bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer Simulations of Proton Discharge from Aqueous Solutions on Metal Electrodes
Authors: Spohr Eckhard
Published: February 2020

A reactive trajectory approach for the study of proton discharge from aqueous environments on charged metal surfaces is reviewed. It is based on an extension of a minimalistic empirical valence bond (EVB) model to study proton transfer in the bulk. Extensive quantum mechanical density functional theory calculations were parametrized for the EVB force field [1]. The model is used to investigate reactive (discharging) proton trajectories which were started in the bulk of a water film adsorbed on charged metal electrodes. The results indicate a transition between a reaction-dominated regime at moderate negative charges, where the rate constant increases exponentially, to a “transport limited'' regime where the transfer rate is almost independent of the surface charge density (at highly negative surface charge densities) [2,3].

Extensions of the model to electrolyte solutions are discussed along corresponding results of trajectory calculations that introduce background electrolytes with and without specific ion adsorption are presented. In NaCl solutions, e.g., it is found that the discharge rate is slowed down relative to that in pure water. We discuss how this phenomenon is associated with adsorption site-blocking by ions from the electrolyte, and with the reduced number of water pathways for Grotthuss style proton hops as a consequence of the presence of hydration shells containing water molecules in unfavourable arrangements for proton transfer. Further mechanistic insight can be gained from temperature dependent studies [4].

[1] F. Wilhelm, W. Schmickler, R. R. Nazmutdinov, and E. Spohr, “A model for proton transfer to metal electrodes,” J. Phys. Chem. C, vol. 112, pp. 10814–10826, 2008.

[2] F. Wilhelm, W. Schmickler, and E. Spohr, “Proton transfer to charged platinum electrodes. A molecular dynamics trajectory study,” J. Phys.: Condens. Matter, vol. 22, p. 175001, 2010.

[3] F. Wilhelm, W. Schmickler, R. Nazmutdinov, and E. Spohr, “Modeling proton transfer to charged silver electrodes,” Eletrochim. Acta, vol. 56, pp. 10632–10644, 2011.

[4] W. Schmickler, F. Wilhelm, and E. Spohr, “Probing the temperature dependence of proton transfer to charged platinum electrodes by reactive molecular dynamics trajectory studies”, Electrochim. Acta 101, 341, 2013.

This work was supported by Deutsche Forschungsgemeinschaft through Collaborative Research Group FOR1376 “Elementary Reaction Steps in Electrocatalysis: Theory meets Experiment” and through the Cluster of Excellence RESOLV (EXC 1069).
Electrode/Electrolyte Interface with Various Redox Couples
Authors: Frackowiak Elzbieta , Menzel Jakub , Meller Mikolaj , Fic Krzysztof
Published: February 2020

Typical electrostatic attraction of ions is at the origin of capacitance, however, some faradaic reactions may occur at electrode/electrolyte interface called pseudocapacitive phenomena. Such effects can be initiated from electrode but also from solutions with electroactive species (iodides, bromides, vanadium compounds, di-hydroxybenzenes etc.). Redox reactions are strongly affected by thermodynamics; Pourbaix diagrams indicate range of potential values where faradaic reactions take place. In typical two-electrode capacitor positive and negative electrode quite often operate not equally. One electrode can work in the very narrow range of potentials, e.g. iodides, bromides, di-hydroxybenzenes (0.1-0.4V) giving very high capacitance values (>1000 F/g) whereas the second one operates in the wide voltage limit but supplying moderate capacitance (ca. 100 F/g). Unfortunately electrode with smaller capacitance will affect a total capacitor performance. Selection of two various and well matched pseudocapacitive materials enables to optimize system. Asymmetric configuration with two different redox couples offers interesting capacitor performance with good cycling.

A few examples of pseudocapacitive phenomena originated from electroactive species present in electrolyte will be shown. Reactions with cerium-based autocatalytic redox shuttle for brominated species oxidizing malonic acid will be also presented as example of oscillating systems. They can serve as great source of pseudocapacitance and may significantly enhance total capacitance of the system. Detailed physicochemical and electrochemical characterization of electrode materials supported by modelling will reflect the role of texture, structure, conductivity of materials as well as concentration of species in electrolytic solutions on capacitor performance.

