bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Electrode Compressibility in Vanadium Redox Flow Batteries
Authors: Park Su Mi , Kim Hyun-Jong , Kim Haekyoung 
Published: February 2020

Vanadium redox flow batteries (VRFBs) have been investigated for their potential utility as large energy storage systems due to their advantageous performances in terms of long cycle life, high energy efficiency, low cost, and flexible design. Carbon materials are typically used as electrodes in redox reactions and as a liquid electrolyte support. The activities, surface areas, and surface morphologies of carbon materials must be optimized to increase the redox flow battery performance. Here, the compressibility of carbon electrode was controlled with the thickness of carbon felts for the same thickness of electrode. The efficiencies with discharging current of VRFB were measured and characterized. The cyclic performances were also characterized with various flow rates. VRFB-2F has the lower compressibility than VRFB-3F. VRFB-2CF has the 5 mm thickness of carbon felt in 5 mm of electrode and VRFB3F has the 8 mm thickness of carbon felt in 5 mm of electrode thickness, which were compressed in VRFB flow cells.
Form the performance measurement with discharging current, VRFB-2CF exhibited 88.7 % of columbic efficiency (CE) and 63 % of energy efficiency (EE) at discharging current of 25mA/cm2, which are higher than those of VFRB-3CF (82.5 % of CE, 57.6 % of EE). VRFBs were tested for cyclic performances with 20 times under 50mA/cm2 of charging current and 50mA/cm2 of discharging current. VRFB-2CF exhibited over 90% of columbic efficiencies; VRFB-3CF shows 80% of CE. Energy efficiencies of VFRB-2CF are 63 %, 61.3 % and 56.8 % at 18cc/min, 36cc/min, and 54cc/min, respectively which are higher values than those of VRFB-3CF (55.3%, 50.7% and 52.3% at 18cc/min, 36cc/min, and 54cc/min, respectively).
The compactness of VRFB-3CF is higher than that if VRFB-2CF, which are concerned with the electrolyte-coupled mass transport. The effects of compactness of electrode will be discussed in terms of the mass and charge transfer polarization.
Carbon Nanotubes Grown on Metal Microelectrodes for Dopamine Detection
Authors: Yang Cheng , Venton Barbara Jill 
Published: February 2020

Directly growing of carbon nanotubes (CNTs) on microelectrodes using chemical vapor deposition (CVD) can provide a dense and vertically aligned CNT film. Vertically-aligned CNTs grown on carbon fibers microelectrodes can detect dopamine, but the low conductivity of the carbon fiber may lead to slow electron transfer kinetics and the intrinsic electrochemical activity of carbon fibers makes evaluating the effect of CNT enhancement difficult. In this study, we compared vertically-aligned CNTs gown on metal wires and carbon fibers as microelectrodes. Scanning electron microscopy shows that aligned CNTs can be grown on metal wires, particularly Tantalum and Niobium wires. Using fast-scan cyclic voltammetry, CNT-coated niobium (CNT-Nb) microelectrodes had higher sensitivity and lower DEp values compared to CNTs grown on carbon fibers or other metal wires. The limit of detection for dopamine at CNT-Nb microelectrodes is 11±1 nM, which is approximately five times lower than CNT grown CFMEs. Using Langmuir isotherms to model adsorption/desorption processes revealed that dopamine oxidation is more reversible at CNT based microelectrodes than that for CFMEs. CNT-Nb microelectrodes were useful for monitoring stimulated dopamine release in anesthetized rats. Other neurochemicals could also be detected, including ascorbic acid, DOPAC, serotonin, adenosine, and histamine and the enhancement for dopamine was greater than ascorbic acid at CNT-Nb electrodes. This study demonstrates that CNT-grown metal microelectrodes, especially CNTs grown on Nb are useful for sensitive monitoring of neurotransmitters.

