanostructures, such as fullerenes, carbon nanotubes, nanodiamond, and mesoporous carbon; functionalize their surface; or assemble them into three-dimensional networks has opened new avenues for material design. Carbon nanostructures possess tunable optical, electrical or mechanical properties, making them ideal candidates for numerous applications ranging from composite structures and chemical sensors to electronic devices and medical implants.Unfortunately, current synthesis techniques typically lead to a mixture of different types of carbon rather than a particular nanostructure with defined size and properties. In order to fully exploit the great potential of carbon nanostructures, one needs to provide purification procedures that allow a selective separation of carbon nanostructures, and methods which enable a control of size and surface functionalization. Oxidation is a frequently used method for purification of carbon materials, but it can also damage or destroy the sample.In situ Raman spectroscopy during heating in a controlled environment allows a time-resolved investigation of the oxidation kinetics and can identify the changes in material structure and composition, thus helping to accurately determine optimal purification conditions. However, while carbon allotropes such as graphite and diamond show unique Raman signals and allow a fast and straightforward identification, the interpretation of Raman spectra recorded from nanostructures containing mixtures of sp, sp2 and sp3 bonded carbon is more complex and the origin of some peaks in Raman spectra of nanocarbons is not yet fully understood.In this study we applied in situ Raman spectroscopy to determine conditions for selective oxidation of carbon nanostructures, such as nanodiamond, nanotubes, carbidederived carbon and carbon onions; accurately measure and control the crystal size; and improve the fundamental understanding of effects of temperature, quantum confinement and surface chemistry on Raman spectra of nanocrystalline materials. Thermogravimetric analysis, X-ray diffraction and high-resolution transmission electron microscopy were used to complement Raman spectroscopy in order to facilitate the analysis and the interpretation of the results.This work has improved our understanding of oxidation of carbon materials, especially selectivity of the oxidation process to different carbon structures in a broad temperature range. The results of this study have been used to develop simple and environmentally friendly procedures for purification and surface functionalization of carbon nanoparticles and nanoporous materials.Ph.D., Materials Science and Engineering -- Drexel University, 200

Phonon Confinement Effects in the Raman Spectrum of Nanodiamond

Nanodiamonds (ND) exhibit unique properties due to their small size and high surface-to-volume ratio compared to bulk diamonds. A reduction in crystal size also affects ND Raman spectra. The confinement of optical phonons in nanocrystals (\u3c10 nm) results in asymmetrically broadened Raman lines, which are shifted toward lower wavenumbers. The phonon confinement model (PCM) relates the observed changes in the Raman spectra to the crystal size and can be used for size characterization at the nanoscale. While the PCM was successfully applied to a variety of materials including Si and BN, results remained unsatisfactory in the case of ND. In order to improve the agreement between the predictions of the model and experimental Raman spectra of ND, effects such as crystal size distribution, lattice defects, and the energy dispersion of the phonon modes were taken into consideration and incorporated into the PCM. This work has shown that phonon wave vectors from small vibrational domains lead to a broad shoulder peak at ~1250 cm-1, that is often observed in the Raman spectrum of ND

Nitrogen Doped Graphene Generated by Microwave Plasma and Reduction Expansion Synthesis

The article of record as published may be found at http://dx.doi.org/10.1166/nnl.2016.2055This work aimed to produce nitrogen doped graphene from Graphite Oxide (GO) by combining the Expansion Reduction Synthesis (RES) approach, which utilizes urea as doping/reducing agent, with the use of an Atmospheric Plasma torch (Plasma), which provides the high temperature reactor environment known to thermally exfoliate it. The use of this combined strategy (Plasma-RES) was tried in an attempt to increase the surface area of the products. The amount of nitrogen doping was controlled by varying the urea/GO mass ratios in the precursor powders. X-ray diffraction analysis, SEM, TEM, BET surface areas and conductivity measurements of the diverse products are presented. Nitrogen inclusion in the graphene samples was corroborated by the mass spectral signal of the evolved gases generated during thermal programmed oxidation experiments of the products and by EDX analysis. We found that the Plasma-RES method can successfully generate doped graphene in situ as the urea and GO precursors simultaneously decompose and reduce in the discharge zone. When using the same amount of urea in the precursor mixture, samples obtained by Plasma-RES have higher surface area than those generated by RES, however, they contain a smaller nitrogen content

