bluuebunny/crossref_metadata_2025 huggingface dataset:
Inkjet Printed Nanoparticle Electrochemical Platform for Breast Cancer Detection
Authors: Krause Colleen E. , Carvajal Susanita , Fera Samantha , Jones Abby L , Baldo Thaisa , Mosa Islam , Rusling James F
Published: February 2020

Inexpensive disposable sensor platforms have the ability to revolutionize personalized cancer diagnostics. Monitoring levels of specific biomarker proteins in serum can provide further insight into a patient’s disease status enabling for physicians to diagnose and treat patients on the spot. Electrochemical sensors are among the most popular for point –of-care use due to ease of detection, low instrumentation cost, and the ability to be miniaturized and automated. A typical electrochemical cell consists of a counter, working, and reference electrodes. Miniaturization and production cost of electrodes have been improved by patterning electrodes on a substrate surface. Common methods however, are time consuming and costly therefore limiting rapid prototyping. Described here is an inexpensive commercially scalable way to integrate these electrodes on a single test chip to detect clinically relevant breast cancer biomarker Human Epidermal Growth Factor Receptor 2 (HER-2) in serum. The sensor platform consists of an inkjet printed gold nanoparticle -working 8-electrode array (WEA) and counter electrode (CE), along with an inkjet printed silver electrode that was chlorinated with bleach to produce a Ag/AgCl quasi-reference electrode (RE). The WEA featured an excellent nanostructured surface to build immunoassays. Therefore, capture antibodies were bound to a chemically modified surface on the WEA and placed into a simple microfluidic device. A full sandwich immunoassay was assembled following a simultaneous injection of HER-2, biotinlyated antibody, and polymerized horseradish peroxide labels into the microfluidic device housing the WEA. A clinically relevant detection limit of 12 pg mL-1 was achieved in a total assay time of under 20 mins. Excellent reproducibility and sensitivity of the biosensor were observed through recovery assays preformed in human serum, containing hundreds to thousands of competing proteins. Following this rapid assay protocol these sensor platforms could easily be adapted for multiplex detection of a panel of proteins for breast cancer screening
Online Sensor Device for Rapid Escherichia coli Detection in Water
Authors: Ramanujam Ashwin , Keogh Rebecca , Goettge John , Muthuvel Madhivanan , Carroll Ronan , Botte Gerardine G.
Published: February 2020

A novel, online probe to detect the concentration of Escherichia coli (E.coli) in water has been developed. Chronoamperometry was used to record the electrochemical current response from different E.coli concentrations based on their interaction with a locally formed catalyst on electrode surface, which occurs when a fixed potential is applied. A number of current responses that are specific to some known E.coli concentrations were recorded and used to develop a linear least squares regression model. The probe founded on this model had a detection limit of 104 CFU/ml and percent error consistently less than 15% on log scale with a detection time of 10 minutes. The major advantage of this sensor lies in its rapid detection and on-site integration, minimizing the need for continuous physical monitoring.

Keywords:

Electrochemical sensor; Escherichia coli detection; Online probe
Honeycomb Support Structures to Stabilize PMMA Mold during LIGA Processing of High Aspect Ratio Gratings for XPCI Systems
Authors: Baca Kalin R , Arrington Christian L. , Hollowell Andrew E , Finnegan Patrick Sean , St. John Christopher R. , Pillars Jamin R. , Dagel Amber L , Singh Varshni
Published: February 2020

X-ray phase contrast imaging (XPCI) allows for medical and non-destructive testing of soft tissue [1]. High aspect ratio (HAR) gratings (100:1) are difficult to achieve and are a key element of XPCI gold gratings PMMA lithography, molding, and electroforming (LIGA) process [2]. Development of uniform, continuous HAR gold gratings over a large area is difficult as they easily tilt and delaminate. One technique for stabilizing the mold during development is to incorporate relief structures into mold, providing more surface area at the bottom, which results in segmented gratings [2]. In the current work, honeycomb supports are used to stabilize the PMMA mold during development and plating to realize continuous gratings centimeters in lateral length. Our goal is to fabricate micron size HAR gratings ~10 cm in lateral length that are ideal for XPCI applications enabling larger field of view for the XPCI imaging.

Honeycomb structures were patterned on a 100 mm substrate. A sheet of PMMA is then bonded and fly cut to desired height. An x-ray exposure then patterns the PMMA mold prior to the fabrication of the top honeycomb structure. The gratings are then developed and electroplated having structural support on both sides. The use of bottom and top honeycomb arrays provide unique mechanical support to the fragile PMMA mold during development and electroplating of the HAR grating.

Momose, A. and W. Yashiro, X-ray Phase Measurements with Talbot Interferometry and Its Applications. International Conference on Advanced Phase Measurement Methods in Optics an Imaging, 2010. 1236: p. 195-199.

Mohr, J., et al., High Aspect Ratio Gratings for X-Ray Phase Contrast Imaging. International Workshop on X-Ray and Neutron Phase Imaging with Gratings, 2012. 1466: p. 41-50.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Figure 1: Schematic of mold stabilization design (left), honeycomb pattern (right)

Figure 1
Advanced Anion Conducting Multiblock Copolymer Membranes with Hydrocarbon Backbones
Authors: Huang Garrett , Mandal Mrinmay , Liu Lisha , Kohl Paul A
Published: February 2020

While research and development has been focused primarily on proton exchange membrane (PEM) devices in recent decades, devices based on anion exchange membranes (AEM) have garnered increased interest as a potential cost-saving alternative. To be viable for use in electrochemical devices, AEMs must have good long-term alkaline and thermal stability, high hydroxide ion conductivity, lower water uptake, high molecular weight, and low oxygen or fuel permeability.

