bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Ordered Mesoporous Metal Oxide Thin Films: From Room Temperature Ferroelectrics to Tunable Magnetic Materials
Authors: Brezesinski Torsten
Published: February 2020

Advances in sol-gel processing and polymer templating have enabled the preparation of several important mesostructured materials with different pore symmetries and unprecedented properties. However, especially the synthesis of structurally and compositionally well-defined metal oxides with a crystalline wall structure is challenging for various reasons.

In the first part of this talk, I will describe the preparation of a series of high quality, ordered mesoporous metal oxide films of thickness ≤500 nm by the dip-coating method using a soft-templating process (via coassembly of hydrolyzing salt precursors and an amphiphilic diblock copolymer) and their characterization by advanced imaging, diffraction, and spectroscopic methods. In the second part, I will show that the general idea of combining nanomagnetism and electrochemical energy storage concepts can be applied to mesoporous metal oxide films with spinel and perovskite structures, [1-4] and discuss the structure-property relationships of room temperature ferroelectrics, [5] among others.

[1] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn and T. Brezesinski, Chem. Mater. 26 (2014) 5745.

[2] C. Reitz, C. Suchomski, D. Wang, H. Hahn and T. Brezesinski, J. Mater. Chem. C 4 (2016) 8889.

[3] C. Reitz, D. Wang, D. Stoeckel, A. Beck, T. Leichtweiss, H. Hahn and T. Brezesinski, ACS Appl. Mater. Interfaces 9 (2017) 22799.

[4] L. A. Dubraja, C. Reitz, L. Velasco, R. Witte, R. Kruk, H. Hahn and T. Brezesinski, ACS Appl. Nano Mater. 1 (2018) 65.

[5] L. A. Dubraja, R. Kruk and T. Brezesinski, Adv. Electron. Mater. (2018) https://doi.org/10.1002/aelm.201800287.
(Invited) High-Voltage β-Ga2O3 vertical Power Diodes and Transistors with Fin Channels
Authors: Li Wenshen , Hu Zongyang , Nomoto Kazuki , Jinno Riena , Nakamura Tohru , Jena Debdeep , Xing Huili Grace
Published: February 2020

For high voltage and high current applications, vertical power devices are preferred over the lateral counterparts, due to the unaltered footprint with elongated drift region width and the generally higher current density. The development of vertical power devices relies on the ability to epitaxially grow thick drift layers with low defect density and precisely-controlled net doping concentration, often on the order of 1016 cm-3 or lower. One of the unique advantages of β-Ga2O3 over SiC and GaN is the availability of melt-growth methods for the production of high quality single-crystal substrates, which provide excellent platform for homoepitaxy. Recently, high quality thick epitaxial layers grown by halide vapor phase epitaxy (HVPE) have been developed, and β-Ga2O3 vertical power devices have seen rapid developments. In this work, we discuss our recent advancements on high-voltage β-Ga2O3 vertical power diodes and transistors with fin channels.

The ultra-high critical breakdown field of 6-8 MV/cm in β-Ga2O3 is another key advantage of this material. While the high critical field leads to a high projected Baliga’s figure-of-merit, it also brings tremendous challenge to the management of the electric field in power devices, especially with the absence of native p-type doping up till now. One example is the Schottky barrier diodes, in which the electric field at the top surface must be controlled to be much lower than the critical field in order to avoid excessive tunneling current. Another example is the device periphery, where proper edge termination designs are required to avoid premature breakdown due to field crowding. To suppress the electrical field at the surface, we adopted fin channels with metal-insulator-semiconductor (MIS)-based sidewall in Schottky barrier diodes. We show that the charge-coupling effect in these structures allows for effective reduction of the electric field at the top surface, therefore effectively reducing the leakage current due to tunneling. The gated fin channels with sub-micron channel width also allow for the realization of normally-off vertical transistors. A general trend of the electric field peak at the bottom corners of a fin channel is discovered, which provides important guidance for the design of vertical fin channel devices. With the help of field-plating at the device periphery, we show that the breakdown voltage of the fin channel transistors can be much improved. With these field management techniques, we achieved state-of-the-art figure-of-merits in both the fin channel diodes as well as transistors.
(Invited) Thermal Characterization of Ultra-Wide Bandgap Gallium Oxide Electronics
Authors: Choi Sukwon
Published: February 2020

To extend further the electrical performance envelope of wide bandgap (WBG) power and radio frequency (RF) electronics based on gallium nitride (GaN) and silicon carbide (SiC), device engineers are actively pursuing the development of generation-after-next ultra-wide bandgap (UWBG) devices. At the time being, aluminum gallium nitride (AlGaN), β-gallium oxide (Ga2O3), and diamond are technologically relevant UWBG materials that have bandgaps larger than that for GaN (3.4 eV). In particular, the availability of melt-grown substrates for the Ga2O3 materials system offers a clear economic advantage over SiC and GaN device technologies.

While UWBG Ga2O3 devices are built to operate under higher power densities compared to current state-of-the-art WBG counterparts, the thermal conductivity Ga2O3 is lower than those for GaN and SiC by an order of magnitude. Therefore, self-heating is a major challenge for devices based on this materials system. Electro-thermal interactions that lead to self-heating in Ga2O3 devices need to be accurately assessed and understood to accomplish the successful transition from WBG devices to the UWBG technology.

