This PDF file contains the front matter associated with SPIE Proceedings Volume 8814, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Transition-metal catalysts, fullerenes, graphitic carbon, amorphous carbon, and graphite flakes are the main impurities in carbon nanotubes. In this study, we demonstrate an easy and optimum method of cleaning SWCNTs and evaluating their purity. The purification method, which employed oxidative heat treatment followed by 6M HNO₃, H₂SO₄, HNO₃:H₂SO₄ and HCl acid reflux for 6h at 120°C and microwave digestion with 1.5M HNO₃ for 0.5h at 210°C which was straightforward, inexpensive, and fairly effective. The purified materials were characterized by thermogravimetric analysis and nuclear techniques such as INAA, XRF and XRD.

Having remarkable characteristics, carbon nanotubes (CNTs) have attracted a lot of interest. Their mechanical, electrical, thermal and chemical properties make CNTs suitable for several applications such as electronic devices, hydrogen storage, textile, drug delivery etc. CNTs have been synthesized by various methods, such as arc discharge, laser ablation and catalytic chemical vapor deposition (CCVD). In comparison with the other techniques, CCVD is widely used as it offers a promising route for mass production. High capability of decomposing hydrocarbon formation is desired for the selected catalysts. Therefore, transition metals which are in the nanometer scale are the most effective catalysts. The common transition metals that are being used are Fe, Co, Ni and their binary alloys. The impregnation of the catalysts over the support material has a crucial importance for the CNT production. In this study, the influence of the support materials on the catalytic activity of metals was investigated. CNTs have been synthesized over alumina (Al₂O₃), silica (SiO₂) and magnesium oxide (MgO) supported Fe, Co, Fe-Co catalysts. Catalyst – support material combinations have been investigated and optimum values for each were compared. Single walled carbon nanotubes (SWCNTs) were produced at 800°C. The duration of synthesis was 30 minutes for all support materials. The synthesized materials were characterized by thermal gravimetric analysis (TGA), Raman spectroscopy and transmission electron microscopy.

The future energy demand is expected to increase significantly due to an increasing world population and demands for higher standards of living and better air quality. Hydrogen is considered as an energy carrier because of its high conversion efficiency and low pollutant emissions. It can be produced from various sources and transformed into electricity and other energy forms with a low pollution. The catalytic decomposition of hydrocarbon has been seen as a really useful method for production of pure hydrogen and for the environmental concern. The objective of this study was to assess the impact of catalyst composition and processing parameters on CO_x–free hydrogen production and to produce an available solid form of co-product carbon as carbon nanotubes via catalytic decomposition of methane. The optimum experimental conditions for methane decomposition have been investigated. Fe, Co and Ni are used as catalysts (nano materials) over different substrates as SiO₂ and MgO to produce hydrogen at optimum temperatures.

Carbon nanotubes (CNTs) with their high mechanical, electrical, thermal and chemical properties are regarded as promising materials for many different potential applications. Chemical vapor deposition (CVD) is a common method for CNT synthesis especially for mass production. There are important parameters (synthesis temperature, catalyst and calcination conditions, substrate, carbon source, synthesis time, H₂ reduction, etc.) affecting the structure, morphology and the amount of the CNT synthesis. In this study, CNTs were synthesized by CVD of acetylene (C₂H₂) on magnesium oxide (MgO) powder substrate impregnated by iron nitrate (Fe (NO₃)₃•9H₂O) solution. The synthesis conditions were as follows: at catalyst calcination temperatures of 400 and 550°C, calcination time of 0, 15, 30 and 45 min, hydrogen concentrations of 0, 50 and 100 % vol, synthesis temperature of 800°C and synthesis time of 30 minutes. The synthesized materials were characterized by thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), X ray diffraction (XRD) and Raman spectroscopy. Effects of H₂ reduction on catalyst calcination and CNT synthesis were investigated.

Graphene’s unique mechanical, electrical, and thermal properties have made it a very attractive material desired for use in future technologies. Over the recent years, there have been many breakthroughs in research on graphene. Recently, the focus of the latest research has shifted towards scaling graphene production for commercial use by industry. The most promising method for scaling graphene growth for industry usage is chemical vapor deposition (CVD). CVD is a low cost, economic and scalable method for producing graphene. However, consistently producing high quality graphene quickly on a large scale has eluded researchers. Here we detail a method for reducing growth time required to produce high quality, large area graphene by adjusting the fluid mechanics of the CVD.

This contribution deals with the fabrication of electrode and supercapacitor cell using a new dynamic air-brush deposition technique. This method allows to achieve extremely (ou highly) uniform mats with finely tuned thickness and weight in a completely reproducible way. Using this deposition technique, we have analyzed the effect of mixture of CNTs and graphene/graphite on the electrode and cell properties (energy, power and capacitance). using a mixture of 75% of graphene/graphite and 25% of CNTs we increased the power by a factor 2.5 compared to bare CNTs based electrodes. We also analyzed the effect of the weight firstly on the capacitance and specific energy and then on the specific power. We were able to reach a specific power of 200kW/Kg and a specific energy of 9.1Wh/Kg with an electrode having a surface of 2cm² and a weight of 0.25mg composed by 50% of CNTs and graphene/graphite (using a common aqueous electrolyte). using our deposition technique we are able to achieve supercapacitors with ad-hoc characteristics simply modulating the weight and the concentration of the mixture in a completely reproducible way.

