bluuebunny/crossref_metadata_2025 huggingface dataset:
The Electrified Oil/Water Interface in the Presence of Divalent Ions
Authors: Diaz-Romero Diana , Olvera de la Cruz Monica , Guerrero-Garcia Guillermo Ivan
Published: February 2020

Experimental advances in X-rays scattering have made possible to measure the distribution of ions near oil-water interfaces in the presence of applied electric fields with atomic precision. However, the interpretation of such experimental data depends strongly on a reliable representation of the ionic cloud or electrical double layer close to these liquid interfaces. In this work, simulations and theory are used to study the electrical properties of the interface between two immiscible electrolytes in the presence of divalent ions, when both solvents are confined by a pair of charged electrodes. Ion correlations, ionic excluded volume effects, image charges, and solvation energies are included in the simulations to quantify the relevance of these effects beyond widely used classical mean-field theories. Electrochemical experimental data are also used to evaluate the performance of these theoretical approaches.
New Method to Determine Eley-Rideal Barriers for 2e- and 4e- Oxygen Reduction Reactions in Fuel Cells
Authors: Yu Ted H. , Tsai Ho-cheng , Ravishankar Sundararaman , Goddard William A
Published: February 2020

We use atomic level simulations with density functional theory (DFT) to calculate barriers on Pt and Pd catalysts for Eley-Rideal (ER) reactions during the oxygen reduction reaction (ORR) in fuel cells.  In our new method, we simulate the hydrogen coming into the reaction from H+ in the solution.  Our method of calculating potential dependent ER barriers in fuel cells does not use external potential or nonzero charged calculations.  The barriers are determined using a single nudged elastic band (NEB) calculation.  A new scheme determines simultaneous zero-capacitance anode/cathode barriers.  An accurate solvation method is used to include the effect of water solvation1

The following new ER calculated barriers supplement our previous calculations of Langmuir-Hershelwood (LH) barriers2.

OOHad + H+ + e- -> HOOHad

OHad + H+ + e-  -> HOHad

OOad + H+ + e- -> OOHad

OOHad + H+ + e- -> HOOHad

OOHad + H+ + e- -> 2OHad

Using the combined ER and LH barriers, we determine the rate determining step for ORR for Pt and Pd at different potentials.  The ER barriers calculated agree well with previous methods3.  They also can predict whether a catalyst favors the 2e- or 4e-ORR. 

Figure 1:  The barriers differ significantly for 2e- and 4e- ORR on Pt and Pd.  For Pd, HOOH formation is favored by 0.06 eV at 0.8 V.  On the other hand for Pt, water formation is favored by 0.33 eV at 0.8 V.  The Pt water formation barrier also agrees with previous methods3.

References:

1.            R. Sundararaman, K. Letchworth-Weaver and T. A. Arias, J Chem Phys 137(4), 044107 (2012).

2.            T. H. Yu, T. Hofmann, Y. Sha, B. Merinov, D. J. Myers, C. Heske and W. A. Goddard, J Phys Chem C (117), 26598-26607 (2013).

3.            V. Tripkovic, E. Skulason, S. Siahrostami, J. K. Norskov and J. Rossmeisl, Electrochim Acta 55, 7975-7981 (2010).

Figure 1
Molecular Simulation and Performance Prediction of High-Temperature Molten-Salt Batteries
Authors: Li Hao-Yu , Chen Chung-Fu , Cheng Yi-Chia , Hong Che-Wun
Published: February 2020

This research aims to enhance the discharging rate and to improve the overall performance of a high-temperature molten salt battery. We use molecular dynamics (MD) simulation techniques to develop some novel ternary and quaternary molten electrolytes to replace conventional binary LiCl–KCl ones [1]. These novel electrolytes are listed in Table I  and their molecular structures are shown in Figure 1. These molecular structure configurations are based on their minimal total energies and we use Hamiltonian dynamics to predict their trajectories and subsequent properties.

Our simulation results are consistent with the results of previous experimental studies regarding the LiCl-LiBr-based ternary (LiCl–LiBr–NaCl & LiCl–LiBr–NaBr) and quaternary (LiCl–LiBr–NaCl–KCl & LiCl–LiBr–NaBr–KBr) electrolytes. The simulation results with greater ionic conductivity and higher melting points are consistent with experimental results reported by previous literatures [2, 3]. The tendency is shown in Figure 2. In addition, the MD results have found that the lithium ion mole fraction in the molten-salt electrolytes affects the ionic conductivity significantly as shown in Figure 3.

This paper demonstrates that MD simulation technique is a useful tool to screen various design ideas on the multi-component electrolytes in a more efficient way. The molecular composition of each component of the molten-salt electrolytes can be optimized using this simulation technique instead of trial-and-error experiments. The target region shown in Figure 4 is easy to easy to achieve through this computational technique.

REFERENCES

P. Masset, and R. A. Guidotti, J. Power Sources, 164, 397 (2007).

S. Fujiwara, M. Inaba, and A. Tasaka, J. Power Sources, 196, 4012 (2011).

S. Fujiwara, U. S. Patent, US008221912B2 (2012).

Figure 1
Modelling of Transport Processes inside Rechargeable Oxide Battery
Authors: Erfurt Viktoria , Braun Waldemar , Singheiser Lorenz , Berger Cornelius M.
Published: February 2020

Change of electricity supply infrastructure based on renewables (photovoltaic, wind, biomass, etc.) requires large storage capacities to ensure continuous electricity supply if photovoltaics or wind turbines are not in operation due to weather conditions. At high temperatures of around 800 °C modified planar solid oxide fuel/electrolyzer cells (SOFC/SOEC) can be used as storage devices (Fig. 1). The concept of SOFC/SOEC can be transferred to a so-called rechargeable oxide battery (ROB). Instead of directly fueling the cell with mixtures of hydrogen and steam in the now sealed-off fuel compartment a metallic component is integrated which will be converted to metal oxide during discharging (Fig. 2) and back to metal during charging by reducing the metal oxide (Fig. 3).