Acknowledgements

The authors would like to acknowledge a financial support from Swiss-Polish project INGEC.
A Study on the Oxygen Redox Reduction in Ionic Liquid-Based Electrolytes for Li/O2 Battery Application
Authors: Soavi Francesca , Monaco Simone , Arbizzani Catia , Mastragostino Marina
Published: February 2020

Low volatility, thermal and electrochemical stability and good conductivity of ionic liquids (ILs) make them “key electrolytes” for the development of Li/O2 batteries which are considered the most promising high-energy systems for a market success of electric vehicles of long driving range. Particularly, hydrophobic pyrrolidinium salts of bis(trifluoromethanesulfonyl)imide feature a high stability toward superoxide that is formed during the discharge/recharge of Li/O2 batteries. Under the European LABOHR Project, the oxygen redox reaction (ORR) and O2 diffusion coefficient and solubility, which are crucial parameters for Li/O2 battery operation, have been investigated in such ILs and related to the physical-chemistry properties of the electrolytes. It has also been demonstrated that ILs provide a real possibility for the development of rechargeable Li/O2 batteries that can safely operate even above room temperature. The main achievements of this study are here reported and discussed

Acknowledgement

Work funded by the European Commission in the 7th Framework Programme FP7-2010-GC-ELECTROCHEMICAL STORAGE, under contract no. 265971 “Lithium-Air Batteries with split Oxygen Harvesting and Redox processes” (LABOHR). All the partners of the LABOHR Project are acknowledged for the fruitful discussions on Li/O2 batteries with ionic liquids.

References

[1] www.labohr.eu

[2] S. Monaco, A. M. Arangio, F. Soavi, M. Mastragostino, E. Paillard, S. Passerini, Electrochimica Acta 83 (2012) 94–104.

[3] F. Soavi, S. Monaco, M. Mastragostino, Journal of Power Sources 224 (2013) 115 – 119.

[4] S. Monaco, F. Soavi, M. Mastragostino, J. Phys. Chem. Lett. 4 (2013) 1379−1382.
Spectroscopy of Metal/Electrolyte Interfaces
Authors: Wandelt Klaus R.
Published: February 2020

It is still a long way to reach the same holistic understanding of properties and processes at metal/ electrolyte interfaces as has been reached for surfaces in ultrahigh vacuum (UHV). In order to over-come this backlog i) more surface physisists should venture to "interfacial electrochemistry", because ii) new analytical techniques need to developed which replace all particle beam based methods which work successfully only in vacuum.

In this lecture I will present and discuss investigations of several electrochemical interface pheno-mena as they occur in electro-catalysis, anion-adsorption, metal-deposition, molecular self-assembly, structural phase transitions, etc., using a number of in-situ methods like various modes of optical spectroscopy (IRRAS, RAS, etc.), X-ray diffraction (XRD) and scanning tunneling microscopy/ spectros-copy (STM/STS) as well as (still unavoidably) ex-situ methods like electron spectroscopies (XPS; AES), low energy electron diffraction (LEED) and ion scattering spectroscopy (ISS). As an example Fig.1 shows EC-STM images and IRRAS spectra of a) the "stripe-structure" and b) the "cavitand-structure" of dibenzyl-viologen molecules adsorbed on Cu(100) in HCl-solution. XPS proves the monocationic [dicationic] state of the molecular building blocks in a) [b)], while IRRAS enables a structural refine-ment of the orientation of the individual molecular cations in the respective structure (see models).

References

[1] T.-D. Pham, K. Wandelt, P. Broekmann, Chem. Phys. Chem. 8 (16) (2007) 2318-2320

[2] M.Röefzaad, PhD-thesis, Univ. Bonn, Germany; and M.Röefzaad, K.Wandelt, in preparation

Fig. 1 EC-STM images and IRRAS spectra of a) the "stripe-structure" and b) the "cavitand-structure" of dibenzyl-viologen adsorbed on Cu(100) in HCl-solution (see text)
Spectroscopic and Electrochemical Studies of Reduction Reactions for Remediation and Batteries
Authors: Gewirth Andrew
Published: February 2020

We report on spectroscopic and electrochemical stress studies of reduction reactions relevant for batteries and remediation.

