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Contributed abstracts


Rajendra Kurapati: Dispersibility and functionalization dependent biodeg-radation of graphene oxide

posted 17 Jun 2015, 06:48 by info admin

CNRS, Institut de Biologie Moléculaire et Cellulaire, Laboratoire d’Immunopathologie et Chimie Thérapeutique, Strasbourg 67000

Understanding human health risk associated with the use of the rapidly emerging graphene-based nanomaterials represents a great challenge because of the diversity of applications and the wide range of possible ways of exposure to this type of materials. Herein, we report the biodegradation of graphene oxide (GO) using enzymatic catalysis by peroxidases like myeloperoxidase (hMPO), horseradish peroxidase (HRP) in the presence of a low concentration of hydrogen peroxide. First, we demonstrated the dispersibility dependent biodegradation of GO by hMPO using different GO samples containing different degree of oxidation on their graphenic lattice, where hMPO failed to degrade the most aggregated GO, but succeeded to completely metabolize highly dispersed GO samples. Further to enhance the biodegradability, we covalently functionalized GO with specific molecules like coumarin catechol derivatives. Both types of molecules are known as the good reducing substrates and strong redox mediators to enhance the catalytic activity of HRP. Our results revealed that biodegradation of functionalized GO was faster and more efficient over unmodified GO. Over all, our work may give an adequate solution for the serious concerns raised for developing graphene-based nanomaterials.

(Ref: R. Kurapati, A. Bianco et al. Dispersibility-Dependent Biodegradation of Graphene Oxide by Myeloperoxidase. Small, 2015 10.1002/smll.201500038).

 

Rajendra Kurapati is currently a Postdoctoral Fellow at CNRS, Institut de Biologie Moléculaire et Cellulaire, Laboratoire d’Immunopathologie et Chimie Thérapeutique in Strasbourg. He is mainly interested in biomedical applications as well as nano-toxicology of carbon-based materials including newly emerging 2-dimensional materials. He received his M.S. degree in Chemistry from University of Hyderabad (20008) and a Ph.D. in Material Science and Engineering (2014) from Indian Institute of Science where he investigated the drug delivery and antimicrobial applications of self-assembled graphene oxide/polymer materials. After finishing his Ph.D., he spent 8 months as a postdoctoral researcher in the Laboratory of Biomaterials at the Indian Institute of Science studying graphene oxide/nanoparticles composites for bioimaging applications before joining the group at IBMC, Strasbourg in April, 2014. His awards include a Ph.D. fellowship from the Council of Scientific and Industrial Research (CSIR), India (2008-2014) and Lectureship in

Chemistry by CSIR/UGC, India in 2007.

Lasse Karvonen: Optical properties of grain boundaries in chemical vapor deposited MoS2

posted 17 Jun 2015, 06:41 by info admin

Aalto University, Department of Micro and Nanosciences, FI-02150 Espoo, Finland

Chemical vapor deposited (CVD) molybdenum disulphide (MoS2) flakes are studied by Raman, photoluminescence and multiphoton microscopies. We use simultaneous second- and third-harmonic generation imaging methods to study the crystal orientations and the grain boundaries of CVD grown MoS2 flakes We show that grain boundaries with large mis-orientations in the crystal structure are clearly observable with Raman, photoluminescence and second-harmonic generation imaging methods. However, these methods have difficulties in distinguishing grain boundaries without mis-orientation or with a small mis-orientation in the crystal structure. In addition to that, we show that third-harmonic generation imaging is very sensitive for the grain boundaries regardless of the crystal mis-orientation. Our multiphoton imaging results demonstrate that third-harmonic generation imaging is a much faster technique than Raman mapping with better sensitivity compared to the photoluminescence mapping and second-harmonic generation imaging methods, and therefore more suitable for high-volume and large-size sample characterization.