An interesting metal / metal oxide system is iron/iron oxide which results in a reasonable open circuit voltage of approximately 1.02 V per cell at 800 °C due to the dissociation pressure of e.g. iron oxide (FeO) in the range of pO2≈10-18bar.

Oxidation and reduction rates strongly depend on the exact atmospheric compositions, the surface area, the porosity, and the diffusion velocities in the storage component. Latter will change due to the chemical expansion (change of pore sizes) during charging and discharging of the battery. Also the formation of oxide or metallic layers on top of the storage components can massively influence the reaction kinetics.

Therefore, in this study a 1D and a 2D model are developed to simulate the gas diffusion in the prevailing H2O/H2 atmosphere from the cell to the storage component (and back) as well as the gas-solid reaction in the porous iron/iron oxide. The model is implemented using the Navier-Stokes equations and the method of finite elements in Matlab.

The redox process which takes place within the microscopic pores of the metallic storage material can be described by the following equations:

Me + H2O ⇌ MeO + H2

2Me + 3H2O ⇌ Me2O3  + 3H2

3Me + 4H2O ⇌ Me3O4 +4H2

In addition, the formation of volatile oxides or hydroxides has to be considered which may cause long-term degradation of the storage components:

Me + 2H2O ⇌ Me(OH)2 + H2

MeO + H2O  ⇌ Me(OH)2

Me3O4 + 2H2O + H2 ⇌ 3Me(OH)2

The degradation process reduces the performance of the battery along with its recyclability and lifetime. Therefore the degradation should be held as low as possible. Thus, the model contributes to identifying the critical processes in the battery and will allow for optimizing both the battery design and the operation conditions.

Figure 1
Self-Assembly, Transport, and Thermodynamics in Nafion Membranes: Insight from Dissipative Particle Dynamics Simulation
Authors: Vishnyakov Aleksey , Lee Ming-Tsung , Neimark Alexander V.
Published: February 2020

Composed of perfluorinated backbone with sulfonate sidechains, Nafion self-assembles upon hydration and segregates into interpenetrating hydrophilic and hydrophobic subphases.  This segregated morphology determines the transport properties of Nafion membranes that are widely used as compartment separators in fuel cells and other electro-chemical devices, as well as permselective diffusion barriers in protective fabrics. We introduce a coarse-grained model of Nafion, which accounts explicitly for polymer rigidity and electrostatic interactions between anionic sidechains and hydrated metal cations. By means of dissipative particle dynamics (DPD) and Monte Carlo (MC) simulations, we explore geometrical, transport, and sorption properties of hydrated Nafion-type polyelectrolyte membranes. Novel methodology will be presented for calculating water adsorption isotherms and transport coefficients as a function of the degree of hydration.
Electrooxidation of Ethanol and Formic Acid on Core-Shell Nanoparticles with Different Platinum Shell Thickness
Authors: Gorzkowski Maciej T. , Polczynski Piotr , Jurczakowski Rafal Robert , Lewera Adam
Published: February 2020

Core-shell nanoparticles with platinum as the shell and less expensive metal as a core allow for important reduction of the amount of expensive and rare platinum used while maintaining similar platinum active surface area.

More efficient use of platinum is not the only benefit of core-shell nanoparticles. Platinum monolayer deposited on the core made from another metal exhibits modified catalytic and electronic properties. Partially responsible for this behavior are:  i) charge transfer from the core metal and ii) changes induced by modified lattice parameter. The  monolayer shell forms a so called “pseudomorphic monolayer” with lattice parameter equal to that of metal forming the core, resulting in altered conduction band width and center of d-band energy in relation to Fermi edge. In the case of platinum shell on a palladium core, contracted Pt lattice leads to broadening of the conduction band and shifting d-band center closer to the Fermi edge.

Core-shell nanoparticles with platinum shell have been widely investigated as the catalyst in the process of oxygen reduction, but data available on their properties as the catalysts for oxidation of small organic molecules is scarce. Experimental investigation of such properties of core-shell nanoparticles with different platinum coverage and different platinum shell lattice parameter due to changes in shell thickness is an important step in determination of relation between electronic properties of the material used and reaction mechanism. Understanding this relation is crucial in constructing more effective direct ethanol fuel cell anode catalysts.
(Invited) Electrocatalysis of Ammonia Oxidation Reaction on Pt(100) in Alkaline Solutions
Authors: Katsounaros Ioannis , Jirkovsky Jakub S , Lopes Pietro Papa , Strmcnik Dusan , Kang Yijin , Stamenkovic Vojislav R , Gewirth Andrew A. , Koper Marc T. M. , Markovic Nenad M
Published: February 2020

The oxidation of ammonia is an essential process in the nitrogen cycle, with important applications in energy conversion ("ammonia electrolysis"), environmental protection (removal of ammonia from waste streams), electrosynthesis (hydroxylamine production via nitrate or nitric oxide reduction) or sensors (ammonia sensors for a wide range of applications). The conversion of ammonia to nitrogen gas, which is the desirable process in most of these applications, is typically difficult to achieve even though N2 is thermodynamically the most favorable product. Among the three basal planes of platinum, Pt(100) is unique in converting ammonia selectively to nitrogen. This presentation deals with the mechanism of the ammonia oxidation on the Pt(100) single-crystal electrode in alkaline solutions, investigated by basic electrochemical methods coupled with in-situ infrared spectroscopy and online electrochemical mass spectrometry. Our study particularly focuses on the nature of the adsorbed intermediate species and thereby on their role in the N-N coupling and in the observed deactivation.

