bluuebunny/crossref_metadata_2025 huggingface dataset:
DFT Investigation of Porphyrin Aggregates
Authors: Sabuzi Federica , Stefanelli Manuela , Monti Donato , Conte Valeria , Galloni Pierluca
Published: May 2020

Owing the attractive potential applications of porphyrin assemblies in photocatalysis, sensors and material science, nowadays studies concerning porphyrin aggregation are largely diffused. These chromophores can organize in elaborated architectures by an assorted set of non-covalent interactions (i.e. π–π stacking, H-bonding, metal coordination, hydrophobic effect, and electrostatic forces) between the tetrapyrrolic macrocycles, mostly in J-or H-aggregated species, where the aromatic platforms are stacked side by side and face to face, respectively. UV-vis spectroscopy allows the identification of the porphyrin arrangement within the aggregates, through the modified spectral features of the porphyrin monomer following the interaction among the porphyrin units. Despite plenty of experimental investigations dealing with the self-organization of porphyrin both in solution and at the solid state, computational studies are still limited.

In this communication, a computational examination of the different porphyrin aggregation approaches will be presented, taking into account the amphiphilic [5-{4-(3-trimethylammonium)propyloxyphenyl}-10,15,20-triphenylporphyrin] chloride, whose aggregation behavior has been previously experimentally investigated. In particular, the definition of appropriate functionals to study and characterize porphyrin aggregates, to get more insights on the kind of the interactions responsible for the formation of the specific noncovalent systems (J-, H-, T- or cation-π aggregates) experimentally observed will be proposed.

Fig. Calculated structures of J-type (left) and cation-π (right) dimers of [5-{4-(3-trimethylammonium)propyloxyphenyl}-10,15,20-triphenylporphyrin] chloride.

Figure 1
Redox Control Recombination in Axially Linked “Donor – Aluminum(III) Porphyrin – Fullerene” Reaction Center Models
Authors: Poddutoori Prashanth K , Zarrabi Niloofar , Lim Gary N. , Seetharaman Sairaman , D'Souza Francis
Published: May 2020

Aluminum(III) porphyrins (AlPor) are well suited for the construction of axially linked multicomponent donor-acceptor systems. The axial hydroxide reacts with carboxylic acids or alcohols to form covalent ester or ether linkage, respectively. Moreover, they bind Lewis bases such as imidazole or pyridine to form a coordination bond with the Al center. They hold high fluorescence quantum yields with adequate singlet and triplet state lifetimes, as well as rich redox chemistry with two reversible oxidation and reduction processes. They can act as either a photosensitizing electron acceptor or donor with a wide variety of redox and optically active compounds. By exploiting these unique properties, we have designed several donor-AlPor-acceptor systems to mimic the reaction center complex of natural photosynthesis. In these systems, we have studied the electron transfer processes in perpendicular to the porphyrin plane. The optical studies showed that the excitation of AlPor results in a sequential electron transfer between redox-active units to generate long-lived radical pairs. I will discuss some of these systems to show how the recombination dynamics depend on the redox potentials.
Using the Electrode Potential to Orient Single Molecules in Nanoscale Electrical Junctions
Authors: Borguet Eric
Published: May 2020

Charge transport through and between molecules is central to important processes in nature. Studying the conductivity of single molecules can contribute to a better understanding of charge transport, and also help to develop building blocks of molecular electronics, light harvesting devices, etc. We measure the conductivity of molecules using the Scanning Tunneling Microscope break-junction (STM-BJ) method that utilizes repeatedly formed circuits where one or a few molecules are trapped between two electrodes, at least one of which has nanoscale dimensions. The statistical analysis of thousands of measurements yields the conductance of single molecules.

One particular interest is the role of the molecule-electrode contact and orientation in charge transport. In the simplest analysis this contact can present a substantial barrier to charge injection, which can have important consequences in devices such as dye sensitized semiconductor nanoparticle solar cells. Our most recent developments include controlling the orientation of the molecule in the junction using the electrode potential so that we can measure conductance along different molecular axes, accessing elements of the anisotropy of the molecular conductance tensor. Specifically, when the molecule is oriented flat, with the molecular plane parallel to the electrode surface, charge transport is measured perpendicular to the molecular plane. This approach can be applied to molecules that do not have suitable molecular anchoring groups for traditional STM-BJ measurements, and allows us to determine the importance of anchoring groups in charge transport in molecular junctions.
Kinetics of Adsorption and Desorption of Non-Covalent Self-Assembling Systems
Authors: Hipps K W , Gurdumov Kirill , Mazur Ursula
Published: May 2020

Self-Assembling systems that rely on non-covalent forces to drive ordering are the subject of intense study. Of particular interest are redox active systems like porphyrins and phthalocyanines that can generate self-assembled monolayers (SAMs) at the solution-solid interface. These offer the potential of creating highly ordered films from the simple process of solution dipping. In recent years, it has become clear that kinetics plays a significant role in determining the structure of these films. However, very little is known about the rates and mechanisms of the formation and stability of these interesting surface layers. In this talk we will present new data and models for the adsorption and desorption kinetics of non-covalent SAMs on gold surfaces. As might be suspected, the adsorption and desorption rates do not follow simple Langmuir behavior. Also, the potential for multilayer growth must be considered.
Electron-Triggered Metamorphism in Porphyrin-Based Self-Assembled Supramolecular Polymers
Authors: Chowdhury Shagor , Kahlfuss Christophe , Dumont Elise , Saint-Aman Eric , Demets Grégoire Jean-François , Ramos Ana Paula , Frath Denis , Chevallier Floris , Bucher Christophe
Published: May 2020