 

Lasse Karvonen is currently a post-doctoral researcher in the Department of Micro and Nanosciences at Aalto University in Finland. He is primarily interested in the linear and nonlinear optical properties of atomically thin materials such as graphene, MoS2 and other metal dichalcogenides. He received his PhD degree from Aalto University (2013) with the thesis title of Nanostructures for photonic applications.  After finishing his PhD, he has been working as a project manager in the Finland Distinguished Professor –project, in which he is doing close collaboration with the researchers in College of Optical Sciences in University of Arizona. He is staying in University of Arizona from two to four months every year.

Jean-Paul Mazzelier: High frequency electro-optics mixing with graphene based devices

posted 17 Jun 2015, 06:32 by info admin

Physics Research Group, Thales Research & Technology, Palaiseau, France

High frequency signals are more and more carried over optical fibers that exhibit electromagnetic immunity, low propagation losses, very large bandwidth. Optical telecom fibers operate at 1.55 µm and optic to electric conversion is performed with InGaAs semiconductors. Graphene, thanks to its remarkable energy band structure, operate also at 1.55 µm and can be easily integrated on silicon photonic-electronic platform. Moreover the very high mobility of charge carriers in graphene should allow fabricating very high frequency optoelectronic devices.

We have demonstrated high frequency (up to 30 GHz) electro-optic mixers based on graphene. A graphene film obtained by chemical vapor deposition was transferred on a Si/SiO2 substrate. Then a graphene based coplanar waveguide was fabricated and generic photomixing functions were demonstrated. Indeed, coupling an optically carried signal at frequency f1with an electrical signal at frequency f2 (both f1 and/or f2 up to 30GHz) provides frequency up and down conversion, i.e. generate signals at frequencies f1+f2 and f1-f2. This device is an essential block for future wide bandwidth graphene based telecom low cost modules.

 

Jean-Paul Mazellier is currently Research Engineer in the Micro & Nano Physics Laborarty from Physics Research Group of Thales Research & Technology. Thales activity domain is aerospace, space, ground transportation, defence and security (61.000 employees, present in 56 countries). Jean-Paul Mazellier research domain covers carbon based nanomaterials from carbon nanotubes for field emission devices, nanodiamond for chemistry and biology domains, and graphene for high frequency opto-electronics. He received his B.S. degree in Physics from Pierre and Marie Curie University (Paris 6, 2006) and an Engineer diploma from Ecole Centrale Paris (2006). He received a Ph.D. in microelectronics engineering (2009) from Institut National Polytechnique Grenoble where he studied the electrical and thermal properties of nanodiamond as well as its integration in advanced microelectronics devices.  He worked as research engineer in the R&D section of Electricité de France (EDF, European leader in energy production and providing) studying reliability of electronics components for nuclear plants control. He joined Thales Research & Technology by end of year 2011. His awards include a best Ph.D. student work from Institut National Polytechnique Grenoble (2010).


Jakob Jørgensen: Tunable band gap opening in graphene by high-temperature hydrogenation

posted 17 Jun 2015, 06:23 by info admin

iNANO and Department of Physics and Astronomy, Aarhus University

 

Functionalization of graphene on Ir(111) with hydrogen represents a possible route towards a band gap opening in the otherwise semimetallic material.[1] XPS data on hydrogenated graphene on Ir(111) have shown that hydrogen binds to the carbon atoms of graphene with different energies depending on the carbon position in the Moiré superstructure[2]. Here we present a combined Scanning Tunnelling Microscopy (STM) and angle resolved photoemission spectroscopy (ARPES) study of hydrogen structures and the corresponding band gaps obtained following exposure of a hot graphene coated Ir(111) surface to atomic hydrogen. The hot surface favours the binding of hydrogen only in the most stable positions yielding a well organized hexagonal pattern of hydrogen clusters. Images suggest that the clusters are confined to the FCC sites of the Moiré[3] pattern contrary to room temperature deposition where extended clusters are observed1. ARPES measurements reveal a highly tunable band gap depending on the sample temperature during hydrogenation with values ranging from 450 meV at room temperature, 281 meV at 645K to 148 meV at 675K. We are thus able to tune the gap merely by adjusting the sample temperature.

