bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Photocatalytic Efficiency of Self-Organized TiO2 Nanotube Layers Due to Secondary Materials
Authors: Sopha Hanna , Krbal Milos , Ng Siowoon , Zazpe Raul , Prikryl Jan , Macak Jan M.
Published: February 2020

The self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 10 years motivated for their possible range of applications including photo-catalysis, solar cells, hydrogen generation and biomedical uses [1,2]. The synthesis of 1D TiO2 nanotube structure is carried out by a conventional electrochemical anodization of valve Ti metal sheet. The main drawback of TiO2 is its applicability in the UV light (wavelengths < 390 nm).

One of the major issues to extend the functional range of nanotubes is to coat homogenously tube interiors by a secondary material. It has been shown that additional ultrathin surface coating of TiO2 by secondary materials such as Al2O3 [3], ZnO [4] or MgO [5] annihilates electron traps at the TiO2 surface and thus increases the photogenerated concentration of charge carriers. Recently, it has been demonstrated that just a single cycle of Al2O3 [6] or ZnO [4] deposited by atomic layer deposition (ALD) efficiently improves charge transport properties of the heterostructure while gradual passivation appears with increasing ZnO thickness due to stronger band-bending [4].

The presentation will focus in on the coating of the nanotube arrays by various secondary materials using ALD. The deposited materials influence strongly photo-electrochemical properties of nanotube layers. Experimental details and some recent photocatalytic [7, 8] results will be presented and discussed.

References:

[1] J. M. Macak et al., Curr.
Opin. Solid State Mater.
Sci.,
2007, 1-2, 3.

[2] K. Lee et al., Chem. Rev., 2014, 114, 9385.

[3] R. Zazpe et al., Langmuir, 2017, 33, 3208.

[4] A. Ghobadi et al., Sci. Rep.,
2016, 6, 30587.

[5] H. Park, et al., J. Electroceram.,
2009, 23, 146.

[6] J-Y. Kim et al., Nanotechnology,
2014, 25, 504003.

[7] H. Sopha et al., Appl. Mater. Today,
2017, 9, 104.

[8] S. Ng et al., Adv. Mater. Interfaces
2017, 1701146.
(Sensor Division Outstanding Achievement Award) Electrochemical Sensors: From Beakers to the Skin and the Mouth
Authors: Wang Joseph
Published: February 2020

Electrochemical sensors have experienced remarkable changes in recent years. Particular recent attention has been given to wearable sensors owing to their considerable promise for monitoring the wearer’s health and wellness. The medical interest for wearable systems arises from the need for monitoring patients over long periods of time. These devices have the potential to continuously collect vital health information from a person’s body and provide this information to them or to their healthcare provider in a timely fashion. Such sensing platforms provide new avenues to continuously and non-invasively monitor individuals and can thus tender crucial real-time information regarding a wearer’s health. This presentation will discuss recent developments in the field of wearable electrochemical sensors integrated directly on the epidermis or within the mouth for various non-invasive biomedical monitoring applications. Particular attention will be given to non-invasive monitoring of metabolites and electrolytes using flexible amperometric and potentiometric sensors, respectively, along with related materials and integration considerations. These include advanced materials for imparting remarkable stretchability and self-healing abilities to enable epidermal biosensors to endure extreme deformations experienced by the human skin. The preparation and characterization of such wearable electrochemical sensors will be described, along with their current status and future prospects and challenges.
Using Air Liquid Interface for studying Mechanical Deformation of Cells in Microfluidic Channels
Authors: Sen Prosenjit , Singh Kotesa Rahul , Ananthasuresh G. K.
Published: February 2020

Biological cells are known to respond to changes in their environment by changing their mechanical response. For several diseases (e.g. diabetes, spherocytosis) changes in mechanical properties of cells have been corelated with the progression of the disease. Changes in cells mechanical properties has also been corelated with their development and age. With the advent of advanced microfluidic characterisation techniques, the mechanical response of a large number of cells can be measured at the single cell level. These studies help in investigating fundamental questions in cell biology. These analysers are called microfluidic cell transit analysers. In this work we introduce a novel cell-transit analyser where an air-liquid interface is used as a mechanical element to induce deformability in cells. This technique enables both static and dynamic deformability measurements in live cells ex vivo.

The devices were fabricated using PDMS microchannels bonded to glass substrates. The air-water interface is formed using manually controlled syringes. A syringe pump was used to flow the cell containing samples. In this work, stiffer air-water interface (surface tension 72 mN/m) to deform more compliant Red Blood Cells (effective 20 mN/m) in micro-channels. As the interface stiffnesses are of similar order, the air-water interface also deforms. In the static mode, measurement of the air-water interface deformation allows us to measure the Laplace pressure drop and hence estimate the stiffness of the Red Blood Cells. Using our technique, we estimated the stiffness of a single RBC was measured to be 18±2 mN/m which is in good agreement with previous reports.

In the dynamic mode the RBC containing buffer was flowed from one side and air pressure was applied at the two perpendicular channels to create stable air-liquid interfaces with desired constriction widths. This allows us to perform high throughput measurements (>100 cells/s) of deformability index (DI) and transit time for different air-liquid interface constriction widths. The adjustments in constriction width can be made in real time and can be tuned to widths as small as 2µm by controlling the air-pressure. The technique also eliminates the cell-substrate interactions due to the use of a virtual wall.

