Poster abstracts 2017

Mohammad Hassan Ramezan zadeh: Iron oxide reinforced carbon nanotubes as promising nanofillers for biosensing applications of polymer films

posted by info admin

Mohammad Hassan Ramezan zadeh, Majid Seifi

Department of Physics, Faculty of Science, University of Guilan, Rasht 41335, Iran

Carbon nanotubes (CNTs) have been widely investigated owing to their exceptionally structural and physicochemical properties which make them great candidates for numerous applications, such as, hydrogen storage, capacitors, sensors, biomarkers etc. [1, 2].
We have studied the influence of single walled carbon nanotubes coated with iron oxide nanoparticles (SWCNT-iron oxide nanocomposites) on the electrochemical properties of 2- dimensional polymer matrices and applied them as the frontier materials in electrochemical biosensors.
In the present study, first, we synthesized SWCNT-iron oxide nanocomposites by following  a same methodology reported previously [3], and then used them as nanofillers in gelatin films to make them applicable materials for electrochemical sensing in different branches, such as food industry, high-tech packaging, new medicine, biomedical devices, agricultural industry etc. 
This novel work could increase the different real-life applications of electrochemical biosensors for modern mankind as well as the over-increasing elderly population health care issues.

1. Irina V. Zaporotskova, et al. "Carbon nanotubes: Sensor properties. A review." Modern Electronic Materials 2.4 (2016): 95-105.
2. Xiaoxing Zhang, et al. "Mechanism and Application of Carbon Nanotube Sensors in SF6 Decomposed Production Detection: a Review." Nanoscale research letters 12.1 (2017): 177.
3. Mohammad Hassan Ramezan zadeh, et al. "Preparation and study of the electrical, magnetic and thermal properties of Fe 3 O 4 coated carbon nanotubes." Chinese Journal of Physics (2017).

I am developing new apparatuses about increasing polymers' structural, physical and biological properties by using carbon nanotubes and nanoparticles. Polymers such as chitosan, PVA, etc. The applications are supposed to be in various regions like biomedical, medical, life, food and environmental sciences.

Li-Zhi Huang: Hierarchical MoS2 nanosheets on flexible carbon felt as an efficient flow-through electrode for dechlorination

posted 19 Jul 2017, 06:28 by info admin

Li-Zhi Huang,Steen Uttrup Pedersen, Emil Bjerglund Pedersen, Marianne Glasius, Hans Christian B. Hansen and Kim Daasbjerg

Interdisciplinary Nanoscience Center (iNANO), Aarhus University

MoS2 is well-known as an efficient catalyst for the hydrogen evolution reaction. For the first time, we show that MoS2 is also a promising electrocatalyst for reductive dehalogenation of chlorosubstituted carboxylic acids in water. Molybdenum disulphide nanosheets were grown directly on flexible/soft carbon felt using a facile hydrothermal method. The MoS2 nanosheets loaded carbon felt was used as flow-through electrode for reductive dechlorination of trichloroacetic acid at environmentally relevant conditions resulting in a much more efficient process than using metal electrodes. Atomic hydrogen produced from water reduction at the MoS2 surface can be exploited to accomplish a complete dehalogenation, yet with a dramatic drop in the Faradaic efficiency due to the concomitant dihydrogen evolution. Doping of the MoS2 catalyst with transitional metals resulted in an increase in the Faradaic efficiency as well as the complete dechlorination of trichloroacetic acid to acetic acid. The edge sites of MoS2 is believed to be responsible for the indirect dechlorination involving atomic hydrogen. With the cobalt doped MoS2 catalyst 100% full dechlorination was accomplished at an applied potential of -1.1 V vs. Ag/AgCl using a flow rate of 1 mL min-1. Both catalyst synthesis, electrode preparation, and setup of the electrochemical flow cell are straightforward and readily up-scaled, demonstrating the potential of this methodology in practical applications.

Li-Zhi Huang is currently a post-doc at Interdisciplinary Nanoscience Center (iNANO), Aarhus University. He is primarily interested in synthesis and environmental application of 2D materials including MoS2, graphene etc.. Li-Zhi Huang obtain his PhD at University of Copenhagen focus on synthesis of 2D iron oxide materials. He has reported for the first time the synthesis of single sheet iron oxides which are tabular iron oxides with one nanometer thick and with an ordered 2D structure. After finishing his PhD Li-Zhi Huang has been awarded an individual postdoctoral grant (DKK. 2.249.920) from Danish Council for Independent Research&Technology. Thus, he continued his research on the synthesis and environmental application of 2D materials. 

