bluuebunny/crossref_metadata_2025 huggingface dataset:
Probe Sensor Using Nano-Structured Multi Walled Carbon Nanotube Yarn for Direct Selective and Sensitive Dopamine Detection
Authors: Al-Graiti Wed , Foroughi Javad , Yue Zhilian , Feng Xu- , Wallace Gordon , Chen Jun
Published: February 2020

Dopamine (DA) is an important neurotransmitter in the central nervous system. Insufficient or excessive level of DA related to Schizophrenia and Parkinson diseases[
1
]. Therefore, early detection of DA represents a hot topic in biosensing field. Recently, electrochemical bio-sensor (ECB) based on carbon material has received a great attention as an inexpensive and simple analytical method with remarkable detection sensitivity for neurochemicals detection[
1
]. Therefore, ECB’s fabrication and structure have attracted researcher’s efforts to obtain higher sensitivity and highly selectivity simultaneously. Traditional film-based ECB have shown some disadvantages such as large sizes, random structure, time consuming for film fabrication and low efficient[
2
]. As a result, a new biosensor based on nano carbon material designed in a probe style has been considered as an excellent candidate for sensing stimulation as they have aligned and packed structure which provides a bridge for electrons transfer and that enhances electrical conductivity, also, fibres can be fabricated in small sizes which gives the ability to be implanted with low tissue damages, in addition, simplicity of handling and ability to be grafted with different materials[
3
].

The aim of this study is to develop hybrid multi wall carbon nanotube yarn due to fascinating properties for CNTs (i.e. high surface area, fast electron kinetics transfer, reduced electrode fouling, wide electrochemical potential window, bio-compatibility, grafting ability, and increased sensitivity and selectivity (high efficient)). In a typical bio-sensing system, DA has been used with ascorbic acid (AA) and uric acid (UA) (as coexistence compounds[
4
]) for investigating both sensitivity and selectivity of the prepared CNT yarn viacyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. CV and DPV results have demonstrated selective and sensitive detection of DA in a sea of AA and UA with the potential to be a promising probe bio-sensor for real-time measurement.

References:

1. Jackowska, K. and P. Krysinski, New trends in the electrochemical sensing of dopamine. Analytical and Bioanalytical Chemistry, 2013. 405(11): p. 3753-3771.

2. Zhao, J., et al., Carbon Nanotube Nanoweb–Bioelectrode for Highly Selective Dopamine Sensing. ACS Applied Materials & Interfaces, 2012. 4(1): p. 44-48.

3. Hu, C. and S. Hu, Carbon Nanotube-Based Electrochemical Sensors: Principles and Applications in Biomedical Systems. Journal of Sensors, 2009. 2009: p. 40.

4. Bi, H., et al., Carbon-nanotube-modified glassy carbon electrode for simultaneous determination of dopamine, ascorbic acid and uric acid: The effect of functional groups. Sensors and Actuators B: Chemical, 2012. 171–172: p. 1132-1140.

Figure 1
Plasmonics Enhanced Spectroscopic and Electrochemical Analysis
Authors: Xia Xing-Hua
Published: February 2020

The localized surface plasmon resonance (LSPR) arises from the collective oscillation of conduction electrons of metal nanostructures which can be used to monitor recognition events of biomolecules at single nanoparticles1. The enhanced electric field around the nanostructures due to LSPR will significantly enhance the Raman scattering, fluorescence and IR spectra, which enable the realization of single molecule detection. In addition, the LSPR will excite high-energy electron-hole pair (referred to as “hot electrons” and “hot holes”) emerging on metal surface. The energetic charges will considerably affect the electrochemical reactions occurring at the nanoparticles. When the plasmonic metallic nanostructures are coupled to other substrates, for example, the semiconductor (i.e., TiO2, MoS2), the plasmon-excited hot electron-hole at nanoparticle surface can communicate with the conductance and valence bands of the semiconductors, resulting in variation in electro/photocatalytic activity. In this talk, we will start with the study on the possibility of LSPR for monitoring biomolecules and their recognition events at single nanoparticles.1 Then, we report the LSPR enhanced IR for biosensing.2 In the third part, we will show how the LSPR accelerates electrochemical reactions of electroactive biomolecules such as glucose on gold nanoparticles and hydrogen evolution reaction at molybdenum disulphide nanosheets.3 Based on the plasmonics accelerated electrochemical reactions (PAER), high sensitive electrochemical biosensors for detection of glucose and other electroactive biomolecules have been constructed.

1. (a) Y. Zhao, et al. Anal. Chem. 2013, 85: 1053; (b) B. Jin, et al. Langmuir, 2012, 28: 9460; (c) J.Y. Xu, et al. Chem. Comm. 2012, 48: 3052; (d) W.J. Bao, et al., Chem. Commun. 2014, 50: 7787; (e) Y. Zhao, et al. Chem. Commun. 2014, 50: 5480.

2. (a) J.Y. Xu, B. Jin, Y. Zhao, K. Wang, X.H. Xia, Chem. Commun. 2012, 48: 3052; 187. (b) B. Jin, G. X. Wang, D. Millo, P. Hildebrandt, X. H. Xia, J. Phys. Chem. C 2012, 116: 13038; (c) B. Jin, W. J. Bao, Z. Q. Wu, X. H. Xia, Langmuir 2012, 28: 9460; (d) J. Y. Xu, T. W. Chen, W. J. Bao, K. Wang, X. H. Xia, Langmuir 2012, 28: 17564; (e) W. J. Bao, Z. D. Yan, M. Wang, Y. Zhao, J. Li, K. Wang, X. H. Xia, Z. L. Wang, Chem. Commun. 2014, 50: 7787.