The effect of mixing methods on the dispersion of carbon nanotubes during the solvent-free processing of multiwalled carbon nanotube/epoxy composites

The article of record as published may be found at: http://dx.doi.org/10.1002/polb.23225Several solvent-free processing methods to disperse multiwalled carbon nanotubes (MWCNTs) in bisphenol F-based epoxy resin were investigated, including the use of a microfluidizer (MF), planetary shear mixer (PSM), ultrasonication (US) and combinations. The processed mixture was cured with diethyl toluene diamine. Three complimentary techniques were used to characterize the dispersion of the MWCNTs in cured composite samples: optical microscopy, micro Raman spectroscopy, and scanning electron microscopy (SEM). For sample MF þ PSM, optical micrographs and Raman images showed reduced agglomeration and a homogeneous distribution of MWCNTs in the epoxy matrix. SEM analysis of fractured specimen after tensile testing revealed breakage of nanotubes along the fracture surface of the composite. A comparison of the MWCNT dispersion in the epoxy samples processed using different methods showed that a combination of MF and PSM processing yields a more homogeneous sample than the PSM or US þ PSM processed samples. Mechanical testing of the composites showed about 15% improvement in the tensile strength of samples processed by the MF þ PSM method over other methods. Thermogravimetric analysis (TGA) results showed a small decrease in the onset degradation temperature for poorly dispersed samples produced by PSM compared with the well-mixed samples (MF þ PSM). These results strongly suggest that the MF þ PSM processing method yield better-dispersed and stronger MWCNT/epoxy composites

ARPA-E Program: Advanced Management Protection of Energy Storage Devices (AMPED) - Fifth Quarterly Project Report - FY14 Q1

Technology has been developed that enables monitoring of individual cells in high- capacity lithium-ion battery packs, with a distributed array of wireless Bluetooth 4.0 tags and sensors, and without proliferation of extensive wiring harnesses. Given the safety challenges facing lithium-ion batteries in electric vehicle, civilian aviation and defense applications, these wireless sensors may be particularly important to these emerging markets. These wireless sensors will enhance the performance, reliability and safety of such energy storage systems. Specific accomplishments to date include, but are not limited to: (1) the development of wireless tags using Bluetooth 4.0 standard to monitor a large array of sensors in battery pack; (2) sensor suites enabling the simultaneous monitoring of cell voltage, cell current, cell temperature, and package strain, indicative of swelling and increased internal pressure, (3) small receivers compatible with USB ports on portable computers; (4) software drivers and logging software; (5) a 7S2P battery simulator, enabling the safe development of wireless BMS hardware in the laboratory; (6) demonstrated data transmission out of metal enclosures, including battery box, with small variable aperture opening; (7) test data demonstrating the accurate and reliable operation of sensors, with transmission of terminal voltage, cell temperature and package strain at distances up to 110 feet; (8) quantification of the data transmission error as a function of distance, in both indoor and outdoor operation; (9) electromagnetic interference testing during operation with live, high-capacity battery management system at Yardney Technical Products; (10) demonstrated operation with live high-capacity lithium-ion battery pack during charge-discharge cycling; (11) development of special polymer-gel lithium-ion batteries with embedded temperature sensors, capable of measuring the core temperature of individual of the cells during charge-discharge cycling at various temperatures, thereby enabling earlier warning of thermal runaway than possible with external sensors. Ultimately, the team plans to extend this work to include: (12) flexible wireless controllers, also using Bluetooth 4.0 standard, essential for balancing large-scale battery packs. LLNL received $925K for this project, and has$191K remaining after accomplishing these objectives.This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.DE-FOA-000067

MEMS Solar Generators

Using MEMS bimaterial structures to build highly efficient solar energy generators. This is a novel approach that utilizes developments in the area of bimaterial sensors and applies them in the field of solar energy harvesting.Approved for public release; distribution is unlimited