bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of the Carbon-Matrix in the Performance of Lithium-Sulfur Cell
Authors: Agostini Marco , Lim Du-Hyun , Matic Aleksandar 
Published: February 2020

Li-battery technology is today mainly developed as small energy delivery systems for portable devices.
1
However, in recent years the growing interest in renewable energy and in electric vehicles exploiting electric power requires the development of new, high capacity and long life batteries.
1
In this context Li-S battery technology became of great interest due to the high theoretical energy density of 3500 Wh kg-1, estimated to lead to 3-5 times increase in practical energy density compared to commercial Li-ion battery today available.
2

Even though the Li/S battery system has been widely investigated, several issues related to the lithium-sulfur electrochemical reaction still hinder the practical realization of this technology. Indeed, the electrochemical reaction mechanism involves a series of steps with formation of soluble polysulfide species.
3
This dissolution leads to the loss of active material from the solid electrode and to the “shuttle effect” of the polysulfide with consequent capacity reduction and limited cycling-life of the battery. Furthermore, sulfur has a very low electronic conductivity thus requiring the addition of a conducting matrix.

In this contribution we present the role of the carbon-matrix on the performance of Li-S cells based on liquid and solid electrodes. Various carbon and carbon-sulfur compounds have been taken into account and investigated. We demonstrated how the surface area, the pore structure and the free volume in the electrode are the significant driving forces to improve the Li-S electrochemical reaction.

References

(1) B. Scrosati, J. Garche, J. Power Sources. 195 (2010) 2419-3046.
(2) Y. Yang, G. Zheng, Y. Cui, Energy Environ. Sci.6 (2013) 1552-1558.
(3) X. Ji, L.F. Nazar, J. Mater. Chem. 20 (2010) 9821−9826.
(Invited) SWCNT:C60 Solar Cells from Aqueous Separation Techniques
Authors: Flavel Benjamin S 
Published: February 2020

In our work we develop new methods to scale-up aqueous separation techniques for the fabrication of inks and large area thin films of carbon nanotubes. This allows us to study the interaction of polymer-free single chirality and polychiral mixtures of nanotubes with acceptors such as C60 for energy applications such as solar cells. We are using transfer matrix calculations to theoretically calculate the optimal layer thicknesses within a nanotube solar cell and show that light absorption can be tailored to nanotube’s primary (S11) or secondary (S22) absorption peak, or a combination thereof. Upon using large diameter, (9,8), and mixtures of carbon nanotubes we then investigate the required net driving energy for SWCNT exciton dissociation onto C60 and establish a family of (n,m) species that can efficiently be utilized in polymer-free SWCNT:C60solar cells. Possible strategies to extend this diameter limit are discussed.
[1] M. Pfohl, K. Glaser, A. Graf, A. Mertens, D. Tune, T. Puerckhauer, A. Alam, L. Wei, Y. Chen, J. Zaumseil, A. Colsmann, R. Krupke, B. S.Flavel, Probing the Diameter Limit of Single Walled Carbon Nanotubes in SWCNT:Fullerene Solar Cells, Advanced Energy Materials, 6, 2016, 16008900 . DOI: 10.1002/aenm.201600890
[2] M. Pfohl, K. Glaser, J. Ludwig, D. D. Tune, S. Dehm, C. Kayser, A. Colsmann, R. Krupke, B. S. Flavel, Performance Enhancement of Polymer-Free Carbon Nanotube Solar Cells via Transfer Matrix Modeling, Advanced Energy Materials, 6 2016 1501345. DOI: 10.1002/aemn.201501345.
Diameter-Dependent Excitation Energy Transfer for Enhanced Semiconducting Single-Walled Carbon Nanotube Solar Photoconversion
Authors: Ihly Rachelle , van Bezouw Stein , Arias Dylan , Cambre Sofie , Campo Jochen , Ferguson Andrew John , Johnson Justin C. , Wenseleers Wim , Blackburn Jeffrey L. 
Published: February 2020