3. (a) Y. Shi, J. Wang, C. Wang, T.T. Zhai, W.J. Bao, J.J. Xu, X.H. Xia, H.Y. Chen, J. Am. Chem. Soc. 2015, 137: 7365; (b) 3. C. Wang, Y. Shi, X.G. Nie, Y. Zhou, J.J. Xu, X.H. Xia, H.Y. Chen, Science Advances, in revision.
Enabling Local Electrochemistry in Fast, High-Resolution Scanning Probe Microscopy
Authors: Kirchhofer Nathan D. , Proksch Roger , Rutgers Maarten , Revenko Irene
Published: February 2020

Due to their exceptional sensitivity, scanning probe microscopes enable detailed interrogation of surfaces and interfaces. When correlating spatial information to additional scanning probe surface measurements (such as force, electrical potential or conductivity, impedance, thermal mapping, viscoelastic parameters, redox activity, and more), spatial resolution is often limited. In this work, we present the development and demonstrate the utility of an electrochemical assembly (probe, potentiostat, and sample cell) for use with a high-resolution, fast scanning Cypher atomic force microscope that enables measurements of highly-localized electrochemical signals. These measurements bear on various metrologies such as electrochemical scanning tunneling microscopy (EC-STM), scanning electrochemical microscopy (SECM), and electrochemical strain microscopy (ECSM), and relevant results will be presented.

Figure 1. The first-generation electrochemical cell for use with a lower-resolution scanning probe microscope.

Figure 1
An Novel Electrochemical Sensor for Indole-3-Acetic Acid Detection Based on the Peroxidase-like Activity of Hemin/Boron Nitride Composite Nanocomposite
Authors: Xu Qin , Tang Jiaqian , Liu Fengping , Hu Xiaoya
Published: February 2020

An amperometric sensor for the detection of indole-3-acetic acid (IAA) at low potential was firstly established based on the hemin/boron nitride (hemin/BN) nanocomposite. The hemin/BN nanocomposite was prepared by a simple and facile hydrothermal method. It exhibited peroxidase-like activity for the catalytic oxidation of IAA in the presence of oxygen. The consumption of oxygen has a linear relationship with the concentration of IAA in the range from 0.5 uM to 0.08 mM with a detection limit of 0.1 uM (S/N=1/3). This sensor was unaffected by many interfering substances, and was stable over time. The work broadened the application of hemin/rGO in electrochemical sensor areas and provided a new method for IAA detection.
Mesoporous Hollow MnO2 nanotubes Confined Sulfur As Cathode
Authors: Diao Guowang , Wu Zhen , Ni Lubin
Published: February 2020

The lithium–sulfur battery is receiving intense interest because its theoretical energy density exceeds that of traditional lithium-ion batteries at a much lower cost, but practical applications are still hindered by capacity decay caused by the polysulfide shuttle. Here, we fabricate the mesoporous hollow MnO2 nanotubes as efficient sulfur hosts. To begin with, the self-standing carbon nanofibrous membranes are prepared via electro spinning and high-temperature carbonization, followed by an in situ redox reaction in KMnO4 solution to coat the carbon nanofiber (CNF) template with MnO2 nanosheets until the CNFs are consumed. The synthesized mesoporous hollow MnO2 nanotubes are composed of an inner shell of packed MnO2, and an outer shell of mesoporous sheet like MnO2, which provide physical confinement and chemical interaction and show excellent efficiency for trapping the polysulfides. With a high sulfur content of 73 wt%, in the composite and a areal sulfur mass loading of 2 mgcm-2 in the electrode, the sulfur- mesoporous hollow MnO2 nanotubes electrode delivered a specific capacity of 1213 mAhg-1 at 0.5 C and maintained a stable cycling performance at 1 C over 300 cycles.

References

[1] Huang Y, Liang Z, Miao Y E, et al. Diameter-Controlled Synthesis and Capacitive Performance of Mesoporous Dual-Layer MnO 2 Nanotubes[J]. Chemnanomat, 2015, 1(3):159–166.

[2] Liang X, Hart C, Pang Q, et al. A highly efficient polysulfide mediator for lithium–sulfur batteries[J]. Nature Communications, 2015, 6:5682-5682.

[3] Zhen L, Jintao Z, Lou X W D. Frontispiece: Hollow Carbon Nanofibers Filled with MnO2 Nanosheets as Efficient Sulfur Hosts for Lithium-Sulfur Batteries.[J]. Angewandte Chemie International Edition, 2015, 54(44) .

Acknowledgement

This work was financially supported by the National Natural Science Foundation of China (Grant No. 21273195), a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
Facile Synthesis of Graphitic Carbon Nitride /Iron Oxide Composites and Their Enhanced Electrochemical Performance in the Supercapacitor and Enzyme-Free Glucose Sensor
Authors: Liu Lin , Lyu Hongying , Teng Zhenyuan , Wang Chengyin , Xue Huaiguo
Published: February 2020

The graphitic carbon nitride (g-C3N4)/iron oxide (Fe2O3) composites have been prepared by a simple pyrolysis method using Prussian blue (PB) and melamine. The as-prepared g-C3N4/Fe2O3 composites exhibit a large specific surface area and porosity, which exerts the synergistic effect on their electrochemical performance in the supercapacitor and glucose sensor. The Fe2O3 nanoparticles derived from PB effectively protect g-C3N4 thin layers from restacking and expanding, which provides g-C3N4 layers with defective sites. The g-C3N4/Fe2O3 composites is investigated in KOH electrolyte solution using cyclic voltammetry and charge/discharge techniques. The g-C3N4/Fe2O3 composites facilitates the faster faradic reaction toward electrolytes and delivers highest specific capacitance (660 F∙g−1) and an excellent long cycle life (up to 1000 cycles) in 1M KOH electrolyte at current density of 1 A∙g−1, demonstrating that the porous g-C3N4/Fe2O3 can serve as an excellent electrode material for supercapacitors. In addition, the g-C3N4/Fe2O3 hybrids are also used to fabricate non-enzymatic glucose sensor. The as-fabricated glucose sensor exhibits excellent electrocatalytic activity towards the oxidation of glucose with a response time <3 s and a linear range of 1.0 μM–2.0 mM. The glucose sensor based on g-C3N4/Fe2O3 composites exhibit good anti-interference performance and stability. The g-C3N4/Fe2O3 hybrids has great potential in the application of electrochemical devices.
Core/Shell Fe3O4@PANI and Fe3O4@C@PANI Nanospheres Nanospheres Nanocomposites for High-Performance Electrochemical Supercapacitors
Authors: Diao Guowang , Wu Qianhui
Published: February 2020

