bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacing Photosystem I into Conducting Polymers
Authors: Cliffel David E. , Dervishogullari Dilek
Published: February 2020

Photosystem I (PSI) is one of the primary macromolecular machines that drive photosynthesis in green plants and cyanobacteria. Extracted PSI has been employed successfully as a macromolecular photosensitizer within a host of low-cost electrochemical and solid-state photovoltaic architectures. Over the course of the last ten years, our group has worked on the electrochemical interfaces to incorporate photosystem I in applied photosynthetic systems, and has created a wealth of new approaches in terms of both solid photovoltaic cells, liquid photoelectrochemical cells, and hydrogen fuel generation. These approaches have resulted in numerous publications. Using photosystem I as the key active component, we have been leading an effort to integrate PSI into biomimetic photoelectrochemical cells and devices. For example, we developed a completely organic, transparent, conductive electrode using reduced graphene oxide (RGO) on which a multilayer of PSI could be deposited.

This presentation will also explore our group’s recent efforts to integrate PSI with advanced materials, including the conducting polymers polyaniline (PANI), polypyrrole, polyviologens, and poly(3,4-ethylenedioxythiophene). These composite assemblies enhance charge shuttling processes from individual proteins within multilayer assemblies—greatly reducing charge transfer resistances and improving overall efficiency of photocells. These PSI/conducting polymer composites can be prepared by either electrochemical co-polymerization from a bath of PSI and aniline or a vapor-phase Friedel-Crafts grafting procedure. The group has reported two new prototype solid-state devices in which PSI or PSI/PANI is sandwiched between energetically appropriate electrodes. The group has also succeeded in stabilizing PSI films via crosslinking to create “wet” photoelectrochemical cells with greater performance and longevity. Finally, our current work is aimed at building new prototypes using PSI in solid state interfaces for scalable solar energy conversion. Finally, the incorporation of PSI into conducting polymer frameworks holds promise for improved conductivity and orientational control in the photoactive layers in these devices.
Effortless Devising and Theranostic Applications of Nanomaterial Modified Biosensors: An Expanding Horizon
Authors: Chatterjee Sanghamitra
Published: February 2020

Electrochemistry has always provided analytical techniques characterized by instrumental simplicity, moderate cost and portability. Over the last decade the use of nanomaterials has had a great impact on biosensing. One major advantage of nanomaterials is their potential to be utilized as non-invasive diagnostic tools. Another is the capacity for combining multiple modalities within a single probe. Nanomaterials are also ideally suited to be applied as drug-delivery systems, which may facilitate the development of a new generation of theranostics with exquisitely sensitive chemical and biological sensing capabilities. Carbon based nanomaterials are the most widely used in electroanalytic and electrocatalytic sensing applications. Carbon nanomaterials offer unique advantages that span several domains, such as a high surface-to-volume ratio, high electrical conductivity, chemical stability, biocompatibility and robust mechanical strength. A critical feature that has driven the impressive success of the use of carbon based nanomaterials for electroanalytical applications most likely relates to the ability of these nanomaterials to promote electron transfer in electrochemical reactions. A number of electrochemical strategies have been explored in the development of nanomaterials based electrochemical biosensors for theranostic applications. Voltammetric techniques have been extremely useful in measuring blood levels, metabolites and the urinary excretion of drugs following low doses.

Biosensors that are based on carbon nanotubes provide a significant avenue for the detection of biomolecules for in vivo and in vitro applications. Efforts have been made in our group to develop new-fangled approaches for the electrochemical detection of non-steroidal anti-inflammatory drug; antiviral drug and natural alkaloid related to hepatocellular carcinoma. The proposed nanomaterial based biosensors exhibited pronounced analytical performance and provided a new and powerful paradigm in terms of novel and augmented functionality that encompasses a wide variety of applications in clinical diagnostics and biological research. The developed electrochemical biosensors comprised of novel nanomaterials had great potential for enhancing and superseding the capabilities of current molecular diagnostics by allowing rapid and highly accurate diagnoses, the integration of diagnostic and therapeutic capacities and the realization of personalized medicine.
Sensitivity Improvement of a Low-Invasive Type Amperometric Glucose Sensor
Authors: Yasuzawa Mikito , Nakataki Shinsaku , Li Jiang , Kurashina Masashi , Harada Toshihiko
Published: February 2020

Implantable glucose biosensors for continuous glucose monitoring (CGM), are getting more attractive, since they can provide greater insight into the direction, magnitude, duration, frequency and possible causes of glucose fluctuations in response to meals, insulin injections, hypoglycemic episodes and exercise throughout the day. The current commercialized or presented conventional CGM sensor devise are required to have about 1.0 cm in length to be inserted inside the skin. Therefore, it is expected to develop lower invasive type glucose sensor in order to improve the life-quality of diabetic patients.　We have previously reported that the sensor response of a fine tapered needle type glucose sensor, which has a sensing region at the tip, showed good correlation with blood glucose value, even it was implanted in the skin of a rabbit for a length of 1.0 mm [1]. This indicate that the glucose measurement in dermis may provide valuable information comparable to subcutaneous tissue glucose measurement. As part of our low-invasive improvement of the sensor, miniaturization of sensing region is essential, but it may lead to a decrease of response current to glucose. Therefore, at the same time, the improvement of sensor sensitivity is also indispensable. The sensitivity of an enzyme based glucose sensor can be improved by introduction of carbon nanomaterial or mediator, which can increase electrode surface area and the efficiency of electron or mass transport to the transducer. Due to their high chemical stability, high surface area, and unique electronic properties, carbon nanotubes (CNT) and graphene has greatly increased biosensor sensitivity and response speed. On the other hand, electroetching of the electrode surface is an effective method to obtain a higher surface area, which may be responsible for enhanced sensitivity. In this study, introduction of carbon nanomaterial and electroetching technique were introduced to improve the sensitivity of the proposed glucose sensor.