Acknowledgments

This research was supported by a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme to Ioannis Katsounaros under Award IOF-327650, and by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division.
(Invited) Interplay Between Strain, Electronic Structure, and Oxygen Evolution Electrocatalysis in Iridates
Authors: Nie Yuefeng , Tang Runbang , Shen Kyle M. , Schlom Darrell G. , Suntivich Jin
Published: February 2020

The sluggish kinetics of the oxygen evolution reaction (OER) is one of the major sources of the overpotentials in many air-breathing electrochemical energy devices such as electrolyzers and rechargeable metal-air batteries. To increase the OER kinetics and reduce the overpotentials, it is critical to establish the linkage between the catalyst structure and the OER activity and mechanism. In this contribution, we present our effort in establishing this structure-activity connection, using iridates as model electrocatalysts and strain as a tuning knob for understanding the structure-activity connection. We have grown a series of perovskite iridium oxides with different biaxial strains using Molecular Beam Epitaxy (MBE), which we will use as a model system to elucidate how the OER kinetics can be affected by strain. To further connect strain to the physical properties of the iridates, we subject these MBE-grown oxides to ambient pressure X-ray photoelectron spectroscopy, from which we can determine how strain can affect the oxygen adsorption. We use this information to reveal insights into how strain can serve as a material knob to facilitate the OER and the underlying structure-activity relationship in iridates.
On the Effects of Halides on the Hydrogen Peroxide Reduction Reaction in Aqueous Electrolytes
Authors: Jebaraj Adriel J.J. , Georgescu Nicholas , Scherson Daniel
Published: February 2020

The influence of adsorbed species on the kinetics and mechanism of a number of redox reactions has been recognized for decades1. In particular, the adsorption of both chloride and bromide on Pt electrodes in acidic electrolytes, is known to promote the two-electron reduction of oxygen to peroxide instead of the desired four-electron reduction to water 2,3. This contribution seeks to gain insights into the reduction of H2O2 on a polycrystalline Pt electrode in 0.1 M HClO4 solutions containing a few ppm of either Cl- or Br-. The strategy employed makes use of a chronoamperometric method recently developed in our laboratories to determine independently, the effects of potential, E, and coverage of the adsorbate, q, on the peroxide reduction reaction on a Pt rotating disk electrode, RDE

EXPERIMENTAL

All measurements were performed in an all-glass, three-compartment cell in a 1 mM H2O2 in 0.1 M HClO4 solution either neat or containing 10 µM NaCl or 10 µM KBr.  Experiments were performed with a rotating Pt ring-Pt disk electrode, Pt|Pt RRDE, (Pine Instruments, (A = 0.164 cm2) using a bipotentiostat (Pine Instruments). A Pt foil and a reversible hydrogenelectrode in the same solution (RHE) were used as counter and reference electrodes, respectively.   

RESULTS AND DISCUSSION

Shown in Fig.1 are polarization curves recorded at a scan rate,  ν = 10 mV/s  for a Pt disk electrode  in 0.1 M HClO4 containing 1 mM H2O2in the absence (black curve) and in the presence of either 10 mM NaCl or 10 μM KBr (red curve). In contrast to the rather subtle effects of chloride, the presence of bromide gives rise to a substantial, ca. 0.3 V, shift in the onset for peroxide reduction.

 Chronoamperometric curves, i.e. disk current, idisk vs time, obtained in upon stepping the potential from a value Eo, at which its coverage q is negligible 0, to a value Eads at which q attains a finite value are displayed in Fig. 2. The results of these experiments make it possible to correlate the disk current, i, as a function of Eads at fixed q, or as a function of q for a fixed Eadsas illustrated in Panels A and B in Fig. 3, respectively. Implications of these results on the effects of these impurities on the oxygen reduction reaction (ORR) will be discussed.  

ACKNOWLEDGEMENTS

This work was supported by a grant from NSF (CHE-0911621).

REFERENCES

Marković, N. M.; Ross Jr, P. N., Surf. Sci. Reports
2002, 45, 117-229.

Stamenkovic, V.; M. Markovic, N.; Ross Jr, P. N., J. Electroanal. Chem.
2001, 500, 44-51.

Schmidt, T. J.; Paulus, U. A.; Gasteiger, H. A.; Behm, R. J., J. Electroanal. Chem.
2001, 508, 41-47.