Silver is an effective electrocatalyst for the reduction of carbon dioxide to carbon monoxide and other products. Carbon-supported organometallic complexes of Ag with nitrogen-based ligands have been shown to effectively reduce CO2 with performance comparable to that of carbon-supported Ag alone, with increased Faradaic efficiency and less H2 production. The great decrease in the amount of Ag loading required makes these complexes attractive as CO2 reduction catalysts. We employ in situ surface-enhanced Raman spectroscopy (SERS) in order to investigate the mechanism by which CO2 reduction proceeds at silver electrodes in the presence of these nitrogen-based ligands, as well as the structural interactions of the Ag-ligand complex at the electrode interface. We show that an effect of surface decoration is to decrease the affinity of the CO product for the Ag surface, leading to higher rates of CO production.

We also use spectroscopic methods to assess the reduction of nitrate and dinitrogen on lithium electrode surfaces. We show that in contrast to the expected formation of lithium nitride, the material on the Li electrode is more complex, yielding an oxynitride species the presence of which is responsible for the partial passivation on the Li surface under these conditions. We contrast the behavior of nitrate on Li with that occurring on Cu under milder conditions.
3C-SiC on Si: A Biocompatible Material for Advanced Bioelectronic Devices
Authors: Saddow Stephen E. , Frewin Chris , Reyes Meralys , Register Joseph , Nezafati Maysam , Thomas Sylvia
Published: February 2020

Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. Consequently a tremendous amount of international activity has been on-going for over four decades to develop high-power solid state SiC electronics. While this activity has focused on the hexagonal polytypes of SiC, the only form that can be grown directly on Si substrates, 3C-SiC (or cubic SiC) has been researched for non-electronic applications such as MEMS and biosensors. In particular in our group we have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently has been investigating the use of this novel material for clean energy applications. This invited paper will review nearly a decade of activity in this regard, with particular emphasis on the most promising applications: in-vivo glucose monitoring, biomedical implants for connecting the human nervous system to advanced prosthetics, and MEMS/NEMS research aimed at allowing for in-vivo diagnostic and therapeutic systems for advanced biomedical applications.
Nanotubes for Osmotic Energy Harvesting
Authors: Poncharal Philippe , Siria Alessandro , Biance Anne-Laure , Fulcrand Rémy , Blase Xavier , Purcell Steve Thomas , Bocquet Lydéric
Published: February 2020

New paradigms for fluid transport are expected to emerge from the confinement of liquids at the nanoscales [1- 3], with potential breakthroughs in ultra-filtration, desalination, and energy conversion [4]. Nevertheless, advancing the fundamental understanding of fluid transport at the smallest scales requires mass and ion dynamics to be ultimately characterized across an individual channel to avoid averaging over many pores.

To this end, a major challenge for nanofluidics consists in building distinctive and well-controlled nano-channels, amenable for systematic exploration of their properties. In this work [5] we describe the elaboration and exploitation of a new hierarchical nanofluidic device, made of a unique boron-nitride (BN) nanotube that transpierces an ultrathin membrane and connects two fluid reservoirs. Such a transmembrane geometry allows the versatile exploration of fluidic transport through a single nanotube under diverse forcing, including electric fields, pressure drops, and chemical gradients.

Using this device, we discover huge osmotically-induced electric currents generated by salinity gradients, exceeding by two orders of magnitude their pressure-driven counterpart. We show that this result originates from the anomalously high surface charge carried by the BN internal surface in water at large pH, which was independently quantified from conductance measurements. The nano-assembling route using nanostructures as building blocks opens new perspectives to explore fluid, ionic and molecule transport at nanoscales, paving the way towards biomimetic functionalities. Our results furthermore suggests that boron-nitride nanotubes could be advantageously exploited as membranes for osmotic power harvesting under salinity gradients, making it a prime renewable source of energy.

[1] W. Sparreboom, et al., Nature Nano, 4, 713-720 (2009).

[2] L. Bocquet and E. Charlaix, Chem. Soc. Rev. 39, 1073-1095 (2010).

[3] J. C. Rasaih, et al., Annu. Rev. Phys. Chem. 59 713-740 (2008).

[4] B. E. Logan and M. Elimelech, Nature, 488 313-319 (2012).

[5] A. Siria, et al. Nature, 494, 455-458, (2013).
Carbon Nanotube Thin Films and Hybrid Structures for Supercapacitor and Fuel Cell Applications
Authors: Bekyarova Elena , Palanisamy Ramesh , Itkis Mikhail E , Haddon Robert C
Published: February 2020

The development of low cost and environmentally friendly energy conversion andstorage systems is currently of the utmost priority. Here we discuss the impact of chemical design of carbon nanomaterials on their performance as active materials for supercapacitor and catalyst support for fuel cell applications.