[1] J. Li, P. Koinkar, Y. Fuchiwaki, M. Yasuzawa, Biosens. Bioelectron., 86 (2016) 90.
Label-Free Microchip Biosensor for Telomerase Activity in Acute T Cell Leukemia
Authors: Diaz-Cartagena Diana C , Hernández Griselle , Diaz-Ayala Ramonita , Cunci Lisandro , Cabrera Carlos R
Published: February 2020

In the last decade, researchers are looking for platforms, methods, and techniques that mitigate all the problems that current cancer detection methods have; expensiveness, can not be use in a point of care location, do not detects early steps of the disease and are time consuming tests. Nowadays, various researchers have focused on the development of electrochemical devices that detect telomerase as a cancer biomarker. Using a Roche Diagnostics Accu-Chek Aviva® electrochemical platform and electrochemical impedance spectroscopy (EIS), as a sensing technique, telomerase activity in Acute T Cell Leukemia was detected. The detection limit was 0.980 cells/mL. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to characterize the telomerase substrate DNA probe (TS) self assembled monolayer on the gold electrode surfaces. TS probe is rich in guanines thus form secondary structures know as G-quadruplex. Fluorescence spectra showed characteristic fluorescence of DNA G-quadruplex confirming its formation. Additionally, confocal microscope fluorescence images showed the formation of the DNA G-quadruplex as a result of the TS elongation on the electrode surface after been exposed to telomerase. Western blood and gel electrophoresis were used to confirm telomerase presence in Jurkat nuclear cell extracts and to study the DNA elongation process, respectively. The methods and equipment investigated by our group in this investigations will emerge in a development of an electrochemical label free telomerase biosensor and its implementation as a medical device.

This research work was supported by NSF-Chemistry Grant No. CHE-1152940.

Figure 1
(Invited) Electrochemical Measurement Approaches for Planetary Exploration
Authors: Quinn Richard C. , Thomson Seamus D. , Koehne Jessica E.
Published: February 2020

2018 marks the 10-year anniversary of the landing of the NASA Phoenix spacecraft on the ice-rich northern plains of Mars. The Phoenix Lander carried the Wet Chemistry Laboratory (WCL), a component instrument of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) and was used to perform a comprehensive electrochemical characterization of martian soil in an aqueous solution. Designed to characterize the habitability of the martian surface, WCL contained an array of ion selective electrodes, a conductivity cell, a platinum electrode to measure redox potential, electrodes to perform perform cyclic voltammetry, chronopotentiometry and anodic stripping voltammetry, as well as a set of chemical reagents used to perform a sulfate titration and sample acidification. The measurements made with WCL resulted in a number of major discoveries, including the detection of percent levels of perchlorate on the martian surface, and represent the first, and to date, the only time electrochemical methods have been used for planetary exploration beyond Earth. NASA is now embarking on a new era of astrobiology exploration as plans are being formulated for missions to Ocean Worlds of the outer solar system, including Europa, an ice covered Jovian moon. Based on lessons learned during the development of WCL and its operation on the surface of Mars, we will discuss new design approaches and strategies that will enable the implementation of autonomous microfluidic electrochemical sensor arrays during upcoming missions to these yet to be explored solar system environments.
ABE-Stat: A Palm Sized, Wireless, Open-Source Potentiostat for High Performance Electrochemical Analysis
Authors: Jenkins Daniel McKewn , McLamore Eric , Reyes De Corcuera Jose I
Published: February 2020

Exciting new advances in materials engineering and biological catalysis are making it possible to make high-precision electrochemical measurements at the molecular level. Translating these advances to practical agricultural and biological diagnostics in the field requires portable potentiostat devices with performance rivaling those of expensive benchtop systems. In recent years several open-source potentiostat designs have been made to make biological experimentation more accessible. Here we report on a palm-sized open-source hardware design (ABE-Stat) that interfaces wirelessly through Bluetooth and/or WiFi. A fully operational interface is available for free for Android devices, which includes functionality for cyclic voltammetry, differential pulse voltammetry, chronoamperometry, electrochemical impedance spectroscopy, and measurement of open circuit potential, in 2 or 3 electrode configurations, and language support for English, Spanish, Portuguese, Japanese, Korean, and Chinese. Static current noise is within an order of magnitude of 24-bit resolution measurements, and dynamic precision of applied dynamic potentials is approximately equivalent to the 16 bit resolution of the signal source. The hardware can easily be reprogrammed for other dedicated analytical functionality, including operation in networked industrial environments through WiFi. We anticipate that the availability of this design will help accelerate the commercialization of new electrochemical diagnostic technologies.

