bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple and Effective Gas-Phase Doping for Lithium Metal Protection in Lithium Metal Batteries
Authors: Park Hyeokjun , Moon Sehwan , Yoon Gabin , Kang Kisuk
Published: February 2020

Elemental lithium metal has received a great attention as an ideal high-energy-density negative electrode material for lithium batteries, owing to the highest theoretical specific capacity (3860 mAh g-1) and the lowest negative electrochemical potential (-3.040V vs. standard hydrogen electrode). While these latent merits have been significantly plagued by the catastrophic safety issues of lithium metal anodes, which are tied to chronic problems such as (1) lithium dendritic growth and (2) the high reactivity of metallic lithium in electrolyte, recent intense demands for rechargeable batteries with higher energy density has made lithium metal come into the spotlight again. Moreover, various next-generation batteries including lithium-sulfur (Li-S) and lithium-oxygen (Li-O2) systems with exceptionally high energy density heavily rely on the stable cycling of lithium metal electrode. Thus, the utilization of lithium metal anode in rechargeable system is pivotal not only for the further development of lithium ‘ion’ batteries employing high energy lithium metal anode, but also for the realization of the next-generation battery chemistries. Herein, we propose a facile and cost-effective approach to stabilize lithium metal anode using gas phase doping to the electrolyte. We find that the use of gaseous sulfur dioxide as an electrolyte additive is particularly effective for enhancing the chemical/electrochemical stability of the lithium metal surface among various gas additives. The surface analyses reveal that the reduction of sulfur dioxide gas occurs on the lithium metal and produces a thin layer of inorganic Li-S-O compounds, which aids in the development of artificially uniform SEI layers. It also leads to the homogeneous supply of lithium ions to the lithium electrode throughout the uniform SEI layer. Furthermore, the applicability of sulfur dioxide-induced protection layer is examined in several electrolyte systems including acetonitrile based electrolytes which are highly reactive with lithium metal, confirming the simple and effective gas doping strategy to stabilize lithium metal electrode for various types of lithium batteries. This finding of the enhancement of lithium metal stability using sulfur dioxide gas also suggests the underlying reason for the remarkably long calendar life and high efficiency of lithium-sulfur dioxide primary batteries that have been developed in 1970s. This revisit demonstrates that stable and homogeneous protection layers on the lithium metal induced by sulfur dioxide additives efficiently suppress the selective growth of lithium and provides with a detailed mechanistic study using the combined experimental and computational investigations.
Properties of Silicon-Electrolyte Interphase (SEI) – Individual Components
Authors: Han Sang-Don , Wood Kevin N. , Coyle Jaclyn , Xu Yun , Stetson Caleb , Harvey Steve , Al-Jassim Mowafak , Zakutayev Andriy , Teeter Glenn
Published: February 2020

The stabilization of a solid electrolyte interphase (SEI) is one of the great challenges to utilize superior theoretical capacity (about 3,600 mAh g-1, almost 10 times higher than that of graphite) of a silicon (Si) as an anode in a next-generation advanced lithium-ion battery (LIB). A SEI remains a poorly understood and hardly studied topic relative to the research devoted to battery components due to its intrinsic properties of complexity, reactivity and continuous evolution.1 However, the SEI plays a key role in prevention of further electrolyte reduction and desolvation of Li+ ions, which is directly related to electrochemical performance, lifetime and safety of batteries. For example, the unstable SEI on a Si anode leads to initial irreversible capacity losses, poor cycling stability and a limited cycle life.2-4

In this study each ‘individual’ component of SEI on a Si anode was prepared as a thin film, and the physical, electrochemical, mechanical and structural properties of prepared films were characterized using a variety of analytical equipment including electrochemical impedance spectroscopy, operando X-ray photoelectron spectroscopy, atomic force microscope, Fourier-transform infrared spectroscopy, scanning spreading resistance microscopy and time-of-flight secondary ion mass spectrometry. This study can provide a strong guidance to aid in the development of new electrolytes, additives and binders to stabilize SEI layer on a silicon anode by identifying beneficial components and providing mechanical explanation of a variety of reactions and phenomena in a SEI.

References

M. Gauthier, T. J. Carney, A. Grimaud, L. Giordano, N. Pour, H.-H. Chang, D. P. Fenning, S. F. Lux, O. Paschos, C. Bauer, F. Maglia, S. Lupart, P. Lamp and Y. Shao-Horn, J. Phys. Chem. Lett. 2015, 6, 4653.

B. Philippe, R. Dedryvere, M. Gorgoi, H. Rensmo, D. Gonbeau, and K. Edstrom, Chem. Mater. 2013, 25, 394.

T. Jaumann, J. Balach, M. Klose, S. Oswald, U. Langklotz, A. Michaelis, J. Eckerta, and L. Giebelera, Phys. Chem. Chem. Phys. 2015, 17, 24956.