Abstract: In this work, magnetite (Fe3O4)-based core/shell composites, including Fe3O4@carbon (C), Fe3O4@polyaniline (PANI), and Fe3O4@C@PANI, are synthesized via a facile hydrothermal process. The as-prepared core/shell composites are characterized by transmission electron microscopy, X-ray diffraction powder, and Fourier transform infrared spectroscopy. The electrochemical performances of Fe3O4,Fe3O4@C, Fe3O4@PANI, and Fe3O4@C@PANI are investigated using cyclic voltammetry, galvanostatic charge–discharge measurement, and electrochemical impedance spectroscopy. The results show that the as-prepared nanomaterials are all typical pseudocapacitance capacitors. Carbon shell can significantly increase the electronic conductivity of electrode materials, reduce capacity loss, and improve the reversibility of Fe3O4. PANI coatinglayer can expressively enhance the specific capacitance.Synergistic effect of double shells improves the electrochemical property of Fe3O4.Fe3O4@C@PANI composites display the high capacitance of 322.5 F g-1at 2.5 A g-1,and 87.8 % of which can still be maintained after 3000 charge–discharge cycles. The excellent electrochemicalproperties of Fe3O4@C@PANI evidence their potential application as supercapacitors in energy storage field.

Reference

[1]. Winter M, Brodd RJ (2004) What are batteries, fuel cells, and supercapacitors? Chem Rev 104:4245–4270

[2]. Ko¨tz R, Carlen M (2000) Principles and applications of electrochemical capacitors. Electrochim Acta 45:2483–2498

[3]. Simon P, Gogotsi Y (2008) Materials for electrochemical capacitors. Nat Mater 7:845–854

ACKNOWLEDGEMENTS

This work was financially supported by the National Natural Science Foundation of China (Grant No. 21273195),a Project Funded by the Priority Academic Program Development of

Jiangsu Higher Education Institutions, and the Natural ScienceFoundation of Education Committee of Jiangsu Province(12KJB150023).

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Study about an Experimental Design for CdTe Quantum Dots Synthesis. Analysis of the Optical and Electrochemical Changes after Their Interaction with Hydroxyl Radicals
Authors: Muñoz Eduardo Carlo , Navarrete Emilio Alonso , Henríquez Rodrigo Gonzalo , Schrebler Ricardo Silvio , Córdova Ricardo Alejandro , Aguilar Luis Felipe , Bravo Manuel Andrés
Published: February 2020

Quantum dots (QDs) are semiconductor nanocrystals with diameters in the range of 2-10 nm (10 to 50 atoms) and which exhibit electronic properties between bulk materials and molecules [[i]]. Considering their optical properties, fluorescence processes exhibit real applications in sensor and biosensors fields. In fact, the fluorescent properties of these materials can be tuned depending on the particle size. Generally, a decrease of the QDs size produces an increase in the energy gap between the valence and the conduction band, which induces to a shifted of the emission wavelength toward shorter values [[ii]].

In this work we examined an optimization of the synthesis parameters of CdTe QDs using a Doehlert experimental design. The synthesis employed Na2TeO3 and CdCl2 as precursors, mercaptosuccinic acid (MSA) as capping agent, NaBH4 as reducing agent and Borax/Citrate as buffer in a reflux system. The synthesis parameters optimized were: temperature, pH, molar ratio of precursors and reaction time.

After, an analysis of the optical and electrochemical changes after the interaction with hydroxyl radicals was carried out. The optical changes were studied by time-resolved fluorescence measurements evaluating the fluorescence lifetime observing different quenching processes. On the other hand, changes in the differential capacitance of the QDs deposited on different electrodes were studied by means of Electrochemical Impedance Spectroscopy (EIS). The changes in these properties were studied in absence and presence of hydroxyl radicals produced by a Fenton reaction.

[
[i]
] Ekimov, A. I. & Onushchenko, A. (1981). "Quantum size effect in three-dimensional microscopic semiconductor crystals". JETP Lett. 34: 345–349.

[
[ii]
] Medintz I L, Clapp A R, Brunel F M, Tiefenbrunn T, Uyeda H T, Chang E L, Deschamps J R, Dawson P E and Mattoussi H. Nature.
Mater. (2006) 5:581.

Figure 1
Electrochemical Analysis of Optical Switchable Filter with a NiO Thin Film for High-Performance Incubators
Authors: Tajima Kazuki , Nakagawa Machiko , Oishi Yoshihisa , Ohta Hidenobu
Published: February 2020

An optical switchable light filter was fabricated from all solid-state materials of ITO/W-Ir-O/Ta2O5/NiO/ITO for use in preterm infant incubators. The materials were fabricated by magnetron sputtering. The as-prepared NiO film was stored in a thermostat/humidistat bath to create the nickel hydroxide, and its basic properties were also investigated by electrochemical and optical analysis. The filter also contained a W-Ir-O thin film, because the widely used WO3 thin film shows an unsuitable electrochromic color change to dark blue. The W-Ir-O thin film did not absorb the longer wavelengths in the visible range, which is required for incubators. The filter changed between pale yellow and dark yellow when a voltage was applied. The fabrication of filters with a suitable color change for incubators requires further investigation.
Preparation and Characterization for Ionic Liquid Coated Graphene Oxide Nanoparticles
Authors: Chen Songqing , Zhu Xiashi
Published: February 2020

The tremendous potential of ionic liquids (ILs) as an alterna-tive to environmentally harmful ordinary organic solvents is well recognized. ILs have attracted extensive attention and gainedpopularity in analytical chemistry [1] covering different application fields like chromatography, electrochemistry or extraction techniques [2].