Stimuli-responsive self-assembled molecular materials are currently subject to intense research activity. This growing interest stems largely from the myriad of exciting applications envisioned for dynamic supramolecular assemblies, also known as dynamers, in materials science, sensing, catalysis and electronics. Enormous technologic interests are for instance at stake in being able to devise molecular objects that could respond to external stimuli by changes in structure and function. These particular properties can lead to applications in various domains as (i) in molecular electronics, (ii) in analytic science, with switchable hosts allowing the controlled binding/release of pollutants or drugs, (iii) in materials science with the development of adaptive supramolecular polymers.

Our group has been focusing over the past few years on the development of tailor-made redox-controllable molecular and supramolecular systems involving electrogenerated pi-radicals as key responsive and/or assembling elements [1, 2]. In this lecture, we will focus on the physico-chemical properties of a series of porphyrin-based molecular tectons whose self-assembly can be controlled with optical or electrical stimulus. The dynamic properties of these stimuli-responsive molecular architectures and molecular materials will mainly be discussed on the basis of electrochemical, spectroelectrochemical and ESR experiments supported by quantum chemical calculations [3-6].

References :

[1] C. Kahlfuss, E. Saint-Aman, C. Bucher (2016). Redox-controlled intramolecular motions triggered by π-dimerization and πmerization processes In T. Nishinaga (Ed.), Organic Redox Systems: Synthesis, Properties, and Applications (pp. 39). New-York: John Wiley and sons.

[2] H. D. Correia, S. Chowdhury, A. P. Ramos, L. Guy, G. J.-F. Demets, C. Bucher, Polymer International
68, 572 (2019).

[3] S. Chowdhury, Y. Nassar, L. Guy, D. Frath, F. Chevallier, E. Dumont, A. P. Ramos, G. J.-F. Demets, C. Bucher, Electrochimica Acta
316, 79 (2019).

[4] C. Kahlfuss, S. Denis-Quanquin, N. Calin, E. Dumont, M. Garavelli, G. Royal, S. Cobo, E. Saint-Aman, C. Bucher, Journal of the American Chemical Society
138, 15234−15242 (2016).

[5] C. Kahlfuss, T. Gibaud, S. Denis-Quanquin, S. Chowdhury, G. Royal, F. Chevallier, E. Saint-Aman, C. Bucher, Chemistry - A European Journal
24, 13009 (2018).

[6] C. Kahlfuss, R. Gruber, E. Dumont, G. Royal, F. Chevallier, E. Saint-Aman, C. Bucher, Chemistry - A European Journal
25, 1573 (2019).

Figure 1
Site Isolation of Catalytically Active Mn(III)-Porphyrin into Porous Materials
Authors: Lee Suk Joong , Yoon Jong Ho
Published: May 2020

Porous materials (PMs) including porous coordination polymers (PCPs), metal–organic frameworks (MOFs), porous organic polymers (POPs), and polymers with intrinsic microporosity (PIMs), have received much attention and they often show novel and/or enhanced performances in wide range of applications such as catalysis, separation, gas storage, drug delivery, biosensing, and imaging. Although they can be successfully obtained by controlling the growth conditions, their fabrication is still a major challenge because of lack of information regarding the crucial factors for the precise control of particles during the synthesis. Furthermore, the translation of building blocks into well-defined structures, whose properties and functions are regulated in the building block level, still remains very challenging. In this regard, metalloporphyrins would be good building blocks for the construction of such functional materials witnessed by a wide range of molecular architectures, such as molecular boxes, self-assembled arrays, CPs and MOFs with various applications. Particularly, Mn(III)- and Fe(III)-containing metalloporphyrins are often used to fabricate various functional molecular architectures and to mimic the extraordinary behavior of enzymes in both homogeneous and heterogeneous catalytic systems.In the case of homogeneous catalysis, these materials have frequent trouble with fast catalytic degradation because of µ-oxo dimer formation or ligand oxidation. To avoid the catalyst degradation, the heterogenization of homogeneous catalysts, such as immobilization and/or site-isolation of homogeneous catalysts using supporters are widely used alternative strategies. In this regard, I like to present the preparations and heterogeneous catalytic uses of Mn(III)–porphyrin in various porous materials (PMs).