Polar groups in the polymer backbone are susceptible to nucelophilic attack by the hydroxide ion, which is a major concern for the long-term stability of these materials. In the past, AEMs containing aryl ether bonds degraded under alkaline conditions. Alternatively, materials with a fully hydrocarbon polymer backbone have been shown to provide a route to low-cost and chemically resilient AEMs.

In this study, several new classes of AEMs with fully hydrocarbon backbones were synthesized and characterized. Multiblock copolymers with tethered quaternary ammonium conducting groups were chosen to promote phase segregation and enhance the ionic conductivity. The AEMs were made from vinyl addition and ring-opening metathesis polymerization (ROMP) of norbornenes. These results were compared to a previous study involving AEMs made from partially fluorinated poly(arylene ether)s. The mechanical and thermal stability, ionic conductivity, long-term alkaline stability of all classes of polymers are discussed in detail in the context of performance in an AEM fuel cell or electrolyzer.

Figure 1
Study of the Protein Bovine Serum Albumin (BSA) and the Triblock Copolymer P103 Interface By Differential Capacitance
Authors: Soltero Martinez J. Félix Armando , Velasco Brenda , Larios-Duran Erika Roxana , Rosales Rivera Luis Carlos
Published: February 2020

Triblock copolymers are considered as non-ionic surfactants due to their self-assembling nature. Triblock copolymers can form structures similar to micelles and larger structures at a certain concentration and temperature. The triblock copolymers used here are biodegradable, water-soluble and are formed by chains of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), which can be arranged as A-B-A or B-A-B; where A are chains of PEO and B chains of PPO. And in this case they are referred by the commercial name Pluronics. The physicochemical properties of these surfactants (Critical micellar temperature (CMT), critical micellar concentration (CMC), density, molecular weight, etc.) depend on their molecular weight, the number of PPO and PEO chains present in the triblock copolymer, on the solvent (polar or no polar) and on the presence of salts in the solution.

Applications of triblock copolymers are diverse; for instance, in the field of biotechnology they have been used for the controlled release of drugs, proteins, DNA. However, even when these compounds are already used and applied in several topics, there is a lack in the knowledge concerning to the effect of the interactions of them with other compounds, such as biopolymers. The main interest is to understand the effects of these interactions in the characteristic shape or size of aggregates formed by triblock copolymers. In order to obtain information about this topic, an initial approach is to study the interactions of some triblock copolymer and some well-characterized protein, as bovine serum albumin (BSA). BSA protein is cheap, easy to isolate and purify. In this way, BSA is an excellent option for the interactions study that exist between proteins and triblock copolymers.

The objective of this work is to contribute to the knowledge of the interactions of triblock copolymers and proteins through the use of electrochemical techniques to obtain information about the amount of species adsorbed on the electrodes, as well as the size of the interface formed by the interaction of both, protein and triblock copolymers, once they are adsorbed on a metal surface. This information is important in the design of the sensors and is also necessary for the application of drug delibery and other fields of bioengineering and biomedicine.

Thus, this investigation is focused on the interaction between BSA and the termosensible triblock copolymer Pluronic® P103 (PEO17-PPO60-PEO17). The interactions are studied by the adsorption of both compounds onto a gold disk electrode immersed in a phosphate buffer solution. Some electrochemical techniques, such as cyclic voltammetry and Differential-capacitance vs. Polarization potential are presented and analyzed in a wide range of temperatures and different P103 and BSA concentration. The thickness of the interface and the effect on the polarization potential are reported.
Synthesis of Ti|IrO2-SnO2-Sb2O3 electrodes without Chloride Precursors and Their Electrochemical Applications
Authors: Reyes Adrián , Sánchez David , Serrano Ricardo Agustín , Medel Alejandro , González-Fuentes Miguel A. , Méndez Erika
Published: February 2020

Electrochemical oxidation depends enormously on the electrode materials used during electrolysis. Dimensionally Stable Anodes (DSA) represent a good option for electrochemical oxidation applied to wastewater treatment due to the ability of generating hydroxyl radicals. These radicals are strong, non-selective oxidizing agents, which are able to react with organic pollutants and mineralize them. However, this kind of electrodes is commonly synthesized from chloride precursors, which represents an environmental problem, because they can form undesirable chlorinated by-products during the electrolysis. Some DSA electrodes such as PbO2, SnO2-Sb2O5 and TiO2 are promising anodes due to their high over-potential for oxygen evolution, which leads to the ability of OH radical production; however, their main drawback is the low chemical stability [1, 2]. This disadvantage prevents their use in environmental applications and causes the search for other materials with better properties. In this work we present the synthesis as well as its electrochemical application of a DSA electrode composed of Ti|IrO2-SnO2-Sb2O3. The purpose is enhancing the chemical stability and prolonging the electrode lifetime. The Pechini concept was used to this material, but with the advantage that no chloride precursors were employed [3]. Cyclic voltammetry (CV), X-ray diffraction (DRX), Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) were used to characterize the as-prepared electrode. The electrocatalytic properties were evaluated by electrochemical degradation of tartrazine in aqueous media as well as dibenzothiophene in organic media. Results showed that noncracked oxide layers were obtained and that the electrode has a great capability for the electrochemical degradation of both molecules.