Figure 1
Activity of Nafion
Authors: Rathuwadu Nadeesha , Leddy Johna 
Published: February 2020

The activity of protons and water content in Nafion films are considered for different electrolytes and electrolyte concentrations in the solution. A model of activity effects in Nafion will allow optimization of operating conditions for systems such as fuel cells and sensors where proton exchange membranes and films significantly impact system response. Cyclic voltammetry (CV) experiments were undertaken for Nafion films on electrodes with tris(2,2ʹ–bipyridyl)dichloro–ruthenium(II) hexahydrate (Ru(bpy)3
2+) as the redox probe. The probe was equilibrated into Nafion from the electrolyte solution that contain different inert electrolytes at various concentrations. The glassy carbon working electrode was modified with a recast Nafion film made by drop casting Nafion suspension and then evaporation of the casting solvents. Terahertz spectroscopy experiments are used to find the dielectric constant of the recast Nafion film. The dielectric constant in Nafion is needed to calculate activity coefficients in Nafion.
From the data obtained at the Nafion modified electrodes, ip (ip is peak current) varies with inert electrolyte cation. For plots of ip versus v
1/2 (v is scan rate), inert electrolytes with the same cation had similar slopes where the observed peak currents ranked as H+ > Na+ > K+. Cations with smaller hydration energies are more easily exchanged into Nafion. The redox probe had no voltammetric response with high concentrations of the smaller cation electrolytes, consistent with little probe in the film. However, even for small cation electrolytes, at sufficiently low electrolyte concentrations, Ru(bpy)3
2+ yields a voltammetric response. From the slopes of ip versus v
1/2, Cfilm Dfilm
1/2 is found, where Cfilm and Dfilm are the concentration and the diffusion coefficient of Ru(bpy)3
2+
in the film. Cfilm Dfilm
1/2 does not change with the electrolyte concentration. Convolution will further refine determination of Cfilm Dfilm
1/2 and the dielectric constant will allow further evaluation of activity effects in Nafion.
Comparisons in Voltammetry of Phenylenediamine Based Ureas on Platinum and Glassy Carbon Working Electrodes
Authors: Cedano Mario , Smith Diane K. 
Published: February 2020

“Proton-coupled electron transfer” (PCET) reactions are essential to many of the fundamental chemical processes of biological systems. PCET has been studied for some time, but it is only recently that the role of H-bonding intermediates has been explored. One such H-bonding system under investigation consists of a phenylenediamine based urea that undergoes an apparent self-PCET reaction where one urea is oxidized by two electrons to the quinoidal cation, followed by the transfer of a proton and deactivation of the other half of the ureas. Reversibility of this process is due to the second electron transfer and proton transfer occurring through a H-bond complex between the oxidized urea and the dimethylamino group on an electroinactive urea.
In this study it was sought to observe possible differences in voltammetry of the phenylenediamine based urea system using different working electrode surfaces, in this case: platinum and glassy carbon working electrodes. Differences in voltammetry were observed between platinum and glassy carbon in methylene chloride. These differences appear to be due to faster heterogeneous electron transfer on glassy carbon than on platinum. In order to further explore this faster rate of electron transfer that is observed on glassy carbon, the working electrode surface was methylated, intentionally disrupting the electrode surface. The resulting voltammetric behavior of the phenylenediamine based urea system using this compromised electrode was similar to that of platinum, suggesting that the rate of electron transfer on glassy carbon was slowed down.
Further voltammetric experiments are being conducted in other solvents due to the solvent-dependence of the phenylenediamine based urea system. Possible differences in voltammetry between platinum and glassy carbon electrodes are currently being explored in dimethyl sulfoxide.
Solid-State Reaction Assisted Synthesis of Co-Doped MnO2 Nano-Composite Materials for Supercapacitor
Authors: Feng Wanru , Zhang Guangli , He Ping , Lei Wen , Wen Jianwu , Wang Fu 
Published: February 2020

Electrochemical supercapacitors are charge–storage devices that have greater power density and longer cycle life than batteries, and they possess higher energy density compared with conventional capacitors. Based on the different operation mechanisms, supercapacitors can be classified into two different categories: double-layer capacitors and pseudocapacitors [1,2]. Recently, relatively cheap oxide alternatives with similar characteristics have been developed to replace ruthenium oxide as electrode materials for use in pseudo-capacitors due to their low cost and no-toxicity. MnO2 has been used as one of the promising electrode materials for supercapacitor mainly because of its abundance in nature, low price, environment friendliness, wide charge/discharge potential range and large specific area [3].
In this work, a mechanically assisted solid-state reaction method was employed to prepare Co-doped MnO2 nanocomposites for supercapacitor electrode materials. It was found that the specific capacitance of 2.3 wt% Co doped MnO2 composite electrode was up to 340.1 F g-1 in 1.0 M KCl solution (Figure 1). Additionally, as prepared Co doped MnO2 composite electrode showed other desirable electrochemical properties, including good stable electrochemical properties, excellent reversibility and the long cycle life (Figure 2), demonstrating that it had potential advantages for the fabrication of electrochemical capacitor.