B. T. Young, D. R. Heskett, C. C. Nguyen, M. Y. Nie, J. C. Woicik, and B. L. Lucht, ACS Appl. Mater. Interface 2015, 7, 20004.
(Invited) The Advantages of the Nemaska Electrochemical Process to Directly Synthesize High Purity Lithium Hydroxide
Authors: Magnan Jean-François
Published: February 2020

Nemaska Lithium has developed an electrochemical process to produce high purity lithium hydroxide directly using a green and low cost hydroelectric power as the main resource. This electrochemical process converts directly the lithium sulfate extracted from spodumene concentrate into lithium hydroxide and sulfuric acid of high purity. In comparison with the conventional chemical process who produce technical grade lithium carbonate and sodium sulfate by-product using soda ash, the Nemaska electrochemical process has significant advantages. The quality of the product is higher, the operational cost is lower and the benefits for the environment are huge. The advantages of the Nemaska process will be discussed in detail. The growing demand for high-purity batteries grade lithium hydroxide monohydrate for the synthesis of cathode materials for rechargeable lithium batteries will also be discussed.
Preparation and Characterization of Monovalent Cation Selective Membranes Prepared By a Double Pore-Filled Technique
Authors: Choi Young-Woo , Lee Mi-Soon , Jeong Nam-Jo , Yang Seung-Cheol , Choi Ji-Yeon
Published: February 2020

In order to minimize membrane fouling in electrochemical systems using ion exchange membranes, we are having developed monovalent cation selective membranes prepared by a pore-filled technique. The transparent pore-filled membranes indicated that the porous PE substrate was successfully filled with polymer electrolyte by UV irradiation. The weight ratio of anion polymer electrolyte layer was 0.20 and 0.59. The dimensional stability and area resistance of the monovalent selective membranes increased with the weight content of anion polymer electrolyte. Lab-made monovalent selective membranes showed low ion permeability. However, they have similar permeability ratio between NaCl and MgCl2 (or CaCl2) than CMV, and the flux of the sample was slightly higher than commercial membrane. Further characterizations of the resulting membranes will be performed, and reported in the near future.
(Invited) Self-healing Polysaccharide-based Hydrogels as Injectable Carriers for Neural Stem Cells
Authors: Mei Chen Yong , Zhao Wei , zhao Jingyi , Zhang Pengbo , Zhang Qiqing
Published: February 2020

Self-healing injectable hydrogels can be formulated as three-dimensional carriers for the treatment of neurological diseases with desirable advantages, such as avoiding the potential risks of cell loss during injection, protecting cells from the shearing force of injection. However, the demands for biocompatible self-healing injectable hydrogels to meet above requirements and to promote the differentiation of neural stem cells (NSCs) into neurons remain a challenge. Herein, we developed a biocompatible selfhealing polysaccharide-based hydrogel system as a novel injectable carrier for the delivery of NSCs. N-carboxyethyl chitosan (CEC) and oxidized sodium alginate (OSA) are the main backbones of the hydrogel networks, denoted as CEC-l-OSA hydrogel (“l” means “linked-by”). Owing to the dynamic imine cross-links formed by a Schiff reaction between amino groups on CEC and aldehyde groups on OSA, the hydrogel possesses the ability to self-heal into a integrity after being injected from needles under physiological conditions. The CEC-l-OSA hydrogel in which the stiffness mimicking nature brain tissues (100~1000 Pa) can be finely tuned to support the proliferation and neuronal differentiation of NSCs. The multi-functional, injectable, and self-healing CEC-l-OSA hydrogels hold great promises for NSC transplantation and further treatment of neurological diseases.
(Invited) Utility of Biomolecular Motors for Studying Collective Dynamics of Active Soft Matters and Future Application in Molecular Robotics
Authors: Kakugo Akira
Published: February 2020

Self-propelled biomolecular motor systems, such as microtubule-kinesin are intricate natural machines with capability of converting chemical energy into mechanical work with high efficiency. In recent years the biomolecular motor systems have emerged as promising candidates for studying active self-assembly which has been based on the in vitro gliding assay of the motor systems. Several strategies have been developed to demonstrate active self-assembly of the biomolecular motors which offered a wealth of organized and complex structures. Here we discuss the latest progress in the active self-assembly of microtubules-kinesins with an emphasis on the emergence of various structures, relevant design parameters for controlling their polymorphism, and their future potentials.
(Invited) Polymer Simulations Under External Fields
Authors: Washizu Hitoshi
Published: February 2020

In order to design next generation functional polymers, not only the structure but the dynamics under external field should be understood. In this paper we report our simulation approach to investigate the structure and dynamics.

Polymer brush is used for the model system of very low friction such as synovial joints. Recently, polymer brush is focused as a functional binder of sodium ion secondary battery. Since sodium ions are hard to make passive film, or SEI (solid electrolyte interphase) layer on the negative electrode, functional polymer binder help to stabilize the atmosphere around the electrode. We simulate the ionic conductivity of polyelectrolyte binder system under external electric field. The conductivity depend on the polymer structure, such as hardness and linear charge density of the polymer chain.