In this work, we will demonstrate the use of an integrated optical thermography scheme (Raman thermometry, thermoreflectance imaging, and infrared thermography) to study the steady-state and transient thermal characteristics of Ga2O3 Schottky Barrier Diodes (SBD) and lateral Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFET). In addition, we will report our recent progress on the development of a 2-D transducer-assisted Raman thermography technique suitable for Ga2O3 devices, which overcomes limitations associated with current state-of-the-art methods.
(Invited) Limits to Phonon Thermal Boundary Resistance across GaN Interfaces
Authors: Hopkins Patrick
Published: February 2020

As material length scales decrease below typical vibrational heat carrier (e.g., phonon) mean free paths, the thermal boundary resistances (TBR) at heterogeneous material interfaces become the dominant thermal resistances that dictate temperature rises, thermal runaway, and power density at failure in a wide array of devices. In this work, I will discuss the phonon scattering processes that dictate the thermal boundary conductance (TBC, the inverse of TBR, so TBC = 1/TBR) across GaN-based interfaces, including the maximum limits to TBC at GaN interfaces and the roles of point defect scattering and interfacial layers on GaN TBC. I will first present experimental measurements of the TBC from 78−500 K across isolated heteroepitaxially grown ZnO films on GaN substrates. This data provides an assessment of the underlying assumptions driving phonon gas-based models, such as the diffuse mismatch model (DMM), and atomistic Green’s function (AGF) formalisms used to predict TBC. Our measurements, when compared to previous experimental data, suggest that TBC can be influenced by long wavelength, zone center modes in a material on one side of the interface as opposed to the “vibrational mismatch” concept assumed in the DMM; this disagreement is pronounced at high temperatures. At room temperature, we measure the ZnO/GaN TBC as 490[+150,−110] MW m-2 K-1. The disagreement among the DMM and AGF, and the experimental data at elevated temperatures, suggests a non-negligible contribution from other types of modes that are not accounted for in the fundamental assumptions of these harmonic based formalisms, which may rely on anharmonicity. Given the high quality of these ZnO/GaN interfaces, these results provide an invaluable, critical, and quantitative assessment of the accuracy of assumptions in the current state of the art computational approaches used to predict phonon TBC across interfaces. I will then turn my discussion to focus on the role that interfacial imperfections, such as point defects and continuous films at the interface, have on GaN TBC. These results demonstrate the large variability that can occur in TBC at GaN-based interfaces based on interfacial non-idealities.

1. J. T. Gaskins, et al. "Thermal boundary conductance across heteroepitaxial zno/gan interfaces: Assessment of the phonon gas model," Nano Letters, 18, 7469–7477 (2018).

2. B. F. Donovan, et al. "Thermal boundary conductance across metal-gallium nitride interfaces from 80 - 450 K," Applied Physics Letters, 105, 203502 (2014).
(Invited) Design and Energy Application of Piezoelectric Biomaterials
Authors: Yang Rusen
Published: February 2020

Multifunctional materials have received increasing attention in recent years. Owing to their inherent biological nature as well as piezoelectric properties, piezoelectric biomaterials are considered as promising candidates for application in fields ranging from electrochemical energy storage to biological systems. Rational material design is important to enhance their piezoelectric and biological activity. Herein, recent advancements to piezoelectric biomaterials like peptide-based micro/nanostructures are provided. Synthetic methods, morphological features, and piezoelectric performance of piezoelectric biomaterials are presented. The effect of growth direction, phase and structure of piezoelectric biomaterials on their piezoelectric activity are discussed. The applications of piezoelectric biomaterials in the field of nanogenerators are provided at the end.

Reference:

Yuan, T. Lei, Y. Qin, R. Yang, Flexible electronic skins based on nanogenerators and piezotronics, Nano Energy, submitted

Nguyen, S. Kelly, R. Yang, Piezoelectric peptide-based nanogenerator enhanced by single-electrode triboelectric nanogenerator, APL Materials
5, 074108 (2017)

Nguyen, R. Zhu, K. Jenkins, R. Yang, Self-assembly of diphenylalanine peptide with controlled polarization for power generation, Nature Communications
7, 13566 (2016)

Nguyen, K. Jenkins, R. Yang, Epitaxial growth of vertically aligned piezoelectric diphenylalanine peptide microrods with uniform polarization, Nano Energy
17, 323 (2015)
(Invited) Design Integrated Microfluidic Chips for in Vitro Diagnosis
Authors: Li Bor-Ran
Published: February 2020

A biosensor is generally defined as an analytical device, which converts the biochemical responses into the quantifiable electronic signals. Its extensive utilities in medical diagnosis, toxicity testing, chemical analysis, food industry, and many other areas for quantitative assessments has appeared. Quartz crystal microbalance and field-effect transistor based devices have been demonstrated to possess exceptional characteristics and outstanding performance while conjugated with the advanced nanotechnology. However, both devices still have to face the nonspecific binding issue, which is a headache for researchers on all biosensor platforms. In our research, we have efficaciously reduce 95% nonspecific binding via immobilize the zwitterionic layer on the surface of the chip. Moreover, we integrate microfluidics, nanoparticles, rapid surface modification on several bio-sensing platforms to efficiently pretreat specimens and detect target bio-molecules. In addition, a series advanced microfluidic ships are designed for lymphocyte isolation, active sperm sorting, and nanoparticle synthesis.