Tremendous progress and innovation has ushered the incorporation of semiconducting single-walled carbon nanotubes (s-SWCNTs) as active components into organic/inorganic/hybrid solar cells and thermoelectrics. For solar photoconversion, strong and tunable absorption is necessitated, suggesting that s-SWCNTs can play a role as light-harvesting components, however the narrow and distinct excitonic optical transitions found in s-SWCNT systems limit broad-band absorption. As such, we introduce encapsulation of small molecules within the endohedral volume of s-SWCNTs as a route to increase and extend light absorption in regions outside s-SWCNT excitonic transitions. Creation of this self-assembled supra-molecular system can strongly modify the opto-electronic properties of both the s-SWCNT and encapsulated molecule.
We investigate excitation energy transfer occurring from encapsulated dye molecules to s-SWCNTs, which results in luminescent SWCNT excitons. We exploit the high-throughput and chiral selectivity of polyfluorene wrapping methods to generate dispersions of s-SWCNTs with dye encapsulation. We demonstrate that the selectivity of the polyfluorene polymer for semiconducting chiral distributions is not affected by the presence of encapsulated molecules. Tracking the excited state transient absorption signatures of excitation energy transfer provides detailed information regarding dynamics of both the encapsulated dye and s-SWCNTs. We observe sub-picosecond excitation energy transfer of excitons generated in dye molecules to the surrounding s-SWCNTs. Photoluminescence excitation maps reveal that the absorption of encapsulated dye molecules depends sensitively on the diameter of the s-SWCNT in which they are encapsulated. We consider a simple molecular exciton model to describe aggregate formation within the s-SWCNT endohedral volume, which reveals that the dye molecules adopt unique aggregate structures that are defined both by a competition between intermolecular interactions between the dye molecules and confinement effects due to the s-SWCNT diameter. Small molecule encapsulation in s-SWCNTs serves as a strong platform to control intermolecular interactions in small molecule systems through confinement, which opens up the possibility of enhancing photo-induced extraction of energy and charge in s-SWCNTs solar photoconversion systems.
Fullerene-Grafted 3D Graphene As Electrical Energy Storage Material
Authors: Cerón Maira R. , Biener Monika M. , Campbell Patrick G. , Biener Juergen , Echegoyen Luis 
Published: February 2020

Supercapacitors have the potential to replace Li ion batteries as the next-generation electrical energy storage technology in demanding applications due to their high power density and excellent cycling stability. Graphene-based supercapacitor electrodes are particularly promising because they feature high surface area, good electrical conductivity, and chemical inertness. Researchers at Lawrence Livermore National Laboratory have developed tailored fullerene-grafted 3D mesoporous graphene macro-assemblies (GMAs) (Figure 1) for electrical energy storage applications by anchoring fullerene molecules to the 3D graphene backbone. Fullerene-grafted graphene (C60-GMA) materials promise to overcome the current charge storage limitations of carbon-based supercapacitors by combining the high charge storage capacitance of fullerenes with the high electrical conductivity of 3D-GMAs. In fact, the charge storage capacitance of fullerene (223 mAh/g) is similar or higher than that of today’s standard lithium ion battery electrode materials (177 mAh/g for LiFePO4).
Funding was provided by Lawrence Livermore National Laboratory Directed Research and Development (LDRD) Grant 17-ERD-017. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. IM Release Number LLNL-ABS-716277.

Figure 1. Fullerene-grafted 3D graphene bulk material

Figure 1
Direct Growth of Carbon Nanofibers on Nickel Foam and Its Application As Electrochemical Supercapacitor Electrodes
Authors: Sridhar Deepak , Omanovic Sasha , Meunier Jean-Luc 
Published: February 2020