Figure 1
Highly Sensitive Non-Enzymatic Glucose Sensor Based on Metal-Organic Framework
Authors: Kim Kijun , Lim Hana , Park Young Min , Bae Youn-Sang , Kim Hyun-Jong
Published: February 2020

The reliable and fast determination of glucose is very important in the diagnosis of diabetes, waste water treatment and food industry. Although conventional glucose sensors based on enzymes such as glucose oxidase (GOx) display high sensitivity and selectivity to glucose, their activity is easily affected by the variation in temperature and pH and the presence of other chemicals. To improve this drawback, non-enzymatic glucose sensors that exhibit better device lifetime and stability have been recently proposed.

Metal-organic frameworks (MOFs), a new class of porous materials consisting of metal ions and organic linkers, have attracted interest because of their physicochemical properties such as crystalline ordered structure, tunable pore sizes, large surface areas and thermal stability. Although most MOFs have poor electron-conductivity, they have been investigated actively because of redox properties of metal ions and tunable linker in their structure.

In this study, we synthesized solvothermally MOFs consisting of various transition metal ions and organic linkers as electrocatalysts for glucose sensing. The synthesized MOFs were transformed to stable form for glucose detection by electrochemical treatment and the process was characterized by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM) and N2 adsorption isotherm. By measuring their electrochemical properties from cyclic voltammetry and chronoamperometry analyses, we studied the effect of metal ions and organic linkers on electrocatalytic performance including sensitivity, limit of detection (LOD), linear range and selectivity. As a result of improvement of glucose sensing performance by controlling physicochemical properties of MOFs, a Ni-based MOF showed good electrocatalytic activity with high sensitivity. This study suggests that MOFs can be considered potential electrode materials for non-enzymatic glucose sensors.
Highly Sensitive Electrochemical Determination of Acetaminophen Using Novel Two Step Activated Biomass-Derived Carbon
Authors: Kim Dongwon , Piao Yuanzhe
Published: February 2020

The determination of the concentration of acetaminophen (AC) in the human body is important due to the regular drug safety and public health. However, conventional methods are insufficient because of their expensive, time-consuming and complicated nature. In this study, a novel two-step activation of biomass-derived carbon for the electrochemical detection of AC is presented. The electrode material is prepared by a novel two-step activation process, which involves the initial activation of kelp powder with ZnCl2, subsequently by an activation step with KOH. The activation procedure greatly enhanced the overall pore volume and specific surface area. The characterizations of ZnCl2-KOH activated kelp carbon (ZKAKC) were conducted with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and electrochemical impedance spectroscopy (EIS). The electrochemical characterization of ZKAKC was performed with cyclic voltammetry (CV) analysis of potassium ferricyanide. The detection ability of ZKAKC/GCE toward AC was conducted using CV analysis and differential pulse voltammetry (DPV). The modified electrode showed high sensitivity and selectivity for the determination AC with the detection limit of 0.004 μM. Also, the modified electrode showed good result toward AC even in the presence of 0.1 mM ascorbic acid and 0.1mM dopamine with the detection limit of 0.007 μM. For the evaluation of sensing ability as an actual electrochemical sensor, a real sample test was conducted. The high electrochemical performance was due to the increased physical and electrochemical surface area, which occurred during the two-step activation process. This approach for producing activated carbon is universal for development of new carbon materials and can be applied to different carbon source materials.
(Invited) Dielectrophoresis Studies of Mammalian Cells at High Frequencies (10 ~ 400 MHz)
Authors: Pethig Ronald
Published: February 2020

Most reported studies of the dielectrophoresis (DEP) of biological cells have employed voltage signals of frequency that extend from 10 kHz to around 10 MHz. In this range the DEP response is determined by the dielectric properties of the suspending medium, as well as the size and shape of the cell and the dielectric properties (capacitance, conductivity) of its plasma membrane. An important parameter to determine is the so-called cross-over frequency f
x01, at which a transition from negative to positive DEP occurs on increasing the frequency. Theoretical and experimental evaluations [e.g., 1-5] of f
xo1 have been extensive and exploited in practical applications of DEP, such as the manipulation, separation, and isolation of target cells from mixtures in suspension.

DEP measurements up to 400 MHz have recently been reported [6] for murine myeloma cells. This provided, for the first time, the ability to determine under controlled conditions the value of the cross-over frequency fx02, where the transition from positive back to negative DEP occurs. In agreement with theory, it was found that fx02 is independent of the cell parameters that control fx01, and is predominantly determined by the conductivity of the intracellular medium. The myeloma cells were suspended in buffer media of different osmolarities, with measurements taken of cell volume as well as both fx01 and fx02. Flow cytometry was employed with a potassium-sensitive fluorophore to monitor relative changes in the intracellular potassium concentration. This revealed that the value of fx02 was highly correlated to the concentration of the most dominant cytoplasmic ion, namely potassium.

The implications of these new high-frequency results will be discussed, particularly with regards to the potential of DEP being adopted as a biomarker-free method for sorting and characterizing cells based upon their dielectric properties.

Lei U., Lo, Y. J., IET Nanobiotechnology 2011, 5, 86-106.

Cetin, B., Li, D., Electrophoresis 2011, 32, 2410-2427.