Figure 1
Graphene-Dot-Armored Metallic Nanosponge Catalysts for High-Performance Hydrogen Evolution Reaction
Authors: Nguyen Van-Toan , Nguyen Ngoc Anh , Ha Hyunwoo , Kim Hyun You , Choi Ho-Suk
Published: February 2020

Cotton candy-like metallic nanosponge is suitable as an electrochemical catalyst for effective hydrogen generation because it facilitates the mass transfer of hydrogen gas from the internal structure to the external surface and provides a continuous path for rapid electron transfer, but its large specific surface area is paradoxically capable of accelerating the dissociation of the metallic nanosponge. To protect the metallic nanosponge, we suggest the same concept as the armor made by tiling tiny graphene dots on the surface of the porous structure. It is implemented by one-pot synthesis of graphene dot armored metallic nanosponge, consisting of innovative steps such as intercalating metal ions into carbon dots, exfoliating carbon dots into graphene dots, and growing porous structure guided by attached graphene dots. It not only exhibits excellent long-term stability as expected, but also unexpectedly improves catalytic activity by effectively providing electrons to the strong bonding interface between metal surface and tiny graphene dots. A combined study involving an experimental analysis and density functional theory calculations confirms that the interplay between metal-nanoparticles and graphene-dots not only drives the formation of the unique structure of the graphene-dot-armored metallic nanosponges but also improves both catalytic activity and stability.
(Invited) Electrolyte Oxidation Limits the Life of Alkaline Membrane Water Electrolyzer
Authors: Kim Yu Seung , Li Dongguo , Matanovic Ivana , Lee Albert S , Chung Hoon T
Published: February 2020

Alkaline anion exchange membrane (AEM) water electrolyzers paid significant attention due to the cost benefits over proton exchange membrane electrolyzers. The durability of AEM electrolyzers is one of the critical requirements for the commercially viable systems. We have investigated that the possible performance loss over time is related to the oxidation of polymeric binders used for AEM electrolyzers. In this presentation, the oxidative degradation of the phenyl group is reported using the commercial Pt/C, IrO2 and house-made perovskite oxide catalyst.

Rotating disk electrode experiments exhibited that the oxidation of phenyl group on the oxygen evolution reaction (OER) catalysts is pronounced: The oxidation rate of commercial Pt/C and IrO2 catalysts was > 11% at 1.6 V vs. RHE over the 5-hour chronoamperometric test, while the house-made LA0.85Sr0.15CoO3 catalyst perovskite oxide catalyst exhibited 4.1%. Density functional theory calculations show that the adsorption of the phenyl on the perovskite oxide catalyst is significantly smaller, suggesting that the electrolyte oxidation is related to the adsorption properties of the phenyl group.
MOF Based Electrocatalysts for Electrolytic Water Splitting
Authors: Raja Duraisamy Senthil , Lin Hao-Wei , Chuah Xui-Fang , Lu Shih-Yuan
Published: February 2020

Renewable energy driven electrolytic water splitting is regarded as the most promising way to supply clean hydrogen fuel to answer the present and future energy and environmental issues. However, efficient and mass hydrogen production in industry using the electrolytic water splitting technology has not yet been widely deployed because of the high cost of the noble metal catalysts in acid and the low energy conversion efficiency of the non-noble metal catalysts in base. Although a variety of alkaline water electrolyzers has been constructed, most of them requiring high cell voltages, which is not sufficiently competitive for commercial applications. Hence, it is highly desirable to develop cost-effective, highly efficient, robust electrodes to achieve low overpotentials and high stability at high current densities (such as 500 mA cm-2) for large-scale water splitting. Metal-organic framework (MOF), possessing versatile catalytic activities, remarkable structural diversity, high surface areas, and tunable pore sizes, has been recently demonstrated an outstanding electrocatalyst for electrolytic water splitting. In this presentation, two recent examples are offered to illustrate the development of MOF based electrocatalysts for electrolytic water splitting, one involving a bi-metallic Fe2Ni-MOF and the other synergistically well-mixed Fe- and Ni-MOFs, both grown in-situ on nickel foam as highly efficient durable bifunctional electrocatalysts for overall water splitting at high current densities.
Hierarchical Carbon Nanofiber/Birnessite-MnO2 Nanosheets Cathode for High Performance and Low-Cost Aqueous Rechargeable Zinc Ion Battery
Authors: Chen Xiujuan , Li Wei , Liu Xingbo
Published: February 2020

Abundant and safe charge carrying feedstock with high energy density have made aqueous zinc-ion batteries (ZIBs), specifically the Zn/MnO2 system, a highly promising candidate for large-scale energy storage device. The traditional alkaline Zn/MnO2 batteries have become dominant in primary battery chemistry. Great efforts have been devoted to developing rechargeable alkaline Zn/MnO2 batteries, however, they are plagued by poor cycling stability. Very recently, the Zn/MnO2 systems in near neutral electrolyte have emerged to demonstrate improved capacities, cyclability and rechargeability. However, the commonly used tunnel-type MnO2 cathode with low conductivity usually undergoes phase transition to layered structure upon discharge-charge cycles, leading to collapse of framework and thus poor cycling and rate performance. To address these issues, it is proposed that directly using birnessite-MnO2 with layered structure as a cathode may minimize the “sacrificial capacity” induced by phase transition and integrating birnessite-MnO2 with a conductive substrate may enhance the conductivity.