References

1. D. Y. Shin, J. H. Yoon, S. H. Kim, H. Baik, S. J. Lee,*
Catal. Sci. Technol. 2018, 8, 6306-6310.

2. J. Yi, H. Y. Jeong, D. Y. Shin, C. Kim, S. J. Lee,*
ChemCatChem 2018, 10, 3974-3977.

3. J. Yi, H. M. Ahn, J. H. Yoon, C. Kim, S. J. Lee,*
New J. Chem., 2018, 42, 14067-14070.
Fast and Selective CO2 Reduction into CO with Cobalt Phthalocyanine in a Flow Cell
Authors: Joulié Dorian , Ren Shaoxuan , Salvatore Danielle A. , Torbensen Kristian , Wang Min , Robert Marc , Berlinguette Curtis P.
Published: May 2020

A balance between greenhouse gases production and capture is required to tackle the global warming resulting from them. Carbon dioxide (CO2) is considered as a waste gas but it is also a potential feedstock. Indeed, with the utilization of renewable energies, carbon dioxide electroreduction reaction (CO2RR) can generate useful products within a carbon neutral strategy. Practical CO2 conversion requires catalysts capable of mediating the efficient formation of a single product at high current densities over a long time (1). Among the potential products, carbon monoxide (CO) requires only 2 electrons to be generated which facilitate to reach high faradaic efficiencies. CO is also an important precursor in the chemical industry and its market is large enough to receive this new production method. (2)

High current densities have been hit with copper-based catalysts but these catalysts tend to be nonspecific to only one product. Solid-state catalysts struggle to maintain a relevant selectivity at low overpotentials. They also rely mostly on noble metals or use deposition methods that are not upscalable for an industrial use.

Molecular catalysts can be tuned to be highly selective towards CO at low overpotential but cannot operate CO2RR at relevant current densities for commercial purposes. Best molecular catalysts are close to 100 % faradaic efficiency for CO but the strongest production rate reported is 33 mA/cm² (3). This current density is more than 5 times smaller than the industrial relevant scale. Moreover, these catalysts are usually fragile over time with reported electrolysis less than ten hours.

In this presentation, we will show that Cobalt Phthalocyanine (CoPc) - a widely available and known molecular catalyst - is able to compete with solid-state catalysts. We will illustrate how the CO2 delivery to a gas diffusion electrode can increase the reactivity of a molecular catalyst. We succeed to operate CO2RR with 95% faradaic efficiency for CO at 150 mA/cm² and an overall cell potential of 2.45 V. (4) We will also emphasize how the tunability of such catalysts can lower the reaction overpotential and increase the stability. (5)

1: Ind. Eng. Chem. Res. 2018, 57, 2165−2177

2: Acc. Chem. Res. 2018, 51, 4, 910-918

3: ACS Energy Lett. 2018, 3, 10, 2527-2532

4: Science 2019, 365, 6451, 367–369

5: Nature comm. 2019, 10, 3602
The Effect of Prolyl Hydroxylase Domain-Containing Protein Inhibitors on Porphyrin Accumulation in Cancer Cells
Authors: Matsui Hirofumi , Kurokawa Hiromi , Matano Daisuke
Published: May 2020

Introduction: The authors found that reactive oxygen species (ROS) accelerate both the cancer cellular porphyrin accumulation and the effect of photodynamic therapy. We confirmed that EPO/ EPO receptor was a key of signal transduction. EPO has been known used to be up-regulated at the metabolic acidosis via the stabilization of HIF-1α, a nuclear factor. Since HIF-1α can be stabilized by not only acidosis but also the high concentration of nitric oxide (NO), NO rich cancer cells may involve EPOR. Moreover, the purpose of EPO-EPOR system is likely to survive the hypoxic condition, it may keep intracellular heme/ porphyrins. Recently, prolyl hydroxylase domain-containing protein inhibitors (PHDI) are gathering attention as drugs for anemia. Since these drugs continuously stabilize HIF1, EPO-EPOR system in cancer cells may be activated. Thereby, cancer specific porphyrin accumulation should be accelerated.

Methods: To prove these possibilities, the authors carry out following experiments with gastric and colorectal cancer cells. The existence of EPOR, the amount of ABC transporters (B1, C5, G2) after the PHDI exposure (dose dependency and time dependency) were analyzed by western blotting. Cytotoxicity of both PDT and anti-cancer drugs with or without rEPO was measured with the Cell Counting Kit-8.

Result: (1) EPOR existed in each cell line used in this study. (2) PHDI treatment involved down regulation of ABC transporters (B1, C5, G2) in dose dependently. (3) ABCG2 expression decreased after PHDI treatment. However, its expression re-increased 48 hours after treatment. (4) The pretreatment of PHDI significantly increased the effect of PDT, doxorubicin, paclitaxel, irrinotecan, cisplatin, 5-FU and oxaliplatin even in chemo-resistant cells.