Carbon nanofibers (CNF) are useful for many applications such as polymer reinforcement, electrochemical devices like sensors, batteries, and supercapacitors. The most common method of producing them is by catalytic chemical vapor deposition (CVD) or by electrospinning. CNF growth using CVD is a single step process, unlike electro spinning which requires an additional carbonization step at higher temperatures. In CVD the catalyst is either incorporated directly onto the substrate or introduced with the feed gases. This adds extra cost and set limits to the design of the systems used for the CNF growth process, particularly in cases where porous structures are envisioned.
In supercapacitors, the electrode material is most often painted or deposited with an ink of carbon particles. Directly growing the carbon nanomaterial from the supporting surface would eliminate this step and allow complex geometries. It would also help in achieving a higher capacitance by removing the requirement of a binder material and eliminate the occurrence of agglomeration of the active material inherent in the ink deposition process. Another advantage is the higher conductivity of CNF compared to the commonly used active carbon material. With CNF growing directly of the current collector, the addition of conductive carbon black can possibly be eliminated. Finally, an increase access of the electrolyte to the electrode can be expected due to the natural 3-D nano-architecture formed by the CNF. On the other hand, the micro-scale 3-D structure of nickel foams have been the most sought after substrates (current collectors) in the battery and supercapacitor research as they offer more surface area for the deposition of the required active material, together with being non-corrosive in alkali medium. CNF grown directly on Ni-foams are thus expected to extend the performances of supercapacitor electrodes.
In this work, we have found a novel method of growing dense CNF on nickel foam. Cyclic voltammetry, galvanotactic charge discharge, and electrochemical impedance spectroscopy was made to electrochemically characterize these CNF/Ni-foam supercapacitor electrodes. When tested as a supercapacitor electrode in 6M KOH, our directly grown CNF gives a good aerial capacitance of about 60 mF/cm2 and an energy density of 16 mWh/m2. We believe this nickel foam with CNF to be very useful in supercapacitors and batteries in decreasing the resistance of the electrochemical device and provide additional surface area.
(Invited) Nanographenes and Their Self-Assemblies for Highly Efficient Energy Devices
Authors: Wang Hsing-Lin , Wu Gang , Tretiak Sergei , Yen Hung-Ju , Holby Edward F. 
Published: February 2020

In recent years, the development of novel nanogrpahenes have drawn huge interests mainly because of their use in optical, electronic and energy devices. In our lab, we have developed syntheses of a series of 2D and 3D nanographenes with various functional groups attached to the edge of the nanographene basil planes. These nanographenes reveal long and short range orders in their self-assemblies. Such orders can be clearly visualized by high resolution TEM with well defined d-spacing between nanographene layers. These nanographenes are semiconductors with tunable electronic structures and processibility in organic solvents. We have demonstrated their use for optical and electronic devices. Among other potential application, these high-surface area nanographenes have an excellent cyclic durability and a much enhanced charge capacity as novel anode materials for LIBs. Moreover, theoretical charge capacity of these nanographenes exceeds 2000 mAh/g due to an increased edge to surface ratio and oxygen containing functional groups.

Figure 1
Nitrogen, Phosphorus Dual-Doped Ordered Mesoporous Carbon Electrocatalyst for Oxygen Reduction Reaction
Authors: Zhao Gang , Xu Jianbo , Zhao Tianshou 
Published: February 2020

To investigate the role of P in the dual-doped carbon electrocatalyst for oxygen reduction reaction (ORR) in alkaline media, three samples are prepared by varying the doping orders of N and P. Results show the resultant N-POMC (first doped with P, then N) exhibits an outstanding activity for ORR in alkaline media. The reason lies in the orientation effect of the first doped P on the later doped N, by increasing the ratio of graphitic-N significantly, confirmed by our experimental and DFT calculation. In addition, our results prove that the amount of graphitic-N is important in improving the activity for ORR. The doping strategy in this work is applicable to c0-doping strategy in exploring the synergy effect of different dopants and improving activity for ORR.
Electrocuring Tissue Adhesives
Authors: Steele Terry WJ 
Published: February 2020

The challenge remains on developing bioahesive formulations for tissue fixation. A recently invented electrically charged glue (known as electrocuring adhesive or voltaglue)[1] is being developed. Comparing with light (photocuring)[2], heat (thermocuring)[3], and chemical activation means, the electrocuring allows adhesive to be activated on-demand when an applied voltage potential is raised above a certain threshold. Such adhesive opens a plethora of commercially promising advances and one of them is used for replacing sutures when there is a need to join body tissues together during surgery.
Tissue adhesive requires high adhesion strength, non-toxic byproducts, ease of application onto wet substrates, and on-demand crosslinking. Such a bioadhesive is important for minimally invasive surgery (MIS). Here we present the development of an instant curing adhesive through low-voltage activation. The electrocuring adhesive is synthesized by grafting carbene precursors on polyamidoamine (PAMAM) dendrimers, while incorporating carbon allotropes such as graphene and carbon nanotubes. The electrocuring adhesive is activated at -2V (Ag/AgCl), allowing tunable crosslinking within the dendrimer matrix and on both electrode surfaces. As the applied voltage is discontinued, crosslinking on tissues is immediately terminated, allowing tunable elasticity and adhesive strength as crosslinking initiation and propagation are observed to be voltage and time dependent. The electrocuring adhesive has immediate implications in manufacturing and development of implantable devices and bioadhesives and offers a new route towards addressing current surgical challenges.