In this work, the hierarchical core-shell carbon nanofiber@MnO2 (CNF@MnO2) cathode was prepared by a facile wet-chemistry method, where vertically aligned birnessite-MnO2 nanosheets were in situ grown on the surface of carbon nanofibers. The self-supported CNF@MnO2 cathode showed excellent electrochemical performance for Zn-ion batteries in a near neutral electrolyte due to its structural stability and enhanced conductivity. A high discharge capacity of 306 mA h g−1 has been reached after 100 cycles at current density of 300 mA g−1. Even at a high rate of 1.5 A g−1, CNF@MnO2 still maintained a high capacity of 258 mA h g-1 upon 100 cycles. Such remarkable performance is attributed to the unique core-shell structure and intimate contact between CNF and layered MnO2, in which the conductive CNF core facilitates the electron transfer and layered MnO2 minimizes the structural collapse and promotes the kinetics for co-insertion and extraction of Zn2+/H+ ions. Given the simplicity of preparation, exceptional electrochemical performance and low cost, CNF@MnO2 cathode holds substantial promise for aqueous rechargeable Zn-ion batteries.

Figure 1. Scanning electron microscopy image of carbon nanofiber@MnO2 (CNF@MnO2) cathode for aqueous rechargeable Zn-ion batteries in near neutral electrolyte.

Figure 1
Electrochemical Energy Storage with Mediator-Ion Solid Electrolytes
Authors: Yu Xingwen , Manthiram Arumugam
Published: February 2020

From an electrochemical point of view, many liquid-phase or gas-phase materials exhibiting a high operating voltage and a high intrinsic capacity can potentially be used as electrodes for the development of high energy, low-cost aqueous batteries. However, under the traditional battery operating principle with a porous separator, there is a tendency of shuttling of liquid or gaseous electrodes through the porous separator, which strictly limits the application of liquid-phase or gaseous-phase materials for the development of energy storage systems.1

We have recently developed a new mediator-ion battery concept with alkali-metal-ion (Li+-ion or Na+-ion) solid-electrolyte separators.2 The anode and cathode reactions of the redox couples can be maintained by a shuttling of the alkali-metal ion through the solid-state electrolyte between the catholyte and the anolyte. This unique battery-development strategy can not only eliminate the chemical-crossover problem of the liquid or gaseous reactants, but also circumvent the metal-dendrite problem.3 Based on the unique features, the “mediator-ion” battery concept offers a versatile approach for the development of a broad range of new battery systems.

This presentation will first introduce the basic concept and operating principle of the mediator-ion battery. Then a sequence of mediator-ion batteries with a variety of redox couples we recently developed will be demonstrated.4-8 These novel mediator-ion batteries can be classified into four categories including, (1) meatal anode – inorganic liquid cathode batteries (zinc – bromine, zinc – Ferricynide, and zinc – polysulfide batteries), (2) meatal anode – organic liquid cathode batteries (zinc – quinone batteries), (3) meatal anode – gaseous cathode batteries (zinc – air and iron – air batteries), and (4) organic liquid anode – gaseous cathode batteries (quinone – air and methyl viologen – air batteries). At the end of this presentation, future prospects of this novel battery development strategy will be discussed.

References

Manthiram, X. Yu and S. Wang, Nat Rev Mater, 2017, 2, 16103.

W. Yu and A. Manthiram, Joule, 2017, 1, 453-462.

W. Yu, M. M. Gross, S. F. Wang and A. Manthiram, Adv Energy Mater, 2017, 7, 1602454.

W. Yu and A. Manthiram, ACS Appl. Energy Mater, 2018, 1, 273−277.

W. Yu and A. Manthiram, ACS Energy Letters, 2017, 2, 1050-1055.

W. Yu and A. Manthiram, Advanced Sustainable Systems, 2017, 1, 1700082.

W. Yu and A. Manthiram, Sustain Energ Fuels, 2018, 2, 1452-1457.

W. Yu and A. Manthiram, ACS Appl. Energy Mater, 2018, 1, 2424–2428.
Generation, Isolation, and Analysis of the Charged States of Organic Redox Flow Battery Materials
Authors: Odom Susan A.
Published: February 2020