Keywords: DSA electrode, Ti|IrO2-SnO2-Sb2O3, tartrazine, dibenzothiophene

X. Chen, G. Chen, Anodic oxidation of dyes at novel Ti/B-diamond electrodes, Chem. Eng. Sci. 58 (2003) 995.

X. Chen, G. Chen, F. Gao, P. Yue, High-performance Ti/BDD electrodes for pollutant oxidation, Environ. Sci. Technol. 37 (2003) 5021.

M. H. P. Santana, L. M. Da Silva, L. A. De Faria, (2003). Investigation of Surface Properties of Ru-Based Oxide Electrodes Containing Ti, Ce and Nb. Electrochim. Acta, 48 (13), 1885.
Rapid Electrochemical Detection of Escherichia coli Using a Rotating Disc Electrode
Authors: Ramanujam Ashwin , Neyhouse Bertrand , Keogh Rebecca , Goettge John , Muthuvel Madhivanan , Carroll Ronan , Botte Gerardine G.
Published: February 2020

A novel electrochemical method was developed to detect the concentration of Escherichia coli (E.coli) in water. Chronoamperometry was used to record the electrochemical current response from different E.coli concentrations based on their interaction with a locally formed electrocatalyst, which occurs when a fixed potential is applied. A number of current responses that are specific to some known E.coli concentrations were recorded and used to develop a linear least squares regression model. The probe founded on this model had a detection limit of 105 CFU/ml and percent error consistently less than 15% on log scale with a detection time of 10 minutes. The major advantage of this sensor lies in its rapid detection and simplicity in detection mechanism, since the catalyst can be produced locally as and when required.

Keywords:

Electrochemical sensor; Escherichia coli detection; Rotating Disc electrode
Electrodeposition of Mg-Based Alloys for Anti-Corrosion and Energy Storage Applications
Authors: Castro Pardo Samuel , Ganguli Babu , Vajtai Robert , Ajayan Pulickel M
Published: February 2020

Magnesium has gained a lot of attention due to its inherent properties such as light-weight with a density of 1.7 g/cm3 and the highest strength to weight ratio. Such unique properties make magnesium a suitable candidate for various applications including vehicles, aerospace projects, construction, energy storage applications and medical implants. One of the crucial issues with the use of magnesium on these applications is the tendency of the material to corrode. This is due to the high chemical activity of magnesium, its standard equilibrium potential of Mg/Mg2+ is -2.4 V vs. NHE. To prevent these problems, there have been reported strategies such as formation of alloys with noble metals or inert elements and the protection of the metal with a coating film.1 From the mentioned solutions, the most suitable solutions to prevent corrosion on magnesium without compromising its properties are the formation of alloys using passive elements such as Al, Ni or Cr and the protection of magnesium with a coating film. 2,3

Based on these two solutions, we propose to use aluminum as the second element for the alloy formation to prevent corrosion of magnesium and to enhance its structural, thermal, and electrical performance. In our study, we’ve been able to produce magnesium alloys by electro-co-deposition which have demonstrated to have a lower corrosion behavior compared to pristine magnesium films. Similarly, magnesium-based materials are gaining interest in energy storage application due to two-electron transfer per a reaction and thus a high volumetric capacity compared to the state-of-art Li-ion batteries. Also, they have shown to be safer than Li since Mg during cycling do not form dendrites.4 Herein, we explore the use of electro-co-deposited Mg-Al alloy as electrodes to construct high energy rechargeable Mg batteries.

References

(1) Esmaily, M.; Svensson, J. E.; Fajardo, S.; Birbilis, N.; Frankel, G. S.; Virtanen, S.; Arrabal, R.; Thomas, S.; Johansson, L. G. Fundamentals and Advances in Magnesium Alloy Corrosion. Prog. Mater. Sci.
2017, 89, 92–193.

(2) Liu, R. L.; Scully, J. R.; Williams, G.; Birbilis, N. Reducing the Corrosion Rate of Magnesium via Microalloying Additions of Group 14 and 15 Elements. Electrochim. Acta
2018, 260, 184–195.

(3) Yuwono, J. A.; Birbilis, N.; Liu, R.; Ou, Q.; Bao, Q.; Medhekar, N. V. Aqueous Electrochemical Activity of the Mg Surface: The Role of Group 14 and 15 Microalloying Elements. J. Electrochem. Soc.
2017, 164 (13), C918–C929.

