bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cycloaddition of Nitrile Imines to Graphene. a Theoretical and Experimental Approach
Authors: Barrejon Myriam , Rodriguez Antonio , Gomez-Escalonilla María J. , Carrillo Jose Ramon , Prieto Maria Pilar , Langa Fernando 
Published: February 2020

Graphene is a unique material with outstanding mechanical and electronic properties.1 The modulation of the electronic properties of graphene by chemical functionalization as well as the control over the opening of its band gap are of great interest, because of the potential of this material for a wide range of applications.2

Due to the lower reactivity of graphene, compared to other carbon nanostructures, the range of reactions available for functionalization of this material is smaller than in the case of other carbon nanostructures as fullerene or carbon nanotubes.
Although most of the studies involving graphene functionalization has been performed by amidation of the carboxylic groups at the edges or by using diazonium salts,3 examples of 1,3-dipolar cycloaddition of azomethine ylide have been also described,4 but there are not examples in the literature of cycloaddition of other less reactive dipoles as nitrile imines or nitrile oxides.
In most cycloaddition reactions to [60]fullerene, the LUMO of the fullerene cage is shifted to higher values by 0.15 eV. Nevertheless, we have previously demonstrated that, in the cycloaddition of nitrile imines to fullerenes, affording pyrazolinofullerenes, the LUMO of C60 is not shifted to higher values due to the electron-acceptor character of the pyrazoline ring.5,6 So, cycloaddition of nitrile imines to graphene, if the reaction works, can be useful to modulate the band-gap in a different way than other cycloaddition reactions.
We present here the theoretical and experimental studies on the 1,3-dipolar cycloaddition of nitrile imines to graphene.
References:
[1]V. Georgakilas, M. Otyepka, B. Bourlinos, V. Chandra, N. Kim, K. C. Kemp, P. Hobza, R. Zboril and K. S. Kim Chem. Soc. Rev.
2012, 112, 6156.
[2] F. M. Koehler and W. J. Stark, Acc. Chem. Res. 2013, 46, 2297.
[3] L. Rodriguez, M. A. Herranz and N. Martin, Chem.
Commun. 2013, 49, 3721.
[4] M. Quintana, E. Vazquez and M. Prato, Acc.
Chem. Res. 2013, 46, 138.
[5] M. Álvaro, P. Atienzar, P. de la Cruz, J. L. Delgado, H. García and F. Langa, J. Phys. Chem. B
2004, 108, 12691;
[6] J. L. Delgado, N. Martín, P. de la Cruz and F. Langa, Chem. Soc. Rev. 2011, 40, 5253.
Non-Equilibrium Thermodynamics Approach for QED Heat Conductance Between Graphene and SiC Substrate
Authors: You Dan , Rotkin Slava V. 
Published: February 2020

Our study aims to explore heat transfer mechanism between graphene and polar insulator substrate. We develop a thermodynamic theory of heat transfer between graphene and SiC substrate based on master equation method and establish the difference of our model to the results obtain earlier by Fischetti (Ref.[1]), their equilibrium theory will be compared with the steady state solution of our non-eqilibrium model.
Graphene has attracted much attention due to potential applications in thermoelectric and photoelectric devices. Thermal properties of graphene have been extensively studied both experimentally and theoretically: graphene has very high in-plane thermal conductivity. Thus the thermal applications might be likely limited by the out-of-plane heat transfer [2]. In this context, integration of graphene with a polar substrate, such as SiC, can modify the thermal properties of former [3].
In this paper, we consider strong coupling between the surface plasmon- and phonon-polaritons in graphene and the substrate, respectively. These modes were assumed to provide the efficient QED heat flux channels. Fig.1 (a) shows dispersion relations of two (infinite lifetime) eigenstates E1and E2strongly mixed due to the quasi-electrostatic interaction between surface plasmon- and phonon-polaritons. Such localized surface modes are, in fact, dissipated into reservoir modes representing the bulk of materials, which can be calculated via the corresponding self-energy terms. This interaction between surface modes and their couterparts in the reservoirs (environmental modes) leads to the loss of the quantum coherence and the dissipation of their energy, when driven out of their equilibrium (with the reservoirs). Assuming weak system-reservoir interactions and a short reservoir correlation time, Markovian quantum master equations can be used to describe relaxation dynamics of our system.
Time evolution of the system was theoretically obtained. Assuming different temperatures for substrate and graphene, the coupled system is out of equilibrium which creates an non-zero net heat flux. The dynamics of the system towards the steady state can simulated. The average occupation shows an oscillatory behavior (Fig.1 d and e), here we consider the substrate being at a higher temperature. The heat flow from the surface optical phonon-like modes to graphene and from the substrate into the surface plasmon-like modes are shown in Fig.1b and c. In the steady state (long-time limit), the solution of our model does not coincide with thermal equilibrium state.
This work is supported by AFOSR (#FA9550-11-1-0185).
[1] Z. Y. Ong and Massimo V. Fischetti, Phys. Rev. B 86, 165422 (2011)
[2] A. A. Balandin, S. Ghosh, W. Z. Bao, I. Calizo, D. Teweldebrhan, F. Miao, and C. N. Lau, Nano Lett. 8, 902 (2008)
[3] J. H. Seol, I. Jo, A. L. Moore, L. Lindsay, Z. H. Aitken, M. T. Pettes, X. Li, Z. Yao, R. Huang, D. Broido, N. Mingo, R. S. Ruoff, and L. Shi, Science 328, 213 (2010).