In order to validate the ability of the technique to differentiate cell population based on mechanical response, DI and transit time for cells passing through the air-water interface constriction were measured for healthy and 0.01% Glutaraldehyde (GA) treated RBCs. The DI of the GA-RBCs was found to be smaller than healthy RBCs thereby confirming the effectiveness of the technique in deformability cytometry. Further, the mechanical response of cells to different constriction widths was measured. We found that for differentiating Red Blood Cells of different stiffness using DI and transit time, constriction widths < 4µm are optimum.
3D Printable Soft Conductive Nanocomposites
Authors: Ahmed Kumkum , Kawakami Masaru , Khosla Ajit , Furukawa Hidemitsu
Published: February 2020

3D printing is getting remarkable consideration in recent years in miscellaneous areas and being focused in many hi-tech future possibilities in engineering 1,2. 3D printable conductive polymer composites are gaining massive interest due to their impending application in the field of robotics, tactile, optical displays, microelectrochemical systems and in numerous other applications 3-5. Here in this work we prepared new types of 3D printable nanocomposites with tunable flexibility employing ionic liquid (IL) and micro-walled carbon nanotube (MWCNT) in polymer matrix. The developed soft nanocomposites demonstrated high conductivity and mechanical flexibility and diverse strain%. Thermal properties of the nanocomposites were studied by TGA and we found that thermal stability were very high for all nanocomposites regardless of the composition. Dynamic mechanical analysis (DMA) revealed information about their transition temperature for softening and by modifying MWCNT and polymeric content it is possible to tune this temperature according to desired requirements. The nanocomposites were printed by FDM 3D printer freely and on nonconductive printed base substrate according to the required shape. We also investigated their mechanical and conductive properties by tuning the composition of the constituents in the nanocomposites and discussed about the critical compositions and limitations for 3D printing techniques. These newly developed nanocomposites are expected to create pronounced impact in electromechanical fields to develop soft robotics, actuator and sensor devices.

References

Kalsoom, U., Nesterenko, P. N. & Paull, B. Recent developments in 3D printable composite materials. RSC Adv.
6, 60355–60371 (2016).

Gross, B. C., Erkal, J. L., Lockwood, S. Y., Chen, C., Spence, D. M. Evaluation of 3D Printing and Its Potential Impact on Biotechnology and the Chemical Sciences. (2014).

Wei, X., Li, D., Jiang, W., Gu, Z., Wang, X., Zang, Z., Sun, Z., 3D Printable Graphene Composite. Publ. Gr. 1–7 (2015). doi:10.1038/srep11181

Guo, S., Qiu, K., Meng, F., Park, S. H. & Mcalpine, M. C. 3D Printed Stretchable Tactile Sensors. Mater.
29, 1701218 (2017).

Muth, J. T., Vogt, D. M., Truby, R. L., Mengüç, Y.,Kolesky, D. B., Wood, R. J., Lewis, J. A., Embedded 3D Printing of Strain Sensors within Highly Stretchable Elastomers. Mater.
26, 6307–6312 (2014).

Figure 1
Platinum Thin Film TCD Designed for 3 Omega Sensing of Gas Mixtures
Authors: Lotfi Ardalan , Navaei Milad , Hesketh Peter J
Published: February 2020

Over the last few decades, the world of sensors has been revolutionized by exploring the disciplines of nanotechnology and sophisticated Nano-fabrication process. As a result, gas sensors have become smaller and more robust in the terms of sensitivity and accuracy. Furthermore, these sensors are able to cover a broader range of gases and volatile compounds increasing detection capabilities, allowing detection down to single ppm. However, challenges still exist in detecting certain gases, specifically ammonia. The chemical-based gas sensors for ammonia are not reliable due to several factors such as slow recovery time, sensor base-line drifting, vulnerability to degradation and false alarm [1]. On the other hand, the physical-based ammonia sensing approach has the advantage of fast response time and long-term durability [2], while the thermal conductivity detector suffers a lack of high sensitivity and selectivity.

In an effort to address these challenges, this study is designed to improve the limit of detection of a micro wire thermal conductivity gas sensor that enables the system to detect 100 parts per million for ammonia. The differential 3-Omega measurement technique uses two sensors, one as sensing sensor and the other as a reference [3,4]. It is a harmonic excitation technique that needs a sinusoidal current can produce high thermal stresses that shorten the sensor life-time. To increase the reproducibility of sensor fabrication process, the micro wire TCD sensor material is replaced with platinum. In summary, the new design of micro wire TCD includes optimized shape to bear the high thermal stresses caused by continuous current needed by 3-omega technique and higher stability of the temperature coefficient of resistance with platinum film.

[1] Azad, A. M., Akbar, S. A., Mhaisalkar, S. G., Birkefeld, L. D., & Goto, K. S. (1992). Solid‐state gas sensors: A review. Journal of the Electrochemical Society, 139(12), 3690-3704.

[2] Mahdavifar, A., Navaei, M., Hesketh, P. J., Dimandja, J. D., Stetter, J. R., & McMurray, G. (2015). Implementation of a polysilicon micro electro-thermal detector in gas chromatography system with applications in portable environmental monitoring. ECS Journal of Solid State Science and Technology, 4(10), S3062-S3066.

[3] Lotfi, A., Mahdavifar, A., Struk, D., Stetter, J. R., Navaei, M., & Hesketh, P. (2017). Ultimate Sensitivity of Physical Sensor for Ammonia Gas Detection Exploiting Full Differential 3-Omega Technique. ECS Transactions, 80(10), 1571-1578

[4] Kommandur, S., Mahdavifar, A., Hesketh, P. J., & Yee, S. (2015). A microbridge heater for low power gas sensing based on the 3-Omega technique. Sensors and Actuators A: Physical, 233, 231-238.