(4) Bucur, C. B. Challenges of a Rechargeable Magnesium Battery A Guide to the Viability of This Post Lithium-Ion Battery, 1st editio.; Spinger Briefs in Energy, 2018.
Reaction Mechanism for the Formation of Magnetite Nanoparticles Via Electrochemistry
Authors: Reséndiz Ramírez Rubí , Antaño López René , Rodríguez López Aarón , Larios Duran Erika Roxana , Torres-González Julieta
Published: February 2020

Magnetite is an iron oxide composed of ferrous-ferric oxide, because of its magnetic properties is used in different areas. In literature there are proposals of reaction mechanisms for the formation of magnetite when it is produced electrochemically, however, these do not seem to be very clear since there are inconsistencies in their formulation. In electrochemical synthesis metallic iron is used as a cathode and as an anode in an electrolytic solution, the necessary potential is applied to oxidize iron to form magnetite (Fe3O4). The most stable oxidation state of iron is (III), some authors report that they oxidize to iron III and later reduce one part to iron II to form magnetite. One of the reported inconsistencies is the existence of solids that are formed in the anode that later diffuse to the cathode to be reduced to form the magnetite, other authors support the fact that magnetite is formed in the solution and that the hydrogen is one of the main reactants. In this work we propose a simple mechanism for the formation of magnetite:

Fes + 2(OH-) →Fe(OH)2ads+2e-

3Fe(OH)2ads+ 2(OH-)→ Fe(OH)2•2Fe(OH)3ads+2e-

Fe(OH)2•2Fe(OH)3ads →Fe3O4+4H2O

This mechanism was proposed to be analyzed by EIS with the reaction mechanisms approach. This approach consists of formulating the impedance expression, starting with charge and mass balances using mathematical models, to be able to use this approach it is necessary to have intermediaries adsorbed in the mechanism. With this approach it is possible to obtain a simulated spectrum as a function of the potential by means of theoretical assumptions of the parameters involved, which can be sustained experimentally.
Molybdenum Carbide Electrocatalyst/Support Synthesis and Characterization
Authors: Benavidez Angelica D , Nayak Shanti Kiran , Coker Eric , Garzon Fernando H
Published: February 2020

Transition metal carbides are increasingly gaining attention as electrocatalysts/supports due to their unique properties including structural durability, electronic conductivity, and an electron structure which is somewhat similar to that of noble metals[1]. Molybdenum carbide has shown to be an active catalyst and as a noble metal support, however it is difficult to prepare in high surface area nanoparticle form[2,3]. Most nanoparticle synthesis methods produce residual carbon that blocks surface access. In order to improve materials performance, high surface area, impurity-free molybdenum carbides are needed. With the aid of thermochemical modeling and gas equilibration studies, we have developed a synthesis method that yields high surface area MoC nanoparticles of the metastable cubic phase. These 2-3 nm MoC nanoparticles have surface areas of up to 360m2/g and have been characterized using TEM, XRD, EDS, XPS, and BET. The nanoparticles were tested for their effectiveness for both electrochemical and heterogeneous synthesis of ammonia.

[1] Y. Liu, T.G. Kelly, J.G. Chen, W.E. Mustain, Metal Carbides as Alternative Electrocatalyst Supports, ACS Catal. 3 (2013) 1184–1194. doi:10.1021/cs4001249.

[2] M. Patel, J. Subrahmanyam, Synthesis of nanocrystalline molybdenum carbide (Mo2C) by solution route, Materials Research Bulletin. 43 (2008) 2036–2041. doi:10.1016/j.materresbull.2007.09.025.

[3] A.M. Gomez-Marin, E.A. Ticianelli, Analysis of the electrocatalytic activity of a-molybdenum carbide thin porous electrodes toward the hydrogen evolution reaction, Electrochimica Acta. 220 (2016) 363–372. doi:10.1016/j.electacta.2016.10.101.

Figure 1
Electrochemical Methane Activation and Conversion Using Fe, Co, Cu Oxides/ZrO2 Nanocomposites
Authors: Vazquez Juvencio , Mojica Hebert Rodrigo , Molina Paulina , Acevedo-Peña Prospero , Reguera Edilso , González Montiel Marlene
Published: February 2020

Methane has been widely employed as a feedstock for numerous chemical and electrochemical processes. However, methane activation poses a challenge due to the molecule’s relative inertness, lack of significant polarity and because its bond energy is the highest among all hydrocarbons. Consequently, the ability to activate methane (CH4), or access the C atom to form new bonds is a difficult endeavor [1]. Furthermore, CH4 gas emission has long been ignored and regarded as a trivial matter [2], even though its effect as a greenhouse gas is over 30 times more potent than that of CO2 [3]. In this regard, the oxidation and conversion of CH4 to liquid alcohols is an economical and energy efficient alternative with academic and industry interest.

The present study shows the synthesis and characterization of Fe, Co, Cu oxides/ZrO2 nanocomposites used as bifunctional electrocatalyst for the electrochemical activation of methane, which in conventional alkaline electrochemical systems is always performed at room temperature.

Fe, Co, Cu oxides/ZrO2 nanocomposites were synthesized using an aqueous-phase precipitation technique and their structural, spectroscopic, magnetic and electrochemical characteristics were evaluated.

Methane was electrochemically activated over the three functional electrocatalysts here synthesized. Carbonate anions were used as an oxygen donator to facilitate methane activation while ZrO2 adsorbed and donated carbonate anions to active sites on Fe, Co and Cu oxides where methane was adsorbed and activated. Products formed were studied by gas chromatography.

References:

[1] R. Bergman, Nature, 446, 391 (2007).