Conclusions: PHDI accelerates the effect of PDT and anti-cancer drugs.
Electrochemistry and Spectroscopy of Tri- and Tetracationic Porphyrins
Authors: Osterloh Ryan , Chilingaryan Tatevik , Habermeyer Benoît , Guilard Roger , Kadish Karl M.
Published: May 2020

Water-soluble cationic porphyrins have been shown to possess promising therapeutic potential, through biochemical processes. which depend on solubility as well as the extent of aggregation. under biological conditions. These properties are influenced by a multitude of factors the most important of which are the number of positively charged meso-substituents, the type of counteranion, the central metal ion and the solvent. We have previously investigated mono- di- and tetra-methylpyridyl porphyrins with mainly Cl- counterions and we now turn our attention to trisubstituted derivatives of the type shown at the bottom of the figure. These six new tricationic porphyrins represented as [(TriMPyP)M]3+X-
3 (where M = 2H, ZnII or PdII and X- = Cl- or Tosyl-) containing three N-methyl-4-pyridyl groups and chloride or tosylate counteranions were electrochemically and spectroscopically characterized for the first time. The physicochemical properties of the [(TriMPyP)M]3+X-
3 complexes were compared, under the same solution conditions, to several free base and metal tetracationic porphyrins shown at the top of the figure and represented as [(TMPyP)M]4+X-
4 (where M = 2H, MnIII, FeIII, CoII, ZnII or PdII).

Figure 1
(Invited) Advanced Anode Architectures for Improved Fast Charge Capability
Authors: Karulkar Mohan , Torres-Castro Loraine , Lamb Joshua
Published: May 2020

The ability to fast charge automotive lithium ion batteries is key to enabling wide scale adoption by consumers. A primary challenge to fast charging is lithium plating due to insufficient lithium diffusion rates into the graphite anode. Plating and subsequent poor cycling of plated lithium leads to capacity loss over time, and possible failure due to dendrite-induced short circuit. Sandia National Laboratories and University of Michigan have worked together to develop advanced anode architectures, known as Highly Ordered Hierarchies (HOH), to increase lithium diffusion rates and avoid lithium plating. This work will describe Sandia's latest efforts to characterize and quantify the improvements brought on by these advanced anode structures. High precision cycling and isothermal control during fast charging allow very precise tracking of cycle-to-cycle efficiency and intra-cycle differential coulometry. These methods are used to detect and quantify lithium plating at the earliest stages, and provide a quantitative basis for evaluating the dependence of lithium plating on anode architecture, temperature, and current. We will describe the beneficial effects of HOH anode structures, as well as the beneficial effects of moderate temperature increases. A thorough discussion on experimental conditions will also be conducted, to aid others in performing similar measurements.
(Keynote) Terahertz Nanoplasmonics Technology: Physics, Applications, and Commercialization
Authors: Shur Michael
Published: May 2020

The minimum feature sizes of the Si VLSI reduced to 7 nm in 2017 with the 5 nm Si VLSI reported at IEDM 2019 and 3 nm Si VLSI technology on the roadmap for 2021. These transistors operate in the regime when the electron mean free path for collisions with impurities or lattice vibrations exceeds the device dimension. One new feature of this mode of transport is “ballistic mobility” replacing the conventional mobility and being proportional to the channel length. At high frequencies, the electron inertia in short channel devices plays a dominant role and the waves of the electron density (plasma waves) enable the device response well into the terahertz (THz) range of frequencies. Excitation and rectification of the plasma waves enables numerous application in terahertz sensing and communications. Terahertz sensing enables detection of biological and chemical hazardous agents, cancer detection, detection of mines and explosives, provides security in buildings, airports, and other public spaces, and widely used for industry quality control and radio astronomy applications. A new emerging application is for cyber hardware security to distinguish between faked and genuine VLSI chips and predict the VLSI reliability. THz communications, extensively explored since the beginning of the 21-st century, will enable very high data rates (over 430 GPS demonstrated for the W-band) for applications such as driverless cars, autonomous tactical networking with ground and aerial vehicles, and 4K video and cloud storage applications. THz signals can penetrate through fog and dust. The available bandwidth at THz frequencies, makes them uniquely suited for Wireless Local Area Networks (WLAN) and Wireless Personal Area Networks (WPAN). THz sources and detectors can produce tight beam widths and support low power directional networking. The 200 to 300 GHz band is proposed for the next generation Wi-Fi (beyond 5G) that could be implemented using deep submicron silicon. GaN, p-diamond, and graphene based Terahertz FETs – TeraFETs - will compete with Si for THz applications promising further improvements in THz detectivity and generated THz power. There is, however, a large gap between the advanced experimental and theoretical THz electronics research and currently deployed THz technology. I will discuss the problems facing the THz plasmonic nanoplasmonics technology commercialization and projections for bridging the famous THz gap.

Figure 1
(Keynote) Engineering Research Centers –Past, Present and Future
Authors: Wang Kon-Well
Published: May 2020

During the recent decades, the scientific and engineering community and the federal agencies have explored the potential of large-scale center-type research programs. It has been recognized that many of the most challenging and complex technical problems can only be addressed if researchers with diverse expertise combine their efforts and work across the boundaries between disciplines. The National Science Foundation (NSF) Engineering Research Center (ERC) program is a flagship program in this regard.