The other important function of polymers are the fluid dynamics effect of polymers under external fluid field. As a model system of VII (viscosity index improver) polymers, we simulate the dynamics under shear filed. The dynamics of polymers are studied for bulk system and the confined system. We made simulation algorithm. The Brownian motion of polymer segments are treated by Langevin Dynamics, and the solvent flow is treated by Lattice Boltzmann Method, in order to obtain both high computational efficiency and precise dynamics. We succeed to reproduce the flow dynamics of polymers under shear. Moreover, the model is extended to include long-range interactions of functional groups. In low dielectric constant medium such as lubricant oils, the functional groups interact as ionic groups in high dielectric constant medium such as waters. The specific results shows that the colloidal science in oils have many problems to be solved.
High-Speed AFM Reveals the Detailed Mechanism of Dynamic Protein Adsorption Onto Individual Hydrogel Microspheres
Authors: Matsui Shusuke , Hosho Kensuke , Uchihashi Takayuki , Suzuki Daisuke
Published: February 2020

Hydrogel microspheres, i.e., microgels have both colloidal and hydrogel properties, which are composed of cross-linked hydrophilic polymer network. Due to the colloidal size property and biocompatibility, microgels are promising for advanced bio-nanomaterials such as protein drug delivery vehicles [1]. In order to establish the design concept of such protein carrier, understanding the dynamic interaction between the protein and microgels is essential. Up to now, the dynamic interaction between protein and microgels is well characterize by means of scattering, spectroscopy, and sensor [2]. However, to the best of our knowledge, there are no study that direct visualization during protein adsorption to individual microgels at nanoscale in real-time. Against this background, we visualized individual microgels during protein adsorption onto the microgels at nanoscale in real-time for the first time [3]. This approach, which enabled us to monitor the moment of protein adsorption to individual microgels, was realized by high-speed atomic force microscopy (HS-AFM) [4]. This method allows the direct visualization of the dynamics of biological molecules in action, without significantly disturbing the physiological function of the molecules [5]. We have already monitored the dynamic adsorption behavior of microgels onto solid/liquid interface [6]. The microgels were synthesized through aqueous free-radical precipitation polymerization of N-isopropyl acrylamide, the cross-linker N,N'-methylenebis (acrylamide), and acrylic acid with different content. In this presentation, the effect of protein interaction on the microgels’ dynamics will be discussed.

Partially reproduced with permission from [6] Copyright (2017) John Wiley and Sons.

References

[1] Y. Tahara, K. Akiyoshi, Adv. Drug Deliv. Rev., 95, 65 (2015)

[2] N. Welsch, Y. Lu, J. Dzubiella, M. Ballauff, Polymer, 54, 2835 (2013)

[3] S. Matsui et al., in preparation

[4] T. Ando, T. Uchihashi, T. Fukuma, Progr. Surf. Sci., 83, 337 (2008)

[5] T. Ando, T. Uchihashi, S. Scheuring, Chem. Rev., 114, 3120 (2014)

[6] S. Matsui, T. Kureha, S. Hiroshige, M. Shibata, T. Uchihashi, D. Suzuki, Angew. Chem.; Int. Ed., 56, 12146 (2017)
Analysis of Raman Spectra of Poly(vinylidene fluoride) Solution Under Drying Process
Authors: Yamada Noriyasu , Murasawa Go
Published: February 2020

Poly(vinylidene fluoride) (PVDF) is a thermoplastic fluoropolymer used in tactile sensors and actuators because of its piezoelectricity, flexibility and other unique properties. PVDF shows four crystal structures based on the order of molecular chain: α-, β-, γ-, and δ-phase. The most stable phase of PVDF is the non-polar α-phase, and strong piezoelectricity appears in the β-phase. Thus, the phase transition from α-phase to β-phase are necessary so as to use PVDF as a piezoelectric material. It is generally realized by applying uniaxial stretch and polarization process to α-phase PVDF film. However, we recently found a novel method which converts PVDF crystal structure to β- or γ-phase without the above mechanical deformation processes. This method consists of only the PVDF solution dropping process and the drying process, and therefore, it enables us to print piezoelectric polymer film and create free-from 3D sensors and actuators.

In this study, we investigate the crystallization behavior of PVDF solution under the drying process. First, PVDF solutions are made with several solvents which have different vapor pressures. Second, a droplet is formed on a glass plate with a microsyringe. Third, the time series variations of Raman scattering intensity are measured with the in-house Raman spectrum spectroscopy. Finally, the temporal changes of the crystallization rate are calculated from the result of Raman spectrometry and the crystallization behavior is evaluated by Johnson and Mehl and Avrami equation.
Development of Color Gel System
Authors: Takahashi Mizuki , Saito Azusa , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu , Sato Kei
Published: February 2020

Recently, several full-color 3D printers have been proposed. However, there is no full-color 3D printer using gel as a material yet. The 3D gel printer Soft and Wet Industrial Materials Easy Realizer (SWIM-ER) also performs modeling with monochrome only. To realize a full-color 3D gel printer, there are many problems such as a color gel material, a printing system with multi-material, etc. In this study, we examined pigmented color gel materials. First, several pigments were mixed to prepare a gel solution, which were measured for color. It was found that the addition of the surfactant dispersed the pigment and the fracture from the aggregated part was also improved. For some pigments, the relation between pigment concentration and color gel’s brightness or their saturation was clarified. The color of the neutral color gel made by mixing the specific two pigments was measured. The relation between the ratio and the color when the mixture ratio of the two color pigments was changed became clear. To make all color gel materials, a large amount of sample data of color gel is required. Therefore, we used pipetting robot “Andrew” to automatically prepare color gel materials to improve the efficiency of data collection. We propose an algorithm to determine the recipe for synthesizing the gel of the target color by using this database and a system to automatically synthesize the gel of the target color.
Gel Transistor By Chemically Tunable Hydrogels
Authors: Shiblee MD Nahin Islam , Watanabe Yosuke , Ahmed Kumkum , Makino Masato , Khosla Ajit , Furukawa Hidemitsu
Published: February 2020