When considering organic redox couples as active charge storage materials in redox flow batteries, several characteristics are important, including redox potential, solubility, and stability. Although redox potentials can be reliably estimated using density functional theory calculations, predicting solubility and stability remains a significant challenge, especially when considering the charged states of a material. The majority of reports on the solubility of organic materials have been limited to the uncharged (often neutral) forms of redox couples. Stability is usually probed using electrochemical techniques (e.g. cyclic voltammetry and bulk electrolysis) and with flow cell cycling. Although some instances of in situ spectroscopic analysis of flow cell electrolytes has been reported, for the most part, experimental determination of the failure mechanisms of an organic redox couple has been attempted via post-mortem analysis of an electrolyte after cycling. In none of these experiments is the charged form analyzed separately from components beyond the electrolyte salt and solvent – such as electrode surfaces, membranes, and potential fields – that may lead to decomposition. My group is interested in characterizing the charged forms of organic molecules using methods that allow us to determine the sources and mechanisms of decomposition. Thus, in addition to the standard electrochemical methods and cycling studies, we have focused on the generation and isolation of charged species using chemical means. By isolating the charged species, we are able to measure solubility and analyze stability in controlled environments, choosing when to introduce any component that is not the active species itself. Here I will give an overview of the methods we have used to generate, isolate, and characterize charged organic molecules, as well as and what we have learned, both independent of and complementary to electrochemical methods for analysis.
(Invited) Layered Double Hydroxide Based Nanostructured Photocatalysts for Efficient Solar Fuels
Authors: Zhang Tierui
Published: February 2020

In this presentation, some very recent research progress in my group will be reported on the rational design of nanostructured layered double hydroxides (LDHs) based photocatalysts with heterointerface active sites for photoreduction of CO2 or CO into high value-added hydrocarbons with high selectivity, originating from the adjusted reaction pathway of intermediates. For instance, by constructing heterogeneous interface structure, NiO/Ni nanocatalysts exhibited an unexpectedly high selectivity of 60% for C2-C7 hydrocarbons in the CO hydrogenation reaction under visible-light irradiation.[1-8]

References

T. Zhang, et al., Adv. Mater. 2018, 30 (3), 1704663.

T. Zhang, et al., Adv. Mater. 2017, 29 (42), 1703828.

T. Zhang, et al., Adv. Mater. 2017, 29 (27), 1700803.

T. Zhang, et al., Adv. Mater. 2017, 29 (16), 1605148.

T. Zhang, et al., Adv. Mater. 2016, 28 (43), 9454-9477.

T. Zhang, et al., Angew. Chem. Int. Ed. 2016, 55 (13), 4215-4219.

T. Zhang, et al., Adv. Energy Mater. 2016, 6 (3), 1501241.

T. Zhang, et al., Adv. Mater. 2015, 27 (47), 7824-7831.
Advanced Electrochemical Sensors for Monitoring Relative Humidity and Internal Corrosion Rates of Natural Gas Transmission Pipelines Containing H2s
Authors: Ziomek-Moroz Margaret , Duffy Timothy , Hall Derek M. , Lvov Serguei N.
Published: February 2020

Monitoring the internal corrosion of natural gas transmission lines is required for safe management of natural gas infrastructures. Internal corrosion programs can be strengthened by real-time monitoring of key risk factors such as relative humidity and corrosion rates of the pipeline material. We have developed a membrane-based electrochemical sensor, which functions in gaseous environments, to provide this real-time monitoring capability. The design is based on the sensitivity of the membrane’s conductivity to gaseous water content. We match relative humidity curves to 4-electrode, electrochemical impedance spectroscopy results, and use 3-electrode, linear polarization resistance tests to calculate corrosion rates. Due to the membrane’s atypical current pathways, precise estimation of the sensor’s cell constant was required to interpret the impedance results into relative humidity. We utilize finite-element analysis to obtain our cell constant (14.84 cm-1), and the resulting membrane conductivity values were in good agreement with published data. The sensor was tested in H2S environments to gauge how these results may change with acidic gases that may be present in the natural gas stream.
(Invited) TiO2 Nanotube Arrays: Photoelectrochemical and Photocatalytic Applications
Authors: Schmuki Patrik , Liu Ning , Altomare Marco
Published: February 2020

TiO2nanomaterials have over the last 30 years attracted tremendous scientific and technological interest. Main research direction using TiO2in functional applications are still the use in photocatalysis e.g. for the direct splitting of water into H2and O2to generate the potential fuel of the future, hydrogen, or the use in Grätzel type solar cells. In order to achieve a maximum turn-over rate (by creating a high surface area), usually nanoparticles are used either suspended or compacted to a photoelectrode. Over the past decades various 1D and highly defined TiO2 morphologies were explored for the replacement of nanoparticle networks and were found in many cases superior to nanoparticles. Nanotubes or wires can be grown by hydrothermal or template methods, or even more elegantly, by self-organizing anodic oxidation. The latter is not limited to TiO2but to a full range of other functional oxide structures on various metals and alloys can be formed. These advanced and doped morphologies can be grown on conductive substrates as ordered layers and therefore can be directly used as functional electrodes (e.g. photo-anodes). The presentation will focus on these highly ordered nanotube arrays of TiO2and discuss most recent progress in synthesis and modification for photocatalytic and photoelectrochemical for H2generation.