The use of carbon-based materials in electrochemical double-layer supercapacitors (EDLC) is currently being the focus of much research. Even though activated carbon (AC) is the state of the art electrode material, AC suffers from some drawbacks including its limited electrical conductivity, the need for a binder to ensure the expected electrode cohesion and its limited accessibility of its pores to solvated ions of the electrolyte. Owing to their unique physical properties, carbon nanotubes (CNTs) or graphene could overcome these drawbacks. It has been demonstrated that high specific capacitance could be obtained when the carbon accessible surface area of the electrode was finely tailored by using graphene combined with other carbonaceous nanoparticles such as CNTs¹².In this work, to further increase the specific capacitance of the electrode, we have covalently grafted onto the surface of single-walled carbon nanotubes (SWCNTs), exfoliated graphite or graphene oxide (GO), anthraquinone (AQ) derivatives which are electrochemically active materials. The modified SWCNTs and graphene-like materials have been characterized by Raman spectroscopy, X-ray photoemission and cyclic voltammetry . Then suspensions based on mixtures of modified SWCNTs and modified graphene-like materials have been prepared and transformed into electrodes either by spray coating or by filtration. These electrodes have been characterized by SEM and by cyclic voltammetry in 0.1M H₂S0₄ electrolyte.

In our earlier work¹, we have developed an analytical current transport model of a p-channel Tunnel Field Effect Transistor (T-FET) made from 2D atomically thick Graphene Nanoribbon (GNR). Considering drain-source voltage (V_DS), gate-source voltage (V_GS), carrier mobility (μ) and top gate dielectric (t_OX), the model demonstrates an ON current of 1605 μA/μm for a GNR width of 5nm at 0.275eV band gap. The calculated ON/OFF current ratio of 10⁷ with a very steep Subthreshold-Slope (SS) of 7.07mV/decade is obtained from the I-V_GS transfer characteristics. In the present work, current transport mechanism of graphene T-FETs considering constant and variable electric fields are proposed and corresponding I-V characteristics are obtained. The constant electric field model is based on tunneling mechanism of Esaki tunnel diode. The variable electric field model exhibits linear (Ohmic) I-V characteristics. Contrary to a variable electrical field, constant field model exhibits both linear and saturation regions of operation. Using back gated biasing, the n-channel TFET exhibits negative differential conductivity (NDC) for the variable electric field. The performance of GNR T-FET under constant electric field model is compared with the projected model of nMOSFETs in 2011 ITRS and found that the proposed model exhibits seven times lower power and eight times higher intrinsic speed in the upper GHz range. Such high performance makes graphene T-FET extremely suitable for design of ultra-low power RF integrated circuits.

Nanoscale electronic devices like field-effect transistors have long promised to provide sensitive, label-free detection of biomolecules. In particular, single-walled carbon nanotubes have the requisite sensitivity to detect single molecule events and sufficient bandwidth to directly monitor single molecule dynamics in real time. Recent measurements have demonstrated this premise by monitoring the dynamic, single-molecule processivity of three different enzymes: lysozyme, protein Kinase A, and the Klenow fragment of DNA polymerase I. In each case, recordings resolved detailed trajectories of tens of thousands of individual chemical events and provided excellent statistics for single-molecule events. This electronic technique has a temporal resolution approaching 1 microsecond, which provides a new window for observing brief, intermediate transition states. In addition, the devices are indefinitely stable, so that the same molecule can be observed for minutes and hours. The extended recordings provide new insights into rare events like transitions to chemically-inactive conformations.

Graphene electrodes provide a suitable alternative to metal contacts in molecular conduction nanojunctions. Here, we propose to use graphene electrodes as a platform for effective photon assisted tunneling through molecular conduction nanojunctions. We predict dramatic increasing currents evaluated at side-band energies ~ nħω (n is a whole number) related to the modification of graphene gapless spectrum under the action of external electromagnetic field of frequency ω. A side benifit of using doped graphene electrodes is the polarization control of photocurrent related to the processes occurring either in the graphene electrodes or in the molecular bridge. The latter processes are accompanied by surface plasmon excitation in the graphene sheet that makes them more efficient. Our results illustrate the potential of graphene contacts in coherent control of photocurrent in molecular electronics, supporting the possibility of single-molecule devices.

The interaction of Au particles with few layer graphene is of interest for the formation of the next generation of sensing devices ¹. In this paper we investigate the coupling of single gold nanoparticles to a graphene sheet, and multiple gold nanoparticles with a graphene sheet using COMSOL Multiphysics. By using these simulations we are able to determine the electric field strength and associated hot-spots for various gold nanoparticle-graphene systems. The Au nanoparticles were modelled as 8 nm diameter spheres on 1.5 nm thick (5 layers) graphene, with properties of graphene obtained from the refractive index data of Weber 2 and the Au refractive index data from Palik 3. The field was incident along the plane of the sheet with polarisation tested for both s and p. The study showed strong localised interaction between the Au and graphene with limited spread; however the double particle case where the graphene sheet separated two Au nanoparticles showed distinct interaction between the particles and graphene. An offset was introduced (up to 4 nm) resulting in much reduced coupling between the opposed particles as the distance apart increased. Findings currently suggest that the graphene layer has limited interaction with incident fields with a single particle present whilst reducing the coupling region to a very fine area when opposing particles are involved. It is hoped that the results of this research will provide insight into graphene-plasmon interactions and spur the development of the next generation of sensing devices.