The transport of liquid in the polymeric network of Hydrogels have been discussed for a decade because the gel membrane may use as chemical separator [1]. Here we demonstrate a system that control the flux of solvents by a combination of three types of gels of different swelling behavior as a gel transistor. Poly(dimethyl acrylamide-co-stearyl acrylate and/or Lauryl Acrylate) (PDMMAm-co-SA and/or LA)-based shape memory gels (SMGs) swelling behavior has been observed for different solvents and binary solvent mixtures. It was found that SMGs at all composition showed increased swelling when ethanol composition was increased. On the other hand, when an anionic copolymer was introduced in the DMAA network, swelling behavior was reversed in the presence of high ethanol composition. These oppositely responsive gels were tested for permeability of solvents through them and we successfully developed the gel diode [2]. The unidirectional solvent flow was achieved just like in diode. Information about the gel diode has been utilized to develop a system that simulate a transistor to more sophistically control the flow of liquid mixtures. This findings are expected to create positive impact to develop the gel membrane solvent separator, a hot topic for rectifier, calculator and separator in chemical systems.

References

Tanaka, Phys. Rev. Lett. 40, 820–823 (1978).

Arai, M., Gong, J., Makino, M., KABIR, M.,H., Furukawa, H. SPIE Proc. 9430, 94302A-1
(Invited) Micro-Manipulation of Hydrogel Sheet through Photoresponsive Polymer Dissolution
Authors: Sumaru Kimio , Takagi Toshiyuki , Morishita Kana , Satoh Taku , Kanamori Toshiyuki
Published: February 2020

Various functional hydrogels have been developed, and their applications to the fields of bioengineering have been examined actively. In these situations, we developed novel technologies to manipulate hydrogel sheet and living cells through photoresponsive polymer dissolution.

Firstly, we proposed the fabrication of unique hydrogel microstructures through photolithography. As a photo-acid-generation (PAG) polymer, we synthesized a poly(methylmethacrylate) functionalized with visible- light-responsive PAG group (pPAGMMA), and spin-coated polystyrene surface with the polymer solution. Then we overcoated pregel solution containing hydrophilic polymer (hydroxypropyl cellulose) (HPC) and 1,3,4,6-Tetrakis(methoxymethyl)glycoluril, and carried out micro-patterned light projection. After post-bake and flushing, we obtained crosslinked hydrophilic polymer sheet only in the irradiated area. Due to another property of pPAGMMA getting dissolved in ethanol/water mixture by further irradiation, the cross-linked hydrophilic polymer sheet was lifted from the substrate surface and became swollen in the desired areas by the second micro-patterned projection in ethanol/water mixture. As a result, we obtained various microstructures which were composed of patterned swollen hydrogel sheet partially attached to the substrate in the patterned areas.

Secondly, we developed a novel photoresponsive polymer materials by functionalizing poly(N-isopropylacrylamide) with o-nitrobenzaldehyde (pNBANIPAAm) to implement in situ photocontrol in aqueous systems containing bio-compatible environment. We observed that the polymer exhibited sharp aqueous dissolution upon light irradiation in wide pH range including biological conditions. We prepared closs-linked HPC (cHPC) layer on pNBANIPAAm thin layer and carried out micropatterned light projection in PBS. As a result, we observed that the cHPC layer lifted off of the substrate and swelled while nothing happened in unirradiated areas. Also living cells were manipulated by light in a similar manner.
(Keynote) Preparation and Structural Investigation of Linear and 4-Arm Poly(ethylene glycol) (2 x 4 PEG) Gels
Authors: Shibayama Mitsuhiro , Tsuji Yui , Li Xiang
Published: February 2020

Gel is a 3D polymer network holding solvent molecules inside its network. There are two major heterogeneities in gels. One is spatial heterogeneity, and the other is topological heterogeneity. The spatial heterogeneity is introduced by random cross-linking, so the network structure has both sparse and dense region. The spatial heterogeneity is observed as excess scattering in a light, X-ray, or neutron scattering experiment. On the other hand, the topological heterogeneity is related to the presence of dangling chains, loop structure, and entanglements inside the network, and is investigated by viscoelasticity and/or swelling experiments, or by other means, such as NMR. Because of these inhomogeneities, gels have seldom been applied to structural materials because of their poor mechanical properties. Hence, realization of ideal model networks free from heterogeneities has been strongly anticipated.

Sakai et al. succeeded in fabrication of near ideal polymer networks called “Tetra-PEG gel”.[1] A Tetra-PEG gel is synthesized from two complementary end-functionalized poly(ethylene glycol) (PEG) which is able to react each other. It is pointed out that the Tetra-PEG gel has insignificant small spatial homogeneity and negligible topological heterogeneity, respectively by small angle scattering[2] and mechanical test.[3]

Recently, we extended the above-mentioned method and succeeded in fabrication of multiple model network gels consisting of alternating tetra-functional poly(ethylene glycol)s (PEGs) and bis-functional linear PEGs (2 x 4 gels), where the molecular weight of linear PEG was varied from 200 Da to 20000 Da while that of tetra-functional PEG component was fixed to be 20000 Da.[4] The same level of homogeneities in the network structure as those of Tetra-PEG gels has been confirmed by dynamic light scattering (DLS) and dynamic viscoelastic measurements. Advantages of 2 x 4 gels are that one can independently tune the cross-link density (by the concentration of tetra-functional PEG) and the total polymer concentration. By using a series of 2 x 4 gels, we examined the concentration/cross-link density dependence of the correlation blob, the elastic blob, and geometric blob. We will discuss the scaling rules of these blob sizes as a function of polymer/cross-linker concentrations.

