bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrasensitive CuInS2 Quantum Dots for Detection of Nickel Ions in Drinking Water
Authors: Abdel-Fattah Tarek M , Ebrahim Shaker , Ali Magdy , El Nady Jehan , Soliman Moataz 
Published: February 2020

Quantum dots (QDs) have been applied in many research fields such as chemistry, biology and medicine because of their unique physical-chemical properties such as broad absorption spectra, narrow symmetric emission bands and high photo-stability [1]. QDs showed great promises for detection of organic and inorganic analysts. For example, CuInS2 as QDs have been used for detection of ascorbic acid and folic acid [2]. In this study, a sensitive and simple method based on the fluorescence quenching of CuInS2 quantum dots (QDs) were used for the determination of nickel ions (Ni(II) ions) in drinking water samples. Water-soluble and biocompatible 3-mercaptopropionic acid-capped CuInS2 QDs was synthesized by one step aqueous route. The fluorescence intensity of synthesized QDs significantly decreased in the presence of Ni(II) ions. The emission intensity of CuInS2 QDs has an inversely proportional with the concentration of Ni(II) a linear fit with negative slope. The detection range was for Ni2+ concentration in the range of 133 to 2133 ppm. The method showed good sensitivity and was satisfactorily applied to the determination of Ni2+ contamination in real water samples, obtained from tap water.

References:

[1] Liang JG, Huang S, Zeng DY, He Z, Ji X, Ai X, et al. CdSe quantum dots as luminescent probes for spironolactone determination. Talanta 2006; 69:126–30.
[2]Liu SY, Hua JJ, Su XG. Detection of ascorbic acid and folic acid based on water-soluble CuInS2 quantum dots. Analyst 2012; 137:4598–604.
Etching Studies of Mo in Aqueous Solutions
Authors: Lee Sang-Min , Jung Chan-Yong , Lee Chi-Woo 
Published: February 2020

Molybdenum (Mo) has been a choice of substrate metal for chalcopyrite or kesterite solar cells because of its low thermal expansion coefficient, high melting point, good thermal and electrical conductivity, and high wear resistance. Mo surface, however, is almost always covered with molybdenum oxides, unless kinetic limitations prevail. Previously, we reported the mild electrochemical conditions of forming molybdenum blue as well as molybdenum oxides colored in yellow and red in aqueous solutions. Figure 1 shows the representative changes in resonance frequency and current observed when the potential was applied to the molybdenum/quartz in aqueous solutions. The starting potential was –0.7 V, where the resonance frequency was set to be at the base line. As the potential was scanned up to –0.1 V, apparently the anodic current flew and simultaneously the resonance frequency increased. Near –0.1 V, the sharp increase in current as well as resonance frequency was observed, suggesting the significant dissolution of molybdenum into the solution as molybdenum ions. In this work we wish to report the results of electrochemical quartz crystal microbalance studies of etching of molybdenum in aqueous solutions. The present results may be important in relation to cleaning or polishing of molybdenum, which has been traditionally performed in strong acidic solutions such as mixtures of phosphoric acid and sulfuric acid. Details will be presented at the meeting.
Acknowledgements
Acknowledgements are made for SACHEM’s supply of some samples used in this work. Helpful discussions with Drs. Craig Allen and Paul Vermeulen are greatfully acknowledged.
References.
1. Sang-Min Lee, Young-Ho Kim, Mi-Kyung Oh, Suk-In Hong, Hang-Ju Ko, and Chi-Woo Lee, J. Korean Electrochem. Soc. 13, 89-95 (2010).
2. Sang-Min Lee and Chi-Woo Lee, Bull. Korean Chem. Soc. 33, 1443 (2012)
3. Viswanathan S. Saji and Chi-Woo Lee, Electrochem. Acta, 137, 647-653 (2014).
4. Viswanathan S. Saji, Chan-Yong Jung and Chi-Woo Lee, J. Electrochem. Soc. 162, D465-D479, (2015).