Figure 1
Laboratory Experiments and Undergraduate Research Projects Incorporating Electroanalytical Techniques at Benedictine University
Authors: Ronkainen Niina Johanna
Published: February 2020

Freshman level undergraduate students often receive a superficial introduction to electrochemistry through topics such as redox reactions, oxidation states, electrolytes, and galvanic cells.  Given this level of exposure to electrochemistry, it is often difficult to appreciate the relevance of electroanalytical chemistry to modern society.  Unlike analytical chemistry techniques involving spectroscopy and chromatography, electroanalytical chemistry, specifically modern electrochemical techniques such as voltammetry and amperometry, are underrepresented in most undergraduate chemistry laboratory course curricula.  With the increasing popularity of chemical sensors, biosensors and nanotechnology, electroanalytical detection methods are becoming more commonplace in research laboratories and chemical industry.  In addition to the sensitivity the techniques mentioned offer, voltammetry is often used in characterization of nanomaterials, other redox active species and transducers.  Moreover, electroanalytical methods offer an attractive alternative compared to other analytical methods due to portability, low cost and ease of use of the equipment.  This talk will address the teaching of modern electroanalytical methods and their common applications at the sophomore and senior-level lecture and laboratory courses at a PUI, specifically Benedictine University.  Several of the laboratory experiments and some undergraduate research projects which utilize cyclic voltammetry, linear sweep voltammetry, and amperometry will also be discussed.
Ionic Liquid Facilitated Generation of Functional Biopolymer Composite Materials
Authors: Fox Eric T , Brown Eva Kathryn , Price Tyler , Brusoski Michael , Durkin David P. , Trulove Paul C , Haverhals Luke M. , De Long Hugh C
Published: February 2020

Ionic liquids (IL) have been the focus of materials research for some time due to their unique physical and chemical properties.  Of significant interest is their ability to solubilize biopolymers such as cellulose, chitin, keratin, and silk.  However, full dissolution and regeneration using IL solvents often results in biomaterials with inferior properties compared to the native material.  When natural substrates are only partially dissolved and regenerated through a process called Natural Fiber Welding (NFW), much of the native biomaterial structure can be maintained while still opening up the outermost portion of fibers so that the physical and chemical properties may be manipulated and/or modified.  Furthermore, if functional materials (e.g. magnetic, conductive, capacitive, antimicrobial) are present in the IL-welding solution, these materials may be entrained in and on the surface of the fiber substrate.  In the present work we will discuss the spatially controlled application of the NFW process and how this can be used to generated novel conductive and capacitive structures.
Structural and Photoluminescent Characterization of Na3FMo1-X
W
x
O4
Â (0 â¤ x â¤ 1)
Authors: Sullivan Eirin Courtney
Published: February 2020

Preliminary studies suggest that Na3FMo1-x
W
x
O4 (0 ≤ x ≤ 1) is a new family of self-activating oxyfluoride phosphors with anti-perovskite related structure [1]. These materials are isostructural with the known sodium tungsten oxyfluoride Na3FWO4 [2], as determined by Rietveld analysis based upon neutron powder diffraction data of the molybdenum-containing analogues Na3FMoO4 and Na3FW0.5Mo0.5O4. Photoluminescence studies have shown that upon excitation with λ = 254nm and λ = 365nm, the end members Na3FWO4 and Na3FMoO4 exhibit broad emission maxima centred around 485 nm and 450 nm respectively  Mixed intermediates of the general formula Na3FW1-x
Mo
x
O4 have a broad absorption around λ = 350-365 nm in the near-UV region which is close to the emission from pure GaN LEDs (370 nm) thus may provide novel host lattices for new PC-LED phosphors.

References:

1. E. C. Sullivan, M. Avdeev, and T. Vogt, Manuscript in preparation.

2. I. Hartenbach and T. Schleid, Z. Anorg. Allg. Chem.,
633, 4, 524-526, 2007.

Figure 1
Electrochemical Analysis of Film Forming Mechanisms Relevant to Data Storage Chemical Mechanical Planarization
Authors: Janes Lisa M. , Keleher Jason J
Published: February 2020

With the rapid increase of data storage density, the operation distance between read/write head and media has fallen into the nanometer regime. This requires an atomic level planarization to avoid defects on the surface and  “crashes” of the read/write head media. Chemical mechanical polishing (CMP) has been selected to produce high quality surface finish on a Nickel Phosphorous (NiP) plated substrate, through the removal of a metal complex film formed on the surface. CMP is a process that balances the kinetic/ thermodynamic reactions between the formation of a chemically modified layer and its interaction with the slurry. In order to understand the mechanistic CMP film forming process, electrochemical techniques were developed to probe the impact of organic additives on the surface redox and film forming mechanisms. More specifically, through monitoring the OCP (under abrasive and nonabrasive conditions) versus time, the film removal rate and passivation film formation kinetics can be determined as a function of slurry additives. Using OCP, the film passivation of the metal slurry complex on the surface of a nickel electrode can be monitored as a function of polishing time and related to the film forming mechanism of the CMP process.
Transport and Dynamics of Ionic Species in Block Copolymer Electrolytes Obtained from NMR
Authors: Huynh Tan Vu , Messinger Robert , Bouchet Renaud , Phan Trang N. T. , Maria Sebastien , Deschamps Michaël
Published: February 2020

Solvent-free block copolymers electrolytes are the strongest candidates for solid-state lithium metal batteries, as new polymers based on polyethylene oxide (PEO) and lithium bis(trifluoromethane)sulfonimide (LiTFSI) prevent the formation of lithium dendrites and ensure sufficient conductivity.

Block copolymers based on PEO and either polystyrene (PS) or grafted PS-TFSI were compared to PEO by Nuclear Magnetic Resonance spectroscopy (NMR) in order to quantify and distinguish the transport and dynamics of Li+ and TFSI- and the effect of the polymer matrix.

The self-diffusion coefficients of Li+ and TFSI- can be measured at various temperatures with pulsed-field-gradient (PFG) experiments and compared with electrical conductivity measurements, providing insights on lithium transport properties in each system.