Gagnon, Z. R., Electrophoresis 2011, 32, 2466-2487.

Vahey, M. D., Pesudo, L. Q., Svenssson, J. P., Samson, L. D., Voldman, J., Lab Chip 2013, 2754-2763.

Pethig, R., Dielectrophoresis: Theory, Methodology and Biological Applications, John Wiley & Sons, Chichester 2017.

Chung, C., Pethig, R., Smith, S., Waterfall, M., Electrophoresis, doi: 10.1002/201700433
Mechanical Microsensors for Pulse Measurement
Authors: Garcia-Castro Fatima , De Sagazan Olivier , Simon Claude , Coulon Nathalie , le Bihan France
Published: February 2020

Health parameters measurement is the focus of many researches because of their wide application area. Mechanical sensors have also many interests, especially if their sensitivity is enough high to measure small deformations. Their application can then address pulse measurement or muscle and tendons movements (fig. 1). Mechanical sensor are widely developed. Low temperature technologies allow to fabricate them on many types of substrates including flexible substrates. These sensors require the use of piezoresistive materials. We previously develop mechanical sensors based on microcrystalline silicon resistances.

Microsensors are fabricated on 25 µm thick Kapton. The piezoresistive material is N-type doped microcrystalline silicon deposited by PECVD. The main problem of this thin substrate is the stress induced during the process that deforms and creates cracks in each layer (fig. 2). In order to avoid this phenomenon, various possibilities were studied, first using different structures with nitride silicon layers. A specific cleaning process was also defined and the design of a shadow mask that reduce the surface of the microcrystalline silicon deposit was proposed. The combination of the three methods made that our samples are flatten and the cracks practically disappear. Different designs were then studied in order to obtain a good sensitivity to deformation.

Resistances are characterized under mechanical stresses. Their response to variable deformations was measured. In order to increase the sensitivity of the sensor, a specific electronic circuit is used, including a variable amplification of the measured signal (typically equal to 7). Sensors are placed on a thin layer which shape can be change with pressure variation. Several deformations can then be applied. Sensors are able to response to variable frequencies and different excitation waves like simple delta pulse or complicated signals like the ECG wave. The sensor response to deformation is studied with those different signals and at different frequencies (fig. 3). Several geometries are compared with the aim of obtaining the most sensitive design. The sensitivity to deformation as well as the response time are studied. This shows the feasibility and development of a highly sensitive system for small deformation measurements.

Figure 1
Investigation of Printing Properties on Paper Substrate
Authors: Saha Tonmoy Kumar , Knaus Tyler N , Khosla Ajit , Sekhar Praveen K.
Published: February 2020

In this article, the optimum printing parameters were found when using silver nanoparticle ink to print on Kodak 4-Star photo paper substrate. Fujifilm Dimatix 2831 was used as the inkjet printer.The printing parameters of interest included the number of printing layers, the drop spacing, and curing temperature of the ink. Analysis of Variance (ANOVA) analysis of the experimental data reveals sintering temperature to be significant (p < 0.05) to improve the conductivity. Pattern conductivity and surface roughness were used to identify the optimum printing parameters. The optimum printing parameters were found to be 15 µm drop spacing, two printing layer, and a sintering temperature of 90°C. The best conductivity measured under the above mentioned condition was found to be 5.56 x 106 Ω-1m-1. Further, the bending test indicated that the printed patterns were unaffected (in terms of conductivity) when flexed around a cylindrical support indicating excellent stability under stress. This study paves the way for developing mechanically robust flexible devices with excellent electrical properties for Internet of Things (IoT) applications.
In-Situ Electrical Characterization of Low Temperature Getter Thin Films Activation
Authors: Lemettre Sylvain , Bessouet Clément , Coste Philippe , Lecoq Helene , Sauvage Thierry , Bosseboeuf Alain , Moulin Johan
Published: February 2020

Thanks to their reactivity to gases, getter materials are involved in vacuum packaging to compensate leaks and permeation through the package. After deposition, the material is passivated due to the contact with the air, and must be thermally activated to force the diffusion of the passivation layer inside the film. However, new MEMS technologies imply more fragile devices thus processes with a limited temperature. In this frame, we investigate getter materials presenting a low activation temperature, such as Zr-based alloys.

Moreover, in most investigations of getter films, activation and sorption are characterized separately by room temperature surface analysis techniques in UHV and by sorption experiments under specific gases, respectively. In this work, we have studied the behavior of getter thin films in vacuum as a function of the temperature and the pressure to be as close as possible to the conditions of integration, i.e. wafer bonding. This consisted in following the sheet resistance measured by using the 4-probes technique and comparing electro-thermal properties (resistivity, Temperature Coefficient of Resistance TCR) to pre- and post- characterization (composition, structure).

Thin films of Zr, V, Ti, Zr-Ti, Zr-V and Zr-Co with thicknesses of 300-400 nm have been deposited by co-evaporation in UHV. Their sheet resistance was measured as a function of the temperature under vacuum. The control of the pressure, from 10-6 to 10-3 mbar, allowed to activate the films in different conditions. For as-deposited films, results show that the resistivity and TCR are linked and follow the Mooij rule: the TCR decreases with the resistivity and becomes negative for resistivities higher than 150 µW.cm. The values globally depend on the composition, but separated groups are also linked to the disorder of the structure, from the lowest to the highest: pure metals, Zr-Ti, Zr-V then Zr-Co. In case of Zr-Ti, the grain size directly impacts the evolution of the coupled TCR and resistivity.