Literature: (reviews):

- P. Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed. (2011), 2904

- K. Lee, A. Mazare, P. Schmuki, CHEMICAL REVIEWS, 114 (2014) 9385
Leveraging Electrochemical Technique to Screen for Sepsis As a Point-of-Care-Device
Authors: Tanak Ambalika , Muthukumar Sriram , Hashim Ibrahim A , Prasad Shalini
Published: February 2020

Sepsis is a potentially life-threatening complication of infection which affects more than 30 million people globally [1,2]. There is a growing concern for the debilitating effects of sepsis as it is more common than heart attack and claims more life’s than cancer (world sepsis day 2015). Despite medical improvements, global disparities persist for sepsis detection and treatment. Timely diagnosis with rapid treatment methodology has been reported to improve the chances of preventing adverse complications, and thus, reduce mortality rate. Existing methodology relies on an array of blood tests performed in laboratories which is cumbersome, time-consuming, and provides delayed results. In an effort to minimize the detection time and provide clinically efficient decision making capabilities, we have developed an effective point-of-care screening device as an early stage guide for sepsis. Recent clinical studies have provided insight on the importance of detecting specific biomarkers for diagnosing sepsis. Procalcitonin (PCT) is approved by Food and Drug Administration (FDA) as a biomarker for sepsis[3]. The label-free point-of-care biosensor is designed and fabricated on a flexible hybrid electrode surface. Non-faradaic electrochemical impedance spectroscopy (EIS) technique was implemented to measure the capacitive impedance change unveiling the binding effects of target PCT to the specific capture probe. Specificity and sensitivity of the device is leveraged owing to its unique and targeted assay development strategies allowing to achieve a wide dynamic range of 0.01-100 ng/mL with a detection limit of 0.1 ng/mL. The major advantage provided by this novel technique is the use of undiluted samples without pre-treatment of human serum, plasma and whole blood with low sample volume (<40 uL). Efficient use of the developed biosensor towards practical application was correlated with clinically validated samples. The vision motivating this research was to design an effective sepsis screening device, useful at the hospital using very low patient biofluid sample and provide rapid results with high accuracy. This would allow for medical practitioners to facilitate targeted interventions, there by, offering rapid prognostic approach that can prove to be the cornerstone to provide successful treatment for sepsis and avert severe mortality and morbidity.
(Invited) Glucose Sensor Prepared By the Immobilization of Glucose Oxidase Together with Nanocarbons and Prussian Blue Using Electrodeposition Method
Authors: Yasuzawa Mikito , Jhong Huan-Ping , Kurashina Masashi , Wang Chen-Hao , Chiang Wei-Hung
Published: February 2020

A variety of approaches have been explored in the immobilization of enzyme onto the electrodes. Electrochemical deposition and electropolymerization procedure are interesting, since it allows localization of enzymes onto extremely small electrode surfaces, and permits the formation of multilayer structures. The purpose of these strategies are to immobilize enzyme in a highly active state and, at the same time, provide a membrane preferentially permeable to hydrogen peroxide over endogenous electroactive species, such as uric and ascorbic acids. Improvement of sensor sensitivities are of great attention, since it allow minimizing the size of the sensor and are desirable for the fabrication of implantable biosensor for continuous glucose monitoring. Nanocarbon, such as carbon nanotube and graphene are known to have high electroconductivity. Moreover, Prussian blue (PB) is an efficient redox mediator with the highest catalytic activity toward hydrogen peroxide reduction. In this study, we attempt to prepare an electrode, which both nanocarbon and Prussian blue are immobilized together with enzyme, glucose oxidase, to obtain a glucose sensor with high sensitivity.

In order to immobilize the enzyme together with nanocarbon and Prussian blue, firstly, dispersed aqueous solution of nanocarbon and Prussian blue were prepared using gelling agent Gallen gum. Secondly, electrodeposition was performed using this solution on the platinum electrode, by applying a constant potential of 1.3 V (vs. Ag/AgCl). Finally, the electropolymerization of 0-phenylenediamine was carried out by applying a constant potential of 0.7 V (vs. Ag/AgCl), which will increase the stability of the electrodeposited film by comprehensive polymer film formation. After the enzyme immobilization, the electrode was soaked in phosphate buffer solution (PBS) with stirring for three days in order to remove weakly absorbed enzyme on the electrode. In contrast, electrodes without PB and/or nanocarbon were also prepared in the same procedure for comparison.

　A Quartz Crystal Microbalance (QCM) was employed to investigate the behavior of film formation on the electrode during the electrodeposition. It was evident to see that the electrodeposition of the solution with PB showed ten times higher deposit amount than that without it. The glucose response measurement was performed at an applied potential of 0.6V (vs. Ag/AgCl) in 0.1 M PBS containing 0.1 M sodium chloride at 40 ˚C. All prepared GOx-immobilized electrodes showed good response toward the addition of glucose, while the electrode containing both PB and carbon nanotube provided the highest response current with good long-term stability.
Oxidation Kinetics of Electrospun Compatibilized Immiscible PBI:6FDD Polymer Blends
Authors: Ferraris John P. , Balkus Kenneth J. , Panangala Samitha Dilhani
Published: February 2020