Figure 1
Micromachined Resonators for Sensing System Applications
Authors: Tadigadapa Srinivas
Published: February 2020

In this presentation we will explore the phenomenon of resonance in electrical, mechanical, optical and acoustic domains for sensing applications. The field of micro and nano sensors has rapidly evolved over the last couple of decades with many of the highest performance devices exploiting the phenomenon of resonance for sensing. Micro and nano scale resonator designs, fabrication, and integration of new materials offer unique opportunities for innovative, novel, and robust configurations impacting all aspects of sensor systems. The methods of coupling the resonator to the measurand will be discussed and example sensors for stress, infrared, and rotation (gyroscopic) applications will be presented. Important design considerations such as resonator geometry, the Q-factor, nonlinear behavior, power consumption and packaging will be analyzed. Furthermore, piezoelectric microelectromechanical systems (MEMS) resonant sensors are well known for their excellent mass resolution and have been studied for many applications, including DNA hybridization, protein–ligand interactions, and immunosensor development. And more recently, optical resonant microsensors with high sensitivity have been successfully demonstrated. These advances have allowed for miniaturization and cost-effective manufacturing of such optical resonant sensor devices. Furthermore, chip-scale integration of microfluidics with optics has enabled analyte preparation and delivery for optical interrogation by such sensing structures. The feedback mechanism based on microring, microtoroid and microdisk have been employed for shaping resonant transmission or reflection spectrum to improve spectral resolution. The presentation will conclude with a review the operation and performance of the first MEM-based zero-power wake-up receiver are described. This device uses the high quality factor of a MEM-device to achieve extremely low power sensitivity (-60 dBm at 750 MHz) without consuming power.
Direct Detection of dCas9-mediated Target Gene by Ion Concentration Polarization
Authors: Kim Sung Jae
Published: February 2020

Our group has reported that nanofluidic preconcentration devices utilizing ion concentration polarization (ICP)1, 2 enables simultaneous separation and preconcentration of biomolecules3. Further development of the device which is the main topic of this work enlightens us that the behaviors of accumulated analyte can be categorized into “propagating” and “stacking” behavior depending on the critical mobility which is the function of intrinsic and extrinsic properties of materials. Thus, altering the mobility of target DNA using dCas9 realized optical and direct sequence-specific detection. Therefore, the proposed dCas9-mediated genetic detection methodology based on ICP would provide rapid and direct micro/nanofluidic platform for liquid biopsies.

I.
Introduction

The-state-of-the-art bio- and nanotechnology have opened up an avenue to non-invasive liquid biopsy for identifying diseases from biomolecules in bloodstream, especially DNA. In this work, we combined sequence-specific-labeling scheme using mutated Clustered Regularly Interspaced Short Palindromic Repeats associated protein 9 without endonuclease activity (CRISPR/dCas9) and ion concentration polarization (ICP) phenomenon as a mechanism to selectively preconcentrate targeted DNA molecules for rapid and direct detection.

II.
Results

Theoretical analysis on ICP phenomenon figured out a critical mobility, elucidating two distinguishable concentrating behaviors in the vicinity of a nanojunction; a stacking and a propagating behavior (Figure 1(a), 1(b)). Through the modulation of the critical mobility to shift those behaviors, the C-C chemokine receptor type 5 (CCR5) sequences were optically detected without PCR amplification (Figure 1(c), 1(d), 1(e)).

III. Conclusion

The proposed dCas9-mediated genetic detection methodology based on ICP would provide rapid and accurate micro/nanofluidic platform of liquid biopsies for disease diagnostics, especially PCR-free gene detection.

Acknowledgements

This work was supported by Korean Health Technology RND Project (HI13C1468 and HI14C0559).

References

S. J. Kim, Y.-A. Song and J. Han, Chem. Soc. Rev., 2010, 39, 912-922.

S. J. Kim, Y.-C. Wang, J. H. Lee, H. Jang and J. Han, Phys. Rev. Lett., 2007, 99, 044501.

J. Choi, K. Huh, D. J. Moon, H. Lee, S. Y. Son, K. Kim, H. C. Kim, J.-H. Chae, G. Y. Sung, H.-Y. Kim, J. W. Hong and S. J. Kim, RSC Advances, 2015, 5, 66178-66184.

Fig. 1. Time-lapse images of each concentrating behavior of (a) Sulforhodamine B molecule (stacking regime, convection dominant case) and (b) Alexa 532 molecule (propagating regime, electromigration dominant case). (c) Target genetic sequence binding process of dCas9:sgRNA complex. Schematic for detecting target sequence by dCas9-mediated ICP platform (d) with target gene (positive) and (e) without target gene (negative).