References

[1] J. Ping, F. Gao, J.L. Chen, R.D. Webster, T.W.J. Steele, Adhesive curing through low-voltage activation, Nature Communications 6 (2015).
[2] J.P. Fisher, D. Dean, P.S. Engel, A.G. Mikos, Photoinitiated Polymerization of Biomaterials, Annual Review of Materials Research 31 (2001).
[3] Y.-J. Park, D.-H. Lim, H.-J. Kim, D.-S. Park, I.-K. Sung, UV- and thermal-curing behaviors of dual-curable adhesives based on epoxy acrylate oligomers, International Journal of Adhesion and Adhesives 29 (2009).
(Invited) Noninvasive Detection and Spectral Triangulation of Single-Walled Carbon Nanotubes In Vivo
Authors: Weisman R. Bruce , Lin Ching-Wei , Bachilo Sergei M. , Beckingham Kathleen M. , Yang Hailing , Bast Robert C. 
Published: February 2020

For toxicology studies on carbon nanotubes or the development of nanotube-based diagnostic or therapeutic agents, it is necessary to monitor the presence of nanotubes inside organisms. Preferred monitoring methods are noninvasive and safe, and can be performed on the laboratory mice commonly used in preclinical research. To advance the in vivo optical detection of single-walled carbon nanotubes (SWCNTs), we have recently developed instrumentation and methodology called spectral triangulation. In this method the specimen is diffusely illuminated by a matrix of light-emitting diodes and the resulting short-wave infrared fluorescence from internal SWCNTs is collected by an optical fiber at or near the animal’s skin. The fluorescence is then transmitted through spectral filters to a cooled InGaAs photon counting detector sensitive to the emitted wavelengths. The high sensitivity of this system allows localized SWCNT deposits of ca. 10-8 g to be detected through 20 mm of tissue phantom. In addition, by systematically varying the position of the light collector and measuring emission intensities in two wavelength bands, we can deduce the 3D location of the SWCNT deposit by spectral triangulation computations. Here we report refinements to the method and performance tests with live mouse specimens. The current LED excitation matrix emits at a longer wavelength (near 736 nm) to give higher penetration and reduced SWIR autofluorescence. A new specimen holder gently squeezes the mouse against a thin fused silica window, allowing the light collection fiber to translate only in a plane to significantly reduce scan times. Results on sensitivity limits and 3D triangulation accuracy will be presented from tests in which SWCNTs in Matrigel are implanted into mouse ovaries to simulate an antibody-targeted diagnostic application.
References
C.-W.Lin, S. M. Bachilo, M. Vu, K. M. Beckingham, and R. B.Weisman, Spectral Triangulation: a 3D Method for Locating Single-Walled Carbon Nanotubes in vivo, Nanoscale 8, 10348-10357 (2016).
C.-W. Lin and R. B. Weisman, In vivo Detection of Single-Walled Carbon Nanotubes: Progress and Challenges, Nanomedicine 11, 2885-2888 (2016).
(Invited) Soft Conductors from Carbon Nanotubes
Authors: Pasquali Matteo 
Published: February 2020

Since their infancy, carbon nanotubes (CNTs) were viewed as an exciting new material that combined superior transport properties with great mechanical strength and stiffness—a classical “hard material”. These expectations were based on single-molecule measurements; yet, translation to macroscopic materials proved arduous because CNT did not dissolve easily in liquids, while solvent-less assembly yielded largely disordered structures.
I will present an overview of the past fifteen years of research on assembling well-ordered macroscopic CNT materials, much of it conducted in close collaboration with Bob Hauge. From the perspective of soft matter, CNTs can be treated as hybrids of rodlike polymers and cylindrical colloids. CNTs dissolve spontaneously in acids, and form liquid crystals with intriguing morphology. Because dissolution is spontaneous, CNTs do not suffer mechanical or chemical damage and can reach high concentrations that enable material processing into fibers, thin films, tapes, and three-dimensional structures.
Intriguingly, these macroscopic CNT structures display mechanical and solid-state properties on par with the best metal and carbon fibers—even in the absence of covalent coupling between the CNTs, making them a viable lightweight, corrosion-resistant replacement for metals. Yet, the most surprising property—and perhaps the one that will prove most useful in future applications—was not predicted in the early days (and could not have been predicted based on single-CNT properties): macroscopic assemblies of CNTs display a “softness” that is completely uncharacteristic of highly conductive materials. They can be knotted, sewn with a common sewing machine, woven with a common loom, and still retain their properties—making them a great platform for electronic textiles and wearable devices. Moreover, these materials have intrinsic nanoscale porosity and display extremely low impedance in contact with biological tissue. This makes them a natural interface to the electrical function of the body, where they could be used as restorative patches for electrically damaged heart tissue as well as electrodes for stimulating and sensing the activity of the brain.
The Electrochemical Performance of Nitrogen-Containing Carbon Nanotubes As the Electrode Material of Supercapacitors
Authors: Li Xinping , Xu Guofeng , Deng Fuhai , Li Jianling 
Published: February 2020