The activation in vacuum involves simultaneous and continuous diffusion inside the films and sorption at the surface. The latter cannot be avoided, even at 10-6 mbar, and the resistivity increases with the square root of the time. However, differences of behavior as a function of the pressure can be linked to the gettering efficiency and the diffusion length of oxygen in the material, which depends on both the composition and the microstructure. Crystalline Zr-Ti films behave as Zr and Ti and the grain size directly impacts the diffusion, thus the quantity of oxygen sorbed in the film. The structure of Zr-V or Zr-Co is more complex, which can be either crystalline or amorphous depending on the composition. Large variations in the sheet resistance can be obtained and the high disorder of the structure allow them to sorb more gaseous species than Zr-Ti.
High-Performance Flexible Dual-Mode Sensor Array Based on Fully Inkjet-Printed Electrode for Electronic Skin
Authors: Kim Kyungkwan , Jung Minhyun , Jeon Sanghun
Published: February 2020

Electronic skin, which consists of various functional sensor arrays and can be applied to robot and wearable human-machine interfacing devices by mimicking the functions of human skin, requires flexibility, multifunctional mode, and high-sensitivity. Here, we developed a high-sensitivity, and high-reliability flexible dual-mode sensor with inkjet printable electrode material comprised of organic conductor-elastomer-metal nanoparticles. These involved vertically stacked sensors that utilize different sensing principles, thus enabling the realization of a dual-mode sensor with negligible interference. The pressure sensor has a high sensitivity over a wide-range (3Pa–5kPa), a fast response time (20ms), excellent reliability characteristics (100,000cycles) and a low operating voltage (0.5mV). The temperature sensor with a long bent organic conductor-metal line formed by the inkjet process can distinguish a temperature difference of 0.5 °C, and has a temperature sensitivity of 0.32% per °C. In addition, we demonstrated a dual-mode sensor with a 5×5 array structure that responded quickly and precisely in real-time, without interference effect. The low-resistivity and high-reliability flexible electrode and device structure used in this study are expected to be widely used in the future of soft touch displays, medical devices, and robotic applications.
Degradation of Li-Oxide Garnets in Humidity, Air and Aqueous Solutions: A Study Using a Large Li6.4La3ZrTaO12 Single Crystal
Authors: Hiebl Caroline , Smetacek Stefan , Berendts Stefan , Uecker Reinhard , Redhammer Günther , Limbeck Andreas , Fleig Jürgen , Rettenwander Daniel , Wilkening Martin
Published: February 2020

Lithium-ion batteries are indispensable in our mobile electronic devices. Although considered as promising next-generation storage systems for green energy, safety aspects are of top priority of current research. The root of these safety issues associated with lithium-ion batteries lies in the electrolyte materials used at present. Those are based on flammable non-aqueous liquid electrolytes. Irrespective of these risks they could not been replaced so far because of the lack of inherently safe inorganic solids which should show both very high ionic diffusivities1,2 and a practicable electro­chemical stability. Garnet-type metal oxides,3 such as Li7La3Zr2O12 (LLZO), are being considered as suitable candidates as they fulfil many of the requirements to realize “beyond” Li-ion battery technologies. As an example, to be applicable as a water-protective layer for Li- metal electrodes, the solid electrolyte must be stable in aqueous solutions. In general, the majority of different LLZO types show a high stability in humid environments compared to other solid electrolytes. Upon exposure to aqueous solutions, a Li+/H+ exchange reaction is reported to occur in this class of materials. In certain compounds this exchange is believed to lead to structural changes and degradation of the Li+ conductivity.4

The present work is aimed at investigating degradation phenomena on single crystalline Li6.4La3ZrTaO12 samples in aqueous solutions (distilled water, 0.1 M HCl, saturated LiCl, and 1 M LiOH) as well as the degradation in both humidity and air. While grazing-incidence XRD and SEM helped identify degradation products, broadband conductivity spectroscopy was used to characterize ionic transport parameters of the bulk electrical responses. Albeit the ionic conductivities stay nearly constant the activation energies show drastic changes. As an example, for Li6.4La3ZrTaO12 immersed in distilled water we obtained an activation energy of 0.75 eV in contrast to 0.59 eV of the pristine sample at ambient conditions. This observation can be attributed to the change in the Arrhenius pre-factor caused by the reduction of the number density of Li-ion charge carriers in the garnet.

Financial support by the Austrian Federal Ministry of Science, Research and Economy, as well as the Austrian National Foundation for Research, Technology and Development is highly appreciated.