Figure 1
Electrochemical Reactivation of AISI 409 Ferritic Stainless Steel Sheet Welded By Laser Process
Authors: Almeraya Facundo , Sanchez Gomez Amilcar , Tiburcio Citlalli Gaona , Zambrano Patricia , Cabral José Angel , Ramirez Maria del Carmen , Curiel Francisco , Estupiñan-Lopez Francisco
Published: February 2020

The susceptibility to sensitization in 409 ferritic stainless steel (FSS) weldments was studied, by means of double loop electrochemical potentiokinetic reactivation test (DL-EPR). After the electrochemical test, the microstructure was analyzed by scanning electron microscopy (SEM) and the presence of elements with dispersive energy of X-rays (EDS), with the X-ray diffraction (XRD) technique they were identified present phases in different welds. Microhardness profiles were employed to evaluate the mechanical properties. With the aim of analyze the effect on the degree of sensitization to welding processes and the base material, a methodological analysis of gas metal arc welding GMAW, gas tungsten arc welding GTAW and LASER welding process was performed. The LASER process generated the highest ratio between the reactivation (Ir) and activation (Ia) current, despite it caused less microstructural change. The higher ratio Ir/Ia is attributed to the lack of penetration in the butt join, showing crevice corrosion.
Corrosion Protection Behavior of Patinas on Copper Alloys in Historical Metal Heritage: Electrochemical Study
Authors: Arguelles David , Campechano Clarisa , Galván-Martínez Ricardo , Jimenez Tania , Orozco-Cruz Ricardo
Published: February 2020

All copper base alloys based copper tend to form a layer of oxide (patina), which gives or not protection to the base metal in the environment where they are exposed, this depends on the interaction with various agents such as chlorides (Cl-), sulfur dioxide (SO2), oxides of nitrogen (NOx) and ozone (O3), as well as the influence of solid particles in suspension such as coal, pollen and microorganisms, etc., which create dust deposits on the patina, which They compact by acting as a sponge, retaining moisture and thus favoring the corrosion phenomenon causing mechanical and chemical damage, originating in some cases soluble corrosion products that due to meteorological conditions such as precipitation can be eliminated, leaving the metal in some areas more exposed and ruining with This is the artistic appearance of the monument. [1-5] In this work, the induction of artificial patinas on Cu base alloys (brass and bronze) was carried out. The aim os this work was analyzing their degradation and evolution mechanisms, being these, characteristics of monuments exposed in atmospheres rich in Cl-, SO2 and NOx to achieve it were used solutions of NH4Cl 33% w, CuSO4 15mM and CuNO3 20% w, respectively. [6] After that, they were exposed to the atmosphere, in the port of Veracruz, Mexico., Having an environment of marine-tropical study, as well as the Cl- and SO2 ppm were monitored in strategic points of the City, this by ISO 9225 Standard. [7] For the study of the corrosion mechanism, electrochemical techniques were used, such as Electrochemical Impedance Spectroscopy (EIS) and Electrochemical Noise (EN). For the measurements, a typical three-electrode cell was used in EIS. A working electrode was used (patinated Cu alloy). ), a reference (Calomel Saturated electrode) and an auxiliary one (graphite), for EN two working electrodes and a reference electrode were used, a representative solution was used as electrolyte, which contained the ppm of contaminants that were monitored monthly, the study was complemented with Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform of Attenuated Total Reflection (FT-ATR). The results showed corrosion products typical of the environments that were desired to be characterized, finding; Brochantite (Cu4SO4 (OH) 6) and Atacamite (CuCl2 · (H3O) while CuNOx were more soluble, this was reflected in EIS, where Nyquist spectra with defined semicircles were found typical of load transfer processes, however for the samples with corrosion products of Cu4SO4 (OH)6 in the Bode diagrams it was possible to observe the increase in the Rtc, and the presence of a second time constant, which is related to the stability and compactness of these products.
Study of the Inhibiting Efficiency of an ABS Coating Doped with Lansoprazole on Mild Steel
Authors: Viveros Sandra , Uruchurtu Jorge , Menchaca Carmina , Hernández-Gallegos Miguel
Published: February 2020

Organic inhibitors have had a great boom in the field of research in the last decade, since they have been reported to be good inhibitors of corrosion by having in their chemical composition atoms of nitrogen, sulfur or oxygen, allowing to be absorbed on the surface of the metal, and for having environmentally friendly characteristics. Polymeric coatings have always been good protectors of corrosion in multiple metals in different solutions. Likewise, this project seeks to help the environment with the recycling of this waste polymer being used in multiple areas, mostly in the automotive industry, generating tons of waste in its manufacturing process. On the other hand, the remains of the expired medicines generate thousands of kilograms of garbage, which later become fuel for cement factories, contaminating the environment in a different way.

The aim of this study is to evaluate the corrosion protection of a polymer coating doped with an organic inhibitor extracted from an expired drug on mild steel in alkaline and basic solutions. Electrochemical tests were carried out, such as Electrochemical Impedance Spectroscopy, Electrochemical Noise and Polarization Resistance, and it was characterized by FTIR, XRD, and AFM to confirm the union of both elements.

Electrochemical tests shown, that the system coating/inhibitor had good results in the basic solution, maintaining a constant resistance in the time that the test lasted (2000 hours). Likewise, in the alkaline solution, the system coating/inhibitor indicate an offspring in the resistance, obtaining an inferior behavior that the blank. The FTIR and XRD characterization indicate that in the dissolution, there are no chemical reactions that affect the properties or characteristics of each component. In AFM shows that, although there are some pores in the area, the coating is uniform in the entire surface.
Adhesion of Electrolessly Deposited Ni-P Film on Silicon Wafer Using Gold Nanoparticle Catalysts
Authors: Takasaka Yuichi , Sakamoto Susumu , Matsumoto Ayumu , Fukumuro Naoki , Yae Shinji
Published: February 2020

Formation of adhesive metal films on silicon wafers is important for electrodes of various devices. Autocatalytic electroless deposition has several advantages, e.g. simplicity of process, uniformity of deposited films, and covering on complicated structures. However, adhesion of metal films formed on silicon substrates using conventional pretreatments is not sufficient for the practical applications. We reported that adhesive metal films can be directly formed on silicon substrates by preliminarily depositing gold nanoparticles as catalysts without any other treatments.1-3 When palladium nanoparticles are used as catalysts, heat-treatment is needed before and after plating to obtain adhesive films.4 We also reported that single crystalline gold nanoparticles are epitaxicially grown and gold-silicon alloy is formed at the gold-silicon interface, which improves the adhesion of films.3 In this study, we investigate the factors which affect the adhesion of metal films produced on silicon substrates by the present method.