Chemical modification of single-walled carbon nanotubes (SWNTs) and graphene, is a powerful means to improve the charge capacitance of the materials. By introducing oxygen-containing groups the gravimetric capacity of SWNTs and graphene can be doubled. Furthermore, the combination of 1D SWNTs and 2D graphene affords hybrid structures with enhanced synergistic electrochemical performance.

We also demonstrate the advantages of functionalized SWNTs for the fabrication of SWNT thin film catalyst support layers in polymer electrolyte membrane fuel cells (PEMFCs). Introducing an optimum level of carboxylic groups in the SWNTs allows the fabrication of SWNT-based PEMFC with efficient Pt catalyst utilization. This offers an attractive route to the manufacture of highly efficient fuel cells that meet some of the US DOE 2017 technical targets.
Carbon Nanomaterials As Metal-Free Catalysts for Energy Conversion
Authors: Dai Liming
Published: February 2020

Oxygen reduction reaction (ORR) is an important process in many fields, including energy conversion (fuel cells, metal-air batteries), corrosion, and biosensing. Although Pt nanoparticles have been regarded as the best electrocatalyst for ORR in fuel cells, they are still suffered from multiple problems. For instance, Pt-based cathode electrocatalysts are susceptible to the cross-over effect, long-term instability, and CO poisoning. Furthermore, the high cost of Pt, together with its limited reserve in nature, has been shown to be the “bottleneck” for large-scale commercialization of the fuel cell technology.

Along with the recent intensive research efforts in reducing or replacing Pt-based electrode in fuel cells, we have previously demonstrated that vertically aligned nitrogen-doped carbon nanotubes (VA-NCNTs) produced by pyrolysis of iron (II) phthalocyanine could actively catalyze ORR via a four-electron process free from the crossover and CO poisoning effects with a 3-time higher electrocatalytic activity and better long-term durability than that of commercially available Pt/C electrocatalysts. Similar ORR electrocatalytic activity was also observed for nitrogen-doped graphene (N-graphene). On the basis of these experimental observations and quantum mechanics calculations, we have attributed the observed ORR catalytic activities of the VA-NCNTs and N-graphene to the electron-accepting ability of the chemically-bonded nitrogen atoms, which create a net positive charge (via intramolecular charge-transfer) on adjacent carbon atoms in the nanocarbon structures to readily attract electrons from the anode for facilitating the O2 adsorption and ORR on the cathode. These findings prompted us to develop carbon-based metal-free ORR catalysts by positively charging carbon atoms in the nitrogen-free carbon nanotubes and graphene plane through intermolecular charge-transfer with functionalized/adsorbed moieties. In particular, we have recently used poly(diallyldimethylammonium chloride), PDDA, as an electron acceptor for functionalizing N-free carbon nanotubes and graphene to show remarkable electrocatalytic activity toward ORR. We have also demonstrated that carbon nanotubes and graphene co-doped with N and B showed a synergetic effect toward ORR, and that nitrogen-doped 3D graphene foam (N-GF) could be used as a metal-free electrocatalyst for the reduction of triiodide to replace the Pt cathode in dye-sensitized solar cells (DSSCs). In this talk, we will summarize some of our work on the metal-free ORR catalysts based on carbon nanomaterials, along with an overview on the recent developments in this exciting field.
Highly Efficient Synthesis of Strongly Coupled Reduced Graphene Oxide/Nafion Nanocomposites with Enhanced Mixed Proton and Electron Conduction
Authors: Aragaw Belete Asefa , Su Wei-Nien , Rick John , Hwang Bing-Joe
Published: February 2020

