bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flexible Sheet Heater with Carbon Nanotube Networked Thin Graphite Flakes
Authors: Hong Young Kyu , Kim Byung-Ryang , Shin Jin-Koog , Park Hyeon Ki , Choi Yong Ho , Hong Chan Ho 
Published: February 2020

Carbon nanomaterials have attracted much attention for heater applications due to their outstanding thermal characteristics [1-3]. Also, sheet heaters made from carbon nanomaterials have drawn on going interest of automobile industry as a promising candidate for heater applications due to the flexibility, low power consumption, and rapid response. Despite of potential possibilitis of carbon nanomaterials for heater applications, it is needed to improve the electrical conductivity and mechanical durability for practical use such as seat heater.
In this study, we fabricated sheet heater using thin graphite flakes to improve electrical conductivity and multi walled carbon nanotubes (MWCNT) to ehnance the mechanical stability of sheet heaters. The thin graphite flakes and amide functionalized MWCNT were blended with polyester resin and printed on a PET film by screen printing method. Fabricated sheet heaters show uniform heat distribution compared to conventional wire heater. And then, we fabricated large area heater same as seat heater for automobile application to evaluate the feasibility of the sheet heater. Heating characteristics of the sheet heater was analyzed in correlation with microstructure and electrical characteristics.
This research was financially supported by the Ministry of Trade, Industry and Energy(MOTIE) and Korea Institute for Advancement of Technology(KIAT) through the Promoting Regional specialized Industry
References
[1] Daewoong Jung, Donghyun Kim, Kyung H. Lee, Lawrence J. Overzet, Gil S. Lee, Sensors and Actuators: A 199, 176 (2013).
[2] Hoon-Sik Jang, Sang Koo Jeon, Seung Hoon Nahm, CARBON 49, 111 (2011).
[3] Hyeongwook Im, Eui Yun Jang, Ajeong Choi, Wal Jun Kim, Tae June Kang, Yung Woo Park, and Yong Hyup Kim, Appl. Mater. Interfaces 4, 2338 (2012).
Invited Presentation: Advances in Theory of Nanotube Growth, Nucleation, and Cooperative Effects
Authors: Yakobson Boris I. , Penev Evgeni S. , Artyukhov Vasilii I. , Xiong Lee 
Published: February 2020

We will discuss the developments in theory of sp2-carbon growth [1], the similarities and contrasts between nanotubes and graphene, including the dynamics of defect healing [2]. Comprehensive DFT computations allow one to build a "nanoreactor" diagram of all important energy states, and then to predict the rate of carbon addition, the growth speed in different directions, and thus the shape of growing or shrinking graphene islands. Further, the nanoreactor approach enables understanding the role of auxiliary species, like hydrogen [3] or oxygen [4]. Nucleation statistics of CNT in its relation with the energy of the caps [5] and edges [6] can lead to explanation of recent experimental findings. Cooperative aspects in nanotube arrays will also be discussed [7].
[1] V. Artyukhov et al. Proc. Natl. Acad. Sci.
109, 15136 (2012).
[2] R. Rao et al. Nature Mater.
11, 213 (2012); Q. Yuan, et al. Phys. Rev. Lett.
108, 245505 (2012).
[3] Z. Yan et al. J. Amer. Chem. Soc., 135, 10755 (2013).
[4] Y. Hao et al. Science, 342, 720 (2013).
[5] E. Penev, V. Artyukhov, and BIY (submitted).
[6] Y. Liu et al. Phys. Rev. Lett.
105, 235502 (2010).
[7] L. Xiong and BIY (submitted).
Invited Presentation: Mechanism of Spontaneous Carbon Nanotube Partition in Liquid Multiphase Systems
Authors: Zheng Ming 
Published: February 2020

Ming Zheng1, Constantine Khripin1, Geyou Ao1, Jeffrey A Fagan1, Min Zhang2, Yoichiro Ito2, Hui Gui3, Chongwu Zhou3