The gold nanoparticles were deposited on p-Si (100) substrates by immersing in a 0.5 mM HAuCl4 solution containing 0.15 M HF at 278 K. The Ni-P films were formed on the silicon substrates using a solution containing 0.1 M NiSO4, 0.3 M NaPH2O2, 0.1 M (CH2COONa)2·6H2O, and 0.1 M C4H6O5 at 343 K. The solution pH was adjusted to 4.8 with NaOH. The adhesion of deposited films was examined by a tape test based on JIS H8504 corresponding to ISO 2819 after room temperature aging at atmospheric ambient.

Figure 1a shows the percentage of the area of the Ni-P films that remained on the silicon substrate after the tape test as a function of the film thickness. No peeling occurred for the films thinner than 0.8 µm immediately after the film deposition. As shown in Fig. 1b the starting film thickness of peering increased with aging time and reached the maximum after aging for 7 days. Since the starting film thickness of peering increased with the square root of aging time, we consider that the improvement in adhesion is due to the atomic diffusion of gold into silicon at room temperature. However, the starting film thickness of peering become constant after 7 days aging. This indicates that there are factors which affect the adhesion of metal films other than the formation of gold-silicon alloy.

Acknowledgement

This work was partly supported by JSPS KAKENHI Grant Number JP26289276.

References

S. Yae, M. Enomoto, H. Atsushiba, A. Hasegawa, N. Fukumuro, S. Sakamoto, and H. Matsuda., ECS Trans., 53(6), 99 (2013).

H. Atsushiba, Y. Orita, S. Sakamoto, N. Fukumuro, and S. Yae, ECS Trans., 61(10), 9 (2014).

N. Yamada, H. Atsushiba, S. Sakamoto, N. Fukumuro, and S. Yae, ECS Trans., 69(39), 59 (2015).

V. M. Dubin, J. Electrochem. Soc., 139, 1289 (1992).

Figure 1
Electrochemical Evidence of the Catalytic Activity of Meso-Tetraphenylporphyrin Diacid in the Proton Reduction in Benzonitrile
Authors: Castro-Cruz Hiram Manuel , Macias-Ruvalcaba Norma Angélica
Published: February 2020

Our work shows the electrochemical behavior of meso-tetraphenylporphyrin diacid (H4TPP2+) in tetrabutylammonium perchlorate Bu4NClO4 0.1 M / benzonitrile. On a cathodic sweep and scan rates between 0.1 and 3.0 V/s, H4TPP2+ undergoes two closely spaced consecutive reversible one-electron transfers (Ic’/Ia’ and IIc’/IIa’; Figure 1), which can be assigned to formation of diprotonated porphyrin radical cation (H4TPP•+), and isophlorin H4TPP species, respectively1. In presence of an extra equivalent of HClO4, a new reduction peak, IIIc’, is seen, suggesting that isophlorin H4TPP is being protonated. It is believed that the protonation takes place at one of the meso-positions of the porphyn ring leading to phlorin cation (H4TPFH+). The phlorin cation is electroactive and can be either oxidized (peaks IVa’ and Va’) or reduced (IIIc’)2. As seen in Figure 1, the addition of extra equivalents of H+ to solutions of H4TPP2+ provokes an increase in the current and loss of reversibility of the two reduction processes, Ic’/Ia’ and IIc’/IIa’. This behavior was explained as due to the reaction between the free protons in the medium and the hydrogen atom of the meso-position of the H4TPFH+, in a reaction that produces molecular hydrogen and regenerates the porphyrin diacid.

Digital simulation of the experimental voltammograms of H4TPP2+ indicates that the H4TPP•+ and H4TPP species are stable on the cyclic voltammetry time scale. However, coulometry experiments at the potential of the second reduction process show that at longer time scale, the isophlorin H4TPP undergoes coupled chemical reactions. Voltammograms of the electrolyzed solution exhibit oxidation and reduction signals that are characteristics of H4TPFH+ species, also the presence of the bands at 460 nm and 773 nm in the UV-visible spectrum is consistent with the presence of H4TPFH+ species3,4. It is also demonstrated that the H4TPFH+ species can be reoxidized back to the original H4TPP2+ in a two-electron process.

References.

1. H. M. Castro-Cruz, thesis, UNAM (2017). http://132.248.9.195/ptd2017/junio/410088896/Index.html

2. Y. Cui, L. Zeng, Y. Fang, J. Zhu, C. H. Devillers, D. Lucas, N. Desvbois, C. P. Gros and K. M. Kadish, ChemElectroChem, 3, 228–241 (2016).