Sakai, T. et al, Macromolecules
2008, 41, 5379.

Matsunaga, T. et al, Macromolecules
2009, 42, 1344.

Akagi, Y. et al, Macromolecules
2010, 43, 488.

Tsuji, Y. et al., Gels
2018, 4, 50.
(Invited) Dual-Physical Cross-Linked Tough and Photoluminescent Hydrogels with Good Biocompatibility and Antibacterial Activity
Authors: Mei Chen Yong , Yuan He , Chen Hu , Xiang Wang Mei , Lei Sun
Published: February 2020

Development of novel photoluminescent hydrogels with toughness, biocompatibility, and antibiosis is important for the applications in biomedical field. Herein, novel tough photoluminescent lanthanide (Ln)-alginate/poly(vinyl alcohol) (PVA) hydrogels with the properties of biocompatibility and antibiosis have been facilely synthesized by introducing hydrogen bonds and coordination bonds into the interpenetrating networks of Na-alginate and PVA, via approaches of frozen-thawing and ion-exchanging. The resultant hydrogels exhibit high mechanical strength (0.6 MPa tensile strength, 5.0 tensile strain, 6.0 MPa compressive strength, and 900 kJ m−3 energy dissipation under 400% stretch), good photoluminescence as well as biocompatibility and antibacterial activity. The design strategy provides a new avenue for the fabrication of multifunctional photoluminescent hydrogels based on biocompatible polymers.
(Invited) Liquid/Elastomer Composite Membrane with Dynamically Controllable Gas/Liquid Transport
Authors: Sheng Zhizhi , Hou Xu
Published: February 2020

The development of membrane science and technology is central to fields ranging from waste water treatment, petrochemical industry, to biomedical science. The dynamic controllable multiphase transport and separation under a steady-state applied pressure have great benefits for membrane science, but remain elusive. Besides, the membrane fouling problem remains challenging. Here we will introduce the dynamic controllable gas/liquid separation mechanism of liquid/elastomer composite membranes under constant pressure and its adaptable antifouling property, by solid/liquid/liquid interfacial design, pressure monitoring, and theoretical modelling. This study includes the design of liquid/elastomer composite membrane, the establishment of antifouling configuration, the influence of membrane pore size, deformation manner, and deformation magnitude on the substance transport, and thus the development of gas/liquid separation prototype device with good antifouling stability. We believe that this study will bring new opportunities for many real word applications, such as gas-involved chemical reactions, multiphase flow, multiphase separation, multiphase microreactors, bioinspired microfluidics, fuel cells, and materials synthesis and fabrication. This study will have far-reaching implications for the development of multiphase transport and separation.
(Invited) Stimuli-Responsive Supramolecular Hydrogels
Authors: Ikeda Masato
Published: February 2020

Soft matters inspired by biological systems such as supramolecular hydrogels composed of self-assembled nanofibers exhibiting stimuli-response under aqueous conditions are attractive owing to their numerous potential bio-applications. However, installing response toward structurally complex biochemical stimuli into them remains a challenge. To overcome the obstacle, we developed simple strategy to introduce artificial chemical-stimuli-responsive cleavable groups into peptides to develop self-assembled supramolecular nanofibers capable of showing chemical stimuli-responsive degradation of the nanofibers and the corresponding hydrogel materials. More importantly, we found that the rational combination of the stimuli-responsive supramolecular nanofibers (supramolecular hydrogels) and enzymes enabled us to construct hydrogel materials capable of showing gel degradation (dis-assembly of supramolecular nanofibers) in response to a wide variety of biomolecules. We believe that our simple, but robust strategy and the relevant synthetic molecular tools could offer a variety of stimuli-responsive and bioinspired supramolecular soft materials.

Figure 1
(Keynote) DNA-based Hydrogels
Authors: Luo Dan
Published: February 2020

DNA provides a variety of routes for building up novel materials that can be used for both genetic and generic purposes. Over the last 18 years, my group at Cornell has been engineering DNA as both genetic materials and generic materials at bulk scale. In this talk, I will focus on how we have designed and developed DNA-based hydrogels for real-world applications from diagnostics to pharmaceutics. More specifically, I will elaborate on the creation of the first-ever, all-DNA hydrogel and from which a protein-producing DNA hydrogel (termed P-gel). Besides the chemical crosslinked DNA hydrogels, a physical, entangled DNA hydrogel was also invented in my group. This type of DNA hydrogel has the meta-property in that the hydrogel is both a liquid and a solid. Our DNA P-gel may lead towards the realization of synthetic cells while our meta-DNA hydrogel may become a super condensed ultra-compact DNA (scudDNA) for the direct delivery of DNA-based therapeutics. Recently, we have also created life-like DNA hydrogels that possessed metabolic activities while at the same time was able to move against flow. Other novel, large scale DNA hydrogels will also be discussed. Indeed, DNA has proven to be not only the amazing molecule of life, but also a powerful and versatile molecule for bulk materials.
Multiscale Modeling of Carbon Black Aggregates Dispersion in Polyethylene Melt
Authors: Caputo Stefano , De Nicola Antonio , Milano Giuseppe
Published: February 2020

Carbon black (CB) is a widely used filler in polymer composites materials, known to improve several properties of the medium in which it is dispersed, such as mechanical, electrical and optical ones1.