1. National Institute of Standards and Technology, Gaithersburg, MD, United States.
2. NIH, Bethesda, MD, United States.
3. University of Southern California, Los Angeles, CA, United States
In this presentation, we will explore the mechanism of spontaneous carbon nanotube partition in different liquid phases created by dissolved polymers. In general, carbon nanotube partition is chirality dependent and can be modulated by different chemical species. This provides a scalable and cost-effective way to purify and separate carbon nanotubes dispersed by many different types of surfactants. We show that the separation can be carried out in various schemes, from simple manual multi-step extractions to automated chromatography-based method. Very high purity metal-semiconductor and single chirality CNT separations have been achieved. While a quantitative understanding of the separation mechanism is still lacking, considerable insight has been gained on the role of carbon nanotube hydrophobicity, surface coating and its interaction with other molecules in the liquid phases. A working model of the separation mechanism will be presented.
Unique Molecular Properties of a Paramagnetic Endohedral Metallofullerene La@C82: Its Chemical Reactivities, and Electronic and Magnetic Properties
Authors: Takano Yuta , Veciana Jaume , Guldi Dirk M. , Martin Nazario , Akasaka Takeshi 
Published: February 2020

Endohedral metallofullerenes (EMFs) have attracted special interest as new spherical molecules because they have unusual physical and chemical properties that are imparted by the encapsulated metal atoms.[1] Among the fullerenes in general, paramagnetic EMFs have garnered much attention because of their unique electronic and magnetic properties, quite different from the closely related non-paramagnetic endofullerenes.
La@C82 has extensively been investigated as a prototype paramagnetic fullerene because it is the first endohedral metallofullerene which was reported the successful isolation for the first time. [2] Moreover, it was demonstrated that a family of lanthanum containing fullerenes were produced and that extraction with toluene yielded abundantly La@C82. La@C82 has an electronic structure which is best described as [La]3+[C82]3- with an open-shell electronic character that is a consequence of transferring three electrons from lanthanum to C82 (Scheme).[3] The resulting electron spin imposes a unique chemical reactivity comparable to that of a radical character.[4] The latter is believed to induce magnetism[5] and enhance electron conductivity.[6] In this regard, our group has investigated and revealed unprecedented molecular properties of La@C82.
In this talk, I will present its unique radical reactivity,[4] photo-induced intramolecular electron transfer,[7] and the SAM demonstrating electrochemical switching[5] based on La@C82.

References:
[1] (For reviews of EMFs) (a) Chemistry of Nanocarbons; Akasaka, T., Wudl, F., Nagase, S., Eds.; Wiley: Chichester, 2010. (b) Chaur, M. N. et al.
Angew. Chem. Int. Ed.
2009, 48, 7514. (c) Popov, A. A. et al. Chem. Rev.
2013, 113, 5989.
[2] Chai, Y. et al.
J. Phys. Chem.
1991, 95, 75648.
[3] Nagase, S. et al. J. Chem. Soc., Chem. Commun.
1994, 1837.
[4] (a) Takano, Y. et al. J. Am. Chem. Soc. 2008, 130, 16224. (b) Takano, Y. et al. Chem. Commun. 2010, 46, 8035.
[5] Takano, Y. et al. Chem. Commun. 2013, 49, 8145. (Selected for front cover)
[6] Sato, S. et al.
J. Am.
Chem. Soc.
2011, 133, 2766.
[7] Takano, Y. et al. J. Am. Chem. Soc. 2012, 134, 16103.
Photo-Addition of Amino Acid Methyl Esters to [60]Fullerene
Authors: Moussa Fathi , de Person Marine 
Published: February 2020

Since their discovery in 1985 and early after the development of a method of efficient synthesis, countless studies showed that fullerenes and derivatives exhibit paramount potentialities in several fields of science and technology.
While some authors consider that the chemistry of fullerenes is now well established, several issues remain to be clarified.[1] In particular, the synthesis of poly-adducts is difficult to control because it leads to many isomers.
The photo-addition of amino acids to C60 may be a facile route for C60-poly-adduct synthesis. However, the involved mechanism and the maximum number of adducts remained to be ascertained.
Recently, we proposed two possible mechanisms of photo-addition of glycine methyl ester (GME) to C60. The first one involves the concomitant addition of two GME radicals followed by an unprecedented cyclization mechanism leading to fulleropyrrolydines (FP) formation. The second one involves several steps leading to azomethine ylide (AMY), which undergoes a [2+3] cyclo-addition to C60.
To check this assumption, we used HRMS and HPLC-MS to systematically investigate the composition and the evolution of the reaction mixture during irradiation. Our results show that: 1- AMY is present in the final mixture, which confirm the second mechanism, and 2- the maximum number of adducts on C60 is equal to 6.[2]