Three hydrophobic ionic liquids (ILs) including 1-butyl-3- methylimidazole hexafluorophosphate ([BMIM]PF6), 1-hexyl-3-methyl-imidazole hexafluorophosphate ([HMIM]PF6), and 1-octyl-3- methylimidazole hexafluoro- phosphate ([OMIM]PF6) coated graphene oxide (GO) nanoparticles. The synthesized GO@ILs composite materials were characterized by FT-IR spectroscopy and scanning electron microscopy (Fig.1).

The GO@ILs composite materials exhibited much higher specific capacitance than unmodified GO. It would be interesting for future research to 1) evaluate long-term performance over several thousand charge–discharge cycles, 2) control the extent of functionalization with ionic liquids, 3) attempt to decouple double-layer and pseudocapacitance, if possible, and 4) performelectrochemical experiments in ionic liquid electrolytes to open the voltage window and increase energy storage capabilities[3].

Figure 1
Approaches for Extractive Hydrometallurgy of Niobium and Tantalum from Ethiopian Kenticha Ores
Authors: Berhe Goitom Gebreyohannes
Published: February 2020

A Review Approaches for Extractive hydrometallurgy of niobium and tantalum from Ethiopian Kenticha Ores   Abstract

The Kenticha rare-element pegmatite, a globally important tantalite source in the Neoproterozoic of southern Ethiopia, is a highly fractionated, huge, subhorizontal, sheet-like body, discordantly emplaced in ultramafic host rock. It corresponds to the spodumene subtype of the rare element pegmatite class and belongs to the lithium–cesium–tantalum petrogenetic family. The Kenticha pegmatite is asymmetrically zoned from bottom to top into granitic lower zone, spodumene-free intermediate zone, and spodumene-bearing upper zone. The Kenticha pegmatite is rich in Ta-mineralized rare-element pegmatites.  Thus, need to conduct research in enrichment of Ta2O5 and Nb2O5 and extraction of Nb and Ta into metallic form.

This paper reviews the successful extraction of Nb and Ta from tanatlite ores. Its success normally depends on the physiochemical properties of the ore, choice of leaching extraction solvent. Currently, HF and methyl-isobutyl Ketone has been used for decomposition and separation of Nb and Ta from tantalite ore. Therefore Kenticha atantalite ore containe vaiaty compositions of elements and higher concentration of Li and U. Thus needs further investigation in extraction process in the sence of removing the use of HF for leaching and replacement of traditional organic solvents by “Green Solvents”. This review gives directions for future development of extraction of Kenticha tantalite ore.

Keywords: Kenticha; leaching; magnetic separation; pegmatite, rare-element; solvent extraction, sopdumene; tantalite.
Fabrication of TiO2 Based Microspheres By Spray Drying Method and Their Application for Dye-Sensitized Solar Cells
Authors: Mizuno Maho , Tomita Koji , Kunugi Yoshihito
Published: February 2020

Dye-sensitized solar cells (DSSCs) have received considerable attention since Grätzel et.al.reported a high conversion efficiency using nanocrystalline mesoporous TiO2 film. A typical DSSC consists of a transparent conductive oxide, semiconductor oxide, dye sensitizer, electrolyte and counter electrode. The working electrode is a nanoporous semiconductor oxide that is placed on conducting glass and is separated from the counter electrode by only a thin layer of electrolyte solution. The photoanode of DSSCs is typically constructed using a thick film (~20 μm) of TiO2 or, less often, ZnO or SnO2 nanoparticles. The TiO2 film has a large inherent absorptive surface area for light scattering.

Recently, TiO2 microspheres are of great interest for a great deal of applications, especially in the solar cell ﬁeld. Because of their unique microstructure and light-scattering effect, TiO2 microsphere-based solar cells often exhibit superior photovoltaic performance. Hence, exploring new suitable TiO2 microspheres for high-efficiency solar cells is essential. In this study, we reported the fabrication of TiO2microspheres by a simple spray drying process, and applied for Dye-sensitized Solar Cells.

TiO2 Microspheres were fabricated by spray drying method. TiO2 paste was prepared as follows, TiO2 microspheres (0.2g) was mixed into ethanol (1.8g). The resulting TiO2 paste was printed by doctor blade method on fluorine-doped SnO2-coated (FTO) glass electrodes and sintered at 500 °C for 30 min. DSSCs were prepared by a conventional procedure.

   We are successfully fabricated TiO2 microspheres by spray drying method. According to SEM images of the TiO2 microspheres, particle size was ca. 3mm. We made microsphere TiO2 based DSSCs, and their energy conversion efficiency was 6.5% under AM 1.5 simulated full sunlight (100 mW cm−2) illumination.
Selenium-Decorated Graphene for Peroxynitrite Detection
Authors: Kalil Haitham , Maher Shaimaa , Bayachou Mekki
Published: February 2020

Peroxynitrite (PON, ONOO−) is a member of the reactive oxygen-nitrogen species family. PON is generated in vivo by the diffusion-limited reaction (~2×1010 M−1S−1) of nitric oxide (
·
NO) and superoxide (O2

·

−) radicals. Elevated peroxynitrite levels are associated with several human pathologies, such as arthritis, inflammation, and carcinogenesis, as well as ageing-associated diseases. Thus, the precise detection of this species in biological systems is crucial, not only to understand the genesis and causes of ailments at the tissue/cellular level, but also to suggest and design potential therapies.

The essential trace element selenium (Se) is the catalytic cofactor of important endogenous antioxidative systems of the human body. In the past decade, selenium attracted the attention of many research groups for the understanding of fundamental biological functions and biomimetic applications. Selenium is found in several human proteins (selenoproteins), many of them involved in anti-oxidant defense systems. Therefore, selenium plays a key role in redox regulation as a modulator of reactive oxygen species (ROS). Recently, a number of novel synthetic organoselenium compounds has been prepared and used as antioxidants in medicinal chemistry such as ebselen.