References

[1] Wen Lei, Ping He, Susu Zhang, Faqin Dong, Yongjun Ma. One-step triple-phase interfacial synthesis of polyaniline-coated polypyrrole composite and its application as electrode materials for supercapacitors. Journal of Power Sources, 2014, 266: 347-352.
[2] Wen Lei, Ping He, Yuhao Wang, Susu Zhang, Faqin Dong HongTao Liu. Soft template interfacial growth of novel ultralong polypyrrole nanowires for electrochemical energy storage. Electrochimica Acta, 2014, 132: 112-117.
[3] X Lang, A Hirata, T Fujita, M Chen. Nanoporous metal/oxide hybrid electrodes for electrochemical supercapacitors. Nature Nanotechnology, 2011, 6: 232-236.

Figure 1
Exploration of Chemical Bonding Transformation Mapping to Assist Low-k Dielectric Nanostructure Fabrication
Authors: Chyan Oliver , Rimal Sirish , Mukherjee Tamal , Goswami Arindom , Ross Nick 
Published: February 2020

In leading edge integrated circuit manufacture, reduction of RC time delay by incorporation of porous ultra-low k (ULK) interlayer dielectrics (ILD) into Cu interconnect nanostructure continues to pose major integration challenges. The main challenge is porosity induced to lower the dielectric constant of the ILD has the undesirable side effect of compromising its mechanical and chemical stability. As a result, these materials are more susceptible to the damages caused by RIE plasma etching processes. Besides the challenge of handling weak porous ULK materials, a lack of sensitive metrology to guide systematic development of plasma etching, restoration and cleaning processes is the major stumbling block. To assist in the overall integration effort, we have been actively exploring Multiple Internal Reflection Infrared Spectroscopy (MIR-IR) and associated IR spectroscopic techniques as a sensitive (sub-5nm) characterization tool to assist the fabrication process of ULK nanostructure with targeted critical dimension. In this paper, we will report new findings obtained on chemical bonding modification across fluorocarbon etch residues and low-k dielectric interface after manufacture relevant processing treatments including plasma etching, ashing, UV curing and post-etch cleaning. MIR-IR metrology showed useful spectroscopic details of chemical bonding transformations taking place during plasma etch and strip processing on both blanket and dielectric trench structures. The observed increase of Si-OH and C=O and the decrease of Si-CH3 IR absorption bands correlated well with increasing plasma induced damage, K increases verified by MIS structure, especially for more aggressive stripping process. With functional group-specific chemical derivatization, chemical bonding structure of 1-2 nm post-etch residue on porous low-k trench structure was established. UV-induced modification of fluorocarbon polymer residue to improve its subsequent wet cleaning removal was studied by FTIR, XPS and SEM. The overall goal is to apply new insights on chemical bonding transformation mapping to achieve cleans-friendly plasma etches on creating ULK dielectric nanostructures with minimal dielectric damages.
Proton Channels on Molecular Electrocatlaysts for Hydrogenase Mimics
Authors: Shaw Wendy , Dutta Arnab , Roberts John 
Published: February 2020