Similar experiments with other amino acids are currently performed in our laboratory. Preliminary results suggest that this reaction can be generalized to all amino acid classes.
References :
[1]Martin, N, Chem Commun. 2006, 2093—2104.
[2] de Person M, Coffre A, Skanji R, Ben Messaouada M, Abderraba M, Zhang Y, Moussa F Tetrahedron 2013, 69, 6826-31.
Fabrication and Characterization of Photodetectors Composed of Graphene/Silicon Schottky Junctions
Authors: An Yanbin , Behnam Ashkan , Bosman Gijs , Pop Eric , Ural Ant 
Published: February 2020

Graphene, which shows good electrical conductivity, high optical transparency, and mechanical flexibility, is a promising candidate for transparent, conductive, and flexible electrodes in optoelectronic and photovoltaic devices. Unlike conventional metal electrodes, graphene has the added advantage that its Fermi level and hence workfunction can be tailored by chemical doping or electrostatic gating. As a result, graphene can be used in traditional as well as novel device structures. For that purpose, integration of graphene into conventional semiconductor technologies, in particular those based on silicon, is of utmost importance.
In this talk, we discuss the fabrication of metal-semiconductor (MS) photodetectors [Fig. 1(a)], where chemical vapor deposition (CVD)-grown monolayer graphene [Fig. 1(b)] plays the role of the metal and p-type silicon (p-Si) is the semiconductor. We characterized the photodetector devices and extract important parameters which give insights into their fundamental electronic and optoelectronic properties.
First, we investigate the electronic properties of graphene/silicon junctions as a function of temperature. We find that thermionic emission is the dominant electronic transport mechanism above 260 K with a zero-bias barrier height of 0.48 eV. Using temperature dependent I-Vmeasurements, we investigate the reverse-bias dependence of the Schottky barrier height and conclude that the Fermi level change in graphene due to charge transfer from Si dominates this dependence.
We also characterized the photoresponse of photodetectors based on graphene/silicon Schottky junctions [Fig. 2]. The good photoresponsivity (~0.133 A/W at 633 nm) and external quantum efficiency (>15%) shows the great potential of this type of device for photodetector applications. Furthermore, we performed photoresponse measurements at different chopper frequencies and extracted the bandwidth of the photodetector.
Low frequency electronic noise spectra of the graphene/silicon device are also studied at both forward and reverse bias. The scaling of noise with device current shows SI ~ Iβ
dependence, with β = 1 for forward bias and β = 2 for reverse bias. This β dependence is in agreement with empirical models reported previously. The noise spectra indicate that the electronic transport is dominated by thermionic emission, which is consistent with our temperature dependent I-Vanalysis. Finally, we extracted important device parameters, including normalized photocurrent-to-dark current ratio, noise equivalent power, and detectivity, which are found to be better than those previously obtained for similar detectors based on carbon nanotubes.
Our results provide crucial insights into the fundamental electronic and optoelectronic properties of photodetectors based on graphene/silicon Schottky junctions, which is important for the integration of graphene based materials into existing semiconductor technologies.
Electron Transfer Kinetics on Mono- and Multi-Layer Graphene
Authors: Velicky Matej , Toth Peter S , Valota Anna , Cooper Adam J , Kinloch Ian A , Hill Ernie W , Novoselov Kostya S , Dryfe Robert AW 
Published: February 2020