Figure 1
1/F Noise in MoS2 Field Effect Transistors with Channel Length Variation
Authors: Das Suprem Ranjan , Kwon Jiseok , Claussen Jonathan , Hu Shan , Janes David B 
Published: February 2020

Field effect transistors (FETs) based on emerging nanoscale channel materials have numerous applications including post-CMOS logic for digital computing, communication and biochemical sensing. However, in fundamental level each of these applications requires tight scrutiny of carrier transport as the device operates in the desired regime and in the proposed environment. One of the important characteristics is to analyze the 1/f noise spectroscopy of the electronic device. In this paper we fabricate multilayer (15 atomic layer) MoS2 transistors of two different channel lengths (1µm and 2µm) and study the flicker noise in the devices at room temperature and ambient conditions; both devices being fabricated following the same process flows on a single micro-mechanically exfoliated flake of MoS2; thereby eliminating variability of 1/f noise from fabrication standpoints. Channel dominated 1/f noise with Hooge’s mobility fluctuation model for the devices were extracted from the bias dependent noise spectra. The noise characteristics of the devices are stable over several months of exposure to ambient. The robustness of the channel to its ambient and stability of current fluctuations reveal MoS2as an emerging candidate for reliable sensing.
Figure shows 1/f noise spectra of MoS2 FET with 15 atomic layer thick back-gated channels with Cr/Au source and drain electrodes. Channel lengths of 1µm and 2µm were compared for this study.
Key words: 1/f noise, MoS2 FETs, biochemical sensing

Figure 1
Pi-Extended 2D-Networks of Heteroaromatic Compounds - Towards Two-Dimensional Nanostructured Materials
Authors: Ryan Aoife A. , Berner Nina C. , Cafolla Attilo A. , Duesberg Georg S. , Senge Mathias O. 
Published: February 2020

Graphene and other two-dimensional (2D) materials such as inorganic transition metal dichalchogenides (TMDs) represent key nanostructural materials for use in a range of functional devices including gas and biosensors. The functionalization of nanomaterials is a critical factor for tailoring their surface properties, enhancing their potential applicability in optoelectronics and catalysis to name but a few. Porphyrins can easily be used for the construction of π-extended systems using well-established synthetic chemistry methodologies. [1] These range from organometallic C-C bond forming reactions to introduce tailored substituents at the porphyrin periphery and the construction of porphyrin arrays connected conjugated linkers, to porphyrin tape-like oligomers through oxidative meso-meso and meso-β-fusing reactions. The selective functionalization of these heteroaromatic systems now opens the possibility to combine them with carbon-based aromatic systems to yield mixed π-extended systems with unique photophysical properties. Present studies reveal the emergence of a surface chemistry of such systems where specific reactions, e.g., metallation, remetallation and C-C–coupling can be induced on surfaces. [2] Surface/macrocycle interactions alter the chemical properties of porphyrins and the adsorption of tailored macrocycles onto 2D surfaces could generate novel platform systems for, e.g., the attachment of biomarkers for use as biosensors. Additionally, TMDs, e.g., MoS2, represent a growing area of research due to their fascinating electronic and optoelectronic properties. [3] Through chemical modification of these surfaces it is hoped that attachment of large heteroaromatic systems will further tailor these materials for functional use.