Matteo Miola: Hemin based carbon materials for CO2 electrochemical reduction

posted 19 Jul 2017, 06:23 by info admin

CADIAC, Aarhus University, Aarhus, DK

The development of green, abundant and cheap catalysts for CO2 reduction is a great challenge of the 21st century. The Hemin is a green, abundant and cheap iron (III) chloroprotoporphyrin IX that can be extracted from porcine or bovine blood. In this project the Hemin is embedded in carbon electrically conductive supports using green synthesis processes and tested for the electrochemical CO2 conversion to valuable products.

Matteo Miola started his PhD in Dec. 2015 in the CADIAC (carbon dioxide activation centre) in Aarhus University with the thesis title: synthesis and characterization of green carbon-based nano-materials for high-yield CO2 electroreduction, under the supervision of Professor Kim Daasbjerg and Professor Troels Skrydstrup. He obtained the master degree in Material Science and Engineering in Padova University (Oct. 2015, 110/110 summa cum laude). He spent four months as guest PhD student in LIKAT (Leibniz Institute for Catalysis, Rostock ,DE) under the supervision of Professor Matthias Beller, studying the synthesis and characterization of FeNx carbon supported materials for CO2 electroreduction, with focus on the use highly available nitrogen sources and green synthesis development. 

Joachim Dahl Thomsen: Suppression of Intrinsic Roughness in Encapsulated Graphene

posted 19 Jul 2017, 01:08 by info admin

J. D. Thomsen [1], T. Gunst [1], S. S. Gregersen [1], L. Gammelgaard [1], B. S. Jessen [1], D. M. A. Mackenzie [1], K. Watanabe [2], T. Taniguchi [2], P. Bøggild [1], and T. J. Booth [1]

[1] Center for Nanostructured Graphene, Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
[2] National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

Roughness in graphene is known to contribute to scattering effects which lower carrier mobility [1]. Encapsulating graphene in hexagonal boron nitride (hBN) leads to a significant reduction in roughness and has become the de facto standard method for producing high-quality graphene devices. We have fabricated graphene samples encapsulated by hBN that are suspended over apertures in a substrate and used electron diffraction in a transmission electron microscope to measure the roughness of encapsulated graphene inside such structures [2]. We furthermore compare the roughness of these samples to suspended bare graphene and suspended graphene on hBN. The suspended and encapsulated graphene displays a root mean square (rms) roughness down to 12 pm, considerably less than that previously reported for both suspended graphene [3] and graphene on any substrate. Our first-principles calculations of the phonon bands in graphene/hBN heterostructures show that the flexural acoustic phonon mode is localized predominantly in the hBN layers upon hBN encapsulation. These results could lead to new strategies for device fabrication in applications requiring ultimately high performance, and show that layer roughness in artificially fabricated van der Waals heterostructures approaches that in naturally occurring bulk crystals.

[1] E.V. Castro et al, Phys. Rev. Lett. 105, 266601 (2010)
[2] J. D. Thomsen et al, Phys Rev. B, 96, 014101 (2017)
[3] D. A. Kirilenko et al, PRB 84, 235417 (2007)

Joachim Dahl Thomsen is currently a Ph.D. student at the Technical University of Denmark (DTU) in the Nanocarbon group. He is working primarily with in-situ transmission electron microscopy (TEM) experiments involving nanopatterning, defect engineering and in-situ electrical characterisation of graphene and other 2D materials, using microfabricated sample platforms compatible with TEM sample holders. Joachim received his M.Sc. degree in Physics and Nanotechnology from DTU in 2014 where he worked with cleanroom micro-fabrication of flexible arrays of photodetectors in his final project. 