Figure 1
Mechanistic Study of Methanol Oxidation over Platinum Electrode in Alkaline Aqueous Solutions
Authors: Kubota Ryoma , Okanishi Takeou , Muroyama Hiroki , Matsui Toshiaki , Eguchi Koichi 
Published: February 2020

Hydrogen is a clean fuel for stationary, mobile and transportation applications, particularly for fuel cells, but its storage and delivery are still major issues. To overcome these problems, hydrogen has been stored and transported via other chemical compounds, such as alcohols, hydrocarbons, ammonia, etc. Methanol is a promising hydrogen career due to its high volumetric energy density and ease in handling and storage. Direct methanol fuel cells (DMFCs) have been mainly studied with acidic electrolytes and the methanol oxidation mechanism has been clarified to some extent in recent years [1]. However, rare and expensive Pt–based electrocatalysts are normally used in DMFCs. One promising approach to improve this problem is using alkaline electrolytes because of the potential use of non–Pt catalysts. Nevertheless, there are few studies on the methanol oxidation mechanism in alkaline media. In this study, the electrochemical oxidation of methanol over Pt electrode in an alkaline solution was investigated using linear sweep voltammetry and in situ attenuated total reflection infrared (ATR–IR) spectroscopy.
The oxidation current of methanol was observed at approximately 0.4–0.9 V in 0.25 M KOH–0.25 M CH3OH in the linear sweep voltammogram (LSV). In the time–resolved IR spectra acquired simultaneously with the LSV, two characteristic bands ascribable to the adsorbed formic acid species (HCOOad) were detected at 1800 cm–1 and 2000 cm–1 in the potential range of 0.1–0.3 V, and their intensity decreased with an increase in potential [2]. Alternatively, the new bands attributable to the aldehyde species (H
x
CHOad) appeared at 0.2 V in the same wavenumber range. These bands shifted to higher wavenumber with a rise in the potential probably due to the dipole–dipole coupling effect [3], and disappeared above 0.8 V. These results clarified that the formic acid species was oxidized in the initial step of methanol oxidation, followed by the aldehyde species.
Therefore, aldehyde species and formic acid species were found to be the intermediates of the methanol oxidation. Since the aldehyde species existed over Pt electrode even at higher potential of 0.8 V, the development of the electrocatalysts active for the H
x
CHOad oxidation reaction will be required for the enhancement of methanol oxidation in alkaline media.
REFERENCES
[1] N. M. Markovic, H. A. Gasteiger, P. N. Ross Jr, Electrochim. Acta, 40 (1995) 91–98
[2] G. Samjeske, M. Osawa, Angew. Chem. Int. Ed., 117 (2005) 5840–5844.
[3] Y. Y. Yang, J. Ren, H. X. Zhang, Z.Y. Zhou, S. G. Sun, W. B. Cai, Langmuir, 29 (2013) 1709–1716.
Crystal Structures and Electrochemical Properties of Li2TiO3 - LiMeO2 (Me = Cr, V and Mn) Binary System
Authors: Kobayashi Yuki , Yabuuchi Naoaki 
Published: February 2020

Lithium ion batteries are used not only as power sources for portable electronic devices but also for electric vehicles, and the demand for further increase in the energy density is still growing. In this study, we focus on the layered oxide, Li2TiO3, and trivalent chromium, vanadium and manganese ions are substituted for lithium and titanium ions according to the formula of x Li2TiO3 – (1 – x) LiMeO2 (x = 0.5; Me = Cr, V and Mn) binary system. These samples are further reformulated as Li1.2Ti0.4Me0.4O2. Li1.2Ti0.4Me0.4O2 samples were prepared by solid-state reaction from stoichiometric amounts of Li2CO3, TiO2 (anatase type), Cr2O3, V2O3 and Mn2O3 at 900 – 1100 oC in Ar. The results of X-ray diffraction and structural analysis by Rietveld analysis on Li1.2Ti0.4Me0.4O2 (Me = Cr, V and Mn) samples reveal that crystal structures of the samples are different depending on the substituted ions. The Cr- and V-substituted samples crystallize into a layered rocksalt structure (α-NaFeO2 type). Perfect cation ordering is found for the Cr-substituted sample whereas partial anti-site defects between lithium sites (3b sites) and transition metal sites (3a sites) are noted for the V-substituted sample. In contrast, the Mn-substituted sample crystallizes into a cation disordered rocksalt structure. Electrochemical properties of Li1.2Ti0.4Me0.4O2 (Me = Cr, V and Mn) after ball-milling with carbon are evaluated in Li cells at room temperature or 50 oC (Figure 1). Although Li2TiO3 is electrochemically inactive, Li1.2Ti0.4Me0.4O2 delivers reversible capacities of >200 mAh g–1. Reversible capacity of the Mn-substituted sample reaches 300 mAh g–1 at 50 oC, and moreover such large capacity originates from the charge compensation by oxide ions.[1]
From these results, we will discuss the possibility of Li2TiO3-based electrode materials as positive electrode materials for rechargeable lithium batteries.

Reference

[1] N. Yabuuchi, Y. Kobayashi et al., submitted.