References

[1] A. A. Ryan, M. O. Senge Eur. J. Org. Chem. 3700 (2013).
[2] S. Krasnikov, C. Doyle, N. Sergeeva, A. Preobrajenski, N. Vinogradov, Y. Sergeeva, A. Zakharov, M. Senge, A. Cafolla Nano Res. 4, 376 (2011).
[3] G. S. Duesberg Nat. Mater. 13, 1075 (2014).
(Invited) Synthesis, Characterization, and Applications of Single- and Double-Layer Graphene Grown on Epitaxial Metal Films
Authors: Ago Hiroki 
Published: February 2020

To develop graphene’s excellent and unique properties for future electronic devices, the synthesis of large area, high-quality graphene sheets with a controlled number of layers and well-defined structure is important. Here, we present our work to grow high-quality graphene with controlled orientation. Our method is based on heteroepitaxial CVD using highly crystalline metal catalyst deposited on single crystalline substrates, such as sapphire and MgO [1-6]. We investigated the CVD growth of single-layer graphene on Cu(111) and Cu(100) and found that the orientation of the graphene is strongly influenced by the underlying Cu lattice [2-4]. Large hexagonal graphene domains with a lateral size of 50-100 μm are aligned on the Cu(111) surface [5]. On the other hand, the orientation of graphene on Cu(100) has two main domain orientations, reflecting the symmetry mismatch between graphene and Cu(100) lattice. The carrier transport across the neighboring domains merged with the same orientation was investigated. We found a higher carrier mobility for devices inside one domain (mean value is 7,200 cm2/Vs at 280 K) than those with a domain interface in the channel (2,000 cm2/Vs), suggesting that the domain interface acts as a scattering site even when they merged with the same orientation [6].
Moreover, we have realized the selective growth of double-layer graphene on the heteroepitaxial metal films, which is expected to be applicable to semiconductor devices. The growth mechanism and the stacking order of the double-layer graphene will be discussed. Finally, our recent progress on the synthesis of two-dimensional heterostructures, such as graphene-MoS2 and graphene-NbS2hybrid structures, will be also presented [7,8].
[1] H. Ago et al., ACS Nano, 4, 7407 (2010). [2] B. Hu et al., Carbon
50, 57 (2012). [3] C. M. Orofeo et al., Carbon, 50, 2189 (2012). [4] Y. Ogawa et al., J. Phys. Chem. Lett., 3, 219 (2012). [5] H. Ago et al., Appl. Phys. Exp., 6, 75101 (2013). [6] Y. Ogawa et al., Nanoscale, 6, 7288 (2014). [7] W. Ge et al., Nanoscale, 5, 5773 (2013). [8] H. Ago et al., submitted.
Preparation and Photoelectrochemical Properties of Multilayered WS2 Coated Titanium Dioxide Nanocomposites
Authors: Lu Rongteng , Du Kang , Liu Guohua , Yang Changping , Wang Kaiying 
Published: February 2020