3. G. Peychal-Heiling and G. S. Wilson, Anal. Chem., 43, 550–556 (1971).

4. G. L. Closs and L. E. Closs, J. Am. Chem. Soc., 85, 818–819 (1963).

Figure 1
Polystyrene/Ceria Core/Shell Abrasive Based Slurry for Highly Enhanced Oxide-Film Polishing Rate and Scratch-Less in Chemical-Mechanical-Planarization
Authors: Jeong Gi Ppeum , Yun Sang su , Son Young hye , Yoon Seok Jin , Nam Hae won , Park Jin-Hyung , Park Jea-Gun
Published: February 2020

The SiO2-film chemical-mechanical-polishing (CMP) is essential process for Shallow Trench Isolation (STI) and Inter Layer Dielectric (ILD) CMP. The key performance parameters are high polishing rate and scratch-less in SiO2-film CMP. In SiO2-film CMP, wet-ceria was widely used for scratch-less SiO2-film CMP. However, the wet-Ceria abrasive has crystalline sharp <100>, <100>, and <111> facet, which resulted in generating scratches on SiO2-film by stick and slip mechanism after SiO2 CMP, as shown in Fig.1. Thus the scratches induced by wet-ceria abrasives can be a major cause of poor device operation and yield drop in the memory device manufacturing. In our study, therefore, we designed a novel SiO2-film CMP slurry using the PS/ceria core/shell as an abrasive to enhance SiO2-film polishing rate and scratch-less after SiO2-film CMP.

PS/ceria core/shell particles were synthesized, which are relatively soft and round by using polystyrene and ceria particles. Figure 2(a) shows the synthesis mechanism of PS/ceria core/shell, illustrating that Ce4+ ion was added in the PS of negative charge to form Ce4+ seed on the surface and grow it during 7 h with 70 ℃. The TEM image of the synthesized PS/ceria core/shell was shown in Fig. 2(b). First, we investigated the polishing rate of SiO2-film using PS/ceria core/shell abrasives. The polishing rate of SiO2-film was 564 Å/min when using PS/ceria core/shell and 350 Å/min when using wet-ceria as abrasives, as shown in Fig.3. This result means that the real contact area of PS/ceria core/shell is larger than that of 70 nm size wet-ceria. Second, we measured the surface roughness [root-mean-square (RMS) at 10 x 10-um scanning area] of SiO2-film and the surface defect such as scratch after CMP. The surface roughness of SiO2-film was 0.327 nm using wet-ceria and 0.202 nm using PS/ceria core/shell, respectively, as shown in Fig. 4(a). The number of scratch was 51-ea in 10-mm2 area and the deepest depth of scratch was 18 nm using 70 nm size wet ceria. However, the number of scratch was 10-ea in 10-mm2 area and the deepest depth of scratch was 2.3 nm using PS/ceria core/shell, as shown in Fig. 4(b). These results indicate that the hardness of PS/ceria core/shell is smaller than that of 70 nm size wet-ceria. In our presentation, we will review the mechanism for improving CMP performance such as high polishing rate, low surface roughness and scratch-less after CMP when using the PS/ceria core/shell abrasive based slurry.

* This research was supported by the MOTIE(Ministry of Trade, Industry & Energy (10085643) and KSRC(Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device. This work was financially supported by the Brain Korea 21 Plus Program in 2018 and Research & Business Development Program Announcement funded by the MOTIE (N0002026).

Figure 1
An Effect of Plasmonic Welding of Agnws on EAP Actuator
Authors: Park Bong Je , Park Sun Tak , Yun Sung Ryul , Park Seung Koo
Published: February 2020

Carbon grease, CNT, graphene, and AgNWs have been generally used as materials of EAP actuator compliant electrode for large displacement. Carbon grease can withstand for large displacement, but has low optical transparency and mechanical stability. Even though CNT, graphene and AgNWs are transparent compared with carbone grease, they should be thickly coated to secure a stable electric conductivity so that compliant electrodes are still opaque and limited to their applications. In order to verify plasmonic welding effect on AgNWs, we chose 1.75μl/cm2 among different AgNWs concentrations due to its high transparency. Glass substrate which is spary coated with 1.75μl/cm2 AgNWs was put into the chamber and irradiated with 500W halogen lamp. After the irradiation with different time, sheet resistance was measured 4 point probe. Sheet resistance does not change too much until 120 sec, 35 Ω/sq, gradually decreases, and has a minimum value of 19 Ω/sq at 180 sec. After then, sheet resistance increases and shows 198 Ω/sq at 240 sec. In order to confirm plasmonic welding effect on deformation of DE actuator exactly, deformation should be measured with the same DE actuator before and after plasmonic welding. In our conventional DE actuator fabrication process, acrylic frames are used to hold DE membrane. However, they are so vulnerable to heat that it can be easily twisted during plasmonic welding. Therefore, DE actuator (diameter of active area : 30mm) was fabricated by conventional fabrication process with perforated glass frame instead of acrylic frame. We measured its displacement with input voltage by Polytec PSV-500 scanning vibrometer before and after plasmonic welding. Concentration of AgNWs is 1.75μl/cm2 and plasmonic welding time was 180sec welding. The displacement of DE actuator before plasmonic welding was 51μm, 143μm, 320μm, 647μm, 1123μm, 1690μm, and 2240μm at 1 KV, 1.5 KV, 2 KV, 2.5 KV, 3 KV, 3.5 KV and 4Kv, respectively. After plasmonic welding, the displacement of DE actuator was 58μm, 159μm, 358μm, 717μm, 1242μm, 1876μm, and 2512μm at 1 KV, 1.5 KV, 2 KV, 2.5 KV, 3 KV, 3.5 KV and 4Kv, respectively.