In this work, we prepare and investigate interfaces based on the electrochemical deposition of selenium nanoparticles. We prepared surfaces of electrodeposited elemental selenium (Se) and selenium-decorated graphene-based nanostructures on glassy carbon electrodes and carbon fiber microelectrodes. We have used several physicochemical methods to characterize these PON-sensitive interfaces, including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, and UV-vis on ITO transparent electrodes. We tested these interfaces for electrocatalytic sensing of peroxynitrite. We found that selenium-modified graphene platform is sensitive to peroxynitrite in solution, and it provides a viable interface for electrochemical sensing of this analyte. We observed that there is a synergistic effect of the presence of graphene as a substrate for selenium nanoparticles in the electrocatalytic detection of PON. In this paper, we will present our findings using this new PON-sensitive interface. We will compare and contrast the performance of the various modified carbon electrodes in terms of PON sensitivity using cyclic voltammetry and dose-response chronoamperometry.
the Relationship Between Brightness of Aluminum Films Fabricated Using an AlCl3-1-Ethyl-3-Methylimidazolium Chloride-Toluene Bath and Molecular Structure of Additives
Authors: Gunji Takao , Kaneko Shingo , Tanabe Toyokazu , Ohsaka Takeo , Matsumoto Futoshi
Published: February 2020

In our previous study, we showed that the addition of 4-pyridinecarboxylic acid hydrazide (4-PCAH) to an EMIC/AlCl3/toluene mixture improved the brightness of the deposited Al film [1]. The prepared Al films clearly reflect the characters on the surface so that the characters can be read. The reflectivity of the Al surface prepared with EMIC/AlCl3/toluene/4-PCAH was 84% at 450 nm; to the best of our knowledge, this is the highest value achieved. In this study, to elucidate why the addition of 4-PCAH to the EMIC/AlCl3/toluene bath effectively improves the brightness of the electrodeposited Al surfaces, a systematic series of molecules as additives were studied, and the results obtained for each molecule were compared carefully to determine the relationship between the brightness of the prepared Al surface and the molecular structure of the additive.

The effect of additives, such as 4-PCAH and its analogs, on the surface brightness, electrodeposition efficiency and chemical composition of prepared Al films was examined using SEM, visible light reflectance measurements and XPS. The decrease in the surface roughness of the Al films causes the high surface brightness. The strong relationship (Fig. 1) between the high brightness and molecular structure of the additives included in the bath was elucidated via a systematic study of various additives. 4-PCAH achieved the highest surface brightness of the electrodeposited Al films prepared with various additives used in this study.

[1] X. Fang, K. Uehara, S. Kaneko, S. Sato, T. Tanabe, T. Gunji, F. Matsumoto, Electrochemistry 84 (2016) 17-24.

Figure 1. (A)Micrographs of the Al film surfaces obtained by the electrodeposition of Al from EMIC/AlCl3/toluene/4-PCAH baths, (B) Summary of the relationship between the reflectance of the prepared Al films at a wavelength of 450 nm and the molecular structure of the additive. Preparation conditions of the Al film: deposition time 2 h, constant current density 8 mAcm-2; bath composition: EMIC:AlCl3= 33.3 : 66.7 (mol%), toluene concentration: 9.25 M, additive concentration: 1.8 mM.

Figure 1
Electrochemical Properties of High-Voltage Spinel Positive Electrodes Prepared with Non-Fluorine PAN-Based Binders
Authors: Tanaka Shinichi , Narutomi Takuya , Suzuki Shigeru , Yabuuchi Naoaki
Published: February 2020

For the application of lithium batteries with high energy density, high voltage spinel oxides are considered as promising candidates for a positive electrode of rechargeable lithium batteries. However, it is needed to reexamine the battery components including, electrolyte, conductive carbon, separator, and binder. In this study, we focused on the polyacrylonitrile (PAN) possessing high oxidation resistive properties, and synthesized non-fluorine PAN-based copolymer prepared by graft polymerization of PAN and an adhesive polymer. Electrochemical properties of LiNi1/2Mn3/2O4composite electrodes prepared with PAN-based copolymer are examined and compared with those of PVdF used as the binder.

LiNi1/2Mn3/2O4 was prepared by solid-state reaction from stoichiometric amounts of Li2CO3, NiCO3･2Ni(OH)2･4H2O, and MnCO3 at 1000 °C for 12 h followed by heating at 700 °C for 48 h in air.[1] Thus obtained sample was used as the positive electrode active material. PVdF (TA6010, Solvay) and non-fluorine PAN-based copolymer were used as binders. The electrode active material (AM) and acetylene black (AB, HS-100, Denka) were mixed with the binders, and NMP was added to adjust the viscosity of slurry. The slurry was uniformly pasted on to aluminum foil, and then dried in a vacuum. Compositions of electrodes were AM : AB : PVdF = 80 : 10 : 10 and AM : AB : PAN-based polymer = 80 : 10 : 5 in weight ratios. Electrochemical measurement was carried out using a two-electrode cell (TJ-AC, Tomcell Japan) consisting of the composite electrode, separator (polyolefin microporous membrane), electrolyte solution (LiPF6dissolved in EC : DMC = 3 : 7 by volume) and Li foil as a negative electrode.

Electrochemical properties of the LiNi1/2Mn3/2O4 composite electrodes prepared with different binders are compared in Li cells at 50 oC in Figure 1a. Reversible capacity of the composite electrode with non-fluorine PAN-based polymer reaches >130 mAh g-1 after the 30 cycles test, which is much better than that of PVdF. Moreover, Coulombic efficiency for charge/discharge cycles at 50 oC is effectively improved by using non-fluorine PAN-based polymer as the binder as shown in Figure 1b. A study on X-ray photoelectron spectroscopy reveals that the PAN-based binder has better coatability for active materials and conductive carbons compared with PVdF. Electrolyte decomposition at elevated temperatures is proposed to be suppressed by difference in coatability as the binder.