We measured 7Li NMR relaxation rates at various magnetic fields and temperatures, and we were able to extract complex correlation functions describing the fluctuations of the 7Li quadrupolar interaction inside the polymer matrix, yielding insights into cation dynamics with three different timescales. These results obtained from NMR can be compared to molecular dynamics or theoretical calculations.
Graphene Based High Performance Energy Storage Devices
Authors: Liu Tianyuan , Kavian Reza , Lee Seung Woo
Published: February 2020

Graphene based materials have provided versatile platforms in developing electrodes in energy storage devices, such as rechargeable batteries and supercapacitors, utilizing their unique physical and chemical properties. We have explored the potential of functionalized graphene to develop positive electrodes for rechargeable batteries (Li ion and Na ion batteries). Graphene electrodes were prepared by two different self-assembly processes. Firstly, graphene hydrogel was assembled by a hydrothermal reduction process. After vacuum drying process, densely packed graphene films were obtained. The graphene films delivered a high gravimetric specific energy of ~140 mAh/g in Li-cells. The electrochemical performance of the electrode showed a positive correlation with the amount of oxygen group, indicating the importance of the surface redox reactions of the oxygen functional groups. Secondly, additional surface redox reactions were introduced into the graphene electrodes by functionalization with a redox-active component, tetrahydroxyl-1,4-benzoquinone (THQ). The functionalized graphene electrodes delivered high gravimetric capacities of ~165 mAh/g in Li-cells and ~120 mAh/g in Na-cells with high redox potentials over ~3 V vs. Li or Na. These results propose that graphene based materials can be promising candidates for positive electrodes in both Li- and Na-ion batteries.
Electrospun Carbon Nanofiber Supports for Bioelectrodes
Authors: Do Duyen Van Thuy , Gumeci Cenk , Calabrese Barton Scott
Published: February 2020

A high surface-area electrospun carbon nanofiber (CNF) support for bioelectrodes is introduced to enhance enzyme utilization.1 This study employed Glucose Oxidase (GOx) in redox hydrogel system, which mediated electron transfer via Osmium (Os2+/Os+) centers, to create a glucose bioelectrode. The strategy was to enhance the transport of electrons via the redox mediator by reducing the average hydrogel thickness at fixed hydrogel volume. The tunable electrospun carbon fiber enables of hydrogel film thickness of hydrogel film by uniform distribution on small fibers. Glucose oxidizing current density made from electrospun carbon nanofiber and several commercial counterparts suggest a possibility for a cheap fibers, in a diameter range below100 nm, that enable high current density (~8.5 mA cm-2) comparable to carbon nanotubes (CNTs).

To adjust electrospun CNF size, varied concentrations of Polyacrylonitrile (PAN)/ Dimethylformamide (DMF) precursor solution (7 wt% to 14 wt%) was spun in a high voltage field prior to oxidation stabilization and carbonization in Argon environment at two temperatures, 850°C and 1100°C.2 Graphiticity of CNFs was improved with the increasing heat treatment temperature (shown by Raman spectroscopy), leading to higher conductivity of bioelectrode. CNFs based on 7 wt% PAN/DMF carbonized at 1100°C had a diameter of 150 nm (Figure 1b), a decrease from the 250 nm PAN fiber (Figure 1a), and showed good performance in electrochemical characterization compared to MWCNTs electrode (Figure 2).

Acknowledgement

We thank Buckeye Composites Inc. and Pyrograf Products Inc. for providing material samples.

Reference

(1)       Wen, H.; Nallathambi, V.; Chakraborty, D.; Calabrese Barton, S. Carbon Fiber Microelectrodes Modified with Carbon Nanotubes as a New Support for Immobilization of Glucose Oxidase. Microchim. Acta
2011, 175, 283–289.

(2)       Bhardwaj, N.; Kundu, S. C. Electrospinning: A Fascinating Fiber Fabrication Technique. Biotechnol. Adv.
2010, 28, 325–347.

Figure 1
(Dielectric Science & Technology Division Thomas D. Callinan Award) Boron Carbon Nitride Thin Films for Low-k Dielectric Interconnect and Optical Applications
Authors: Sundaram Kalpathy B , Prakash Adithya , King Sean W.
Published: February 2020

New microprocessor CMOS technologies require interlayer dielectric materials with lower dielectric constant than those used in current technologies to meet RC delay goals and to minimize cross-talk. Silicon oxide or fluorinated silicon oxide (SiOF) materials having dielectric constant in the range of 3.6 to 4 have been used for many technology nodes. In order to meet the aggressive RC delay goals, new technologies require dielectric materials with k < 3. Boron carbide nitride (BCN) shows promise as a low dielectric constant material with good mechanical strength suitable to be used in newer CMOS technologies. BCN ternary system exhibits exceptional properties and attract much attention from mechanical, optical and electronic perspectives. BCN thin films contain interesting phases such as diamond, cubic BN (c-BN), hexagonal boron nitride (h-BN), B4C, β-C3N4. Attempts have been made to form a material with semiconducting properties between the semi metallic graphite and the insulating h-BN, or to combine the cubic phases of diamond and c-BN (BC2N heterodiamond) in order to merge the higher hardness of the diamond with the advantages of c-BN, in particular with its better chemical resistance to iron and oxygen at elevated temperatures.

For optical applications, the deposition of BCN coatings on polymers is a promising method for protecting the polymer surface against wear and scratching. BCN films have high optical transparency and thus can be used as mask substrates for X-ray lithography.