Figure 1
A Study on Making a Stable Loop Profile and Improving Bonding Time in Wire Bonding Process
Authors: Nam KwanHyub , Ryu JangWoo , Lee Sungho , Kim Hyunjoong 
Published: February 2020

Wire bonding is one of the most important processes in assembly of semiconductor. And the most competitive technology in wire bonding is making advanced loop profile. Therefore, as the growth of high-density and high-stacked die packages, it is essential to develop a highly lowed loop profile because wire bonding process is so sensitive in the semiconductor trend. Making a lowed loop profile is a key technology for today’s wire bonders. However, the conventional Folded Loop (FL) profile always accompanies many problems, such as critical faults due to un-stability at the neck of wire loop and long bonding time due to a lot of folding steps. These kinds of problems cause much of the un-efficient operation in the wire bonding. Therefore, we should develop an advanced loop profile to meet using more stable loop profile and applying speedy bonding time. The usual folded type loop profile can be developed by improving the shape of wire neck formation and reducing the kink steps for making lowed neck formation. In this paper, we propose a Very-Very Lowed Loop (VVLL) profile and it is the improved method to realize a fast and reliable loop profile in wire bonding process.
Fig.1 shows that the result of the conventional FL profile and its 6-folding steps.
Fig.2 describes 4-folding steps of the proposed VVLL profile and the bonding results.
Fig.3 includes the critical problems of FL profile appeared at the loop neck position. Cracks are caused by 6-folding steps and direct touching of a capillary tool. In addition, the loop variation is also happened due to bouncing effects while realizing loop trajectory.
Fig.4 depicts the advantages of VVLL. By decreasing the number of bending steps, it is possible to deconcentrate the stress and to reduce variation in the neck position of wire loop.
Fig5 is shown how the one cycle bonding time is speedy by converting the folding method from FL to VVLL. It can reduce 2-steps of folding motion.
To sum up, VVLL profile is significantly efficient to realize a fairly lowed and stable loop profile for state of the art high-tech semiconductor.

REFERENCE

Harman, George G. Wire bonding in microelectronics. McGraw-Hill, 2010

Brunner, Jon, Ivy Wei Qin, and Bob Chylak. "Advanced wire bond looping technology for emerging packages." Electronics Manufacturing Technology Symposium, 2004.

Wang, Fuliang, Yun Chen, and Lei Han. "Modeling and experimental study of the kink formation process in wire bonding." Semiconductor Manufacturing, IEEE Transactions on 27.1 (2014): 51-59.

Figure 1
Deposition and Dissolution of Lithium through a Lithium Carbonate Thin Film in an Ionic Liquid Electrolyte
Authors: Kotake Hiroki , Tachikawa Naoki , Yoshii Kazuki , Katayama Yasushi 
Published: February 2020

Li-ion batteries are used widely for portable energy storages because of large capacity. Generally, the carbonate-based organic solvents are used as the electrolytes. Most of these organic solvents decompose during the first charge, resulting in formation of the solid electrolyte interphase (SEI) film, which plays an important role for Li-ion batteries on the active materials. Although there are many reports about the SEI film, its nature and function have not been clarified yet. We have already reported that lithium phosphorous oxynitride (LiPON) film acts as an artificial SEI film in 1-butyl-1-methylpyrrolidinium (BMP+) and 1-ethyl-3-methylimidazolium (EMI+) bis(trifluoromethylsulfonyl)amide (TFSA–) ionic liquids containing LiTFSA, and LiTFSA-glyme solvate ionic liquid. [1,2] Ionic liquids are expected to be the alternative electrolytes for Li-ion batteries, since ionic liquids have low flammability and low volatility, which are expected to improve safety of the batteries. However, the SEI film formed by the decomposition of ionic liquids is not preferable for deposition and dissolution of lithium. In this study, deposition and dissolution of lithium through a Li2CO3 thin film prepared by RF magnetron sputtering were investigated in BMPTFSA containing LiTFSA.
The Li2CO3 thin film was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractrometer, and X-ray photoelectron spectrometer (XPS). All the electrochemical measurements were performed using an airtight three-electrode cell. The Ni electrode with or without the Li2CO3 thin film was used as a working electrode. Li foil was used as a reference and counter electrode. After electrochemical measurements, the electrode was washed with dimethyl carbonate (DMC) and characterized by SEM and XPS.
SEM observation and XPS measurement showed that the Ni substrate was covered with the Li2CO3 thin film completely. The Li2CO3 thin film on the substrate was X-ray amorphous. However, the crystalline domains were observed sparsely by TEM observation. The deposition and dissolution of lithium were possible through the Li2CO3 thin film in BMPTFSA containing 1 M LiTFSA. Although the cathodic current attributed to the decomposition of the electrolytes was observed on the Ni electrode, it was suppressed on the Ni electrode with the Li2CO3 thin film. These results indicate that the Li2CO3 thin film has the possibility to act as an artificial SEI film. The depth analysis by XPS revealed that lithium deposited between the Li2CO3 thin film and Ni electrode. From AC impedance measurement, the ionic conductivity of the Li2CO3 thin film was estimated to be 1.3 × 10−8 S cm−1.