Together with these results, we will further discuss mechanisms of improved electrochemical properties by using non-fluorine PAN-based binders and possibility of rechargeable lithium batteries with the high-voltage positive electrode.

References

 [1] K. Ariyoshi, Y. Iwakoshi, N. Nakayama, and T. Ohzuku. J. Electrochem. Soc., 151, A296 (2004).

Figure 1
Selective Copper Electrodeposition to a 3D Copper Nanostructure
Authors: Kobayashi Yuma , Arai Susumu
Published: February 2020

Introduction

Three-dimensional (3D) copper nanostructures are expected to be applied as current collectors for lithium ion battery anodes due to their high electrical conductivity and large specific surface area. The production of 3D copper nanostructures usually requires complicated fabrication steps; however, we have developed a simple method for the production of 3D copper nanostructures.1) There is a disadvantage with this method in that the 3D copper nanostructure is likely to collapse due to low mechanical strength. Reinforcement of the 3D structures is thus considered to be one of the most effective methods to address this problem. This study aims to develop a reinforcement technology using a plating method that is applied after fabrication of the 3D copper nanostructures. The reinforcement technology employed here was viafilling plating technology. This technology is also expected to improve the adhesion to the substrate by selectively depositing copper to the bottom of the 3D nanostructure.

Experimental

A 3D copper nanostructure plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + 3×10-4 M polyacrylic acid) and a selective copper plating bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4 + additives) were prepared. A copper sulfate bath that does not contain additives was also employed for comparison. Pure copper and phosphorus-containing copper plates were used as the cathode and anode, respectively. Electrodeposition was conducted under galvanostatic conditions (1 A dm-2) without agitation at 25 °C. In addition, the influence of agitation on selective copper deposition was also investigated. Air agitation, magnetic stirring and a cathode rocker were used. The phase structure and microstructure of the deposits were analyzed using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively.

Results and discussion

Figures 1a and 1d show a surface and cross-sectional SEM images of the 3D copper nanostructure before selective copper electrodeposition. Figure 1b shows a surface SEM image of the 3D copper nanostructure after electrodeposition without additives. The 3D nanostructure was not observed, because copper was deposited on the surface of the 3D nanostructure. The 3D nanostructure seems to have been deformed by the copper deposited on the surface, according to cross-sectional observations (Fig. 1e).Figure 1c shows a surface SEM image of the 3D copper nanostructure after electrodeposition with additives. The surface morphology is almost the same as the bare 3D nanostructure shown in Figure 1a because copper deposition at the surface of the 3D nanostructure is suppressed. Thus, the 3D nanostructure was maintained, and copper was deposited selectively at the boundary of the 3D nanostructure and the substrate, according to cross-sectional observations (Fig. 1f). Agitation also affected the selective copper deposition, and the results of agitation tests will be discussed at the meeting.

References

S. Arai and T. Kitamura, ECS Electrochem. Lett., 3(5), D7-D9 (2014).

Figure 1
Synthesis of Atomically Thin Pt Monolayer on HOPG
Authors: Kuroiwa Eri , Takimoto Daisuke , Nutariya Jeerapat , Shen Zhongrong , Ayato Yusuke , Mochizuki Dai , Sugimoto Wataru
Published: February 2020

High specific surface area is essential for Pt electrocatalyst. However, nanoparticles become less stable as the particle size decreases. Two-dimensional nanosheets are expected to have comparable or ever larger specific surface area than nanoparticles. Furthermore, nanosheets should be more stable than nanoparticles due to the two-dimensional bonding.

 Synthesis of Pt nanosheets with 1 nm thickness has previously been reported1). However, non-reactive Pt atoms still exist in the core of nanosheets, thus the utilization of Pt may be low. The purpose of this research is the synthesis of Pt nanosheets with atomic-scale thickness (nanosheets with 1 or 2 Pt monolayers).

 Highly oriented pyrolytic graphite (HOPG) was freshly cleaved using adhesive tape and then immersed into a diluted RuO2 nanosheet colloid for 2 minutes to coat RuO2 nanosheets on HOPG (RuO2 nanosheet/HOPG). Atomically thin Pt monolayer was deposited on the surface of RuO2 nanosheet/HOPG by vacuum evaporation2). Cyclic voltammetry was conducted to dissolve the RuO2nanosheets. The morphology and thickness were characterized by atomic force microscopy (AFM), and the chemical state of the nanosheets on HOPG was determined by X-ray photoelectron spectroscopy (XPS).

Redox peaks at ~0.1, 0.65, 0.8 vs. RHE, which are characteristic of RuO2 nanosheets, disappeared after potential cycling between 0.05 and 1.55 V vs. RHE for 50 cycles, suggesting the dissolution of RuO2 nanosheets. AFM observation showed that the thickness of RuO2 nanosheets were 1.11±0.18 nm and the thickness of the as-deposited Pt on RuO2 nanosheets were 0.34±0.25 nm. Taking into account of the diameter of Pt atom as 0.28 nm, 1-2 monolayer of Pt was deposited on RuO2 nanosheets. The thickness of the nanosheet after cycling decreased to 0.40±0.08 nm, agreeing with the dissolution of the RuO2 support. The chemical state of Pt and Ru before and after electrochemical dissolution was studied by XPS. Pt 4f5/2 and Pt 4f7/2 peaks were observed before and after cycling, while Ru 3p1/2, Ru 3p3/2 peaks disappeared after cycling. Based on CV, AFM and XPS analysis, it is concluded that a Pt monolayer with atomic thickness was successfully prepared on HOPG by using RuO2 nanosheets as a structure directing scaffold and subsequent dissolution of RuO2nanosheets.

1) A. Funatsu, H. Tateishi, K. Hatakeyama, Y. Fukunaga, T. Taniguchi, M. Koinuma, H. Matsuura, and Y. Matsumoto, Chem. Commun., 50, 8503 (2014).