In this work, the deposition and characterization of amorphous thin films of boron carbon nitride (BCN) are reported. The BCN thin films were deposited by radio frequency (rf) magnetron sputtering technique. The BCN films were deposited by sputtering from a high purity B4C target with the incorporation of nitrogen gas in the sputtering ambient. Films of different compositions were deposited by varying the ratios of argon and nitrogen in the sputtering ambient. Investigation of the oxidation kinetics of these materials was performed to study high temperature compatibility of the material. Both the dielectric and optical properties seem to be sensitive to carbon and nitrogen content in the films.
Ageing Effects on Sputtered YSZ Thin Films and Gold Electrodes for Electrochemical Sensor Applications
Authors: Subramaniam Kiruba Mangalam , Rajeswara Rao L L , Jampana Nagaraju
Published: February 2020

8mol%

Yttria Stabilized Zirconia (8YSZ) is one of the most studied solid electrolytes. With increasing demand to miniaturize electrochemical sensors and solid oxide fuel cells using 8YSZ thin film electrolytes, it is vital to study the ageing effects of 8YSZ thin films. Although ageing effects in bulk YSZ had been previously studied, no work has been reported on YSZ thin films. This paper reports the fabrication, characterization of RF sputtered, polycrystalline 8YSZ thin films and the effect of prolonged heat treatment on the ionic conductivity and surface morphology. The films are annealed at 10000C for three hours before starting the aging experiment. With electrochemical sensor applications in mind, the ageing temperature was chosen to be closer to exhaust gas temperature (i.e, 6500C). The results show that there is no significant variation in the ionic conductivity and activation energy values of 8YSZ thin films (250 nm) before and after 15000 minutes of heat treatment at 6500C. The conductivity of YSZ film is constant at 0.057Scm-1 throughout the course of high temperature soaking in spite of significant grain growth. The grain size of the film is found to increase from 15nm in as deposited film to 60nm in aged film. The activation energy value before and after heat treatment was 0.98eV. After 15000 minutes, the YSZ film started developing cracks in the vicinity of thick film gold electrode and the conductivity values deteriorated. However, no cracks are present in the (bare) YSZ sample without any electrodes. Hence the conductivity deterioration is attributed to the cracks on YSZ triggered by the presence of thick film gold electrode. YSZ samples are aged with three types of thin film gold electrodes on them i) 200nm Au without Ti adhesion layer ii) 200nm Au with 10nm Ti adhesion layer and ii) 200nm Au with 10nm Ti adhesion layer in 45nm trench on YSZ. The electrodes without adhesion layer completely de-wetted itself in 48 hours. Ti/Au layers showed re-crystallization induced porosity after 48 hours and gradually disintegrated around 100hours. In the third type where Ti/Au layers were deposited on a 45nm trench on 250nm YSZ thin film. This buried electrode seemed more promising and continuous up to at least 15000 minutes.

Figure 1
Effect of Thickness on Electrical and Reliability Characteristics for Dense and Porous Low Dielectric Constant Materials
Authors: Cheng Yi-Lung , Kao Kai-Chieh , Wu Chang-Sian
Published: February 2020

Thickness-dependent dielectric electrical and reliability characteristics in the dense and porous low-k films were investigated in this study. The experimental results obtained from metal-insulator-silicon (MIS) structures indicate that the dielectric strength and the dielectric breakdown time of low-k dielectric films were inversely proportional to the dielectric physical thickness. A inverse power law combined with an critical thickness for dielectric breakdown characteristics was proposed and well-fitted the experimental results. Additionally, the dense low-k films exhibited a higher critical thickness and a higher power law constant value, indicating that their breakdown behaviors are more related to the film thickness as compared to the porous low-k films.
From the Bottom up and Back: Nature-Inspired Electrochemical Platforms for Bioenergy and Bioremediation
Authors: Reguera Gemma
Published: February 2020

In Nature, highly efficient and diverse consortia of microbes cycle carbon and other elements while generating energy for growth. Driving these reactions are organisms with the ability to extract electrons from the chemical substrates and transfer them to insoluble and soluble metals. One group in particular, Geobacter bacteria, can couple their metabolism to the reduction of insoluble minerals such as iron and manganese oxides. This natural process can be mimicked in electrochemical reactors, which provide a poised electrode as electron sink to drive the growth and catalytic activity of the bacteria. Whether alone or in partnership with other microbes, such Nature-inspired reactors show promise for the treatment of agricultural, industrial, and human wastes while generating added-value products and enabling water reuse. Geobacter cells are also able to reduce toxic metals such as uranium. To do so, they have evolved an electroactive cell envelope containing abundant metalloproteins. The electroactive envelope also serves as an anchor and charge injection system for conductive hair-like protein filaments or pili. The pilus filaments protrude from the cell, efficiently bind the uranium, and function as protein nanowires to reductively precipitate the radionuclide and mineralize it outside the cell. This effectively prevents the mobility of the uranium contaminants and protects the cells and other living components of the ecosystem, including humans, from exposure. Using genetic engineering approaches, we have mass-produced selected components of the Geobacter respiratory network and assembled them in vitro to develop nanostructure biomimetic interfaces for the bioremediation of uranium. From the nanoscale to the macroscale, the electroactivity of these microbes is used as inspiration to develop materials and devices for bioenergy and bioremediation application.
Exploration of Ammonia Production in Blue Green Algae By Bioelectrocatalytic Methods
Authors: Lyon Jacob , Paschkewitz Timothy , Leddy Johna
Published: February 2020

Ammonia is an important compound to many industries around the world.  Most of the fertilizers used by crop growers have ammonia as an essential ingredient.  It can also be useful as a fuel source, offering greater energy density per unit than hydrogen, and greater safety.  Currently, the predominant method for producing ammonia on an industrial scale is by the Haber-Bosch process.  This process uses steam evolution of methane to provide H2 gas, which is then combined with N2 gas over an iron catalyst to form NH3.  This process requires large amounts of energy as well as high temperatures and pressures. 