The ERCs are interdisciplinary, multi-institutional centers that join academia, industry, and government in partnership to produce transformational engineered systems and educate individuals that are adept at innovation and primed for leadership in the global economy. They operate at the interface between the discovery-driven culture of science and the innovation-driven culture of engineering. Since the ERC program’s inception in 1984, NSF has funded over 70 ERCs across the United States. The NSF funding level has been at about $4 million per year for each ERC for up to 10 years, during which time the centers would develop partnerships with industry, universities, and other government entities to sustain them upon graduation from NSF support. Throughout the years, the ERCs have contributed significantly to the technical community and the nation; educated more than 12,000 engineering graduates with interdisciplinary training, produced a tremendous amount of high impact publications, patents and licenses, and spin-off companies. Studies have estimated that the total downstream market value of ERC innovations to the U.S. economy is well over tens of billions of dollars. Recently, NSF funded the National Academies of Sciences, Engineering, and Medicine (NASEM) to conduct a study to create a vision for future research centers in engineering (A New Vision for Center-Based Engineering Research, 2017, The National Academies Press). Building upon the NASEM’s recommendations, NSF developed a roadmap for the next generation of ERCs (Gen-4), which emphasizes cutting-edge research efforts that are convergent and will lead to strong societal impact. A Gen-4 ERC will have interacting foundational components that cover convergent research, workforce development, culture of diversity and inclusion, and innovation ecosystem. This presentation will provide an overview of the NSF ERC program to date, as well as new opportunities for the Gen-4 ERCs.
(Invited) Nanomanufacturing Research and Advanced Manufacturing at the National Science Foundation
Authors: Cooper Khershed
Published: May 2020

Nanomanufacturing is the fabrication of nano-scale (1-100nm) building-blocks (nanomaterials, nanostructures), their assembly into higher-order structures (components and devices), and the integration of these into larger scale systems. Nanomanufacturing Research is the study of processes to manipulate and control matter at the nanoscale in 1-, 2-, and 3-dimensions, reproducibly. The National Science Foundation has been at the forefront of nanomanufacturing research since the beginning of the National Nanotechnology Initiative was announced in 2000. This talk covers basic research activities and accomplishments in nanomanufacturing, scalable nanomanufacturing, and scalable nanomanufacturing for integrated systems. Today, the nanomanufacturing program is part of the Advanced Manufacturing (AM) Program. The AM program is an amalgam of previous manufacturing research programs that explored nano, additive and subtractive manufacturing, and materials engineering and processing. It seeks new ideas in, across and outside these domain areas and encourages interdisciplinary research that bring manufacturing to new application areas, and that incorporate challenges and approaches outside the customary manufacturing portfolio to broaden the impact of America’s advanced manufacturing research. In this presentation, the AM program’s goals and its participation in cross-divisional activities, such as NSF’s Big Ideas, are also described.
(Invited) Synthesis of Monochiral CNTs
Authors: Lashmore David , Bystricky Pavel , Bulmer John
Published: May 2020

The conductivity of CNT yarn or wire depends on chirality, alignment, doping, lack of contamination, residual amorphous carbon, and twist angle. All these factors must be well controlled to obtain good conductivity. This talk addresses one of these issues, the synthesis of all metallic tubes, and as it happens these tend to be of predominately the same chirality. The synthesis and characterization of monochiral tubes are difficult due to variable bundle strain and the consequent shift in the Radial Breathing Mode Peaks. In this presentation, we present a method for compensating for this strain phenomenon that utilizes the known strain-free position of the G band. We also present TEM data of SWCNT metallic carbon nanotube material as is, and with amorphous carbon removed. The latter is important to analytically determine the crystal structure and diameter of the tubes. We found that: (1) the tubes are remarkably consistent in diameter, (2) the diameters ranged from about 1.2 to 2.5 nm but most bundles were about 1.7nm consistent with our TEM and Raman findings, and finally (3) We found that all the tubes resided in bundles that vary in size. We used both acetylacetonate and benzyl alcohol as carbon sources. We showed by TEM the bundles are monochiral.
Synthesis and Characterization of Cellulose Acetate- Titanium (IV) Tungstomolybdate Nanocomposite Cation Exchangers for the Removal of Selected Heavy Metals from Aqueous Solution
Authors: Woldegebriel Belay Minase
Published: May 2020

Novel Cellulose acetate titanium (IV) tungstomolybdate nanocomposite cation exchanger was synthesized by sol-gel method by incorporating cellulose acetate polymer into inorganic exchanger, titanium (IV) tungstomolybdate. Different techniques including FTIR, XRD, TGA SEM and BET were used to characterize the exchanger. The Cellulose acetate titanium (IV) tungstomolybdate (CATTM) behaved as a good cation exchanger with IEC of 1.64 meq g-1 for Na+ ions. The sequence of ion exchange capacity for alkali metal ions was found to be K+> Na+> Li+ and that for alkaline earth metal ions was Ba2+ > Ca2+ >Mg2+ .These orders revealed that the ions with smaller hydrated radii acquired larger ion exchange capacity. The pH titration curve indicated that the material obtained as such is a bi functional strong cation exchanger as indicated by a low pH (~2.25) of the solution when no OH- ion was added. Thermal analysis of the material showed that the material retained 55% of its ion exchange capacity up to 600°C. Adsorption behavior of metal ions in different solvents with varying concentration has also been explored and the sorption studies revealed that the material was selective for Cr(III) and Pb(II) ions. The analytical utility of the material was investigated by performing binary separations of selected metal ions in a column based on the distribution coefficients of the metals. Cr(III) and Pb(II) were selectively removed from synthetic mixtures of Cr(III)-Cd(II), Cr(III)-Fe(III), Pb(II)-Cd(II) and Pb(II)-Fe(III). Antimicrobial activity of the synthesized inorganic compound was evaluated and showed a considerable antibacterial activity against Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli and Shigella flexneri. The inorganic counterpart has also exhibited a promising antifungal activity against Aspagilus niger and Fusarium oxysporim.