Carbon nanofibers (CNFs) were fabricated by blending PBI (Polybenzimidazole) and 6FDD (6FDA-DAM-DABA, a copolymer of 4,4-hexafluoroisopropylidene diphthalic anhydride (6FDA), 2,4,6-trimethyl-1,3-phenylenediamine (DAM) and 3,5-diaminobenzoic acid (DABA)). PBI and 6FDD are immiscible polymers comprising PBI as continuous phase and 6FDD as dispersed phase. PBI:6FDD polymer blend was compatibilized with 2-methylimidazole (2-MI). Pure polymers, immiscible blend (PBI:6FDD 50:50), and compatibilized polymer blends (PBI:6FDD 50:50 blend with 9% 2-MI and 20% 2-MI) were electrospun. As spun fiber mats were subjected to thermal stabilization at 450 °C and carbonize and 1000 °C under nitrogen gas flow. Carbonized CNFs were exposed to react with CO2 at 1000 °C. The kinetic equation f = 1-exp(-atb) was applied to evaluate constants a and b, in order to get a better understanding of the oxidation reaction of different carbon materials. The specific surface area (SSA) was calculated using QSDFT (quenched solid density functional theory) method.
Hierarchical Porous Carbons Synthesized By CO2 Conversion with CaCO3 Nano-Template
Authors: Park Jae Hyun , Kim Yun Kon , Lee Jae W.
Published: February 2020

The technology to convert CO2 into valuable compounds has attracted attention as a key technology to mitigate global warming. Among them, carbon derived from CO2 has been widely used as an electrode material due to its highly porous property. However, it is difficult to control the porosity of the carbon material, and the synthesis conditions for the CO2 conversion into the porous carbon require a high energy cost. In this study, CO2 was converted into porous carbons with hierarchical micro-, meso-, macro-pores using NaBH4 as a reducing agent and CaCO3 as a nano-template at mild atmospheric pressure and temperature. The prepared CaCO3-templated hierarchical porous carbons had high specific surface area (1262 m2/g) with large pore volume (3.21 cm3/g). In addition, it had unique interconnecting pore structure which leads to the improvement of supercapacitive performance. CPC1_700, which was synthesized through an equivalent mass of CaCO3 and NaBH4 at 700 °C, exhibited a high capacitance of 270 F/g at 1 A/g, and retained its capacitance up to 170 F/g at high current density of 20 A/g. Furthermore, even without a pseudocapacitive behavior, it showed superior normalized capacitance of 21.4 µF/cm2 and relaxation time constant of 0.27 s compared to previous reported carbon materials. During long-term cycling, the capacitance was stable and remained above 90% up to 10,000 cycles. Thus, the facile CO2 conversion method and resultant CPCs are promising to be practical applications for supercapacitor electrode materials.
Crystallization of Atomic Layer Deposited MgO Thin Filmsas a Buffer Layer for Rocksalt Beo Film Growth
Authors: Lee Hoin , Wang Bowen , Hwang Cheol Seong
Published: February 2020

Rocksalt structure beryllium oxide (BeO) thin film has been highlighted as an exceptional high-k dielectric material for various semiconductor device application because it can have a very high-k value of > 200 and high band gap of ~ 10 eV simultaneously. However, this was an only theoretical expectation based on the first-principles calculation. Also, the stable crystal structure of BeO is wurtzite at normal thermal Atomic Layer Deposition (ALD) processing conditions of which k-value is only ~8, whereas the rocksalt structure BeO could be stabilized only under an extremely high-pressure condition (> 100 GPa). Therefore, it is expected that the usual ALD process of BeO film may result in the wurtzite structure film.

Considering the interfacial tensile strain offered by the larger MgO lattice parameter with a cubic-based rocksalt crystal structure, which is 4.21 Å while BeO lattice parameter is 2.70 Å for hexagonal-based wurtzite crystal structure and 3.62 Å for cubic-based rocksalt crystal structure, the adoption of cubic-based MgO as a buffer layer may enable the transition of BeO crystal structure from wurtzite to quasi-rocksalt. This work reported the optimization of both Thermal and Plasma-Enhanced ALD (TALD, and PEALD) process and post-annealing conditions of MgO and their influences on the crystallization properties of BeO on top of the MgO buffer layer, observed by X-Ray Diffraction (Figure 1 (a), (b)), Transmission Electron Microscope Selected Area Diffraction. Moreover, the electronic properties of MgO and BeO thin films, especially leakage current and dielectric constant, were verified through the measurement of Metal-Insulator-Metal (MIM) device (Figure 1 (c)).

This work, thus, attempted to grow MgO film by TALD, and PEALD as a buffer layer for the rocksalt BeO film growth. Although the growth of the BeO film on top of the rocksalt MgO film is ongoing project, this work can provide a fundamental step toward the final goal of rocksalt BeO film growth by an ALD method.

Figure 1
Investigation on Electrical Properties of Hydrogen Doped Sputtered Boron Carbon Nitride Thin Films
Authors: Nehate Shraddha Dhanraj , Sundaram Kalpathy B.
Published: February 2020

Interlayer dielectric materials (ILD) play a crucial role of isolating electrically conductive and semiconducting features on the devices [1]. Due to constant scaling down of device dimensions, the interconnect delay (τ = R x C) can be reduced by decreasing resistance of conductor and capacitance of ILD. Reduced capacitance can be achieved by high quality insulating film with low dielectric constant. Boron carbon nitride (BCN) films have achieved attention due to their complicated crystalline structure and unique properties. Atomic bonding similarities amongst boron, carbon and nitrogen allow formation of compounds with wide compositional range. BCN compounds are expected to combine the excellent properties of diamond, B4C and BN with their properties adaptable depending on their composition and structure [2, 3].