References
[1] N. Tachikawa, R. Furuya, K. Yoshii, M. Watanabe, Y. Katayama, Electrochemistry, 83, 846 (2015).
[2] R. Furuya, N. Tachikawa, K. Yoshii, Y. Katayama, and T. Miura, J. Electrochem. Soc., 162, H634 (2015).
Noncovalent Functionalization�of Quinone Derivatives on 2D Graphene for High Performance Pseudocapacitive Electrodes
Authors: Boota Muhammad , Chen Chi , Bécuwe Matthieu , Miao Ling , Gogotsi Yury 
Published: February 2020

Redox-active organic materials have recently gained significant attention from small to large scale energy storage systems due to their natural abundance and sustainability.1,2 However, they degrade upon moderate cycling mainly due to their poor conductivity, which limits their usage. One option to tackle this issue is to deposit organic materials on conductive carbons. Herein, we report 3D interconnected xerogel composed of 2,5-dimethoxy-1,4-benzoquinone (DMQ) decorated on reduced graphene oxide sheets (DMQ@rGO), via one-step hydrothermal method. The DMQ performed dual role in the composite: 1) it provided high redox capacitance and 2) served as a spacer to mitigate rGO sheet aggregation. When binder-free optimized composition of DMQ@rGO was tested as a pseudocapacitive electrode, it showed high capacitance (650 F/g, 780 F/cm3 at 5 mV/s) and excellent capacitance retention of 99% after 25000 cycles at 50 mV/s in 1 M H2SO4. Furthermore, we used density functional theory calculations to explore the charge storage mechanism, binding energies, adsorption orientation of the molecules, charge redistribution and density of the states.

References:

1 B. Huskinson, M. P. Marshak, C. Suh, S. Er, M. R. Gerhardt, C. J. Galvin, X. Chen, A. Aspuru-Guzik, R. G. Gordon and M. J. Aziz, Nature, 2014, 505, 195–8.
2 M. Boota, B. Anasori, C. Voigt, M.-Q. Zhao, M. W. Barsoum and Y. Gogotsi, Adv. Mater., 2015, 28, 1517–22.
Vertical Distribution of Ammonium Ion Concentration to the Air-Cathode of a Single-Chamber Microbial Fuel Cell
Authors: Motoyama Ayuri , Ichihashi Osamu , Hirooka Kayako 
Published: February 2020

A microbial fuel cell (MFC) is a promising technology for wastewater treatment that can achieve removal of organic matter from wastewater and electricity generation simultaneously. In addition, it is known that not only organic matter but also ammonia in wastewater can be removed by single chamber microbial fuel cell (SCMFC). However, little is known of this ammonia removal mechanism. Some researchers reported that reduction of ammonium ion concentration occurred through biological nitrification / denitrification process by biofilm on the surface of an air-cathode in the SCMFC. Meanwhile, there is another hypothesis that ammonia volatilization occurs through the air-cathode as a result of decrease in the degree of ammonia dissociation and promotion of conversion to ammonia molecule, induced by local pH increase near the air-cathode. However, no direct evidence about the ammonia volatilization has not been reported. Therefore, in this study, SCMFC with a new (biofilm-less) air-cathode was operated and vertical distribution of ammonium ion concentration to the air-cathode was measured. If ammonia volatilization occurs, a sharp decrease in the concentration must be observed near the air-cathode. In our previous study, the vertical pH distribution to the air-cathode was measured with an ion selective microelectrode. Therefore, we applied this method to a micro-ammonium ion electrode.

The concentration of ammonium ion at 10 mm from the air-cathode was 2 mM and there was a trend to decrease gradually as it approached to the air-cathode. Especially, the concentration of ammonium ion decreased sharply at approximately 0.6 mm from the air-cathode, and it became less than one-tenth within the distance of 0.5 mm. In our previous study under almost the same operational condition, the maximum pH was observed on the surface of the air-cathode, and it was about 9.3. Since the fraction of ammonium ion dissociation under this pH is about 50 % at most, the sharp decrease in the ammonium ion concentration cannot be explained only by this reason. Hence, something that caused the decrease in ammonium ion concentration must have happened near the air-cathode. The effect of nitrification can be denied because the biofilms were not formed on the surface of the air-cathode. From these above reasons, it is natural to think that ammonia volatilization through the air-cathode occurred in this study.

