bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
(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
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.
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.
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.

References

[1] A.K. Manohar, S. Malkhandi, B. Yang, C. Yang, G.K. Surya Prakash, S.R. Narayanan, Journal of The Electrochemical Society, 159 (2012) A1209-A1214.
[2] R.D. McKerracher, C.P.d. Leon, R.G.A. Wills, A.A. Shah, F.C. Walsh, ChemPlusChem, 80 (2015) 323-335.
[3] D. Lei, D.C. Lee, A. Magasinski, E. Zhao, D. Steingart, G. Yushin, ACS Appl Mater Interfaces, 8 (2016) 2088-2096.
[4] W. Jiang, F. Liang, J. Wang, L. Su, Y. Wu, L. Wang, Rsc Adv, 4 (2014) 15394-15399.
[5] C.-Y. Kao, Y.-R. Tsai, K.-S. Chou, Journal of Power Sources, 196 (2011) 5746-5750.
[6] A.R. Paulraj, Y. Kiros, B. Skårman, H. Vidarsson, Journal of The Electrochemical Society, 164 (2017) A1665-A1672.
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.