Figure 1
Positive – Positive Symmetric Cell Study on the Compatibility of Different Electrolyte Additives with Li[Ni0.6Mn0.2Co0.2]O2
Authors: Liu Yulong , Dahn Jeff R
Published: February 2020

Electrode/electrolyte compatibility plays a critical role to increase the energy density and longevity of lithium-ion cells. A sound understanding of the interactions between electrode and electrolyte allows us to design better electrolyte formulation with more suitable additives. Nevertheless, the study of electrode/electrolyte interaction is difficult to carry out in a full lithium-ion cell due to the interactions between positive and negative electrodes, such as the migration of oxidation products and dissolved transition metal to the negative electrode1, and the effect of different negative electrodes on the surface layer composition of positive electrode2. In recent years, there has been quite a few experimental techniques developed aiming to solve this problem3,4. Among them, symmetric cells are excellent test vehicles where performance is exclusively determined by the compatibility of the electrode of interest with the electrolyte of choice.

In this study, the compatibility of two electrolyte additives, vinylene carbonate (VC) and prop-1-ene-1,3-sultone (PES), with uncoated polycrystalline Li[Ni0.6Mn0.2Co0.2]O2 were studied using positive-positive symmetric cells with electrodes hand-made from powder. Each symmetric cell was constructed with one fresh electrode and one delithiated electrode prepared using a coin-cell half cell. These symmetric cells were then cycled at 40oC with 10 cycles of C/10 followed by 1 cycle of C/30 repeatedly between ±0.9 V, ±0.8 V, ±0.7 V, ±0.6 V, ±0.5 V, which correspond to half cell voltages of 4.39 V, 4.35 V, 4.29 V, 4.22 V and 4.15 V vs. Li/Li+, respectively. It was found that for all symmetric cells cycled with the chosen voltage cut-offs, the cells containing VC showed better capacity retention compared to those with PES. This is surprising because in full Li-ion cells operated above 4.3 V, the opposite was found to be true by Lin Ma et al. 5

The symmetric cell building method in this work can also be used to study electrode/electrolyte compatibility when machine-made electrodes are not readily available to researchers.

References

A. J. Smith, J. C. Burns, D. Xiong, and J. R. Dahn, J. Electrochem. Soc., 158, A1136 (2011)

E. Björklund, D. Brandell, M. Hahlin, K. Edström, and R. Younesi, J. Electrochem. Soc., 164, A3054–A3059 (2017)

D. J. Xiong et al., J. Electrochem. Soc., 164, A340–A347 (2017)

C. Shen et al., J. Electrochem. Soc., 164, A3349–A3356 (2017)

Lin Ma et al, J. Electrochem. Soc. 161, A2250-A2254, (2014).

Figure 1
Evidence of Direct Link between Side Reaction and Capacity Fading in Lnmo
Authors: Dumaz Philippe , Rossignol Cécile , Bouchet Renaud
Published: February 2020

Since their market introduction in 1991, lithium (Li)-ion battery is the main solution to power electronic portable devices, and after almost three more decades of development this technology is embedded in modern electric and hybrid cars. However, its maturity leaves little gap to increase its energy density in the order of 250 Wh.kg-1. In order to increase their energy density, a promising solution is to use positive materials with high potential (up to 5V vs Li + / Li) [1] . The spinel LiNi1/2Mn3/2O4 which owns a capacity of 147 mAh/g and a potential of 4.8 V vs Li + / Li, enables to reach a high energy density (at least 20% higher than the state of the art Li-ion technology), However, this operating potential is largely above the electrochemical stability range of conventional electrolytes based on carbonate solvents [2] . Cycling tests reveals a low coulombic efficiency induced by electrolyte oxidation and capacity loss induced by material degradation [3] . A simple model based on coulombic

efficiency has been developed to quantify the solvent decomposition current. By comparing values obtained on thin film and composite electrode, we proved that the electrolyte oxidation mainly happen on the surface of the LNMO, with a main reaction that can simply be written as: Li + + EC + NMO → EC + + LiNMO where EC stand for a solvent electrolyte molecule and EC+ the product of the solvent oxidation.

The rate of solvent decomposition is kinetically controlled by the charge-transfer, therefore a simple anodic Tafel expression has been used to model the current density due to this mechanism and has been compared to our model based on coulombic efficiency. Tests at different C rates indicate that the longer the electrode stays at high potential, the higher is the capacity fading, showing that the product of electrolyte oxidation seems to be involved into material degradation. In order to get a more deep insight into these parasitic reactions (oxidation of the electrolyte, active material degradation), cells were tested at different temperatures (10, 25 and 50°C). Especially, we have obtained that coulombic efficiency is strongly improved when the operation temperature is decreased, in full agreement with thermal activation of the electrolyte decomposition Inter estingly, we obtained a lower capacity fading which demonstrates the strong link between faradic efficiency (electrolyte oxidation) and material degradation.