Since TiO2 was discovered for water-splitting to generate hydrogen under UV light, plenty of techniques have been explored to obtain suitable sensitizers for visible-light adsorption in order to increase the activity of water-splitting reaction for hydrogen generation [1-3]. Among them, dispersing a 2D graphene andsimilar layered material on TiO2 nanoparticle exhibits highly photocatalytic activities (i.e. MoS2) [2].
In this paper, graphene-liked WS2 was chosen due to its activity as HER (hydrogen evolution reaction) catalyst and relatively abundant storage [4]. The expected composite was formed through high energy ball milling technique which makes WS2 disperse on the surface of TiO2nanoparticles [5].
The composites consist of 99.5% TiO2 and 0.5% WS2and were prepared by high energy ball milling for five different periods of time-2hours, 4hours, 8hours, 16hours and 32hours. To identify phase evolution of the as-prepared nanocomposites during high energy ball milling procedure, X-ray diffraction (XRD) was performed to examine phase transition, which is shown in Fig.1. It can be seen that, with increasing milling time, the crystallization decrease at first and increase after further milling.
To further study the photoelectrochemical (PEC) characterization of composites after ball milling, a three-electrode setup was used, which is shown in inset of Fig. 2. This three-electrode device consists of a reference electrode (Ag/AgCl), a Pt wire counter electrode, a quartz container filled of 0.5M Na2SO4 aqueous solution and a working electrode. Sintered composites on indium-tin-oxide (ITO) glass substrate acts as the working electrode. Fig.2 shows the PEC measurement results of pure TiO2 and milled composites with milling time for 2hours, 8hours and 32hours. As can be seen, composite reaches the best photocurrent response with 8 hours milling. It is obvious that compared to pure TiO2 sample, adding of WS2and high energy ball milling make positive effect to composites.
In summary, the structure of TiO2 and WS2 nanocomposites through high energy ball milling has been studied by X-ray diffraction. Photoelectrochemical properties of the TiO2 coated with few layered WS2 shows the optimization photochemical response for 8 hours milled nanocomposites. This work provides a facile and low cost process for large amount production of few layer doped TiO2nanocomposites.

References

[1] A. Fujishima, K. Honda, Nature, 238 (1972) 37.
[2] Q. Liu, Z. Pu, A. M. Asiri, A. H. Qusti, A. Q. Al-Youbi, X. Sun,. J Nanopart Res 15 (2013) 1.
[3] W. Zhou, Z. Yin, Y. Du, X. Huang, Z. Zeng, Z. Fan, & H. Zhang, Small, 9(2013) 140.
[4] D. Merki, X. Hu, Energ Environ Sci, 4 (2011) 3878.
[5] H. C. Nazareno, Y. Zhao, K. Wang, IEEE Nano (2014)

Figure 1
Numerical Simulation of Single Solid Oxide Fuel Cell Performance By Coupling Dynamics of Electrochemical Flows with Thermal Impact on Solid Electrolytes
Authors: Chaudhary Tariq Nawaz , Chen Baixin 
Published: February 2020

It has been recognized that the thermal impact is the major concern for the electrolyte of Solid Oxide fuel cells (SOFC) due to the high temperature operating conditions. Therefore, it is necessary for engineering design to understand the mechanism of heat transfer from fuel/air reacting to the anode and cathode for cell designs. A numerical model has been developed for a single solid oxide fuel cell by coupling dynamics of electrochemical reacting flows, heat transfer, and thermal strengths of solid porous electrodes for analysing the cell performance. The Finite element method (FEM) is used for numerically solving the set of transportation equations. The developed model is applied to simulate the bench mark case of International Energy Agency (IEA) for both the co-flow and counter flow. The comparison shows a good agreement with the errors of 13% in current density value and 4% in maximum temperature with those of bench mark case. In case of co-flow the maximum temperature about 1109 °C is found at fuel outlet side. In case of counter flow the maximum temperature is 1118 °C and is observed at fuel inlet side. Predicted temperature distribution is applied to estimate the thermal stresses developed in the cell. Modelling results from simulations of a single unit of the SOFC cell operated at temperature of 900 °C, pressure of 1.01 bar, and the Reynolds number of 44.7 and 0.646 for air and fuel flows under adiabatic boundary condition, show that the maximum thermal stress produced in the cell is about 2600 MPa in the electrolyte at about 5mm away from the fuel inlet. Another case is simulated by considering convective heat flux boundary condition at top and bottom of the cell. The maximum thermal stress produced in this case is about 1820 MPa. The details of model development and the more results from the simulations will be reported in the full paper for predicting the effects of the thermal deformation of anode and cathode on the performance of a SOFC.
Challenges for Li-Ion Batteries Working at High Temperatures
Authors: Oltean Gabriel , Gustafsson Torbjörn 
Published: February 2020