Hydrogen fuel production from solar water splitting using an artificial photosynthetic device is the Holy Grail for sustainable energy generation. In the design of such a device, the development of new functional materials with high simultaneous transport of protons and electrons is an important quota of the work for an efficient energy system. In here, reduced graphene oxide (RGO)-Nafion nanocomposite membrane with both high proton and electron conductivity was successfully synthesized using a simple solution casting method followed by a hot press thermal reduction process at a temperature higher than the thermal stability of Nafion. Interestingly, in the hybrid material, the strong-coupling effects, exerted by the electron withdrawing groups of Nafion and the functional groups of RGO, have played an important role in the improvement of both electron and proton conductivity. The strong coupling interaction phenomena are proved by IR, Raman and X-ray photoelectron spectroscopy. The proton conductivity of the material increased by two order of magnitude (~30 times), from 7.30x10-3 for recast Nafion to 2.20x10-1 S cm-1 while the electron conductivity reached 2.20x10-2 S cm-1 with 5 wt.% of RGO/Nafion nanocomposite in wet condition. The electron conductivity of this same nanocomposite increased 5 times, from 4.40x10-3 for RGO to 2.15x10-2 S cm-1 at ambient condition. The presence of RGO in Nafion increases the water uptake by left oxygen-containing functional groups. The electron withdrawing groups of Nafion (-CF2 &-SO3H) are responsible for the increased electron conductivity of RGO. The proton conductivity of composite is further enhanced by the alignment or morphological change of the membrane’s proton channels during hot press thermal reduction. The proposed synthesis is a simple, environmentally benign and scalable process to produce Nafion/RGO nanocomposites without complex dispersion or chemical reduction processes.
Carbon Nanostructures: Interactions with Biological Systems
Authors: Da Ros Tatiana
Published: February 2020

The interest on functionalized carbon nanostructures in the nanomedicine field is constantly increasing and many different approaches have been used to study the interactions and the effects of these nanomaterials on cells.

In this contribution we will mainly focus our attention on the analysis of genome expression of a cell line, comparing the results obtain before and after the treatment with two compounds, and taking into account the in vitro results obtained previously using traditional cytotoxicity test.
Gd-EMF-IL-13 and 177lu-EMF-IL-13 Endohedral Metallofullerene: A Targeting Diagnostic and Therapeutic Platform for Glioblastoma Multiforme Brain Tumors
Authors: Kiselev Boris , Zhang Jianyuan , Murphy Susan , Li Tinghui , Sheng Zhi , Dorn Harry C
Published: February 2020

Glioblastoma multiforme (GBM) brain tumors represent a devastating disease with no really effective treatment. GBM carries a life expectancy from the time of diagnosis of about 14 months.In this paper we report results for a novel carbonaceous platform, namely, endohedral metallofullerenes (Gd-EMF-IL-13 and 177Lu-EMF-IL-13), as a new multi-modal “theranostic” platform for the diagnosis and treatment of infiltrative GBM tumors. The targeting modality is a cytokine, interleukin-13 (IL-13), which is over-expressed in human and animal GBM cell lines, and is a key addition to the nanoparticle platform that has not been previously employed in therapeutic EMF studies. Our recent results for preparing and in vivo results for multi-modal endohedral metallofullerenes will be the focus of this presentation.1

References:

1. Zhang, J.; Stevenson, S.; Dorn, H.C. Trimetallic Nitride Endohedral Metallofullerenes: Discovery, Structural Characterization, Reactivity, and Applications. Accounts of Chemical Research, 2013, 46(7), 1548-1557
Double Impact of Modified Single-Walled Carbon Nanotubes in Nanomedicine: Vehicles for Gene Therapy and Theranostic Agents
Authors: Alidori Simone , Mulvey Justin J. , McDevitt Michael R. , Scheinberg David A.
Published: February 2020

In this work we demonstrated that single-walled carbon nanotubes (SWNTs) can be successfully exploited as tools to effectively deliver imaging agents, drugs or genetic material to tumors or selected tissues and offer significant advantages over antibody-based approaches or if compared to other nano-materials. In particular, the nanotubes can carry a substantial amount of cargo as compared to a monoclonal antibody, but can still be rapidly eliminated from the circulation by renal filtration, like a small molecule, due to their high aspect ratio, a property distinct from other nanoparticles. We describe how chemically modified SWCNTs can be used to stabilize, transport and deliver siRNA inside cells in vitro and in vivo in mice, allowing for the knockdown of specific genes. The optimization of SWCNTs and RNA constructs is essential for specific and efficient systemic delivery of gene-vectors to cellular targets. Our results have been applied to constructs that were able to silence the expression of protein more effectively and with lower cytotoxicity than a conventional transfecting agent, in vitro and in vivo. A second strategy involves the use of SWCNTs as multimodal platforms to target tumors in a two-step approach in which nanotubes modified with morpholino oligonucleotide sequences bind to cancer cells after pre-targeting with antibodies modified with complementary morpholino sequences. The nanotubes can carry fluorophores or radioisotopes, and are shown to selectively bind to and kill cancer cells in vitro and in tumour-bearing xenografted mice. Furthermore, the in vivo assembled constructs were demonstrated to internalize inside the targeted cancer cells. Conjugates labeled with alpha-particle-generating 225Ac were found to clear rapidly, thus mitigating radioisotope toxicity, and were shown to be therapeutically effective in vivo. Finally, the nanotube conjugates were labeled with both alpha-particle and gamma-ray emitting isotopes, at high specific activities, showing their potential use as powerful theranostic agents.
Invited Presentation: Electrochemically Induced Stresses in Energy Related Materials
Authors: Sheldon Brian W.
Published: February 2020