[1] Tarascon et al. Nature Mater. 2011

[2] Yi et al. J. Power Sources, 2016

[3] Pieczonka al. J. of Phys. Chemistry, 2013
Solid-State Lithium Lanthanum Titanate-Polymer Composite Electrolyte for Lithium Ion Batteries
Authors: Yang Hui , Wu Nianqiang
Published: February 2020

Three dimensional (3D) pervoskite-type Li0.33La0.557TiO3 nanofibers have been incorporated with a polymer matrix to form a solid-state composite electrolyte. This flexible solid-state electrolyte composite membrane exhibits high ionic conductivity at room temperature, a large electrochemical stability window and good mechanical stability in symmetric Li|electrolyte|Li cell.
In Situ NMR Measurements of Lib Electrolytes -Revealing the Network of Reactions in a Battery
Authors: Wiemers-Meyer Simon , Winter Martin , Nowak Sascha
Published: February 2020

The class of lithium ion battery (LIB) electrolytes most commonly used nowadays is under investigation for at least two decades. These electrolytes, consisting of organic carbonates and LiPF6, are known to undergo not only electrochemical reactions due to their limited electrochemical stability but also chemical reactions due to their sensitivity to hydrolysis. The interplay of chemical and electrochemical reactions as well as their interactions with cathodes, anodes and their surfaces are not yet fully clarified. To study these reactions different analytical techniques can be applied. This usually requires an extraction of the electrolyte from the battery involving a high risk of sample alterations due to volatile and highly reactive substances.

To overcome this issue a battery cell set-up for in situ NMR measurements of liquid electrolytes has been developed.1 It enables non-invasive investigations providing molecular information from the inside of an intact battery. The cylindrical battery cell consists of two electrodes in a heat-sealed polymer tube that is small enough to be placed in a standard 5 mm NMR glass tube (see Figure). To ensure gas tightness the NMR glass tubes are sealed with epoxy resin. All the common electrode materials including transition metal oxides, graphite as well as lithium metal can be applied as active electrode materials.

Electrochemical tests demonstrate a sufficient rate performance and a good cycling stability of the in situ cells. NMR measurements of the cells provide well-resolved spectra not distorted by the solid battery components. Furthermore, it can be shown that a loss equal or less than 0.1 % of the working electrode capacity by a one-electron reaction forming hydrogen or fluorine containing compounds is sufficient to reach the limit of detection (capacity: 1 to 6 mA h, 400 MHz NMR spectrometer). Hence, the sensitivity of this method is considered high enough to detect any significant electrochemical formation of soluble compounds exhibiting clear 1H or 19F NMR signals.

The results so far show that the in situ cells enable investigations on the passivating properties of the solid electrolyte interphase on the anode (SEI) by monitoring the formation of compounds electrochemically formed on the anode. Furthermore, they revealed temperature and potential dependent fluorination reactions of electrolyte solvents on the cathode surface. In addition, the measurements provide insight into reactions of the electrolyte that probably influence the SEI and are preventable by the cathode depending on the cathode material and processing. NMR spectroscopy also offers a method to investigate transition metal dissolution from the cathode active material since paramagnetic species, e.g., Mn2+, Ni2+ and Co2+ have a strong impact on the relaxation of nuclear spin magnetization.

1) S. Wiemers-Meyer, M. Winter and S. Nowak, Phys. Chem.
Chem. Phys, 2017, 19, 4962-4966.

Figure 1
The Forgotten Concept of the Three-Phase Boundary
Authors: Petrovic Slobodan , Garche Juergen
Published: February 2020

The safety and overall operation of lithium metal batteries depends largely on the prevention of lithium dendrite build. Numerous methods have been proposed for dendrite suppression such as use of external pressure, modification of the nucleation sites for dendrite initiation and the use of solid electrolytes. Each of these approaches shows promise, but neither has led so far to a practical solution. A conceptually different design approach involves the use of high-surface area, 3D structures. Electrodes built on the principle of porous or three-dimensional substrate enable low current densities, while still offering high overall current. The low current density in turn enables long Sands time and prolonged lithium deposition without dendrite build. The entire concept relies on the creation of a high-surface area current collector in direct contact with both the electrolyte and the active material. This is the, often forgotten, principle of the three-phase boundary. The principles of creating large three-phase boundary are used to design the pore structure and to balance the distribution of the electrode components. While the effective design of the three-phase boundary is critical for both charge and discharge reactions in the lithium metal battery, it’s principles are more obvious during the discharge reaction. It is demonstrated how the effective three-phase boundary affects the cell performance.

A high-surface area porous silicon current collector is used for the metal silicon anode as well as for the air cathode. The study depicts the fundamental behavior and dependence of lithium dendrite build on the current density at the anode. Cycling of a symmetrical cell demonstrates stable voltage and current, with no capacity fade, i.e., no dendrite build, for C rates below a critical value. Figure 1 depicts stable capacity during cycling, while figure 2 shows reduction in impedance as the cycling progresses.

Further suppression in dendrite creation is demonstrated through the geometrical effects of the structure as well as by modifying the nature of the current collector. The application of this 3D structure for the air cathode is also evaluated and modeled.
Transport Mechanisms of Li+ in Electrolytes and Solid Electrolyte Interphases
Authors: Bedrov Dmitry , Dong Dengpan , Ebrahiminia Mahsa , Hooper Justin B.
Published: February 2020

We employ atomistic molecular dynamics simulations utilizing polarizable force fields to study ion correlated motion and transport mechanisms of Li+ in several electrolytes and solid electrolyte interphases (SEIs). Specifically, we investigate ion-ion correlated motion and the influence of these correlations on the overall conductivity as well as Li+ transport and transference numbers. We demonstrate that depending on interaction with surrounding matrix, the Li+/anion correlated motion can provide either positive or negative contribution to the overall ionic conductivity and substantially influence the transference number. We will compare Li+ transport in conventional carbonate-based electrolytes (EC/LiPF6, DMC/LiPF6, and EC:DMC/LiPF6), tetraglyme/LiTFSI, and bulk solid electrolyte interphases comprised of alkyl carbonate oligomers (Li2EDC, Li2BDC, Li2PDC, Li2CO3, etc.).