Since the first isolation of graphene monolayer via mechanical exfoliation in 2004, many other production methods have emerged in the following years. These methods include chemical vapour deposition, liquid phase graphite exfoliation, graphite oxide reduction and epitaxial growth, each having its pros and cons. The unique properties of graphene, such as high electron mobility, large specific surface area, mechanical strength and high transparency, ignited an enormous research interest to explore the electrochemical properties of graphene sheets, with potential uses in many immediate applications such as energy storage, solar cell technology and corrosion protection. Understanding how the electron transfer kinetics of a redox reaction between the graphene surface and a molecule compares to graphite or other carbon based materials is crucial to future use of graphene as a ‘supreme’ electrode material.1

Herein, the electrochemical response of mono-layer and multi-layer graphene electrodes, prepared using both chemical vapour deposition and mechanical exfoliation, is presented. Experiments were carried out using a microinjector, micromanipulator and optical microscopy, enabling precise deposition of size-controlled droplets on the flake surface.1 The insulating substrates used for flake preparation include inorganic materials and organic polymers. Graphene/graphite flakes were characterised using optical microscopy, Raman spectroscopy and atomic force microscopy.
The electron transfer rate at the basal planes, edge planes and boundaries between graphene flakes was determined using voltammetric techniques. The redox couple, number of graphene layers, presence of defects and nature of the substrate are all shown to have a significant effect on the electrochemical activity.2-3 Furthermore, the stability of the droplets on the surface depends on various factors, such as the solvent choice, electrolyte content, number of graphene layers, underlying substrate and method of flake preparation.
1. Valota, A. T.; Toth, P. S.; Kim, Y. J.; Hong, B. H.; Kinloch, I. A.; Novoselov, K. S.; Hill, E. W.; Dryfe, R. A. W., Electrochimica Acta, 2013, 110, 9-15.
2. Valota, A. T.; Kinloch, I. A.; Novoselov, K. S.; Casiraghi, C.; Eckmann, A.; Hill, E. W.; Dryfe, R. A. W., ACS Nano, 2011, 5 (11), 8809-8815.
3. P. S. Toth; A. Valota; M. Velicky; I. Kinloch; K. Novoselov; E. W. Hill; R. A. W. Dryfe, Chemical Science,
2013, DOI:10.1039/C3SC52026A.
First Principles Study of the Role of Defects for Graphene Lithiation
Authors: Yildirim Handan , Zhao Zhijian , Chan Maria K. Y. , Greeley Jeff 
Published: February 2020

Since the discovery of freestanding graphene, this 2D structure is considered as a potential alternative for graphite, because of its outstanding electronic and mechanical properties. It has attracted much attention as a promising electrode material for electrochemical energy storage devices such as Li-ion batteries due to high surface area and superior electronic conductivity. For Li-ion battery applications, graphene is used as a buffer layer to suppress the large volume expansion observed in high capacity anode materials and as a coating material to enhance conductivity. It was shown that graphene sheets prepared by reduction of graphite oxide (GO) deliver a reversible capacity and good cycling stability. Large variation in the capacity is reported by several studies for graphene, which is prepared with the exact similar techniques. Such discrepancy is suggested to result from the disordered and/or ordered structure of graphene sheets affecting lithium storage capacity, suggesting that the structural characteristics influence the resulting electrochemical performance.
Note that earlier experimental studies have identified the existence of defects such as Stone-Wales and double vacancy defects, as well as grain boundaries in graphene. Thus, for complete understanding of the electrochemical performance of graphene, the role of different types of defects on the electrochemical performance should be identified as well as the defect density influence should be evaluated. Such comparative study along with pristine graphene can provide vast amount of information not only for the electrochemical performance, but also, for the structural and electronic structure differences with the types of defects, defect densities, and Li concentration.
In this study, we use density functional theory to build atomistic level understanding of topological defects in graphene and their role on the electrochemical performance. Li configurations are generated combining an algorithm whose results are tested using a genetic algorithm method. We explore the effect of each defect type on Li adsorption and obtain an atomic level understanding of the interaction between defected graphene and Li. The electrochemical performance of these defective sheets under varying Li concentration is studied, and compared with those obtained for pristine graphene. Furthermore, the effect of defect density on the electrochemical performance is evaluated. Lithiation voltages as function of each defect type will be reported and compared with those of the pristine graphene. The results are expected to shed light on the role of each defect type on the electrochemical performance of graphene as an alternative anode material for Li ion batteries.
XAFS Study on the Structures of Catalysts for Photoelectrochemical Hydrogen Evolution and CO2 Reduction Prepared By the Incorporation of Metal Complexes within Viologen Multi-Layers Formed on Si(111) Surfaces
Authors: Masuda Takuya , Sun Yu , Morita Yuki , Fukumitsu Hitoshi , Uehara Hiromitsu , Takakusagi Satoru , Chun Wang-Jae , Kondo Toshihiro , Asakura Kiyotaka , Uosaki Kohei 
Published: February 2020