Acknowledgments

This research was financially supported by Grant-in-Aid for Japan Society for the Promotion of Science Fellows (Project No. 15J0490902).

Figure 1
In Situ Tuning of Magnetization Via Double Layer Charging and Topotactic Li Insertion in Polymer-Templated Mesostructured Thin Films
Authors: Reitz Christian , Brezesinski Torsten 
Published: February 2020

Mesostructured mixed-metal oxide thin films have received much attention in recent years, as they have great potential for future device applications. Advances in polymer templating over the past years have enabled the preparation of a variety of important materials in the form of thin films. However, despite the progress made, complex metal oxides (other than binary systems) often exhibit an ill-defined nanoscale structure after thermally-induced crystallization and removal of the porogen, mainly for stability reasons.
Here, we describe the self-assembling synthesis of large-pore mesoporous mixed-metal oxides, with special emphasis on La1–x
Ca
x
MnO3 (LCMO) and alpha-LiFe5O8 (LFO). Electron microscopy, GISAXS, XRD, XPS, TOF-SIMS, and RBS all show that these materials can be templated to produce high quality thin films that are phase pure and thermally stable to over 600 °C. For LCMO, we demonstrate that the surface charge carrier density can be tuned by double layer charging using an ionic liquid electrolyte.[1] Peak-to-peak magnetization modulation values of up to 10% have been achieved, (to our knowledge) the highest thus far reported for electrolyte-gated mixed-valence manganese oxides. Furthermore, we demonstrate that the topotactic Li insertion into LFO allows for the intriguing possibility of controlling the r.t. bulk magnetic state in a highly reversible manner. Overall, both approaches are promising and should be applicable to other magnetic nanomaterials.
[1] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn, and T. Brezesinski, Chem. Mater. 26, 5745 (2014).
Direct Evaluation about Structure and Optical Property of Individual Multi-Shell Quantum Dot By TEM
Authors: Uehara Masato , Sato Yohei , Terauchi Masami 
Published: February 2020

Quantum dots (QDs) such CdSe nanocrystals attract much attention owing to their promising applications in light emitting devices and biomedical tags. They are usually coated by the wider band materials such CdS and ZnS in order to improve the photoluminescence quantum yield together with the chemical protection. However, it is not clarified the relationship between optical properties and core/shell particle structure, and we should optimize the coating treatment condition and the core/shell structure (shape and thickness), throughout many experiments.
It is important to clarify the relationship between optical properties and particle structure. Direct evaluation about the optical properties of the individual particles is very effective. As we all know, TEM is a powerful tool for the shape structure evaluation of nanoparticle. In addition, even the optical properties from UV to NIR of individual single nanoparticles can be evaluated by the HR-EELS using the monochromator TEM.
In this study, we have investigated the particle structure and optical property using advanced TEM technique. We have synthesized CdSe, CdSe/CdS and CdSe/CdS/ZnS multi-shell particles. The optical properties of individual single nanoparticles have been evaluated by HR-EELS using the monochromator TEM in addition to the usual particle structure evaluation by HR-STEM and EDX.
All nanoparticles were synthesized in an organic solvent with some ligands such as amine, oleic acids and trioctylphoshine. The synthesized and refined core CdSe particles were re-heated together with CdS raw material in an organic solvent, and we have obtained the CdSe/CdS core/shell particles. The CdSe/CdS/ZnS core/shell/shell particles have been also obtained in the similar treatments. We have evaluated the particle size and shape by STEM. Their size and shape was homogeneous. CdSe core particles were spherical and ca. 5 nm. CdSe/CdS and CdSe/CdS/ZnS particles were cubic shape, and ca. 10 nm and 15 nm. In STEM-EDX analysis, we have been able to confirm the core/shell and core/shell/shell structure. We could obtain some spectral structures attributed to interband transitions in the CdSe core and CdS shell by EELS analysis. However, the spectral structure about ZnS outer shell could be hardly confirmed. This would be attributed the low crystallinity of ZnS. Through the detail investigation of spectra, dielectric property of multi-shell nanoparticle is clarified and relation with the photo luminescent property will be discussed.
[Acknowledgement] The research was partially supported by JSPS KAKENHI Grant Number 26286026, Grant-in-Aid for Scientific Research (B). In addition, this STEM observation was partly supported by Advanced Characterization Platform of the Nanotechnology Platform Japan sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.