Vishal Panchal: Scanning gate microscopy on epitaxial graphene: unexpected carrier-type inversion

posted 19 Jul 2017, 01:04 by info admin

Vishal Panchal1, Héctor Corte-León1,2, David M. A. Mackenzie3, Olga Kazakova1 and Dirch H. Petersen3

1. National Physical Laboratory, Teddington, TW11 0LW, United Kingdom
2. Royal Holloway, University of London, Egham, Surrey, TW20 0EX, United Kingdom
3. Center for Nanostructured Graphene, Technical University of Denmark, Lyngby, 2800 Kgs, Denmark

Applications that require a large number of graphene devices to behave in a precise manner can benefit greatly from large scale uniformity. Currently, the variability of epitaxial graphene thickness leads to devices formed from a mixture of 1LG/2LG. The exact shape, size and location of 2LG islands have been shown to greatly alter the performance of devices in applications such as resistance metrology [1] and environmental sensors [2].
We present local electric field sensitivity maps of Hall cross devices of 1-2LG imaged using electrical scanning gate microscopy (SGM). These experimental results are compared to theoretical maps obtained from equivalent finite element simulations for qualitative comparison. Using both these techniques, we observe abrupt inversion in the voltage response of the device when locally gating 2LG islands compared to 1LG. These manifests from differences in charge neutrality point of 1-2LG, and the ability of the SGM tip bias to manipulate the carrier density and mobility.
We further derive an analytical model to extract directly the carrier type and sheet carrier density from SGM measurements. With this we observe carrier type inversion between 1LG and 2LG. Thus, we demonstrate that SGM is an effective tool for studying gating effects in graphene devices with 10's of nm scale spatial resolution. Moreover, these results prove that strategical device design with specific 2LG structures can be used to enhance sensitivity of devices to electric fields.

1. T. Yager et al., Nano Letters, 13, 9, 4217-4223 (2013)
2. V. Panchal et al., 2D Materials, 3, 1, 15006 (2016)

Vishal Panchal received his MSci degree in Physics in 2010 from Royal Holloway, University of London, UK. In 2014, he completed his Ph.D. at the National Physical Laboratory, in affiliation with Royal Holloway, University of London. with a dissertation on "Epitaxial graphene nanodevices and their applications for electronic and magnetic sensing". Since then, Vishal has been hired as a Higher Research Scientist by the Quantum Detection Group at the National Physical Laboratory. Additionally, he completed a 6 month secondment in 2016 at the National Institute of Standards and Technology working on growth and electrical/optical characterization of epitaxial graphene nanoribbons on SiC(0001).

Vishal's current scientific interests include nano- and micro-scale studies on graphene and other related 2D materials. His expertise are in local electrical and optical characterizations with functional scanning probe microscopy techniques such as Kelvin probe force microscopy, conductive atomic force microscopy, scanning gate microscopy, scattering scanning near-field optical microscopy, etc.

Diana Aznakayeva: Carbon Nanotubes Composites for Objects Invisibility

posted 19 Jul 2017, 00:40 by info admin

Diana Aznakayeva, Emir Aznakayev

School of Physics and Astronomy, University of Manchester, Manchester, M1 3OJ, UK; 
Electronics Department, National Aviation University, Kiev, 03058, Ukraine

Among the requirements for a modern airplane is a requirement of their invisibility, i.e. low reflectivity with respect to electromagnetic radiation. The reflectivity of the airplane is determined primarily by its construction and dielectric properties of its surface materials. The dielectric properties of different composites from carbon nanotubes were investigated. Experimental investigation of electromagnetic radiation absorption with composites poly-tetrafluorethylene (F4) - CNT with different concentration of CNT was provided. 
These composites are effective surface materials for invisibility of objects. It is found that under decreasing of thickness of the carbon nanotubes composite rapid drop of passing monochromatic electromagnetic radiation intensity is observed. The sample thickness range varies from 0.1 mm to 0.6 mm. This phenomenon is explained due to changing in orientation of the carbon nanotubes. It leads to increased efficiency of monochromatic electromagnetic radiation absorption by the objects. The changes in the intensity of absorbed electromagnetic radiation after passing a laser (monochromatic) radiation through the composite sample F4-CNT of different thickness are presented in Figure (Dependence of the intensity of absorbed electromagnetic radiation I, mJ from thickness d, mm of composite sample F4-CNT).