The volume changes that are associated with composition changes in a solid can induce significant stresses, when these expansions or contractions are physically constrained. These phenomena are important in a variety of energy-related materials, where they lead to complex interactions between electrochemical and mechanical driving forces. We have employed in situ measurements of these stresses along with a variety of other in situ and ex situ characterization methods, to obtain critical information about how the relevant mechanisms operate in different types of materials. One example is ceria electrolytes in solid oxide fuel cells, where oxygen potential gradients across the electrolyte can lead to large stresses. These stresses, caused by differences in the oxygen content of the ceria, are significantly enhanced by grain boundary contributions that can be interpreted with space charge effects.

In Li ion battery (LIB) electrodes, Li insertion and removal can also lead to very large stresses and complex deformation behavior. One area of interest here is the solid-electrolyte interphase (SEI) layer, where we have recently shown that substantial near-surface stresses occur during SEI formation on graphitic carbon anodes. These results imply that stresses can be engineered during SEI formation, to enhance the stability of these critical passivation layers. Another concern in is the mechanical integrity of interfaces in composite electrode structures. Here, we have used patterned thin film structures to understand the response of bi-material interfaces during Li cycling. The integrity of these interfaces is critical for cycling stability and capacity retention in rechargeable Li ion batteries.
Oxygen Nonstoichiometry, Defect Structure and Chemical Expansion of Advanced Perovskite and Double Perovskite Oxides
Authors: Zuev Andrey , Sereda Vladimir , Ivanov Ivan , Malyshkin Dmitry , Tsvetkov Dmitry
Published: February 2020

Perovskites and double perovskites based upon substituted oxides LnBO3-δ and LnBaB2O6-δ, respectively, where Ln=lanthonoid, B=3d-transition metal, are the state-of-the-art materials for a variety of different devices for moderate high temperature applications such as solid oxide fuel cells (SOFCs) and mixed ionic and electronic conducting (MIEC) membranes. The unique feature of the oxides is their ability to undergo both thermal expansion and that induced by the defects of oxygen nonstoichiometry in the oxide lattice. The latter is chemical or defect-induced expansion. This property is extremely sensitive to the defect structure of the oxide material. Despite it is generally recognized that point defects are responsible for chemical expansion its mechanism is still controversial topic. Different reasons such as changing Coulomb forces, atomic packing, local structure, preferred coordination, association between dopants and vacancies and others are discussed in this respect. If electronic defects have localized nature then another reason may lead to chemical expansivity. Within the framework of such assumption the oxygen vacancy formation is accepted to be accompanied by the reduction of 3d-metal cations. As a result, average size of the B-site cations increases due to the apparent substitution of “large” B(z-1)+ for smaller Bz+. Oxygen vacancy formation may also contribute to chemical expansion observed due to a change of coulomb interaction between ions. If oxide lattice chemical expansion is caused by a change of mean ionic radius due to reduction of most reducible cation then a model allowing its calculation can be developed. In order to do it the following assumptions should be accepted. (i) A closely packed lattice of oxide is formed by ions with rigid spheres. (ii) Expansion in each of three space directions is of equal value. The latter seems to be valid only for oxides with pseudo-cubic structure such as perovskites but this is not the case for layered double perovskite.

The model proposed for pseudo-cubic oxides was shown in this work to coincide completely with experimental data on chemical expansion for the perovskite La0.7Sr0.3Co0.9Fe0.1FeO3-δ. On the contrary, chemical expansion of PrBaCo2O6-δ along
a
axis and contraction along
c
axis were found to compensate each other completely in the double perovskite and, therefore, its volume (overall) chemical expansion becomes negligible. As a result the cell volume linearly increases with temperature in air contrary to simple cubic perovskites such as La0.7Sr0.3Co0.9Fe0.1O3-δ.
Tunable Carbon Nanotube Mesh Fabricated Via Surfactant Assisted Direct Deposition for High Performance Transparent Electrodes
Authors: Abdel-Fattah Tarek M , Dushatinski Thomas
Published: February 2020

This study involved the deposition of multi-walled carbon nanotubes (MWCNTs) onto plastic, polyethylene terephalate (PET), substrates. The MWCNTs were suspended in an aqueous solution via the assistance of an ionic surfactant, sodium dodecyl sulfate (SDS). The SDS/MWCNT complexes in solution were attracted to the PET substrate because of electrostatic forces that were demonstrated by contrasting poor coverage on glass substrates.