1 V. Epp, O. Gün, H.-J. Deiseroth, M. Wilkening, J. Phys. Chem. Lett. 4 (2013) 2118.

2 M. Uitz, V. Epp, P. Bottke, M. Wilkening, J. Electroceram. 38 (2017), 142.

3 Thangadurai et al., Chem. Soc. Rev. 43 (2014) 4714.

4 C. Ma, E. Rangasamy, C. Liang, J. Sakamoto, K. L. More, M. Chi, Angew. Chem. Int. 54(1) (2015), 129-133.
Improvement of High Rate Performance of a Lithium Ion Battery Composed of Laminated LiFePO4 Cathodes/ Graphite Anodes with Porous Electrode Structure Fabricated with a Pico-Second Pulsed Laser
Authors: Tsuda Takashi , Ando Nobuo , Tanabe Toyokazu , Itagaki Kaoru , Soma Naohiko , Nakamura Susumu , Hayashi Narumi , Matsumoto Futoshi
Published: February 2020

Development of lithium ion batteries (LIBs) helps promote the spread of electric vehicles (EVs) over the world. Everyone is expected that the next generation of eco-friendly and high-performance EVs that was driven with LIBs become very popular in our daily life in the future. However, it will take a long time before it becomes widespread because of two reasons; the performance of the electric vehicles cannot satisfy the demands of daily life, and LIBs are expensive. The achievement of charging and discharging with high current densities is one of the requirements for high performance LIBs in EVs, almost all of LIBs cannot satisfy the requirement specification (high rate performance) for the next generation of LIBs. When the present LIBs are charged and discharged with high current densities to shorten the charging time and to accelerate the EVs in shorter time, respectively, the charging and discharging capacities largely drop, and the rechargeable performance is seriously damaged. In order to improve the high rate performance of the present LIBs, selection of materials, optimization of cathode and anode particle sizes, composition of cathode and anode layers for active materials, binder and conductive additives, coating of the active material surfaces and design of cells and electrodes have been examined. Each examination has achieved some success in the point view of high rate performance. However, recently, improvement of the high rate performance in the present LIBs unfortunately reaches a deadlock. Therefore, in this study, we propose strongly one of the solutions for the improvement of high rate performance with our developed laser technology. In this study, we developed preparing a porous graphite anode and a lithium iron phosphate (LiFePO4, LFP) cathode with a pico-second pulsed laser, in which through-holes having 20 mm diameters and an opening rate of 0.5% were formed on the graphite layer/copper (Cu) anode and the LiFePO4 layer/aluminum (Al) cathode. The cells composed of porous cathodes and anodes exhibited improvement of the high rate discharging performance when compared with those of cells prepared with non-porous cathodes and anodes and with cells prepared with cathodes and anodes prepared with conventional porous current collectors. The formation of holes on the anodes and cathodes can be prepared simply and speedily with the pico-second pulsed laser to increase the accessibility of the anode and cathode materials to Li+, resulting in the enhancement of the rate performance of the electrodes. The mechanism of the improvement of the high rate discharging performance was discussed with the results of electrochemical impedance spectroscopy (EIS).
Capacity Limited Cycle Life of Cu/Sn Doped Nano-Iron/Carbon Electrodes in Alkaline Electrolyte
Authors: Paulraj Alagar Raj , Kiros Yohannes , Skårman Björn , Vidarsson Hilmar
Published: February 2020

Large-scale energy storage system is essential for storing and integrating the intermittent renewable energy such as wind and solar into the electricity grid. This system needs to show a high round-trip efficiency (80%), longer-life cycle (5000 cycles) and favorable cost ($100/kWh) as specified by the U.S Department of Energy (DOE) [1]. Ni-Fe and Fe-air are among the cheapest and long life batteries that could meet the DOE performance target. However, iron electrodes used in this system needs to be improved in terms of discharge capacity, rate capability, Faradaic efficiency and cycle life [2].

Recently, nanomaterials have exhibited a high initial capacity whereas after few cycles the capacity faded fast due to particle agglomeration and increase in resistance by the discharged product [3-5]. To avoid this phenomenon, we have used the Cu-doped Core/Shell structure Nano-Iron/Iron Carbide that showed 367 mAh g-1 with stable performances for more than 200 cycles [6]. In this work, Cu/Sn-doped iron carbon composite was utilized and achieved high initial capacity between 457 and 600 mAh g-1 around 90% efficiency. We have tried to limit the electrode capacity by adjusting the depth of discharge (DoD) and extend the cycle life to more than 500 cycles.

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Silver Nanoparticles Deposition on TiO2 Nanotubes for Ethanol Oxidation
Authors: Forero Leydy Carolina , Leal da Silva Elen , Aguzzoli Cesar , Rosas-Barrera Kevin Leandro , de Fraga Malfatti Célia
Published: February 2020

Nowadays, a significant part of the research has focused on the development of electrocatalysts for the ethanol oxidation, seeking to reduce conventional fossil fuels [1]. The TiO2 nanotubes obtained by electrochemical anodization in fluorine-based electrolytes are the most commonly used materials as catalysts, due to their efficiency, chemical stability, large surface areas and high catalytic activity [2]; however, the deposition of noble metals as Ag in the TiO2 nanotubes could significantly improve the catalytic activity of TiO2 for the oxidation of ethanol [1]. In this work, the development and characterization of metals supported in TiO2 nanotubes is sought for the application in electrocatalysts. Nano particles of Ag in nanotubes of TiO2 have been synthesized by the cathodic sputtering at different times of deposition, characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (FEG- SEM) and the cyclic voltammetry technique. Therefore, catalytic activity for the ethanol oxidation has been studied. Taking everything into consideration, the results of the cyclic voltametry show a characteristic behavior of an Ag electrocatalyst for the electrooxidation of ethanol in basic medium. A comparison made with the cyclic voltammetry technique of the different deposition times employed shows that there is no significant difference in the oxidation of ethanol.