Key Words; Binary separations, Cellulose acetate, Characterization, Nanocomposite, Sol-gel method.
A Study of the Electrical Properties of the Polydopamine Coating of CNTs: A New Path to Fabricate Copper-Carbon Composites
Authors: Duhain Antoine , Lamblin Guillaume , Lenoble Damien
Published: May 2020

In present days, the continuous miniaturization of electronic devices comes along with a problematic reduction of their life-time. This is due to the underlying current density being operated increasingly close to the maximum current-carrying capacity (ampacity) of the materials (copper, gold...) used in the conduction channels of micro-circuitry. In this respect, there is a growing attention for new materials with higher ampacity and copper-carbon nanotube (CNT) composites could constitute a promising alternative. The interest of such copper-carbon composites relies on the combination of the complementary properties of both materials: the high conductivity of copper and the high ampacity of CNTs.

However, the fabrication of an efficient Cu-CNT composite still remains a huge challenge and, up to now, the metal filling of a CNT matrix using electrochemical methods systematically requires an organic solvent based solution, which is not industrially and ecologically friendly. This constitutes an important drawback of those types of fabrication paths.

A new promising way to fabricate such a composite by electrochemistry is shown in our work (see figure 1). It is based on the coating of CNTs by polydopamine (pda) cross-linked with copper ions. The coated CNTs are sprayed to form a matrix and the interstices are then filled with metallic copper by using an electrochemical step in aqueous solution.

It is relevant to study how pda impacts the CNT surface conductivity and to try to increase it in order to promote electron transfer through the copper-CNT interface. In this respect, we want to evaluate the conductivity of CNT surface by using AFM probing. To assess the impact of pda, we compare conductivity values of uncoated CNTs with coated CNTs. We also show the change in conductivity when the coated CNTs are annealed at different temperatures under inert atmosphere conditions. To better understand the electrical properties, we characterize the CNT coatings before and after thermal treatment with FTIR, STEM, XPS, and DSC, which in particular shows the transformation of the pda layer and the formation of well-dispersed nuclei on the CNT surface.

Figure 1
Analysis on Temperature Dependent Corrosion of Tantalum in Acidic Fluoride Media
Authors: Punathil Meethal Ranjith , Srinivasan Ramanathan
Published: May 2020

Tantalum (Ta) exhibits excellent corrosion resistance in most aqueous media as it forms chemically inert thin oxide layer when exposed to air or water. Due to the high corrosion resistance, Ta is used in chemical industries as lining material for piping, tanks and vessels (1). Although Ta possess excellent corrosion resistance, it dissolve very slowly in acidic fluoride media. In the present work, the corrosion rate of Ta in acidic fluoride media at different temperatures were measured from weight loss experiment and compare with the results of electrochemical Tafel extrapolation.

The weight loss experiments were performed with Ta sheets of 2.5 × 2.5 cm with 1 mm thickness. Prior to the experiments, Ta sheets were polished with 0.3 µm alumina powder and cleaned by ultrasonicated in ethanol, rinsed in deionized water and dried with nitrogen gas. The temperature of the HF solution was maintained using a water bath and double-walled polypropylene beaker set up. The weight loss experiments were performed in various concentration of HF from 250 to 1000 mM HF and the experiments were also conducted by adding 250 mM KF/ H2SO4 into 500 mM HF solution to study the key HF dissociated species responsible for the corrosion of metal. The weight loss was measured at different temperature of the solution varied from 30 to 60 °C for any concentration of HF solution. In most of the experiments, the weight difference before and after the experiments were used to calculate the dissolution rate. A few experiments were also conducted wherein the weight was continuously monitored, so that the dissolution rate can be monitored as a function of time.

The experimental dissolution rates of Ta in various concentrations of HF at different temperatures are shown in Fig. 1. An analysis of the results shows that corrosion of Ta is assisted by both undissociated HF and species. The activation energy of the reactions were estimated using Arrhenius expression, and the results show that Ta corrosion in acidic fluoride media is very sensitive to temperature and will proceed at rapid rates at high temperatures.

The corrosion of Ta in acidic fluoride media at room temperature was also characterized using several electrochemical techniques, viz. Tafel extrapolation, electrochemical impedance spectroscopy and linear polarization. A comparison of the results of weight loss experiments show that Tafel extrapolation over predicts the corrosion rate, in most of the conditions. The EIS spectra obtained at OCP shows multiple loos (capacitive and inductive) in most of the concentrations and equivalent circuit analysis was used to estimate the R
P value. The XPS analysis was also performed to understand the different metal oxide species present during the corrosion process. The results indicates that the dissolution process of Ta occurs viz. multiple intermediate steps.