The solutions were deposited onto the PET films and allowed to interact for different amounts of time resulting in films that had decreasing resistivity and transparency because of increasing thicknesses.

The ratio of SDS to MWCNT to solvent, water in this case, was from an optimized MWCNT colloid study.1 The ratio used was 10:1:1000 respectively by weight. The excess surfactant was removed at different times using the spin coating technique. Films were then rinsed in water to remove excess surfactant caught in-between the nanotubes in the mesh and then dried in an oven.

The best thin film had an average resistivity of 110 Ω/sq at 81% transmittance at 550 nm and a thickness of ± 2 um. Their performance is similar to indium tin oxide thin films as cathodes. The MWCNT and SDS composite thin films will be tested in optoelectronic applications such as solar cells and liquid crystal displays.

References

1 Rastogi, R.; Kaushal, R.; Tripathi, S.; Sharma, A.; Kaur, I.; Bharadwaj, L. Comparative study of carbon nanotube dispersion using surfactants. 2008, J. Colloid Interface Sci. 328, 421-428.

2 Jo, J.; Jung, J.; Lee, J.; Jo, W. Fabrication of Highly Conductive and Transparent Thin Films from Single Walled Carbon Nanotubes Using a New Non-ionic Surfactant via Spin. 2010, ACS Nano. 4 (9), 5382-5388.
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.
Aromaticity As Driving Force for Bingel-Hirsch Derivatization of Endohedral Metallofullerenes
Authors: Osuna Sílvia , Garcia-Borràs Marc , Swart Marcel , Luis Josep Maria , Echegoyen Luis , Solà Miquel
Published: February 2020

Functionalization of EMFs is mainly achieved via cycloaddition reactions, principally through Diels-Alder (DA), 1,3-dipolar and nucleophilic [2+1] Bingel-Hirsch (BH) additions. It has been shown that the strain induced by the inner metal cluster on the carbon structure plays an important role in determining the regioselectivity of the EMF exohedral functionalizations.1 Electronic effects are also essential due to the formal charge transfer from the metal cluster to the fullerene cage.2 In DA and 1,3-dipolar cases, the best criterion for chemical-reactivity predictions of EMFs is provided by a combination of short bond lengths, high pyramidalization angles, and appropriate shape of some of the LUMOs.1 However, there are some recent experimental examples of BH cycloadditions on non-IPR EMFs where the usually employed reactivity parameters are not able to reproduce the experimental observations.3 In this communication, we unveil that the driving force behind the BH addition on EMFs is the aromaticity. We have explored the complete BH reaction mechanism for Sc3N@D3h
-C78 considering all non-equivalent addition sites. This system is the perfect scenario for investigating the BH addition as the encapsulated metal cluster cannot freely rotate and, therefore, the effect of the cluster on the BH reactivity is directly investigated. Our results clearly show that the BH addition is governed by the aromaticity of the fullerene rings.4 The aromaticity of the carbon cage of the first step intermediate of the reaction dictates the BH addition. Based on these observations, we have proposed some general aromaticity-based rules that correctly predict the most suitable BH addition sites for experimentally studied EMFs.5

[Figure 1 here]

S. Osuna, M. Swart and M. Solà, J. Am.
Chem. Soc., 2009, 131, 129.

M. Garcia-Borràs, A. Romero-Rivera, S. Osuna, J. M. Luis, M. Swart and M. Solà, J. Chem. Theory Comput., 2012, 8, 1671.

N. Alegret, M. N. Chaur, E. Santos, A. Rodríguez-Fortea, L. Echegoyen and J. M. Poblet, J. Org. Chem., 2010, 75, 8299.

M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis, L. Echegoyen, and M. Solà, Chem. Commun. 2013, 49, 8767.