Hydrogenases interconvert H2 and protons at high rates and with high energy efficiencies, providing inspiration for the development of molecular catalysts. Studies designed to determine how the protein scaffold can influence a catalytically active site have led to the synthesis of amino acid derivatives of [Ni(PR
2NR'
2)2]2+ complexes, [Ni(PCy
2NAmino acid
2)2]2+ (CyAA). It is shown that these CyAA derivatives can electrochemically catalyze fully reversible H2 production/oxidation, a feature reminiscent of enzymes. The reversibility is achieved in acidic aqueous solutions, 1 atm 25% H2/Ar, and elevated temperatures (tested up to 70 ¢ªC) for the glycine (CyGly), arginine (CyArg), and arginine methyl ester (CyArgOMe) derivatives. At pH=1 and 70 C, rates of up to ~300 s-1 H2 production and 20 s-1 H2 oxidation 348 K are observed. The effect of higher pressure and the behavior of complexes without an outer coordination sphere will be discussed. These observations demonstrate that outer coordination sphere amino acids work in synergy with the active site in and can play an equally important role for synthetic molecular electrocatalysts as the protein scaffold does for redox active enzymes.
(Invited) Biological Applications of Nanoparticles for Reactive Oxygen Species (ROS) Scavenging and Sensing
Authors: Boghossian Ardemis Anoush , Sen Fatih , Gibbons Brenna , Sen Selda , Faltermeier Sean , Giraldo Juan Pablo , Zhang Cathy , Zhang Jingqing , Heller Daniel , Strano Michael S 
Published: February 2020

Cerium oxide nanoparticles, or nanoceria (NC), offer a regenerative approach to scavenging reactive oxygen species (ROS). NC have been used to prevent retinal and neuronal degeneration, protecting cells against ROS and radiation damage. Unlike most scavengers, which undergo a depletion in activity upon ROS consumption, NC are regenerative; theoretically, they are able to scavenge for ROS indefinitely so long as a physiological pH is maintained. Our recent work has extended NC applications beyond the human body towards other biological systems, such as plants and chloroplasts. Like retinal cells, plant organelles undergo photodamage caused by ROS generation under continuous illumination. We have demonstrated that NC can regeneratively protect plant-extracted chloroplasts from ROS-induced photodamage to prolong extracellular activity for light-harvesting, energy applications. By engineering the polymeric wrapping around the NC particles, we have demonstrated the ability to tune nanoparticle uptake into the plant chloroplast. This platform has been extended to in vivo applications, where single-walled carbon nanotube (SWCNT)-based complexes have been used to monitor and image ROS flux inside intact plant leaves, enabling not only a photonic chemical sensor, but also a novel, nanobionic approach to augmenting photosynthesis and enhancing plant efficiency.

Figure 1
Porphyrin-Fullerene Based Donor-Acceptor Conjugates for Photocontrol of Cell Membrane Potentials
Authors: Takano Yuta , Numata Tomohiro , Fujishima Kazuto , Murakami Tatsuya , Kengaku Mineko , Mori Yasuo , Imahori Hiroshi 
Published: February 2020

Optical control of cellular functions is a promising approach for therapeutic application because it can realize precise control with resolutions of submicrosecond temporally and submicrometer spatially.1 Among various key factors for controlling cellular functions, cell membrane potential is one of the most important ones because it triggers various biological events such as neuron fire and cell signaling. For maintaining membrane potentials, ion channels play crucial roles to keep or to change cell membrane potentials. Therefore, artificial control of cell membrane potential and selective inhibition/activation of ion channels are considered to be promising therapeutic approach.2

Meanwhile, in electron donor-acceptor linked molecules, photoirradiation triggers intramolecular electron transfer and then charge separated (CS) state is generated. The molecules in CS state demonstrate high oxidizing and reducing abilities, and may induce large dipole which can generate large electric field in nanometer scale. Our group has focused on the photoinduced CS states in the donor-acceptor linked molecules because it may perturb an environment in the cell membrane and may influence function of the proteins therein. Recently, we have reported that such molecules can induce depolarization in the membrane potential of PC12 cells as well as inhibition of the potassium ion flow across the membrane by illumination.3

In this study, a series of amphiphilic electron donor-acceptor linked molecules based on fullerene and porphyrin were systematically designed, synthesized and investigated for photocontrol on cell membrane potentials. Their molecular structures and unique aggregate structures revealed their characteristic photoinduced excited states of the molecules. Utilizing fullerene moiety was found to be a key for formation of the unique aggregates in highly polar solvent and introduction of porphyrin moiety provides a benefit for using light energy efficiently. Successful design of a CS molecule was found to suppress photocytotoxicity of the molecule remarkably and demonstrated its ability for modulation on the membrane potentials which can increase the frequency of the action potential and trigger neuron firing in rat hippocampal neurons by photo irradiation.