Diana Aznakayeva is currently an PhD student at the Manchester University, UK. She is primarily interested in the photonics and electrical and optical properties of atomically thin materials such as graphene. She received her B.S. (2010) and M.S. (2012) degrees in Physics from the National Aviation University (Kiev, Ukraine) where she studied the electrical, optical and mechanical properties of carbon nanomaterials. After finishing her M.S. program, she spent 1 year as researcher at the National Aviation University and from 2014 she is a PhD student at the Manchester University. From 2004 to 2013 she provided the scientific research also in the Institute of Biochemistry, Institute of Physics and Institute of Physics of Metals in nanoscience, optics and electronic properties of nanomaterials. She has more than 60 papers and 1 book. She has different National and International awards for her research.

Mir Masoud Seyyed Fakhrabadi: Modal analysis and vibrational properties of two-dimensional nanomaterials

posted 11 Jul 2017, 06:46 by info admin

School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran

Nanomechanical properties of 2D nanomaterials in general and their vibrational properties in particular are very important for their real engineering applications such as in nanosensors or in nano-electromechanical systems. Besides the experimental techniques to study the vibrational characteristics of different 2D nanostructures, several computational methods are also used for this purpose solely or in combination including quantum-based methods, molecular dynamics, finite element analysis and continuum mechanics. Despite the same goal for all of them that is to obtain the natural frequencies and mode shapes of the nanostructures, each has its own advantages and limitations. This paper aims to illustrate the vibrational properties of the 2D nanomaterials with one-atom thickness (such as graphene and silicon carbide nanosheets) using finite element method and the comparison of the results with those predicted by continuum elasticity. Both of the vibration frequencies and mode shapes are compared and the level of agreement is discussed. The pros and cons of this technique in comparison to the atomic-based methods are investigated. If a molecule adsorbs on the surface of the 2D nanostructures, their vibrational frequencies will change and this change can be attributed to the mass of the molecule. The effects of added mass are also be covered.

Mir Masoud Seyyed Fakhrabadi graduated from BS and MS of Mechanical Engineering from the University of Tabriz. He obtained his PhD degree from the University of Tehran in Nanotechnology on nano-electromechanical systems. After the graduation, he worked as the Postdoc fellow at the University of Freiburg in Germany and at the University of Padova in Italy. He is now working as an assistant professor at the University of Tehran on experimental and computational nanomechanics. His awards include a Marie-Curie Postdoc fellowship at the University of Padova, a Postdoc fellowship offered by German research foundation at the University of Freiburg, award of best PhD thesis offered by Iranian society of mechanical engineering, award of the most distinguished university student entitled by Iranian ministry of science and technology, first rank in all BS, MS and PhD levels, and many other awards and honors.  

Zilong Liu: Mapping the the oxygen configuration on single graphene oxide sheets

posted 11 Jul 2017, 06:42 by info admin

Zilong Liu, Kasper Nørgaard, Marc H. Overgaard, Marcel. Ceccato, Susan L.S. Stipp, and Tue Hassenkam*

Nano-Science Center,
Department of Chemistry, 
University of Copenhagen
Universitetsparken 5, 2100 Copenhagen, Denmark

As one of the main precursors of graphene-related materials, Graphene Oxide (GO) has sparked a heightened interest in a wide range of applications. Critical for these applications are the type of oxygen bond and its spatial distribution on the individual GO sheets. This distribution is not yet well understood. Few techniques offer a resolution high enough to unambiguously identify oxygen configuration. In this work, we provide a novel and label-free spectroscopic technique to map functional group distributions on GO, with higher spatial resolution and chemical specificity using AFM-based infrared nanospectroscopy (AFM-IR). Overcoming conventional IR diffraction limit, the new technique can obtain high spatial resolution at a nanometric level as well as chemical maps that are coupled to topography.We have directly observed oxygen bonding preferentially on areas where graphene is folded, in discrete domains and on edges of GO. lts have interesting implications. Determining atomic position and configuration from precise imaging offers the possibility to link nanoscale structure and composition with material function, paving the way for targeted tethering of ions, polymers and biomaterials.   

Zilong Liu is currently an PhD student of Department of Chemistry at the University of Copenhagen. He is primarily interested in characterizing and investigating properties of atomically thin materials such as graphene, carbon nanotube. He received his M.S. degree in Materials Science and Engineering from China University of Petroleum (2015)  where he used the Molecular Dynamics and DFT calculations to study the self-assembly of functionalized graphene and its gas adsorption and separation effect. His awards include Outstanding Master Graduation Thesis of Shandong Province (2016), Outstanding Master Graduate Students of Shandong Province (2015), One of ‘Ten Outstanding Academic Students’ in China University of Petroleum (2014).