2) Q. Liu, C. Chauvin, and W. Sugimoto, J. Electrochem. Soc., 161, F360 (2014).

Figure 1
Influence of Hydrogen Adsorption on Electrodeposition of Platinum from Chloro Complex Solution
Authors: Yokoyama Ayano , Hagihara Taizo , Fukumuro Naoki , Yae Shinji
Published: February 2020

Platinum (Pt) is widely used as insoluble and catalytic electrodes for electrolysis, automotive catalytic converters, and fuel cells. We have been investigating hydrogen incorporation in electrodeposited metal films and its influence on crystal structure of metals (1-3). It was reported that large amount of hydrogen (content in atomic ratio: x = H/Pt = 0.1) is incorporated in the Pt films electrodeposited from a solution including dinitrosulfatoplatinate(II) (H2Pt(NO2)2SO4, DNS) as a metal source. In this study, an electrochemical quartz crystal microbalance (EQCM) method (4) is used to examine influence of hydrogen adsorption on the electrodeposition and hydrogen incorporation into deposited films of Pt from a chloro complex solution. 

The current-potential and mass increase (Pt deposition rate)-potential curves in 0.024 mol dm-3 K2PtCl4solution adjusted at pH of 0.8 with HCl were measured using an EQCM system (Hokuto Denko, HQ-101D and HZ-5000). A quartz electrode coated with Au, an Ag/AgCl electrode, and a Pt wire were used as the working, reference, and counter electrodes, respectively. The hydrogen content of samples was measured by thermal desorption spectroscopy (TDS). 

Figure 1 shows the current density and mass increase rate versus electrode potential curves for the chloro complex solution. In the first forward potential sweep toward negative potentials of Fig. 1(a), the cathode current and deposition rate of Pt started increasing at +0.3 V vs. Ag/AgCl. Peaks for cathode current and deposition rate appeared at -0.19 V. The current efficiency was 74% at this peak. Then, as the potential was swept to lower potentials, the deposition rate and current efficiency decreased. This decrease in the current efficiency of Pt deposition is caused by hydrogen adsorption. In the return potential sweep (Fig.1 (b)), the cathode current and Pt deposition steeply increased by hydrogen desorption from the Pt surface, and the current efficiency was 113% at the potential of -0.25 V. The hydrogen content of Pt-electrodeposited Au foil (Pt: 1 μm and Au: 20 μm in thickness) increased as the deposition potential of Pt decreased from 0 to -0.3 V, and was much lower than that deposited from the DNS solution. 

Acknowledgements

The present work was partly supported by JSPS KAKENHI (26289276).

 

References

N. Fukumuro, M. Yokota, S. Yae, H. Matsuda, Y. Fukai, J. Alloys Compd., 580, S55 (2013).

N. Fukumuro, S. Kojima, M. Fujino, Y. Mizuta, T. Maruo, S. Yae, Y. Fukai, J. Alloys Compd., 645, S404 (2015).

N. Hisanaga, N. Fukumuro, S. Yae, H. Matsuda, ECS Trans., 50, 77 (2013).

T. Hagihara, K. Yaori, K. Iwakura, N, Fukumuro, S. Yae, Electrochim. Acta, 176, 65 (2015).

Figure 1
Preparation of High Durable Catalyst By Morphological Change of Carbon Support for PEMFC
Authors: Na Hyunwoong , Oh JI-Won , Cho Yong Soo , Choi Hanshin
Published: February 2020

Modified carbon was used as catalyst (Pt) support in polymer electrolyte membrane fuel cells (PEMFC) with the aim of increasing its effectiveness towards the durability. The modified carbon which is formed graphitic carbon (GC) encapsulated nickel nanoparticle on the carbon black surface. It was synthesized by vacuum arc deposition process and then annealing at 723K. GC/Ni/C modified support was achieved by dissolution & precipitation reaction followed by Ni-C binary system. Samples containing 15 wt.% in Ni were prepared and characterized by XRD, TGA and HRTEM analysis. Structural and morphological analyses of the samples showed that the FCC, HCP, Ni3C structure of Ni is existed after Ni deposition. The HRTEM analysis of the samples showed a precipitated carbon which have high crystallinity of nickel surface. The electro-catalyst durable performance was evaluated by 1,500 repetition cycles of anodic sweeping to 1.7 V containing the catalyst. (5 wt.% Pt). The results were also compared to the performance of a commercial catalyst tested in the same way.
Electrocatalysts for Oxygen Reduction Reaction Synthesized from Co-Facial Cobalt Porphyrin and Graphene Oxide
Authors: Yoneuchi Tsubasa , Kato Masaru , Yagi Ichizo
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are used as energy devices, which produce no CO2. Because the Oxygen reduction reaction (ORR) is slow, it limits performance of PEFCs. The ORR involves four-electron reduction (O2 + 4H+ + 4e- → 2H2O) or two-electron reduction (O2 + 2H+ + 2e- → H2O2). The ideal reaction is four-electron reduction. When hydrogen peroxide reacts metal ions in PEFCs, hydroxyl radicals are formed. The radical species induce decomposition of polymer electrolyte membrane in PEFCs. Thereby, the selectivity of the four-electron reduction is an important factor for electrocatalyst development.

In addition, electrocatalysts with higher ORR activity are needed. At the present, platinum group metal alloys (PGMs) are used as ORR electrocatalysts in PEFCs. Since PGMs are expensive and their reserves are limited, electrocatalysts based on earth abundant elements should be prepared. Non-PGM electrocatalysts for the ORR have been intensively studied. For example, Fe- or Co-based electrocatalysts prepared in pyrolysis from carbon and Fe- or Co-based materials.[1,2]These non-PGM electrocatalysts are known to exhibit high catalytic activity for the ORR.