Li-ion batteries working at high temperatures (from 80 to 110 ºC) are thought to be implemented in hybrid electric heavy vehicles. The high working temperature of the battery would facilitate faster charge and discharge rates, allowing the power demands of such an application to be easily reached. Furthermore, sharing a cooling system between the battery pack and other drive train components, such as power electronics, would simplify the thermal management in the hybrid electric vehicle.
Working at higher temperatures could potentially open the possibility of using electrode materials that do not normally work at room temperature due to kinetic limitations. Solid polymer and ionic liquid electrolytes could also be used, as the ionic conductivity and viscosity are improved at high temperatures. Unfortunately, increasing the working temperature of the battery will also present drawbacks. Secondary reactions kinetics are also improved when increasing the temperature, affecting the coulombic efficiency of the cell. Due to safety considerations, liquid electrolytes that are normally used in ambient temperature Li-ion batteries would have to be replaced by safer solid polymer or ionic liquid electrolytes. Finally, issues like the cold-start of hybrid vehicles and prediction of batteries life-time also need to be addressed.
We will present the work done at Uppsala University on high temperatures Li-ion batteries within the Swedish HT-LIB project. Different materials have been tested in half-cells in order to study their cycling performance at 80 ºC. Iron-based cathode materials (LiFePO4 and Li2FeSIO4) were chosen as they are cheap and environmentally friendly, while titanium-based anode materials (Li4Ti5O12 and TiO2) were chosen due to their high working potential versus lithium. The later is beneficial as there is less solid electrolyte interphase formation at those potentials and there is no risk for lithium plating. Finally, cycling of Li-ion whole cells at 80 ºC will be presented.
High Temperature Lithium-ion Batteries (HT-LIB) is a project funded by the Swedish Energy Agency and the collaboration between Chalmers University of Technology, Lund University, Uppsala University and Scania CV AB was created within the Swedish Hybrid Vehicle Centre.
Electrochemical Properties of SnO2 Electrode Fabricated By Liquid Phase Deposition Method
Authors: Mizuhata Minoru , Shibata Yuya , Maki Hideshi 
Published: February 2020

SnO2 nanoparticles which is a wide band gap semiconducting materials has been applied as gas sensor and anode in lithium-ion batteries. SnO2 has larger molecular weight than carbon materials. Compared to carbon materials, SnO2 has less effect of weight change in Li+ ion and Na+ ion, and this is the advantage of weight energy density for SnO2. SnO2 performs a two-stage reaction with Li+ ion and Na+ ion, hence the higher charge/discharge capacity is expected than Sn. Liquid phase deposition (LPD) method is a mild solution process for depositing various metal oxide thin films on the surfaces on various substrates. Moreover this method has been applied synthesis of metal oxide nanoparticles(NPs) by using polymer solution.
The synthesis of SnO2 NPs was carried out as following process: Aqueous [SnF6]2- / HF solution and aqueous H3BO3 solution added into polyethyleneglycol (PEG) and continuously stirred for 10 minutes. The mixed solution was kept at 30 ºC for 24 h. After the LPD reaction time, the mixture was centrifuged and sample was obtained. The synthesized two types of samples were characterized by various characterization tools such as X-ray diffraction (XRD), TEM, SEM, XPS Electrochemical measurement.
In NPs system, All XRD patterns can be assigned to SnO2 rutile. The crystallite size increased with calcination temperature more than 400 ºC. From a TEM observation, a change in morphology by calcination was not confirmed, but it was confirmed that particle size increased because of thermal fusion. In the first CV scans for all samples in Na+ ion systems, the reduction peak value at 0.01 V, which is thought that alloy reaction of Sn with Na is occurred, increased with increase in crystallite size as shown in Fig.1. However, in all samples the integrated reduction area was larger than the integrated oxidation area and the integrated reduction and oxidation area decreased depending on an increase in the cycle number. These results suggested irreversible reaction of Sn with Na. In XPS measurement, Na 1s peak intensity increased with charge, however it remained at fully discharge, and this showed irreversible reaction. Sn 3d5/2 peak shifted higher energy and this is one of the reasons to cause irreversible reaction. In Li+ ion system, charge – discharge measurement on sample as-deposition was carried out at 0.1 C(current density : 78.3 mAh¥g-1). This electrode gave a first cycle discharge capacity of 1015 mAh¥g-1, which is higher capacity than the theoretical discharge capacity of Sn(783 mAh¥g-1). This result indicated that not only alloy reaction described as Sn + xLi+ + xe- ↔ LixSn, but also redox reaction described as Sn + 2Li2O ↔ SnO2 + 4Li+ + 4e- attributed to charge – discharge property. For the results stated above, alloy type metal oxide electrode has advantage of capacity.

Figure 1