[2] A. R. Brandt, G. A. Heath, E. A. Kort, F. O. Sullivan, G. Petron, S. M. Jordaan, P. Tans, J. Wilcox, A. M. Gopstein, D. Arent, S. Wofsy, N. J. Brown, R. Bradley, G. D. Stucky, D. Eardley, R. Harriss, Science, 343, 733 (2014).

[3] D. T. Shindell, G. Faluvegi, D. M. Koch, G. A. Schmidt, N. Unger, S. E. Bauer, Science, 326, 716 (2009).

[4] Neil Spinner and William E. Mustain, Journal of The Electrochemical Society, 160 (11) F1275-F1281 (2013).
Prompting Charge Injection in Aqueous Mesoscopic Photoelectrochemical Cells
Authors: Wang Bo , Zhang Xiao LI
Published: February 2020

Despite high efficiencies have been achieved, conventional mesoscopic dye-sensitized solar cells using organic solvents based electrolytes that generally have the disadvantages of high vapour pressure against reliable encapsulation, and most importantly, are not environmentally friendly. Electrolytes based on water, a cheap, earth-abundant, non-toxic and non-flammable solvent, therefore, attracted considerable research interests. Water based electrolyte would negatively shift the conduction band of TiO2 as the water molecules irreversibly change the interfacial properties of the sensitized TiO2 film. In our work, tungsten doped mesoporous TiO2 nanoparticle aggregates (TNA) possessing high surface area and superior scattering effect, were developed to induce positive shift of the TiO2 conduction band, enhancing the driving force for electron injection and collection efficiencies. The electrochemical impedance spectra indicate a retarded charge recombination and increased electron diffusion length after W-doping. By fine-tuning the W-doping concentration to 0.25 %, aqueous DSCs produced a significant improved open circuit voltage of 712 mV and a short circuit current of 7.05 mA cm-2, leading to an overall increased power conversion efficiency of 3.40 % at 1000 W m-2 simulated irradiation, which is roughly 25 % enhancement compared to that without W-doping photoanode.
Isolating Surface Reactivity of High Energy Cathode Materials through Model Thin Films
Authors: Phillip Nathan Dale , Veith Gabriel M. , Ruther Rose E. , Wood David L
Published: February 2020

Increasing demands for improved energy density in lithium ion batteries for electric vehicles and grid storage has spurred the development of high energy cathode materials. Ni-rich LiNixMnyCozO2 (x > 0.5, x + y + z = 1) cathode systems are frontrunners among the next-generation of Li-ion battery cathode active materials. Despite the material’s high theoretical capacity (~200 mAh/g), commercial adoption has been hindered by a lack of understanding of complex interactions between the electrolyte and the binder, conductive additives, and active material present in composite electrodes. In this study, we isolated the surface reactivity of LiNi0.6Mn0.2Co0.2O2 (NMC622) by physical vapor deposition of thin film electrodes (thickness < 1.5 µm) for characterization and electrochemistry without influence from conductive additives and binders.

Radio Frequency Magnetron Sputtering of homemade NMC622 targets was used to deposit thin films of NMC622 onto Pt-coated Al2O3 substrates which were annealed to achieve the desired layered structure. LiCoO2 thin films were deposited in a similar manner as a baseline for the process. The dependence of crystal structure and stoichiometry on deposition and annealing conditions of these films were determined by XRD, Raman, and ICP-AES. Cathodes were cycled against Li metal in a standard commercial electrolyte of 1.2 M LiPF6 in EC:EMC (3:7 wt%) and extracted in an inert atmosphere glove box for surface characterization after rinsing in DMC. Ex situ XPS and FT-IR analysis of pristine and cycled cells traced a substantial difference in surface species dependent on annealing environments and cycling conditions of thin films. This provided a model system to investigate the influence of thin film coatings such as Al2O3, LiPON, and ZrO2 on the active material alone. The approach developed here may be extended to other promising cathode systems for which the surface chemistry of the active material is not well understood.

Figure 1
Electrochemical Technologies for Developing Countries
Authors: Petrovic Slobodan
Published: February 2020

Batteries and photovoltaics are critical technologies for enabling electrical power for the rural areas in developing countries. The solar PV systems with battery storage are considered the only hope for almost 2 billion people without access to electricity. These forgotten people need electricity for improved basic life necessities such as reading at night, refrigerating food, or charging cell phones for communication.

Solar Hope (www.solar-hope.org) is a unique, non-profit organization that has accomplished over 120 solar PV installations in Africa and South America since 2010. The PV installations were installed for schools, hospitals, orphanages, and for water pumping for whole villages. The volunteers for the organization are the students from the Electrical Engineering and Renewable Energy Engineering program at the Oregon Institute of Technology. A unique concept involves PV system design in classroom and implementation in the field. Through Solar Hope, the students participate in the design, component build, and training, prior to joining the expeditions to remote areas of Africa. Solar Hope has made a huge impact so far by affecting with the installations in the excess of 300,000 people, mostly children. The efforts by Solar Hope also save lives by enabling better treatment of patients in the hospitals and by preventing fires from burning fossil fuels inside.