[1] Y.Q. Liang, Z.D. Cui, S.L. Zhu, Y. Liu, X.J. Yang. (2011). Silver nanoparticles supported on TiO2 nanotubes as active catalysts for ethanol oxidation. Journal of Catalysis. 276–287.

[2] Zhihua Xu, Jiaguo Yu, Gang Liu. (2011). Enhancement of ethanol electrooxidation on plasmonic Au/TiO2 nanotube arrays. Electrochemistry Communications. 1260–1263.
A Novel Method to Suppress Unwanted Anodic Deposition of Manganese Oxide in Zinc Electrowinning
Authors: Furushima Hiromu , Kawaguchi Kenji , Morimitsu Masatsugu
Published: February 2020

Zinc electrowinning produces a high purity of zinc on the cathode from acidic zinc sulfate solutions containing Zn(II) ions and other metal ions, e.g., Mn(II), extracted from zinc ores. Lead alloy anodes are frequently used as the anode, at which oxygen evolution mainly occurs, but unwanted manganese oxide deposition also happens, since the onset potential of Mn(II) oxidation to manganese oxide is less noble than that of oxygen evolution due to a high overpotential of lead alloy to oxygen evolution. This unwanted reaction induces the increase in cell voltage and makes the anode’s lifetime short, so that the anodic deposition of manganese oxide is required to inhibit in zinc electrowinning. This paper presents a novel method to suppress manganese oxide deposition with using amorphous oxide coated titanium anodes which have significantly larger active surface area than the cathode of zinc electrowinning. The new method is constant current electrowinning as same as the present process, although a large difference in actual current densities of the anode and the cathode is effective to suppress the anodic deposition and cathodic dissolution of electrowon zinc at low current density less than 1 mA/cm2.

The anode used in this work is amorphous IrO2-Ta2O5 coated titanium electrodes prepared by thermal decomposition at 340 oC of the precursor solution containing Ir(IV) and Ta(V) at 80 mol% of Ir painted on titanium plates [1]. Constant current electrolysis was carried out in 2 mol/L H2SO4 + 0.1 mol/L MnSO4 + 0.95 mol/L ZnSO4 + 0.02 g/L glue, which were held at 40 oC without stirring, with a two-electrode cell using a zinc plate as the cathode. The geometric surface area of the anode and the cathode was 1 cm2.

Constant current electrolysis was carried out at various current densities for 14 hours which is a typical electrolysis period of zinc electrowinning at low current density during daytime in Japan. The electrolysis at 0.40 mA/cm2 or more resulted in the increase in anode’s weight, and the deposit formed on the anode was found to be δ-MnO2 by XRD, while the current density less than 0.30 mA/cm2 produced no deposit on the anode by electrolysis, even though the electrolyte became light pink after the electrolysis suggesting that Mn(II) was oxidized to Mn(III), but not to manganese oxide. On the other hand, no dissolution of electrowon zinc was observed at 0.15 mA/cm2 or more. From the results, anodic δ-MnO2 deposition can be suppressed at 0.15 to 0.30 mA/cm2 with the amorphous oxide coated titanium anode even for 14 hours without the dissolution of zinc.

Reference

[1] T. Zhang, Ph.D. Thesis, Doshisha University (2015).
Formation of CZTS Absorber By Heat Treatment of Copper Tape Plated with Zinc and Tin Via Electrodeposition for CZTS Solar Cells
Authors: Erawan Hugo fathur rahman , Yokoyama Shun , Takahashi Hideyuki , Tohji Kazuyuki
Published: February 2020

In recent years, the use of solar energy has been rising globally. This is a good trend because solar cells are not only sustainable energy source but also has the flexibility of not needing to be connected to a grid. This means that building solar cells can be highly beneficial especially for people living in rural areas without existing supply of electricity where it is too costly and would take too much time to build a conventional grid system. However, most of the growth of solar cell we have seen this far comes mostly from developed countries (e.g. Japan, USA, and Germany) or quickly developing countries with strong economies (e.g. China and India). It is important that rural areas without existing supply of electricity be electrified by solar energy as well. To achieve electrification of rural areas, it is important that the cost of the solar cell is brought further down to make it more accessible. In this study, we will approach the production of CZTS (copper zinc tin sulfide) solar cells with a new method that can make it more efficient and cheap. CZTS solar cells are very cheap solar cells that uses only abundant and non-toxic materials. Currently, CZTS is deposited on top of a molybdenum film sputtered on glass. This step has the issue of the need of sputtering, which requires a high amount of energy. Here we propose the replacement of glass and molybdenum by copper substrate. The copper substrate could function as the structural support (replacing glass), the conductor (replacing molybdenum), and copper source for CZTS formation.