In this study, electrical properties of hydrogen doped BCN thin films will be investigated. BCN films are sputtered by B4C and BN targets. Films are deposited at different temperatures in presence of hydrogen/argon to investigate the influence of temperature and hydrogen gas on the electrical properties of BCN thin films.

References

[1] S. P. Muraka, M. Eizenberg, and A. K. Sinha, Interlayer dielectrics for semiconductor technologies vol. 1: Elsevier, 2003.

[2] A. Prakash and K. B. Sundaram, "Studies on electrical properties of RF sputtered deposited boron carbon nitride thin films," ECS Journal of Solid State Science and Technology, vol. 4, pp. N25-N29, 2015.

[3] M. K. Mazumder, R. Moriyama, D. Watanabe, C. Kimura, H. Aoki, and T. Sugino, "Ag diffusion in low-k materials (BCN and SiOC) and its challenges for future interconnection," Japanese journal of applied physics, vol. 46, p. 2006, 2007.
Thermodynamically Controlled Microstructure of Binary Alloy for Efficient Electrochemical Conversion of CO2 to C2H4
Authors: Kim Jeong Eun , Yang Ki Dong , Jang Jun Ho , Im Sang Won , Yeo Jia Bin , Nam Ki Tae
Published: February 2020

Since the first development of synthetic plastics, people have been getting a variety of plastics mainly from petroleum, which drove modern civilization. Typically, polyethylene is the most frequently and widely used plastic. But the depletion of fossil fuels and the simultaneous increase in the concentration of carbon dioxide(CO2), which is at a dangerous level, have led to the need to reduce petroleum use and to reduce CO2. The conversion of CO2 to ethylene, the raw material for polyethylene, is a very promising strategy for achieving that. Electrochemically, ethylene can be obtained by reducing CO2 using sustainable electricity.

Cu is reported to be the only single element catalyst that is capable of producing hydrocarbons with more than one carbon such as ethylene(C2H4) from CO2. It is because Cu has moderate intermediate binding energy. However, pure Cu catalyst represents poor C2H4 production efficiency because of the activity and selectivity problem. Therefore, alloying Cu with other elements can be one of the best strategy to enhance the activity and selectivity of the catalysis. However, conventional strategy to alloy Cu with other elements and modify the d-orbital energy failed to enhance selectivity for C2H4 because of the scaling relationship between binding energy of intermediates.

In this work, controlled microstructure of binary alloy was investigated as a new strategy for selective C2H4 production. Based on the thermodynamic database, the microstructure of Cu-X alloy was carefully designed. By adopting the terminal solid solution system, in which phase segregation take place, unlike conventional homogeneous solid solution system, the microstructure of the alloy consisting of lamellar structure could be controlled. In that system, different binding affinities with intermediates of segregated phases were taken advantage of. The synergetic effect between different phases was investigated by controlling the density of phase boundaries based on the understanding on metallurgy of alloy system. As the result, the selectivity for C2H4 increased with the increase of the density of phase boundary, which suggests the CO spillover between CO-selective phase and Cu and the following CO-CO dimerization. This work provided new catalyst design strategy for efficient electrochemical CO2 conversion to targeted chemicals.
Perspectives on the Development and Evaluation of Electrode Materials for Electrochemical Deionization Processes
Authors: Shanbhag Sneha , Liu Xitong , Whitacre Jay , Mauter Meagan
Published: February 2020

Electrochemical de-ionization processes offer great promise in complementing existing water desalination technologies in purifying water over a range of salinity values.1, 2 Theoretical evaluations have demonstrated that these methods demonstrate higher energy efficiency and lower energy requirements in de-ionizing low salinity waters.3, 4 In practical use, the efficiency of these systems can depend on various factors such as operating conditions, salinity of waters, occurrence of parasitic reactions, to name a few. Furthermore, the utility of deionization methods depends on their relative cost at materials, energy and lifecycle levels.

In this work, we first use an assessment of electrochemical deionization methods to emphasize the need for materials research to improve the viability of these processes. We then develop a framework to evaluate efficacy of electrode materials, in these systems. We discuss the advantages and disadvantages of both capacitive and faradaic electrode materials classes used in electrochemical deionization processes.

We demonstrate that solution composition largely influences the performance of each of these electrode materials classes. Specifically, the ion removal capacity and charge efficiency of these electrodes is influenced by solution composition. This reduction in performance results from a combination of several factors such as slow transport in the electrode, competing parasitic reactions or formation of surface films that reduce ion diffusion rates. Despite these challenges, the ion removal capacities achieved with faradaic electrodes often exceeds those offered by capacitive or pseudocapacitive materials. Finally, we propose alternatives such as proper selection of operating conditions, electrode structure and coatings to overcome some of the above-mentioned challenges and achieve improved removal of ions from complex water streams.

References

M. A. Anderson, A. L. Cudero and J. Palma, Electrochim. Acta, 55, 3845 (2010).

S. Porada, R. Zhao, A. van der Wal, V. Presser and P. M. Biesheuvel, Prog. Mater. Sci., 58, 1388 (2013).

J. Landon, X. Gao, J. K. Neathery and K. Liu, ECS Transactions, 53, 235 (2013).

Y. Oren, Desalination, 228, 10 (2008).