Solar Hope requires help from the electrochemical community in form of component donations (e.g., batteries, Solar PV panels, charge controllers, inverters, etc.) as well as monetary contributions to enable the use of electrochemical technologies in developing countries and help improve lives of millions.
A 1D Mathematical Model to Study the Effects of Adhesive Strength on the Electrochemical Performance of Silicon Electrodes for Advanced Lithium Ion Batteries
Authors: Appiah Williams Agyei , Park Joonam , Byun Seoungwoo , Cho Inseong , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

In recent times, commercially available lithium ion batteries (LIBs) employ graphite, with a theoretical capacity of 372 mAh g-1, as their anode material. To enhance the energy density of LIBs, alternative anode materials with higher capacities, such as Li metal, Si, and various alloys, have been extensively exploited. With its advantages of a higher theoretical capacity (4200 mAh g-1), environmental friendliness, and terrestrial abundance, Si is particularly well-suited as an anode material for this purpose. Nevertheless, Si suffers from large volume variations (up to 300%) during lithiation/delithiation processes, leading to pulverization, low cycling efficiency, unstable solid electrolyte interphases (SEI), and permanent capacity losses.

There have been several scientific investigations and strategies to solve the issues related to the large volume changes in Si. Relevant breakthroughs have been made with the help of advanced nanotechnologies in terms of enhancing the cycle life and improving the cycle rate performance. Notable among them is the use of binding materials with improved adhesive properties, such as copolyimide, alginate, poly(acrylic acid) (PAA), carboxymethyl cellulose, polyamide-imide, polyimide, and polymers that form cross-linked networks. Moreover, enhancing the adhesive strength between the Si composite electrode and Cu current collector by coating the latter’s surface with a very thin polymeric layer has significantly enhanced the electrochemical performance of Si anodes. However, the mechanism underlying this improvement in performance was not clearly addressed.

In this presentation, a coupled chemo-mechanical model which considers the contact resistance as well as the influence of the attractive forces inside the contact area between the electrode and current collector was developed to study the effects of the adhesive strength of a binding material on the electrochemical performance of silicon-based lithium-ion batteries. The model predictions were validated with experimental data from coin-type half-cells composed of Li metal, Si electrodes, and Cu current collectors coated with binding materials with different adhesive strengths. The proposed model was used to investigate the effects of the adhesive strength and various cell design parameters on the specific capacity of the Si-based Li-ion cells.
Facilitated Water Transport through Graphene Oxide Membranes Functionalized with Aquaporin-Mimicking Peptides
Authors: Lee Changseon
Published: February 2020

Water purification by membranes is widely investigated to address concerns related to clean water scarcity. Achieving high flux and rejection simultaneously is a difficult challenge using such membranes because these properties are mutually exclusive in common artificial membranes. Nature has developed a method for this task involving water-channel membrane proteins known as aquaporins. Here, the design and fabrication of graphene oxide (GO)-based membranes with a surface-tethered peptide motif designed to mimic the water-selective filter of natural aquaporins is reported. The short RF8 (RFRFRFRF, where R and F represent arginine and phenylalanine, respectively) octapeptide is a concentrated form of the core component of the Ar/R (aromatic/arginine) water-selective filter in aquaporin. The resulting GO-RF8 shows superior flux and high rejection similar to natural quaporins. Molecular dynamics simulation revealed the unique configuration of RF8 peptides and the transport of water in GO-RF8 membranes, supporting that RF8 effectively emulates the core function of aquaporins.
Controllable Synthesis of Circular Graphene Domains By Atmosphere Pressure Chemical Vapor Deposition
Authors: Dai Gui-Ping , Vinodgopal Kizhanipuram , Wu Marvin H. , Jiang Bang-Bang
Published: February 2020

Graphene, as a perfect two-dimensional crystalline structure, has attracted much attention in the research community, owing its unusual mechanical strength (>1Pa), optical transparency and high carrier mobility for various promising applications. Several methods have been used to develop to obtain graphene, such as mechanical exfoliation, thermal decomposition of SiC and chemical vapor deposition (CVD). Among these methods, CVD is considered to be the most promising way for graphene industrial development and scale-up production due to its convenience and economic efficiency. In a CVD process, growth on Cu substrates is particularly attractive since the growth occurs via a self-limiting mechanism, attributed to the negligible carbon solubility in copper.

Yet the CVD graphene shows a lower carrier mobility of a few hundred to a few thousand cm2/(Vs) compared with exfoliated graphene obtained from natural graphite, because of the presence of growth defects and boundaries. In order to attain the predicted theoretical values for graphene, it is critical to improve graphene film quality. Previous studies have shown that seamless merging of graphene domains during CVD is an ideal route to reducing defects and domain boundaries, and produce single crystal graphene to enable further applications. Furthermore, the morphology and edge structure of individual graphene domains strongly influence its properties. It is very important to understand the nucleation stage and the expansion mechanism of the graphene domains to control the morphology of graphene films.

Recent advances in the CVD method yields various interesting graphene domain shapes. Pentagonal, triangular, rectangular, snow-like graphene, twelve-pointed and four-lobed, graphene domains have been successfully obtained. The various shapes of these graphene domains can be achieved by optimizing growth parameters, such as precursor composition, flux, and choice of substrate. However, all of these methods either require liquid-state copper as the substrate or yield irregular circular or other shapes with one or very few separate circular graphene domain. Hence, it would be quite advantageous to grow graphene on a solid-state copper substrate via the simultaneous large scale growth and seamless merging of circular-shaped graphene domains. This provides a very good platform to observe and investigate the growth mechanism leading to large area single crystal graphene sheets.