In this report, an alternative method for ammonia production is explored.  With Anabaena Variabilis, a photosynthetic cyanobacteria, on a carbon electrode, ammonia can be generated at ambient temperatures and pressures at little energy cost, a few tenths of a volt.1,2  A bioelectrocatalytic device has been constructed by immobilizing whole cell a. variabilis in a Nafion film modified with a trimethyl octadecyl ammonium bromide (TMODA) salt at an electrode surface.3  The ammonium salt enlarges the pore size of the Nafion structure while neutralizing the acidic environment of the polymer, and provides a hospitable matrix for the algae cells. The polymer modified electrode provides the driving force and reductive microenvironment to facilitate production of NH3 by nitrogenase and nitrate/nitrite reductase enzymes present in a. variabilis.  Ammonia production by cyanobacteria was increased from basal levels of 2.8 ± 0.4 µM produced over a two week period, to 22 ± 8 µM produced in 20 minutes under mild voltage perturbation, a roughly 104 increase in rate. Control of ammonia producing structures (nitrogenase or nitrate/nitrite reductase) can be accomplished by growing the algae with and without fixed sources of nitrogen in the growth media. The addition of nitrates and nitrites to the electrolyte during voltammetric perturbation varies linearly with ammonia increased with substrate.

References:

[1] Johna Leddy and Timothy M. Pashkewitz, Ammonia Production Using Bioelectrocatalytic Devices, US Patent Application 20140011252.

[2] Timothy M. Paschkewitz. Ammonia Production at Ambient Temperature and Pressure: An Electrochemical and Biological Approach. Ph.D. dissertation. University of Iowa, 2012.

[3] Tamar L. Klotzbach; Michelle Watt; Yasmin Ansari; Shelley D. Minteer. Improving the microenvironment for enzyme immobilization at electrodes by hydrophobically modifying chitosan and Nafion polymers.Journal of Membrane Science, 311, 1-2, 20 March 2008, 81-88.
Bio-Electrochemical Systems in the Subalpine Lake Idro (Italy)
Authors: Cristiani Pierangela
Published: February 2020

The subalpine Lake Idro in the north of Italy is here described from a physico-chemical and electrochemical point of view. The glacial origin of the lake, together with the steep walls of the basin and the maximum depth of 120 m, creates the conditions for the evolution of a stable meromictic condition during the year. The presence of a superficial layer of aerobic water (a mixolimion of about 50 m) and of a deep constant layer under anaerobiosis (monimolimion) makes it a unique environment for electrochemical studies. A peculiarity of this lake is the presence of a cloudy white layer at the chemocline, detected at 40-60 m of depth by scuba divers and never reported in literature. The hydrographic basin is mostly composed of dolomite, the typical rock of the Alps. The general chemical composition is Mg(Ca)CO3, but it could include impurities such as Fe and Mn.

Many are the peculiarities converging to produce a unique environment for Mn cycling in the mixolimion, chemocline, and monimolimion characterizing the lake. On the basis of home-built sensors and a standard multiparametric probe, oxygen, pH, sulphide, conductivity, red-ox and temperature profiles were determined. Strict correlations were found between these parameters and the different oxidation states of Mn (Mn+2, Mn+3 and Mn+4) detected in the water and in the particulate. Equilibria with Fe and other elements have been considered.

A chain of copper alloy (CuNi 70/30) and carbon steel was immersed at different depths in the water down to the bottom of the lake, in a point where the lake depth is the maximum (120 m), to study electrochemical and biological characteristics of the lake. Unique correlations between the chemical-physical parameters and electrochemical characteristics of copper alloys specimens, exposed at different depth in the lake, were demonstrated. The open circuit potential of copper alloys, measured versus the same Ag/AgCl reference electrode used for the sulphide measurements, varied as a function of the oxygen concentration in the different water layers and stabilized in time in each layer (from +200 mV down to -600 mV vs. Ag/AgCl). The results indicated that, in different ways, handmade sensors can be cost effective tools, able to give insight into the redox conditions of water.

The stratification of the lake poses a new interesting studies for MFCs. In this environment,  microbial fuel cells (MFC) might produce power by utilizing the microbial capacity of catalyzing the oxygen reduction at the cathode, and the Mn(OH)2 oxidation at the anode. Another type of MFC might develop power by reduction of Mn2O3.