On the nanoscale level, CB is made essentially by aggregates ranging from ten to few hundreds of nanometers; these aggregates consist coalesced nanoparticles, called primary nanoparticles2. The nanoparticles are composed by many graphitic like stacks, arranged in a sphere.

To obtain materials with tailored properties, it is necessary to achieve a good dispersion of the CB aggregates into the polymer matrix, and this becomes more and more challenging when increasing the filler content.

In this work we address this task by performing simulations in a multiscale fashion, going from an atomistic scale to a granular-continuum scale, in order to gain informations on the process of aggregation and disaggregation of CB in polyethylene melts under shear.

At the first stage we have carried out all-atom molecular dynamics simulations of polyethylene chains in the melt state interacting with a semi-infinite graphite substrate, to get structural and dynamical properties.

In a second stage we have built up the the coarse-grained (CG) model, first by choosing an appropriate mapping scheme for the polymer and CB primary particles and then obtaining suitable potentials for bonded and nonbonded interactions among CG beads. At this scale potential of mean force calculation, through MD-SCF (molecular dynamics - self consistent field) simulations3, will be done to get the force of attraction/repulsion between two primary nanoparticles at various distances.

This force will be used as the input for the granular-continuum scale, in which aggregates of CB nanoparticles in a model fluid are simulated through a coupled CFD-DEM (complex fluid dynamics – discrete element method) method4, to observe in which conditions the disaggregation occurs and how this affects the dispersion of the filler.

Such work has the potential to provide predictive power and can allow for special resin design to ensure adequate filler dispersion/performance.

1 Carbon Black: Science and Technology, J. B. Donnet, 1993, CRC press

2 Encyclopedia of polymer science and technology, John Wiley & Sons, 2002

3 G.Milano, T. Kawakatsu, J. Chem. Phys., 2009, 130, 214106

4 https://www.cfdem.com/liggghts-open-source-discrete-element-method-particle-simulation-code
Control of Molecular Orientation in Naphthalene Diimides
Authors: Nakamura Tomoya , Shioya Nobutaka , Shimoaka Takafumi , Hasegawa Takeshi , Murata Yasujiro , Wakamiya Atsushi
Published: February 2020

Lead halide perovskite solar cells represent attractive cost-effective and solution-processable photovoltaics. At present, the record-high performance perovskite solar cells are based on an n-i-p device configuration, in which metal oxides, such as TiO2, are generally utilized as electron transporting layer. Deposition of metal oxides usually requires high temperature sintering process, which prevents mass production and application to flexible devices on plastic substrates.

Here, we focused on the naphthalene diimide (NDI) skeleton as alternative transparent n-type materials. By introducing hydrogen atoms at the imide moiety (NDI-H), we envisioned the achievement of face-on orientation on the substrates, which is preferable for vertical charge transport, by the formation of intermolecular N–H···O hydrogen bondings. To realize both the solution-processability and the durability to the deposition of the upper layers, we designed NDI-Boc having tert-butoxycarbonyl (Boc) solubilizing groups at the imide moiety, which can be cleaved by simple thermal annealing. Infrared p-polarized multiple-angle incidence resolution spectroscopy (pMAIRS) not only confirmed the cleavage of the Boc group, but also revealed that the molecular orientation of NDI changed from edge-on to face-on during the cleavage process. Furthermore, NDI-H film works as electron transporting layer in n-i-p type planer perovskite solar cells with the power conversion efficiency of 10.7%.
Luminescent Properties of RE-Doped Mullite (Al6Si2O13) Phosphors for Energy Conversion from UV to Visible Rays
Authors: Takahashi Hirotaka , Matsushima Yuta
Published: February 2020

Introduction

Leveraging of solar energy is a key issue in the world. The world’s energy consumption is increasing year by year due to rise in population and improvement of living quality. For the realization of sustainable development, utilizing alternative energy sources rather than fossil fuels is of critical importance.

Using solar cells, such as silicon (Si), is the most popular way for harvesting solar energy. However, light absorbing materials have their intrinsic band gaps, and therefore, the energy range that cells can harvest is limited, which brings power conversion loss. To overcome the problem, combining a solar cell and a phosphor, which is a wavelength conversion material, is important.

Here we report UV-excitable mullite (Al6Si2O13) phosphors doped with REs. Luminescence spectra can be tailored from 390 to 620 nm by changing doping rare-earth ions.

Experimental

Mullite samples were synthesized via a sol-gel process. Al(NO3)3•9H2O, tetraethylorthosilicate (TEOS) and a RE source (or sources) in a form of nitrate or oxide were dissolved in ethanol. Then the pH of the solution was increased to 10 by adding NH3 aq. The precipitate was filtered off by suction filtration and treated at 1400 °C for 6h. For Ce3+, Tb3+ and Eu2+ phosphors, the samples were heat-treated in 5% H2/Ar atmosphere for the reduction of the luminescent centres. For Eu3+ phosphor, the sample was treated in air.