1. Balog, R., et al., Nature Materials, 2010. 9(4): p. 315-319.

2. Balog, R., et al., Acs Nano, 2013. 7(5): p. 3823-3832.

3. N'Diaye, A.T., et al., New Journal of Physics, 2008. 10: p. 16.

 

Jakob Jørgensen is currently a PhD student in Nanoscience at the Interdisciplinary Nanoscience Center at Aarhus University.  He is primarily interested in the electronic properties of graphene. He received his B.S. degree in Nanoscience (2012) and a MSc in Nanoscience (2012) from Aarhus University where he studied functionalization of graphene.

Federico Mazzola: Silver catalyzed Fluorouracil degradation; a promising new role for graphene

posted 17 Jun 2015, 06:11 by info admin

Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway

 

Chemotherapy is a major part of many people’s lives. In the treatment of cancer, the drug is delivered into the body of the patients via catheters. Such catheters are prone to degradation and create unpleasant side effects, causing severe complications to patients. In order to prevent or reduce such a degradation, catheters and the associated delivery apparatus are increasingly coated with Ag-alloys. These coatings are particularly common because of their low reactivity and antimicrobial properties. Surprisingly, the surface reaction between chemotherapy drugs and catheter materials/coatings is generally unexplored. We recently demonstrated that an incredibly strong reaction can occur, with a subsequent release of HF. We further investigated other inert coating-materials, such as graphene, finding no sign of chemical reaction. The research suggests that placing graphene on the internal surfaces of catheters commonly used to deliver chemotherapy drugs into a patients body will improve the efficacy of treatments, and reduce the potential of the catheters failing. We believe that graphene coatings could constitute a potential candidate for the next generation of drugs delivery systems.

 

Federico Mazzola is a PhD student at the Norwegian University of Science and technology (NTNU) under the supervision of Prof. Justin Wells. He has experiences in various synchrotron-based techniques such as Angle resolved photoemission spectroscopy (ARPES), spin-ARPES, resonant photoemission spectroscopy and X-ray photoemission spectroscopy (XPS). He is currently working on the electronic properties of graphene, shallow delta layers in semiconductors, transition metal dichalcogenides and topological insulators under the supervision of Prof. Justin Wells. Previous to this, he got his M. Physics in Condensed Matter Physics at University of Rome, La Sapienza with a thesis project carried out in Denmark at Aarhus University under the supervision of Prof. Philip Hofmann on ARPES-based studies on graphene at the synchrotron facility ASTRID (now ASTRID2) (SGM-3 beamline, Aarhus, DK).

Daniele Stradi: Stacking effects in two-dimensional devices based on gra-phene electrodes

posted 17 Jun 2015, 05:50 by info admin

Center for Nanostructured Graphene, DTU Nanotech, Technical University of Denmark, Kgs. Lyngby 2800, Denmark

Two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDs) are attracting considerable interest as novel materials for atomically thin and flexible field-effect transistor (FET) devices. Recently, a promising FET setup has been proposed which employs graphene as the electrode material to provide gate-tunable resistance at the contact, and van der Waals assembly to protect the device from the environment by encapsulation [1-3]. Using largescale quantum transport simulations, we have investigated the role of the stacking order in a layered device formed by a MoS2 channel contacted by graphene electrodes, with the aim of providing guidelines on how to shape the device in order to achieve maximum performance. We show that the stacking order of the 2D layers dramatically impacts the distribution of carriers at the interface between the graphene and the TMD in the gated device, which ultimately determines its electronic transport characteristics. Our results are relevant for the design of electrode-semiconductor interfaces in FETs based entirely on two-dimensional materials.

1. X. Cui et al., Nature Nanotech., AOL, doi:10.1038/nnano.2015.70
2. Y. Liu et al., Nano Lett., 15, 3030 (2015)
3. Avsar A. et al. ACS Nano, 9, 4138 (2015)

 

Daniele Stradi is Hans Christian Ørsted fellow in the Theoretical Nanoelectronics group (Prof. Mads Brandbyge) at the Center for Nanostructured Graphene and at DTU Nanotech, Technical University of Denmark. His current research interests focus on the investigation of graphene as an electrode material using first-principles quantum transport simulations. He received his B.Sc. degree in Chemistry from the University of Trieste (2009) and his Ph.D. in Theoretical Chemistry from the Autonomous University of Madrid (2013), with a thesis on the chargetransfer properties of organic monolayers self-assembled on epitaxial graphene.