Electrochemical electric double layer capacitors (EDLC) known as supercapacitors are used for high power density, long cycle life and good reversibility of charge/discharge processes[1]. Recent years, many Schiff base transition metal composites acting as an electroactive electrode material deposited on carbon nanotubes(CNTs) have been researched[2]. However, the CNTs tend to be random orientation, twining round and cross linked. So it urgently need to be addressed. In this paper, a given mass of NH4BF4 was added to CNTs and the electrode was prepared by the homodispersion of the raw support material in N-methyl- 2-pyrrolidone (NMP) through sonicating. The slurry was coated on a Ti sheet with the coating mass of 0.3 mg. The electropolymerization of Ni(salen) on the resulting electrode was conducted in a closed three-electrode compartment cell adopted chronoamperometry method. The introduction of NH4BF4 to the CNTs with a specific percentage (5wt. %, 10wt. %, 15 wt. %), and the modified samples were named as NBF5, NBF10, NBF15 respectively and the CNTs without NH4BF4 were taken as a control group and named as NBF0. As the cyclic voltammetric data summarized in Table 1, the values of apparent surface coverage(Γ) and doping level(n) of NBF5, NBF10 and NBF15 didn't appear to be much different from those of NBF0. However, the specific capacitance varied a lot. It can be seen that Cm
of NBF15 is the most among the samples. Figure 1 depicts the GCD plots of the composite and CNTs at the current density of 1.0 mA cm-2. CNTs have symmetric change in the charge/discharge process which is the characteristic of high Coulombic efficiency. It is clear that the composites possess longer charge/discharge time than CNTs which indicating that poly[Ni(salen)] contributes the pseudo-capacitance derived from reversible redox switching between neutral and oxidative states on the basis of electric double-layer capacitance of MWCNTs. Because of the introduction of NBF, it became difficult for CNTs to twint together disorderly. And the morphylogy of the electrode support got homogeneous. NBF-containing carbon nanotube could provide basic sites, and consequently improved the deposition of polymer and enhance the performance of the electrode material.

Acknowledgement

This work is financially supported by the National Natural Science Foundation of China (No. 51372021).

References

[1] D. Kaufman, K.L. Hudson, R. Mcclamrock. Science. 343 (2014) 1210–1211.
[2] Y. Zhang, J. Li, F. Gao, F. Kang, X. Wang, F. Ye, J. Yang. Electrochim. Acta. 76 (2012) 1–7.

Figure 1
(Invited) Single Ion Adsorption on Individual Isolated Single Walled Carbon Nanotube Field Effect Transistors
Authors: Cronin Stephen B. , Bushmaker Adam 
Published: February 2020

The detection of single ions has, for many years, been the domain of large devices such as the Geiger counter, and to date, there have been no studies investigating the effects of ions on materials and devices at the single-ion level, despite the widespread use of gaseous ions to modify material surface properties, for instance by corona discharge. Here, we report on single gaseous ion adsorption onto individual carbon nanotube field effect transistors, which, due to the severely restricted one-dimensional current path, experience discrete, quantized resistance increases of over two orders of magnitude [1]. Switching events were observed during exposure to lightly ionized nitrogen, helium, oxygen, argon and air. This is in contrast to single neutral atom adsorption detection techniques, which have shown only small, barely detectable responses. Only positive ions cause changes, by the mechanism of ion potential induced carrier depletion, which is supported by density functional and Landauer transport theory. Our observations reveal a new single-ion/CNT heterostructure with novel electronic properties, and demonstrate a powerful new system for studying ion adsorption dynamics at the single-ion level.
[1] Bushmaker, A. W. et al. Single-ion adsorption and switching in carbon nanotubes. Nature Communications, 7, 10475, DOI: 10.1038/ncomms10475 (2016).