Results
＆
discussions

Fig. 1 shows the emission spectra of the mullite phosphors doped with Ce3+, Eu2+, Ce3+-Tb3+ or Eu3+. Ce3+ and Eu2+ in mullite show relatively broad peaks around 380 and 410 nm, respectively. These peaks are typically assigned to the 5d-4f transitions in Ce3+ and Eu2+. The Ce3+-Tb3+ phosphor shows green emission with the sharp peaks attributed to the Tb3+ 4f-4f transitions. Absence of an emission peak of Ce3+ indicates the energy transfer from Ce3+ to Tb3+. Red luminescence with the sharp peaks in mullite are attributed to the 4f-4f transitions of Eu3+.

Fig. 2 shows the thermal quenching properties of the mullite phosphors compared with commercially available YAG:Ce3+ and SrSiO4:Eu2+ phosphors [2]. The mullite phosphors maintain more than 50% of the initial intensities even at 200 °C.

Conclusions

We have successfully synthesized red, green and blue phosphors with mullite doped with Ce3+, Eu2+, Ce3+-Tb3+ and Eu3+. They all show good thermal quenching properties, which are comparable with the commercially available phosphors of YAG:Ce3+ and SrSiO4:Eu2+.

Figure 1
Simulation of the Charge Process Incorporating Vanadium Crossover in Vanadium Redox Flow Battery
Authors: Chou Yi-Sin , Yen Shi-Chern
Published: February 2020

The negative electrode reactant of VRFB easily crosses the separator and causes electrolyte imbalance, because of its small ion size. In this study, a 3-D isothermal model of a redox reaction in a porous electrode is formulated. The simulation is performed for the charge current voltage and the ion diffusion phenomenon of the negative electrode. The total current density is affected by the mass transfer to the surface, species crossover, and the electrode kinetics. The simulated battery charging curve was compared with the experimental results. The numerical result is validated against the experiment data. Since the ions of negative electrode easier diffuses to the other electrode, the phenomena is simulated by the overpotential that is related to SOC. Additionally, the components allow the visualization and the organization of the output to make it easily understandable whether the result is acceptable. The simulation results indicate that the edge effect of the concentration of V(II) ion is obvious at the lower SOC. Due to vanadium crossover, the concentration distribution of V(II) ion is near the current collector at the higher SOC. The positive potential distribution is closer the negative. The potential difference is about 0.9 V across the ion-exchange membrane.
Atomistic Simulations of Lithiation Induced Structural Changes in Layered-Spinel Nano-Architectured Li-Mn-O
Authors: Shibiri Beauty , Ledwaba Raesibe Sylvia , Ngoepe Phuti E
Published: February 2020

Maximizing the potential of LIBs requires a firm and comprehensive understanding of the fundamental mechanisms during battery operation, including bulk phase transition of electrode materials, chemical variations at multiple interfaces between different battery components, changes in mechanical properties affecting the structural integrity, and so forth [1]. Atomistic modeling plays a vital role in advancement and understanding of microstructural evolution and mechanical properties of electrode materials. We present progress in the simulated synthesis of Li-Mn-O nanoporous electrode materials, from the atomic perspective using the amorphization and recrystallization technique [2]. The effect of lithiation on structural integrity and intercalation host capability of the LMO electrode are investigated under the NST ensemble. Evolution of a composite structured material is captured on the microstructures snapshots and XRD graphs, particularly co-existing formation of spinel and layered components. The nanoporous materials crystallize successfully although multiple grains are observed for Li1.75Mn2O4 (nanoporous with simulation lattice boxes of 67 Å and 75 Å) and subsequently yield a single crystals for Li2Mn2O4. However, this is not inherent on nanoporous 69 Å with the same concentration. Intercalation induced volume changes are observed during simulation of the discharge process, specifically when the lithium content in the system is increased above 75% (Li1.5Mn2O4). The nanoporous material contracts inwards and such accommodative nature may be attributed to flexing/relaxation into its pore/channel, unlike in the bulk structure, which suffers from drastic volume expansion.

References

[1] W. Li, B. Song and A. Manthiram, Chem. Soc. Rev., 46, 3006−3059, 2017.

[2] T.X.T. Sayle, R.R. Maphanga, P.E. Ngoepe and D.C. Sayle, J. Am. Chem. Soc., 131, 6161-6173, 2009.
Models of Electrochemical Transport in Electrolytes
Authors: Zyskin Maxim
Published: February 2020

I will talk about continuum thermodynamics-based models of electrochemical transport in electrolytes, taking into account thermal, mechanical, and pressure effects, and on using microscopic methods and molecular dynamics simulations to determine model parameters. This work is part of the project on multi-scale modeling of electric batteries.
(Invited) On the Active Sites in the Graphene-Catalyzed Oxygen Reduction Reaction
Authors: Radovic Ljubisa R
Published: February 2020

A critical issue in the impressive worldwide fuel cell research efforts is the possibility of using graphene-based materials in the oxygen reduction reaction (ORR). In the overwhelming literature that has accumulated, much controversy (and even more confusion) exists regarding some of the essential aspects of the reaction mechanism. A consensus can emerge only if interpretations of the abundant experimental evidence are consistent with what is known about the behavior of graphene-based materials, both the novel and the traditional ones, as catalysts in the absence of an electric field, as well as with the well understood gas-phase behavior of sp2-hybridized carbon materials in the presence of dioxygen. From this standpoint, the key issue is whether a reasonable and instructive analogy exists between the mechanism of electron-transfer catalysis on the carbon surface,

e- + C(O2) = C(O2
-)