Elisa Dominese: 1D contact resistance in encapsulated graphene

posted 11 Jul 2017, 06:16 by info admin

Elisa Dominese, Bjarke Sørensen Jessen, Lene Gammelgaard

Politecnico di Milano

When encapsulated in high-quality hexagonal boron nitride, the carrier mobility of graphene approach the theoretical maximum predicted for clean, disorder-free graphene having zero interaction with the surroundings [1]. A surprisingly efficient way to form electrical contact to the buried graphene layer is by a metallic contact to the exposed, one-dimensional graphene edge at the fringe of the heterostructure. The contact resistance is still a bottleneck for many device applications including field effect transistors based on graphene. In this work we study the role of the geometry, size and position of the electrical edge contacts on the gate-voltage dependent contact resistance. An SF6 based etching recipe and the use of thermally controlled heterostructure assembly [2], allows a high degree of control in creating the device and defining the edges.  Inspired by the recently discovered angular dependence of interlayer contact resistance [3] we also study the possibility of angular dependence of edge contacts with respect to the graphene lattice orientation.

1. L. Wang et al., One-Dimensional Electrical Contact to a Two-Dimensional Material. Science 342, 614-617 (2013)
2. F. Pizzocchero et al., The hot pick-up technique for batch assembly of van der Waals heterostructures. Nature Communications 7 (2016)
3. T. Chari et al., Resistivity of Rotated Graphite–Graphene Contacts. Nano Letters 16, 4477-4482 (2016)

Elisa Dominese studies Materials Engineering and Nanotechnology at Politecnico di Milano. She decided to complete her course of study doing the master thesis project abroad joining the Nanocarbon group directed by professor Peter Bøggild at DTU Nanotech. 

David M. A. Mackenzie: Quality Assessment of Graphene: continuity, uniformity and accuracy of mobility measurements

posted 11 Jul 2017, 06:12 by info admin

David M. A. Mackenzie, Jonas D. Buron, Patrick R. Whelan, José M. Caridad  Martin Bjergfelt, Birong Luo, Abhay Shivayogimath, Anne L. Smitshuysen, Joachim D. Thomsen, Tim J. Booth,  Lene Gammelgaard, Johanna Zultak, Bjarke S. Jessen, Peter Bøggild, and Dirch H. Petersen

Department of Micro & Nanotechnology, Technical University of Denmark, Building 345E, 2800 Kgs. Lyngby, Denmark

As the availability of large area graphene increases, accurately assessing uniformity and quality has become critically important. Assessment of the spatial variability in carrier density and carrier mobility (µ) can be time consuming and difficult, but variations must be controlled and minimized. We present a simple framework for assessing the homogeneity of graphene devices. The field effect in large-scale CVD devices [1] (Fig. 1a) and devices of exfoliated graphene encapsulated in hexagonal boron nitride [2] (Fig. 1c) were measured in dual configurations (Fig. 1b inset). We can then derive a gate-dependent homogeneity factor, ß (Fig. 1b/d). Finite element simulations were carried out suggesting that inhomogeneity in spatial doping (as low as 1010 cm-2) rather than inhomogeneity in µ is the significant cause of variations in ß. Such doping variations are shown to lead to systematic errors when calculating µ- errors which are hidden if ß is ignored. In addition, we find that for certain devices Raman mapping (Fig. 1e) can be used as input for finite element simulations and reasonable agreement is found between simulated and experimental gate-dependent electrical data (Fig. 1f). A recent comprehensive study can be found here [3]. 

1. David M A Mackenzie et al 2015 2D Mater. 2 045003
2. F Pizzocchero et al 2016 Nature Comms. 7 11894
3. David M A Mackenzie et al 2017 Nano. Res. DOI 10.1007/s12274-017-1570-y

David Mackenzie is a researcher in the Nanocarbon group based at the Department of Micro & Nanotechnology, Technical University of Denmark. Research interests include fabricating graphene devices, accuracy of electrical measurements, gas sensing measurements, finite element simulations, and Raman spectroscopy.

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