The natural scenario of the Lake Idro suggests studies of new bio-electrochemical technologies that could be applied for environment-depollution purposes.
Pd-Based Metal Aerogels with Promoted Bioelectrocatalytic Behavior
Authors: Wen Dan , Liu Wei , Eychmüller Alexander
Published: February 2020

Aerogels derived from noble metal nanoparticles (NPs) are a new kind of metal materials, which combine the nano-sized scale with that of materials of macro dimensions.[1] These metal aerogels are expected to provide a matrix with high electrical conductivity and high surface area for electrochemical applications. They may also offer inherent catalytic activity and generally fast (reversible) electron-transfer kinetics. In that respect, enzyme-loaded metallic aerogels in combination with their meso/macroporous structure can facilitate electron and mass transfer processes, which are both important for bioelectronic applications, e.g., in electrochemical biosensors and in biofuel cells.[2]

  Here the controlled growth of Pd aerogels has been facilely realized by using calcium ions as the destabilizing agent. The involving Pd aerogels with different porosities and surface areas exhibited faster electrode kinetics and higher activities towards the bioelectrooxidation of glucose when co-immobilized with glucose oxidase (GOD), compared to the Pd NPs and glassy carbon.[3] Based on the Pd aerogels promoted bioelectrocatalysis, we have developed a newly designed metal aerogel-based biofuel cell system. In the text, a commonly used mediator, ferrocenecarboxylic acid (Fc), was integrated into the Pd hydrogel and thus produced a Pd-Fc composite aerogel mediator for GOD at the bioanode. Additionally, bilirubin oxidase (BOD) encapsulated into a Pd-Pt alloy aerogel played a synergetic role towards the reduction of O2, which promoted the direct electrocatalytic reduction of O2 at the biocathode with an onset potential of 0.56 V under neutral conditions. By employing these two bioelectrodes, the assembled membrane-less glucose/O2 biofuel cell showed a maximum power output of 20 μW cm-2 at 0.25 V.[4,5] 

References

[1] N. Gaponik, A.-K. Herrmann, A. Eychmüller, J. Phys.
Chem. Lett.
2012, 3, 8–17.

[2] Gao, F.; Viry, L.; Maugey, M.; Poulin, P.; Mano, N. Nat.
Commun.
2010, 1, 2.

[3] D. Wen, A.-K. Herrmann, L. Borchardt, F. Simon, W. Liu, S. Kaskel, A. Eychmüller, J. Am.
Chem. Soc.
2014, 136, 2727–2730.

[4] W. Liu, P. Rodriguez, L. Borchardt, A. Foelske, J. Yuan, A.-K. Herrmann, D. Geiger, Z. Zheng, S. Kaskel, N. Gaponik, R. Kötz, T. Schmidt, A. Eychmüller, Angew.
Chem., Int. Ed.
2013, 52, 9849–9852.

[5] D. Wen, W. Liu, A.-K. Herrmann, A. Eychmüller, Chem. Eur. J.
2014, 20, 4380–4385.

Figure 1
Non-Destructive Detection of Metabolites in Live Cells Using Single Walled Carbon Nanotubes
Authors: Galassi Thomas Vito , Jena Prakrit Vaibhav , Roxbury Daniel , Budhathoki-Uprety Januka , Horoszko Christopher , Heller Daniel A
Published: February 2020

Proper transport, storage and degradation of macromolecules in cells is vital to their function. Cells and organisms that are unable to properly carry out these processes may exhibit deleterious phenotypes such as impaired endoplasmic reticulum and mitochondrial function. Currently, very few therapies exist for the treatment of such disorders due, in part, to the challenge of detecting the amounts of specific metabolites present within live cells. As such, this work aims to develop a tool with the ability to detect cellular metabolites in a non-destructive, reversible manner in live cells and animals. To achieve this goal, an optical reporter was engineered using single walled carbon nanotubes (SWCNTs). SWCNTs are ideal biomaterials for the engineering of optical probes due to their fluorescence in the near infrared region of the spectrum, lack of photo bleaching, and large Stokes shift. The microenvironment of nanotubes has also been shown to modulate their near infrared fluorescence. In this work, we develop an optical reporter capable of detecting cellular metabolites and demonstrate its use in multiple cell types. Future work will focus on the characterization and validation of our optical reporter, as well as exhibiting its in vivo potential.
Stochastic Sensors Based on Diamond Paste for Screening of Biological Fluids for Neurotransmitters
Authors: Stefan-van Staden Raluca-Ioana , Moldoveanu Iuliana , VAN Staden Jacobus Frederick
Published: February 2020

Diamond paste proved to be one of the best matrices for the design of stochastic sensors. Therefore, different porhyrins were immobilized in diamond paste.

The “signatures” of neurotransmitters were determined. The “signatures” were used to identify these analytes on the diagrams obtained when whole blood was screened. Quantitative analysis was also performed using these microsensors. The results obtained using the proposed microsensors were correlating very well with those obtained using the standard methods used in clinical analysis.

Acknowledgements The present work was supported by the European Commission through the DENAMIC project (Contract-No. 282957) and by UEFISCDI, Romania Contract-no. 186/23.10.2012.
Thermal Properties of Chemically Modified Carbon Nanotubes Dispersed in Polymer Matrices
Authors: Januszko Adam W , Peszke Jerzy , Pawlicka Agnieszka , Czujko Tomasz
Published: February 2020

Keywords: carbon nanotubes, polymer, functional composite, thermal properties of functional composite.

A functional composite (FC) was obtained by mixing polymers from the group of polyacrylic acid ester derivatives and polymethylacrylate, copolymers of polyvinyl alcohol (PVA), polyurethanes, ethoxylate derivatives of silicones and chemically functionalized multiwall carbon nanotubes (FMCN). The result was a subject of temperature dependence measurement on electrical resistivity, as well as mechanical strength and flexibility. FC has presented durable, flexible properties and demonstrated a resistance in the range of 20 - 40 Ω. A silicone composite has presented a best chemical and physical properties in broad range of temperature (up to 100°C). Thermal images were studied using infrared (IR) camera and characterized by histograms. The morphology of the functional composites have been observed by SEM and discussed.

The work also presents number of methods of nanostructures preparation, which are the most commonly used.