In this presentation, I will report the first successful large-scale growth of single-crystal “circular” graphene domains on a solid-state copper substrate during the early stage of CVD operated under atmosphere pressure. The individual circular graphene domains have smooth edges as well as axisymmetric and centrosymmetric shapes which permit seamless merging of adjacent graphene without the effect of orientation.

Figure 1
(Invited) Double Network Hydrogel of Poly(2-hydroxyethyl methacrylate) and Alginate Embedded Hydroxyapatite
Authors: Chen Yen Jung , Kebede Mekuriaw Assefa , Imae Toyoko
Published: February 2020

A facile one-pot method was developed to the preparation of a bone regenerating material which was fabricated by photo-polymerizing 2-hydroxyethyl methacrylate under the addition of cross-linker and initiator in the aqueous mixed dispersion of hydroxyapatite (HAp) and alginic acid. The hydration ratios (hydrated water per dried composite) of the as-prepared HAp-embedded cross-linked double network hydrogels were varied depending on the ratios of alginic acid to water, poly(2-hydroxyethyl methacrylate) to cross-linker, and HAp to alginic acid. Thus, the hydration ratio reached to maximum of 275%.
(Invited) Gel Behavior of Sugar-Based Polymers and Their Composites
Authors: Imae Toyoko
Published: February 2020

Cellulose is a linear sugar-based polymer and a main component of wood pulp which are a material of paper. In this decade, the cellulose nano-fibers are gathering attentions in the material science because of their mechanical properties and environmental suitability. In particular, the 2,2,6,6-tetramethyl-1-piperdinyloxy free radical (TEMPO)-oxidized cellulose nano-fiber (TOCNF) is the ultrafine fiber and have many carboxyl groups on its surface, which are suitable for the chemical modifications. From this viewpoint, we have examined the modifications of TOCNF to develop absorbers. It was demonstrated that the nanocomposites of nanoparticle/dendrimer/TOCNF allowed the diffusion of small molecules in their matrix, although the simple TOCNF formed a film with powerful gas-barrier function. Thus, the availability of these nanocomposites for absorbers were verified; however, the detailed structures of these nanocomposites were not yet confirmed.

In this study, The TOCNF was hybridized with amine-polymers (poly(amido amine) dendrimer and poly(ethyleneimine) with different molecular weights). The hybrids formed transparent gels, and especially the dendrimer led to a homogeneous viscoelastic gelation in the wide range of mixing ratio. The number binding ratios of polymers per TOCNF suggested that the dendrimer partially covered the surface of TOCNF, facilitating the cross-linking, while the poly(ethyleneimine) could vary their conformations to cover the TOCNF at the different concentrations.
(Invited) Shear-Induced Fabrication of Multiple Parallel Gel Filaments Using Aqueous Two-Phase Separation
Authors: Kato Norihiro , Takayama Yuriko , Nagayoshi Keishu , Iimura Ken-ichi , Nasuno Eri
Published: February 2020

Macroscopic structures of gel fibers have been prepared by control of the polymer solution properties and by design of the nozzle and flow path of the microfluidic device. In this research, we investigated a method to simultaneously fabricate hundreds to thousands of gel filaments simply by flowing the polymer solution inside the capillary without spinneret.

An aqueous two-phase separation (ATPS) can be induced by adjusting their concentration in certain combinations of two polymers. The respective polymer concentration in each phase can be determined from the phase diagram, whereas an assembly of heterogeneous polymers generate in each phase. Hydrodynamic properties of pre-gel solution can be controlled by inducing such heterogeneous polymer assemblies.

A co-axial flow double capillary was used to fabricate gel filaments, where an inner capillary (inner diameter 0.7 mm) was fixed at the insert position of an outer capillary. To induce ATPS, an ionic strength for the aqueous solution of sodium alginate (Alg) / polyethylene glycol (PEG) mixture was controlled by NaCl addition. The pre-gel Alg/PEG solution was flown as an inner flow of glass double capillaries, where a crosslinker solution (Ca2+ soln.) was flown as a sheath flow. The obtained gel was composed of multiple parallel gel filaments with a diameter of several micrometers, while a single gel without filament structure was obtained from the homogeneous solution without NaCl addition.

In aqueous solution, the Alg chain has a structure with few entanglements because of its rigidity. The rigid assembly of alginate is mainly caused by guluronic acid block, that is stabilized by diaxial linkages via intramolecular hydrogen bonds. The shear stress generated by flowing the aqueous Alg solution inside the capillary cannot induce deformation of its rigid assembly, results in the single thick gel filament. By complexation with PEG, destruction of regular hydrogen bond was responsible for breaking the rigid structure of Alg. Thus, deformation of Alg/PEG assembly was enabled to elongate as the fibrous structure by the shear stress, followed by gelation in contact with Ca2+ ions at the outlet of the inner capillary. Such shear-induced deformation of the Alg/PEG assembly was studied by measuring viscoelastic properties with a spindle viscometer. Besides, Alg/PEG assembly generation in each phase was determined by size-exclusion chromatography with a multi angle light scattering detector. This presentation will discuss a simple technique for preparing multiple gel filaments simply by passing a polymer solution through a capillary.
(Invited) Relationship Between the Phase Diagram and Hysteresis in Demixing and Remixing for Thermo-Responsive Polymers in Water
Authors: Katsumoto Yukiteru
Published: February 2020