To understand CZTS formation on a copper substrate, first, tin and zinc were deposited on top of a copper substrate by electroplating. After the deposition, the substrate was then heated in an oven with some sulfur source in nitrogen atmosphere at various temperatures and time (this process is called sulfurization). The sulfur would evaporate and react with the copper substrate deposited with tin and zinc. The phase change of the samples were studied to understand the reaction that happened during the sulfurization process to help understand how to grow CZTS by this method. An issue is that the excessive amount of sulfur available during the high temperature reactions reacts with the whole copper substrate turning it into copper sulfide. To prevent the formation of copper sulfide, some modification to the standard sulfurization process are necessary. CZTS can be obtained by reaction of copper sulfide (CuS), zinc sulfide (ZnS), and (SnS). Since SnS can evaporate at lower temperature, a copper substrate with zinc plating on it, that has been sulfurized at lower temperature could be reacted at higher temperature with an SnS source that will provide the tin for CZTS formation. This method has the advantage not having excessive amount of sulfur at high temperature that can convert the whole copper substrate.
Carbon-Free Connected Ru, Ir Based Nanoparticle Catalysts for Polymer-Electrolyte Water Electrolysis
Authors: Sugita Yoshiyuki , Tamaki Takanori , Kuroki Hidenori , Yamaguchi Takeo
Published: February 2020

Oxygen evolution reaction (OER) catalysts for polymer-electrolyte water electrolysis (PEWE) suffered from their low surface area because carbon support cannot be used for OER operating at high potential. Connecting metal nanoparticles enable catalysts to conduct electrons through nanoparticle networks without any support materials while keeping their high surface area. Thus, connected nanoparticle catalysts (Fig. 1 (A)) are promising for OER. Previously, we have developed connected Pt-Fe nanoparticle catalysts with hollow capsule structure for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs).[1]

In this study, we proposed Ru and Ir nanoparticle catalysts for OER in water electrolysis because Ru and Ir have high OER activity. Ru and Ir nanoparticle catalysts were synthesized as follows. First, Ru and Ir nanoparticles were synthesized on silica template (PDDA/SiO2) via polyol method using tetraethylene glycol as reducing agent and Ru(III) acetylacetonate or Ir(III) acetylacetonate as the metallic precursors (M/PDDA/SiO2, M is Ru or Ir). Then, these nanoparticles were treated in supercritical ethanol at 330ºC for 90 min (Ru) or 60 min (Ir) (sc-M/SiO2). Dissolution of SiO2 in 3 M NaOH solution at 85ºC for 3 h made porous hollow structure (M capsule). OER performance were evaluated by electrochemical measurement in 0.1 M HClO4 solution.

Fig. 1 (B) shows TEM image of Ir capsule. Capsule and networks structure of each catalysts were observed by TEM images. All Ru catalysts inactivated for OER at the first CV cycle. OER activity of Ru/PDDA/SiO2 did not improve by heat oxidation treatment in air at 400ºC. Fig. 1 (C) shows OER curves of Ir catalysts. All Ir catalysts showed stable OER. Among them, Ir/PDDA/SiO2 had the highest OER activity. Mass activity at 1.48 V of Ir/PDDA/SiO2 was higher than RuO2
[2], IrO2
[2] and Ir/C­[3] in previous reports as shown in Fig.1 (D). Heat treatment of Ir/PDDA/SiO2 at 200ºC further improved.

In conclusion, we successfully synthesized connected Ru and Ir nanoparticle catalysts. Among them, Ir/PDDA/SiO2 showed the highest OER activity and the activity was further improved by heat oxidation treatment. The results showed that connected Ir nanoparticle catalysts are promising as carbon-free catalysts for water electrolysis.

[1] T. Tamaki, H. Kuroki, T. Yamaguchi et al., Energy Environ. Sci., 8, 3545-3549 (2015).

[2] Y. Lee et al., J. Phys. Chem. Lett., 3, 399-404 (2012).

[3] HN. Nong et al., Chem. Sci., 5, 2955-2963 (2014).

Figure 1
The Novel Perovskite-Type Ru-Doped Sr0.92Y0.08TiO3 Catalyst for Syn-Gas Production
Authors: Kim Ghun Sik , Ham Hyung Chul , Yoon Sung Pil
Published: February 2020

One of the problems of partial oxidation of methane (POM) catalysts is thermally unstabe due to the exothermic reaction. In this study, novel perovskite-type Sr0.92Y0.08TiO3-based catalysts were investigated for syn-gas production, which have strong thermal stability compared to the conventional catalysts prepared by metal dispersion on a ceramic support. Ru-doped Sr0.92Y0.08TiO3 catalysts were fabricated by using the Pechini method. The prepared catalysts were characterized to check the perovskite structure as a function of Ru dopant amount and to understand the details of the activating catalyst mechanism using X-ray fluorescence (XRF), Brunauer-Emmet-Teller measurements (BET), X-ray photoelectron spectroscopy (XPS), Temperature-programmed reduction (TPR), and Transmission electron microscopy (TEM). The reforming of methane over the Ru-doped Sr0.92Y0.08TiO3 catalysts has been extensively investigated and the catalysts showed much higher activity on POM compared with the conventional catalysts. Moreover, the Ru-doped Sr0.92Y0.08TiO3 catalysts exhibited very strong thermal stability, too. After the POM reforming reaction, we have found that the nano-sized Ru is exsoluted on the Sr0.92Y0.08TiO3 catalyst surface. Consequently, the exsolution is the main reason for high activity on POM and good thermal stability.