Amina Kimouche: Electronic states in ultra-narrow metallic armchair gra-phene nanoribbons

posted 17 Jun 2015, 05:34 by info admin

Department of Applied Physics, Aalto University, Finland

There has been tremendous progress in the bottom-up synthesis of graphene nanostructures. In particular, atomically well-defined armchair-terminated graphene nanoribbons (AGNRs) has been shown to provide precise control over the width and edge geometry of the ribbon. By changing the monomer design, the fabrication of a wide range of GNRs including different widths and doping can be achieved. While all the experimentally studied systems have exhibited wide band gaps, theory predicts that every third ANGR (N=3p+2) should be (nearly) metallic with a very small band gap. Here, we target the narrowest possible AGNR belonging to the metallic family that is only 5 carbon atoms wide. Scanning tunneling spectroscopy shows that N=5 ribbon can have bandgaps below 500 meV, which is much less than in the wider N=7 GNRs belonging to the N=3m+1 family. We have performed first principle calculations to support our experimental STS data and to identify fingerprints in the dI/dV maps. This allows detailed understanding of the length-dependent properties of these ultra-narrow GNRs, which is important for their potential use as interconnects in nanoelectronic circuits or in transistor structures.


Amina Kimouche is a postdoctoral researcher at Aalto University. Her current research focuses on probing the structure and electronic properties of materials at the atomic scale using low-temperature scanning tunneling microscopy (STM) and atomic force microscopy (AFM). She received her PhD in Physics (2013) from Joseph Fourier University in Grenoble where she studied the electronic properties of hybrid graphene-based systems by using complex instruments from scanning probe microscopies to synchrotron radiation facilities. Her expertise lies in fabricating and characterizing atomically well-defined nanostructures such as graphene nanoribbons and molecular networks, to study physical phenomena at the nanoscale for future molecular scale electronic circuity.

Sunwoo Lee: Putting Graphene to Work

posted 17 Jun 2015, 01:16 by info admin

Electrical Engineering, Columbia University, New York, NY

 
Despite the great excitements that 2D materials have brought in the past decade, there still are various practical limitations to overcome, while more commercially viable applications need to be identified.  Among such two-dimensional (2D) materials, graphene, the first 2D material discovered, has received the most attention in science/engineering communities owing to its unique physics as well as high commercial potentials.  This talk will discuss a few different approaches to utilize graphene for commercial applications.  In detail, 1) reinforced composite for medical application, 2) graphene metallization, 3) force sensing, 4) incandescent light emission, and 5) RF signal processing will be discussed.  Finally, ongoing efforts on integrating graphene nano-electro-mechanical systems (GNEMS) with conventional CMOS technology, where the benefits of mature CMOS and emerging GNEMS can complement one another, will be presented.

 

Sunwoo Lee is currently pursuing his Ph.D. in Electrical Engineering at the Columbia University.  His primarily interest lies in developing electro-mechanical systems based on atomically thin materials such as graphene for signal processing. He received his B.S. degree in Electrical and Computer Engineering from Cornell University (2010) and a M.S. in Electrical Engineering (2012) from Columbia University.  In addition, he worked on high quality CVD graphene for spintronics applications at Spintronics and Photovoltaic Division in IBM T.J. Watson Research Center, Yorktown Heights, NY in the summer of 2013, and also worked on design and evaluation of next generation MEMS gyroscopes at Product Engineering Division in Analog Devices, Inc., Wilmington, MA in the summer of 2014.  He is a two-time winner of the Qualcomm Innovation Fellowship (QInF) – for ‘CMOS Compatible Graphene Nanoelectromechanical Systems for Next Generation RF Design’ in 2012 and ‘Graphene Resonator Based Mixer-First Receiver on CMOS for Digitally Controlled and Widely Tunable RF Interface’ in 2013.

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