References

1. K. Schulz and J. Papp, Niobium and tantalum: indispensable twins, in, US Geological Survey (2014).

Figure 1
Modeling the Effect of Fast Charge Protocol on the Temperature Rise of a Lithium-Ion Battery during Charge
Authors: Lee Jaewoo , Koo Boram , Shin Chee Burm
Published: May 2020

The lithium-ion battery (LIB) is a preferred power source for battery electric vehicles (BEVs),because LIBs have higher energy density, longer life and higher power density than most other practical batteries. Although there is still a plenty of room to be improved for the cost, life, and safety of the LIB in BEV applications,another important issue to be overcome for the BEV battery is searching for an appropriate fast charge protocol to enable a rapid growth of BEV market. A short charge time, however, results in a rapid temperature rise of an LIB cell during charge. Therefore, it is essential to find an optimized fast charge protocol that can keep the peak temperature of LIB cell below the maximum allowable limit recommended by the LIB manufacturer.

In this work, the effect of fast charge protocol on the temperature rise of an LIB cell during charge is analyzed based on the two-dimensional thermal modeling of the LIB cell under various fast charge protocols. The thermal modeling during fast charge is validated by the comparison of the modelling results with the experimental measurements using IR thermal images and thermocouples. The fast charge protocols are evaluated based on the peak temperatures of the LIB cell after charge.
Relationship between Metallurgical States and Corrosion Resistance of Nitrided Martensitic Steels in Marine Environment
Authors: Creus Juan , Reilhac Pierre , Michel Gregory , Branger Vincent , Frappart Simon , Fleche Denis , Trinh Dao , Feaugas Xavier
Published: May 2020

The objective is focused on the comprehension of the relationship between the metallurgical state and the functional properties of nitrided martensitic stainless steels.

Nitriding is performed by a low temperature plasma treatment (Direct Current mode) in various conditions. Metallurgy of the nitrided layer was characterized at different scales, from the macroscopic to the nanometric ones. An increase of the thickness of the nitrided layer with temperature of the plasma treatment is observed. Precipitation of CrN and others nitrided phases in relation with crystallographic defects is observed. Moreover, the TEM analyses on FIB samples extracted from the surface highlight the formation of a succession of different nitrided layers depending on the nitrogen content : expanded martensite, iron-nitride phases [2].

The electrochemical properties of nitrided samples are also assessed by voltammetry test and extended immersion test. Results highlight differences on the corrosion behaviour of the nitrided X17CrNi16-2 steels with temperature of the plasma treatment. The reactivity evolution is linked to the formation of a “composite” system composed of different layers. SECM was used to understand the reactivity evolution through these layers, and successive surface grinding permits to corroborate the reactivity evolution and to understand the origin of the corrosion resistance evolution after nitriding process.

[1] H.E. Boyer, T.L. Gall. Metal Handbook, Desk edition, ASM, Ohio, USA, 1986

[2] J. Yang &al. Materials and Design, Vol. 32 (2011) 808-814
Hydrogen Absorption By Copper Coated Steel Used Nuclear Fuel Container Materials Under Deep Geological Repository (DGR) Conditions
Authors: Hayatdavoudi Hadis , Noel Jamie
Published: May 2020

The used fuel container is a key barrier to isolate and contain used nuclear fuel in a deep geological repository (DGR). We are probing the possibility that one container failure mode could arise from the presence of hydrogen that could lead to coating delamination at the interface of copper and steel. In this study galvanostatic polarization was used to produce hydrogen electrochemically on a copper surface at various rates and for various durations. Consequently, thermal desorption analysis (TDA) was applied to investigate the hydrogen uptake by the copper metal. Also, focused ion beam (FIB) cutting and scanning electron microscopy (SEM) were conducted to observe surface damage due to the hydrogen charging. The results to date showed that the efficiency of hydrogen absorption by the copper is both current- and time-dependent.
Effect of Metallic Salts on Corrosion Behavior of Carbon Steel with Rust Layer
Authors: Tsuchiya Hiroaki , Jiao Jingyu , Kim Kyung-Tae , Hanaki Koushu , Yamashita Masato , Fujimoto Shinji
Published: May 2020

Recently, deterioration of steel infrastructures such as bridges due to atmospheric corrosion has manifested and therefore, countermeasures against corrosion are strongly desired because rusts formed on carbon steels are poorly protective. In order to improve the protectiveness of rust layer, the understanding on the characteristics of rusts on carbon steels is indispensable. Weathering steels are well-known to exhibit better atmospheric corrosion resistance compared to carbon steel. The improved corrosion resistance of weathering steels is ascribed to protective layers on weathering steels during long-term exposure to the atmosphere. It has been reported that the additive elements such as Cr, Cu, Ni and P used for weathering steels contribute to the formation of protective layers. In the present work, we examined the introduction of various metallic cations into rust layers on carbon steel to modify the structure and composition of rust layers and thereby their resulting electrochemical properties.
Non-Destructive X-Ray Microprobe Characterization of Corrosion at the Polymer/Steel Interface
Authors: Barlow Burke Cameron , Burgess Ian James , Grosvenor Andrew , Situm Arthur
Published: May 2020