M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis, L. Echegoyen, and M. Solà, in preparation.
ESR Studies of N@C60 and Its Derivatives in Polymer Matrices: Advances and Challenges
Authors: Porfyrakis Kyriakos
Published: February 2020

The paramagnetic endohedral fullerene molecule N@C60 is a candidate as an electron spin based quantum information processing element due to its exceedingly long phase coherence lifetime. A lot of attention has been focused on the electron spin properties of N@C60 in different environments. In terms of synthetic chemistry, a significant milestone has been the synthesis of a dimer molecule covalently linking two N@C60 units. The next significant challenge is the ability to control the interaction between multiple spin centres in an array. One potential method to achieve this is to macroscopically align rigid multi spin centre N@C60 molecules by incorporating them into a polymer matrix that is subsequently uniaxially drawn to align the chains. In this talk, I will present our ESR studies of the environment of pristine N@C60 and an N@C60-C60 dimer molecule in polystyrene matrices. I will show that deuteration of the polymer has a marked positive effect on the phase memory coherence time of pristine N@C60. Furthermore, I will show that deuterated polystyrene acts as a suitable polymer matrix for rigid N@C60-C60 dimer molecules, permitting both uniform dispersion and retention of a phase memory time (T
m) of 21µs at 40 K. This timescale is long enough to allow thousands of pulsed sequences to take place in order to manipulate the individual spin centres before decoherence can occur.
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.
Retrieving Precursors Toward Endohedral Metallofullerenes
Authors: Yuan Chao , Deng Lin-Long , Xiao Jun , He Li-Fang , Zhan Zhuang-Ping , Xie Su-Yuan
Published: February 2020

A series of intermediates such as C6, C1
0 and C16 have been retrieved by chlorination from the crude soot of carbon arc, affording insight into endofullerene formation. Identified by HPLC-MS and UV/Vis, production of perchlorinated polycyclic aromatic hydrocarbons (PAHs) such as C6Cl6, C1
0C8, and C16Cl10 from the reaction involving ICl with the crude soot of carbon arc heavily depends on formation of endofullerenes, as exemplified by the arc-discharge synthesis of metallofullerenes encapsulating with lanthanum or dysprosium. The perchlorinated PAHs reduce dramatically in chlorination of the pristine soot in the control trials with arc-discharge of graphite in absence of the typical encapsulated metals, with implication about the polycyclic carbon skeletons (i.e. C6, C1
0, C16) originating from the precursors toward endohedral metallofullerens. The work facilitates the understanding of how and what metals encapsulatable in the fullerene cage.
Crystal Structure and Dielectric Property of Endohedral Water Fullerene
Authors: Aoyagi Shinobu , Hoshino Norihisa , Akutagawa Tomoyuki , Kitaura Ryo , Shinohara Hisanori , Sugimoto Kunihisa , Zhang Rui , Murata Yasujiro
Published: February 2020

Polar water molecules in normal ice have a frozen random orientation even at 0 K due to the three-dimensional network of hydrogen bonds. Encapsulation of the water molecule inside C60 was recently achieved by the molecular surgical approach. The single water molecule trapped inside C60 is completely free from the hydrogen bonds. The easy separation of the H2O@C60 molecules from the empty C60 by high-performance liquid chromatography implies that H2O@C60 has a dipole moment. The dipolar interaction between the caged water molecules without hydrogen bonds in the H2O@C60 crystal could result in a net polarization and ferroelectricity. The crystal structure and dielectric property of pure H2O@C60 crystal is revealed in this study by the synchrotron radiation X-ray structure analysis and dielectric measurement. The crystal has a cubic structure similar to that of the empty C60 crystal except that water molecules are trapped inside the carbon cages. The water molecule rotates around its oxygen atom at the cage center even at 20 K. The rotating water molecules respond to an external electric field due to its permanent dipole moment.
Cocrystallization with Fullerenes for Molecular and Supramolecular Structure Determination
Authors: Ghiassi Kamran , Olmstead Marilyn M. , Balch Alan L.
Published: February 2020

Cocrystallization of fullerenes and endohedral fullerenes with Ni(octaethylporphyrin) (Ni(OEP)) has been widely used as a method of obtaining crystalline materials with sufficient order to allow structure determination by singe crystal X-ray diffraction. However, there are interesting alternative molecules such as bis(ethylenedithio)-tetrathiafulvalene (ET) that also form ordered cocrystals. This talk will discuss cocrystallization of fullerenes and endohedral with alternatives to Ni(OEP) and the structures of the resulting cocrystals and their components.
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.