Multi-electron transfer reactions such as the hydrogen evolution reaction, oxygen evolution reaction and carbon dioxide reduction reaction at semiconductor electrodes have been extensively studied because of the interest in solar-to-chemical energy conversion. Multi-electron transfer reactions at semiconductors are generally slow and a catalyst is required to efficiently promote these reactions. Hence, many groups have examined the modification of the semiconductor surface by catalytic metals. It was, however, found that direct contact of a metal leads to the formation of a Schottky junction and recombination center, resulting in a reduced efficiency.
In this study, we constructed organic molecular layers with viologen moieties as electron transfer mediators and various metal complexes such as PtCl4
2-, PdCl4
2- and AuCl4
- as catalysts for multi-electron transfer reactions on hydrogen terminated Si(111) surfaces and the modified Si(111) electrodes were utilized for photoelectrochemical hydrogen evolution and CO2 reduction reactions. Precise structures of the metal catalysts incorporated with the molecular layers were determined by polarization-dependent total reflection fluorescence (PTRF)-XAFS.
High selectivity for CO2 reduction in preference to the hydrogen evolution reaction was achieved at the Si(111) electrodes modified by molecular layers with viologen moiety and Pd and Au complexes, which are reduced to metallic nanoparticle under operation, and, therefore, actual catalysts for CO2 reduction were Pd and Au metal nanoparticles, which are known to be good electrocatalysts for CO2 reduction. High selectivity for CO2 reduction was also achieved at the Si(111) electrode modified by viologen moiety and Pt complex despite the fact that hydrogen evolution reaction is dominant at Pt metal electrode even in CO2 saturated solution. Pt complex is not reduced to metallic nanoparticle under operation, and, therefore, Pt complex acts as a confined molecular catalyst for CO2 reduction with high selectivity.

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Carbon Supported Metal Oxide Nanoparticles: Hierarchical Porous Structure and Electrochemical Properties
Authors: Zhao Chunxia , Yang Yunxia , Chiang Ken 
Published: February 2020

Energy storage devices made from nanostructured electrodes are reported to be lightweight and possess promising performance. Interest is growing in new energy storage devices that are low cost, lightweight, and deliver high energy and power densities. Supercapacitors are important energy storage devices that can deliver high power during short periods of time, making them attractive for electric vehicle applications.
Porous carbon supported metal oxide materials have been successfully used as electrode in supercapacitors. The efficiency of the electrochemical properties can be improved by using novel electrode with controlled nanostructure, nanoparticle size and electrochemical performance. In this work, hierarchically porous carbon supported metal oxides, including cobalt oxide and molybdenum oxide nanoparticles are designed, aiming to improve metal loading and dispersion with uniform nanoparticles, which in-turn enhances eletrochemical performance.
The hierarchically porous carbon matrix synthesized has bimodal porous structure with 300-400 nm macropores and ~ 20 nm mesopores with a BET surface area of ~370 m2/g. Cobalt oxides and molybdenium oxides were loaded by a wet impregnation method. The electrochemical properties of the synthesized hybrid materials will be demonstrated.
Current results demonstrate that cobalt oxide particles in the synthesized composites can be tuned from < 5 nm to 10 nm and are dispersed uniformly across the carbon matrix with loading as high as 15 wt%. Molybdenum oxide particles also can be well dispersed in the carbon matrix with a high loading up to 40 wt% and the valence of molybdenum can be tuned. We also demonstrate the network of meso- and macro- pores and high surface area offered by this type of carbon materials is promising to achieve high metal loadings and dispersion for better activity and mass transport.