This work used the unique capability of synchrotron x-rays to probe a buried polymer/metal interface with high energy resolution and spatial resolution on the micron scale. X-rays of sufficient energy can penetrate the organic polymer coating and interrogate heavier elements found at the interface. X-ray fluorescence (XRF) spectra can be collected provided the element specific energy of the fluoresced photon is sufficient to penetrate through the polymer coating. We characterized the interface beneath several polymer coatings on steel reinforcing bar after exposure to alkaline potash brine using the Soft X-ray Microcharacterization Beamline (SXRMB) at the Canadian Light Source. Characterization included correlated XRF maps for Fe, Mn, K and Cl as well as micro x-ray absorption near edge spectroscopy (µ-XANES) to analyze Fe corrosion products at certain areas of interest. By collecting Fe XRF maps with an incident beam energy of 7115 eV, we exploited the differences in absorption cross section between Fe metal and oxidized Fe species at this energy. The result is a map with excellent contrast between corroded and non-corroded regions of the interface. This provides a relatively quick means to locate localized anodic zones beneath opaque polymer coatings without a visual indicator (i.e. a blistered region of polymer). XRF maps for K and Cl showed these elements were segregated at the interface with K hotspots providing a surrogate measurement for cathodic activity at the interface. µ-XANES analysis showed evidence of Fe corrosion products that varied somewhat from those reported in previous studies, owing to our efforts to perform sample handling in an inert atmosphere after the exposure to potash brine. The speciation of Fe combined with the spatial distribution of Mn, K, Cl provided evidence to support previous literature models pertaining to mechanisms of coating delamination and the spread of corrosion at the polymer/metal interface.
Corrosion Rate Investigation of Magnesium and Some of Its Alloys in 0.9% NaCl Solution
Authors: Ostapenko Gennady I.
Published: May 2020

Magnesium(Mg)-based biomaterials are candidates for use as biodegradable metals. Mg can dissolve in body fluids, which means that implanted Mg can decompose during the healing process and it will not leave debris after healing is completed. However, uncontrolled degradation can destroy the scaffolds, leading to premature failure of the implant. The rate of magnesium degradation can be controlled by various impurities.

Here, the corrosion of Mg and some of its alloys is investigated by electrochemical impedance and voltammetry methods. In the Figure, for example, the voltammogram (a) and impedance hodograph (b) are shown for an alloy containing 6.0 mass % Zn and 0.5 mass % Zr. In the Table, the corrosion rates are given from impedance measurements as the closest to stationary corrosion conditions.

The corrosion rate is determined by the chemical composition and structure of the oxidation product layer. The shift of the corrosion potential in the anodic direction after cathodic polarization is explained by kinetic difficulties of electrode reactions in the presence of the reaction product layer.

Figure 1
Assessing the Corrosion Pattern of Magnesium Alloy Implants in Simulated Salivary Fluids at Different pH
Authors: Eduok Ubong
Published: May 2020

Magnesium (Mg) alloy implants are formidable structural metals for biomedical applications, they are limited due to Mg chemical reactivity and its susceptible to corrosion. Efficient mitigation control toward Mg corrosion can only be proposed if its degradation kinetics are properly understood in various media. In the biomedical field, the auto-controlled degradation mechanism of orthopedic Mg implants eliminates repeated surgeries while also minimizing the risks associated with these medical procedures. However, their rapid degradation kinetics between living tissues contribute to sudden changes in local pH value, accumulation of unwanted hydrogen gas in bone cavities and subsequent mechanical failure. In this work, we have investigated the degradation pattern of Mg alloy implant in chloride-enriched simulated salivary fluids at different pH at room temperature. The implant demonstrated varying rates of corrosion and passivation within a range of pH of corrosion media. The effects of solution treatment on implant corrosion behavior was vividly studied and the trend of increasing corrosion was low pH > saline pH > high pH. Localized corrosion behavior has been observed by scanning electron microscopy evidence while electrochemical impedance spectroscopy and potentiodynamic polarization techniques revealed increased anodic polarization and charge transfer, respectively. The chemistry and diffraction phases of adhering corrosion products as well as their surface morphologies was also been identified. The implant must have uniformly corroded within the salivary fluids over an extended duration; however, the early corrosion stages reveal localized passivation of oxide films at grain boundaries at low pH.

Most metallic implants made of corrosion-resistant alloys (e.g., cobalt, titanium and nickel) are excellent candidates for oral surgeries. However, most of them cannot serve as bone cements to stabilize dental implants during post-surgery tissue healing; a function that is possible with magnesium-based bone cement [1,2]. The use of these metal-type temporary implants in binding bone structures normally will require a secondary surgery operation to remove them, and this might lead to potential infections. This study features the analyses of the corrosion patterns of Mg alloy implants deployed in orthopedic applications. The salivary pH changes induce corrosion toward septic loosening prior to Mg implant degradation and dental implant infections.

References

[1] A. Mohamed, A.M. El-Aziz, H.G. Breitinger, Journal of Magnesium and Alloys, 7, 249 (2019).

[2] B.M. Sehlke, T.G. Wilson, A.A. Jones, M. Yamashita, D.L. Cochran, Journal of the Academy of Osseointegration, 28, 357 (2013).