C(O2
-) + H2O(aq) = OH-(aq) + C(OOH)

C(OOH) = C=O + OH,

and the proposed mechanism of electrocatalysis:

Ar-C: + O2 → Ar-C(O2)

Ar-C(O2) + H+(aq) → Ar-C(OOH)

Ar-C(OOH) → Ar-C + HO2
-

A clarification can be sought by analyzing the results of the search for ever more effective (electro)catalysts. In this context, structural modifications of the graphene surface are particularly enlightening. Thus, for example, the superior electrocatalytic activity of nitrogen-doped graphene is attributed to the presence of either quaternary or pyridinic nitrogen. Boron is of interest as well, if for nothing else then for its contribution of one electron less than the carbon atoms to graphene’s pi-system. And the presence, or formation, of an embedded MN4 moiety – where M is most often a transition metal such as cobalt or iron – is also of great interest because of the obvious analogy with porphyrin or phthalocyanine structures. Using a heretofore unexplored approach to examine these widely varying graphene-based surfaces, and unifying the evidence based on density functional theory, a compelling case is presented here for the experimentally elusive identification of the active sites (AS) that are responsible for the technologically and economically crucial electron transfer at the fuel cell cathode: AS + O2 + 4e-(aq) + 4H+(aq) = AS + 2H2O. It is also argued, not unexpectedly, that these are essentially the same sites at which analogous oxygen transfer processes - carbon oxidation/combustion, graphene functionalization and oxygen spillover - also occur. Their thermodynamic driving force is shown to be crucially dependent on the details of the electron density distribution and spin pairing processes at the active sites and in their vicinity.
(Invited) Nanocarbons Fabricated By CVD: Medical and Electrochemical Applications
Authors: Munoz-Sandoval Emilio
Published: February 2020

Nowadays, two important fields in carbon nanomaterials are growing with amazing celerity. Both fields are related with life. On the one hand, it is standing-out the use of nanocarbons for cancer studies. On the other hand the concern about water contamination has contributed to the development of toxic material sensors, among which the nanostructured carbon materials have been highlighted. In the present contribution a state of the art of these two important scientific areas is showed. Also, two relevant contributions were our group has participated are discussed, namely cytotoxicity induced by carbon nanotubes in experimental malignant glioma [1] and carbon nanotube sponges as electrochemical sensors [2]. [1] Romano-Feinholz et al. doi: 10.2147/IJN.S139004. eCollection 2017; [2] Kashina et al. in preparation.
(Invited) Assembly of Electrochemically Reduced Graphene Oxide, at the Nano and Microscales, for the Preparation of Functional Coatings.
Authors: Chazaro Ruiz Luis Felipe , Quezada Renteria Javier Alan , Rangel-Mendez José René , Ania Conchi O.
Published: February 2020

Graphene oxide (GO) presents the advantage of being easily dispersed in water, which facilitates the assembly of nano and microstructures by numerous methods, in order to form uniform and thickness-controlled functional coatings. For example, the electrophoretic deposition (EPD) is one of the most used techniques to produce anticorrosive coatings onto metals, including GO and reduced graphene oxide (rGO) coatings. We have used a variation of the EPD process of GO, which consisted in changing the GO’s charge to positive values allowing the electrophoretic deposition of GO onto the cathode (cEPD). The coating diminished by three times the corrosion rate of carbon steel. The preparation of these coatings also implies the understanding of the mechanism through which the electrochemical reduction of the GO is carried out.1 An electrochemical reduction mechanism of GO involving hydrogenation/hydrogenolysis reactions is suggested as the main reason to achieve an effective anticorrosive-coating by cEPD in comparison to the films produced by an anodic EPD. For this reason, we studied the electrochemical reduction of GO in aqueous and organic media containing H+ donor, to investigate the role of H+ in the reduction mechanism. In aqueous electrolyte, in both acid and basic pH, the H+ enhanced the removal of oxygenated groups by electrochemical reduction and promoted the loss of some sp2 domains due to hydrogenation reactions of the graphitic domains. The electrochemical reduction of GO in organic media, free of H+, resulted in the restoration, to some degree, of the sp2 domains. However, the removal of the oxygenated groups seemed hindered when compared to the same process in presence of H+ donor, in the organic solvent, at the same potential intervals.

Considering that through these studies it is possible to choose a route for the preparation of functional films, recently we proceeded to modify electrochemically the rGO through with 5-membered alkyne chains. The resulting rGO film presented lower conductivity, due to the loss of graphitic domains, and an increased hydrophobicity. The modified rGO film was evaluated as an anticorrosive coating for carbon steel, showing a better protection from corrosion in comparison to the protection granted by the regular rGO film.

[1] J.A. Quezada-Rentería, L.F. Chazaro-Ruiz, J.R. Rangel-Mendez, Synthesis of reduced graphene oxide (rGO) films onto carbon steel by cathodic electrophoretic deposition: Anticorrosive coating, Carbon 122 (2017) 266-275.