The effects of the stereoregularity on the hysteresis in demixing and remixing of the aqueous solution of poly(N-isopropylacrylamide) (PNiPAm), which is observed as the dissociation of transmittance curves in heating and cooling, has been studied in detail. For the liquid-liquid phase separation of the monomer model (N-isopropyl propionamide) / water binary liquid, there is no hysteresis in demixing and remixing when the scanning rate (v
T) is slow enough. On the other hand, the aqueous solution of an atactic PNiPAm with 46% of the meso content (m) shows the hysteresis even at a very dilute condition (0.01 wt%) with a slow v
T of 0.01 °C min−1. The difference between demixing and remixing temperatures (Dhys
T) at v
T ® 0 systematically increases as m increases. The effect of stereoregularity is more significant for the cooling (remixing) process of the aqueous PNiPAm solution compared with that for the heating (demixing) process. These results can be interpreted from the phase diagram of the aqueous PNiPAm solution, in which the liquid-liquid phase separation and sol-gel transition coexist [F. Tanaka et al. React. Funct. Polym. 2013, 73 (7)]. Above the cloud point temperature (T
cp), a dilute and a concentrated PNiPAm solutions coexist, and the concentrated phase get into the physical-gel phase. The concentrated PNiPAm solution undergoes the gel-to-sol transition in cooling at a temperature below T
cp, causing the hysteresis in demixing and remixing.
(Invited) Crystal Crosslinking of Metal-Organic Frameworks for Precise Control of Network Structure in Polymer Gels
Authors: Kokado Kenta , Sada Kazuki
Published: February 2020

In a conventional polymer gel synthesis, the control of network structure in the obtained polymer gel is still a challenging problem, since a polymer gel is usually prepared by crosslinking randomly oriented monomers or prepolymers, resulting in the formation of randomly oriented network structure. In this context, we conceived a new idea for preparation of polymer gels, therein, a well-known porous crystal, metal-organic framework (MOF), consisting of organic ligand and metal ion, is employed as the structure-directing agent. In other words, a reactive organic ligand is used to prepare a reactive MOF, followed by crosslinking reaction with guest monomer penetrating into the micropore of the reactive MOF. We named this method as “crystal crosslinking method”, and have achieved outer shape control, outer and inner shape control, and network structure control. In this presentation, we will focus the network structure control. By using anisotropically arranged MOF crystals as the structure template for the crystal crosslinking method, we could obtain polymer gels showing anisotropic shape transformation such as unidirectional shape transformation.
Modeling and Simulations of Aerosol Jet 3D Printed Electrodes for Lithium-Ion Batteries
Authors: Li Jie , Saleh Mohammad , Panat Rahul , Park Jonghyun
Published: February 2020

A complex and controlled 3D electrode architecture with a hierarchical porous lattice structure can significantly improve Li-ion battery performance. To maximize its potential, the correlation between structural features (thickness, shape, porosity) and electrochemical responses must be well understood. In this work, a three-dimensional electrochemical model with the porous theory is used to study the impact of electrode geometry on the battery performance in terms of porosity, dimensions, and morphology. The model is utilized to explore the various electrode structures including, cubic, spherical, X, gyroid, and diamond structure after its fundamental validation with experimental observations.
Anion-Dependent Perturbations in Ionic Liquid Structure Probed By High-Energy X-Ray Scattering
Authors: Coulthard Riley , Pham Tuan Anh , Zobel Mirijam , Buchsbaum Steven , Plata Desirée , Wood Brandon C. , Fornasiero Francesco , Meshot Eric
Published: February 2020

Room-temperature ionic liquids (ILs) are molten salts at room temperature, and their wide electrochemical windows and high ionic conductivities make them promising next-generation electrolytes for energy storage devices. The vast potential cation-anion pairings result in tunable structure and organization of the bulk ILs, which ultimately dictates their properties. However, the amorphous structure of bulk ILs remains poorly understood due to the typically large and flexible nature of the molecules and complex interactions between them.

We employed high-energy synchrotron X-ray scattering to study the structure of a set of archetypal imidazolium-based ILs. We sought to understand perturbations in the structure across 3 popular anions possessing distinctly different geometric features and dipole moments (i.e., PF6
-, OTf-, TFSI-), while also systematically varying the length of the alkyl chain on the cation. In particular, we collected scattering at both high and low angles to compare local and longer-range structural order, respectively, and we leveraged pair distribution function (PDF) analysis to transform our X-ray data to real-space density fluctuations for intuitive inspection and quantitative comparison with simulations. Both classical and ab-initio molecular dynamics (MD) cross-validated these detailed intra- and intermolecular density distributions rendered by our X-ray experiments. This enabled us to use MD to decouple and characterize cation-anion, cation-cation, and anion-anion interactions as well as H-bonding type interactions for each IL studied.

Developing such analytical frameworks for detailed analysis of bulk IL structure as a function of different ions is important toward developing guidelines for engineering cations and anions for targeted applications. Furthermore, understanding the influence of interchanging ions is a prerequisite for applications in which ILs interface with other species, such as other types of ions, nanoparticles, or electrode interfaces.