References:

[1] (For a review) Briele, C. et al. Angew. Chem. Int. Ed.
2012, 51, 8446.
[2] (For a review) Wulff, H. et al. Nat. Rev.
2009, 8, 982.
[3] Takano, Y. et al. J. Am. Chem. Soc.
2012, 134, 6092.

Figure 1
Playing with Fullerene, Carbon Nanotubes, Nanodiamonds and Other Carbon Nanostructures
Authors: DaRos Tatiana , Armuzza Valentina , Gonzalez Dominguez Jose Miguel , Gajewska Agnieszka , Carini Marco 
Published: February 2020

In the last 20sh years the Carbon Nanostructures’ family grew and attract the attention of many researchers working in different fields. Many efforts in the studies of functionalization have been done, especially struggling with the necessity of an easy way to manipulate these structures. Solubility and orthogonal multiple functionalization are the main goals to be achieved when these materials have to be used for biological applications, as oligonucleotides vector, potential antiviral derivatives, or gene expression modulators.
In this communication, an overview of the recent achievements will be presented.

Figure 1
(Invited) Optoelectronic Properties and Electromechanical Resonance Behavior in Individual Suspended Carbon Nanotube Pn-Junctions and Devices
Authors: Cronin Stephen B. 
Published: February 2020

In carbon nanotubes pn-junctions, we observe Zener tunneling behavior and photocurrent generation in quasi-metallic nanotubes1, which have smaller band gaps than most known bulk semiconductors. These carbon nanotube-based devices deviate from conventional bulk semiconductor device behavior due to their low dimensional nature. We observe rectifying behavior based on Zener tunneling of ballistic carriers instead of ideal diode behavior, as limited by the diffusive transport of carriers. We observe substantial photocurrents at room temperature, suggesting that these quasi-metallic pn-devices may have a broader impact in optoelectronic devices. We also explore the role of weak clamping forces, typically assumed to be inﬁnite, in the electromechanical resonance behavior of these suspended carbon nanotubes.2 Due to these forces, we observe a hysteretic clamping and unclamping of the nanotube device that results in a discrete drop in the mechanical resonance frequency on the order of 5−20 MHz, when the temperature is cycled between 340 and 375 K. This instability in the resonant frequency results from the nanotube unpinning from the electrode/trench sidewall where it is bound weakly by van der Waals forces. Interestingly, this unpinning does not aﬀect the Q-factor of the resonance, since the clamping is still governed by van der Waals forces above and below the unpinning. For a 1 μm device, the drop observed in resonance frequency corresponds to a change in nanotube length of approximately 50−65 nm. On the basis of these ﬁndings, we introduce a new model, which includes a ﬁnite tension around zero gate voltage due to van der Waals forces and shows better agreement with the experimental data than the perfect clamping model. From the gate dependence of the mechanical resonance frequency, we extract the van der Waals clamping force to be 1.8 pN. The mechanical resonance frequency exhibits a striking temperature dependence below 200 K attributed to a temperature-dependent slack arising from the competition between the van der Waals force and the thermal ﬂuctuations in the suspended nanotube.
1. Amer, M.R., S.-W. Chang, R. Dhall, J. Qiu and S. Cronin, “Zener Tunneling and Photocurrent Generation in Quasi-Metallic Carbon Nanotube pn-Devices” Nano Letters, 13, 5129 (2013).
2. Mehmet Aykol, Bingya Hou, Rohan Dhall, Shun-Wen Chang, William Branham, Jing Qiu, and Stephen Cronin, "Clamping Instability and van der Waals Forces in Carbon Nanotube Mechanical Resonators" Nano Letters, 14, 2426 (2014).
3. Shun-Wen Chang, Kevin Bergemann, Rohan Dhall, Jeramy Zimmerman, Stephen Forrest, Stephen Cronin, "Non-ideal Diode Behavior and Band Gap Renormalization in Carbon Nanotube P-N Junctions" IEEE Transactions on Nanotechnology, 13, 41 (2014).