Herein we report the synthesis of a non-PGM electrocatalyst with co-facial cobalt active sites and its catalytic activity and selectivity for the ORR. The catalyst was prepared in the pyrolysis process at 900oC for 45 s from two precursors: graphene oxide and a co-facial cobalt porphyrin ion pair. The co-facial cobalt porphyrin ion pair have high selectivity of the four-electron reduction.[3,4] To study the ORR catalytic activity and selectivity, linear sweep voltammetry of the electrocatalyst was recorded at three pHs (pH 1, pH 7, and pH 13) under oxygen. The ORR activity improved with increasing pH and the activity at pH 13 was higher than that of Pt/C. The electrocatalyst showed the highest four-electron selectivity (< 10% H2O2) at pH 13.

We conclude that the ORR activity and selectivity of the electrocatalyst are improved by pyrolysis process.

References

[1] K. Kamiya, K. Hashimoto, S. Nakanishi, Chem. Commun., 48, 10213-10215(2012).

[2] G. Wu, K. L. More, C. M. Johnson, P. Zelenay, Science, 332, 443-447(2011).

[3] J. P. Collman, P. Denisevich, Y. Konai, M. Marrocco, C. Koval, F. C. Anson, J. Am. Chem. Soc., 102, 6027-6036(1980).

[4] A. J. Olaya, D. Schaming, P. F. Brevet, H. Nagatani, T. Zimmermann, J. Vanicek, H. J. Xu, C. P. Gros, J. M. Barbe, H. H. Girault, J. Am. Chem. Soc., 134, 498−506(2012).
Fabrication of Electrochemically Controllable Micropumping System Based on Concentration Gradient of Protons Between Two Gold Microelectrodes
Authors: Fujiwara Hiroki , Shitanda Isao , Hoshi Yoshinao , Itagaki Masayuki , Motosuke Masahiro
Published: February 2020

Design of a micropump is important topic for controlling solution flow in a microchip 1). In this study, we newly fabricated a new electrochemically controllable micropumping system which operates by creating a concentration gradient of protons on two gold microelectrodes. Figure 1 show a schematic illustration of the principle of the pumping system. When anodic and cathodic reactions of hydrogen peroxide occurs on the each gold electrode surface, protons generated on the anode flow thorough the cathode. The protons are normally hydrated in an aqueous solution. Thus, localized water flow generates near the gold microelectrode surfaces.

The gold microelectrodes (5 נ100 um2) were fabricated by photolithography. A microchannel in a microchip was formed by using polydimethylsiloxane (PDMS, 500 um width, 50 um height, 2.5 cm length). 5% hydrogen peroxide solution containing fluorescent substance- modified polystyrene (PS) particle was filled in the microchannel. A polarization curve was measured by using a potentiostat. Current increase was observed from 0 V. Current noise due to oxygenbubble generation occurred when applying the voltage of 0.6 V. Thus the moving direction of the polystyrene particles were observed using a fluorescent microscope while applying a constant voltage of 0.5 V between the gold microelectrodes. PS particles were adsorbed electrostatically on the anode surface when applied a constant voltage of 0.5 V. Next, when stopping the voltage application, the PS particles drastically moved opposite direction of the proton flow (Fig. 1). It is considered that the PS particles moved due to the reaction of water flow 2). We discussed in the moving principle more detail in our presentation.

Reference

1) H. Zhang, W. Duan, M. Lu, X. Zhao, T. J. Huang and A. Sen, Acs Nano, 8 (2014) 8537-8542.

2) J. Wang, Acs Nano, 3 (2009) 4-9.

Figure 1
Screen-Printed Paper-Based Impedimetric Sensor Using Flexible Silver Ink for Sweat Conductivity Measurement
Authors: Watanabe Kazuki , Shitanda Isao , Hoshi Yoshinao , Itagaki Masayuki
Published: February 2020

Recently, electrochemical wearable devices have been attracted attention as a device for evaluating the health condition. Flexibility of a substrate and conductive wiring with low cost is key point to attach the sensor on the human body . Our group has reported several paper-based biosensor and biofuel cells [1,2]. A printable paper-based devise is suitable for disposable wearable sensors.

In this study, we newly prepared a flexible silver ink as a conductive wiring, and a flexible electrochemical impedimetric sensor was fabricated by screen printing using Japanese paper with surgical tape as the substrate for measurement of sweat conductivity. Flexible silver ink was prepared by mixing a silver flakes (Fukuda Metal Foil Powder Co.) and a urethane resin (Dispercoll U42, Sumika Bayer Co. Ltd.) with a commercially available silver ink. Figure 1 shows the schematic illustration of the sensor. Silver wiring was prepared by printing of the flexible silver ink mentioned above on the surgical tape having two holes. The durability of the silver wiring was evaluated by bending test, in which the silver wiring was bended with a constant curvature at 50 times. Commercially available carbon ink was printed on the Japanese paper as a sensor part. It is noted that the carbon layer and silver wiring were connected through the holes on the surgical tape. A conductivity of a test solution (artificial sweat) in the paper was determined by electrochemical impedance measurement. The conductivity of the solution was compared with that estimated using a commercially available conductivity meter (Toa DKK made, CM-25G). The durability of the silver wiring using the silver flake and urethane resin was drastically improved, comparing with that using only commercially available silver ink. The increasing rate of the resistance of the silver wiring using the silver flake and urethane resin after the bending test was 260%. On the other hand, that using only the commercially available silver ink was 580%. Cracks on the silver wiring were found to be suppressed by using the urethane resin. The silver flakes have a role as a binder to connect between silver particles in the ink. The conductivity of the artificial sweat in the paper measured by the sensor was good agreement with that measured by the conductivity meter. Furthermore, in the present paper, we measured change in a human sweat conductivity during the exercise using our wearable sensor.

References

[1] S. Kato, et al.
Chem. Commun.
, 2013,49, 11110-11112

[2] T. Yamaguchi, et al. Chemistry Letters, 2013, 42, 1369-1370

Figure 1