Function-assembly of nano-materials towards electronics, energy and biological applications (4 May 2016)

Resume : Understanding of the role of polymer backbone structure in the aggregation behaviors of conjugated polyelectrolytes (CPEs) is of prime interest as the physical and photophysical properties required for many applications are closely related to the nature of aggregation. In this presentation, we report self-assembly of a set of four positively charged CPEs, which only different in the backbone chemical structure [i.e., phenyleneethynylene (PE) vs. phenylenebutadiynylene(PB)] and connectivity (i.e., with or without flexible linkers along the backbone) upon complexation with linear polyanion hyaluronic acid (HA). Poly(phenyleneethynylene) (PPE) exhibits high planarization along the backbone, evident by ~50 nm red-shifted absorption maximum and increased emission intensity, while a small portion of flexible linkers in the same PPE backbone (PPE-L) slightly decreases the effect. Meanwhile, poly(phenylenebutadiynylene) (PPB) containing small fraction of flexible linker (L) (PPB-L) exhibited high p-p stacking, evident by ~30 nm red-shifted absorption maximum and decreased emission intensity with spectral broadening. The structure-property relationship can be useful to design macromolecular materials for broad electronic or biological applications.

Resume : Here we show that the cooperation and compromise between the mechanical anisotropy and geometric nonlinearity lead to shape selection in spontaneous bending laminates. First we study spontaneous bending of laminates of shape selection and instabilities of circle laminates. Specifically, the transition from spherical cap with single steady state to nearly cylindrical helical laminates occurs when the width goes beyond certain threshold. Moreover, the laminates will be multi-stable in any direction. If continue to increase the width or decrease the thickness of the ribbon, the phenomenon of multi-stability will disappear and show single steady state. Furthermore, if using longer length and narrower width, the ribbon will coil to a ring with the same radius in any direction. Second, we change the circle laminate to square laminate, and illustrate the principles of mechanical anisotropy and geometric nonlinearity in shape selection. Last but not the least, if we decrease the width but increase the length of the rectangle laminate, the morphology shows a ring whatever the geometric mis-orientation angle choose.

Resume : The effective regeneration of fully functional tissues which contains bone structures is one of the primary challenges in regenerative medicine and a major challenge for reconstructive and orthopedic surgery that repairing of bone defects. Currently, the main approaches are surgical reconstruction using autografts or allografts which are convenient but contain some limitations associating with the availability of autografts, the risk of immunogenicity and infection. Undoubtedly, developing biomaterial scaffolds that can mechanically and functionally support and assist in bone regeneration is required. In this report, continuous poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and PHBV/polyaspartic acid (PAA) nanofibers with high porosity, high ratio of surface area to mass and superior mechanical properties were fabricated through electrospinning technic. Despite good mechanical properties and predictable biodegradation kinetics, PHBV and PHBV/PAA nanofibers can not provide a favorable surface for cell adhesion and proliferation due to lack of specific cell-recognition moieties. We employed a calcium-phosphate dipping method to deposit the nano-hydroxyapatite (nHA) on the nanofibers to obtain desired PHBV-nHA and PHBV/PAA-nHA scaffolds with the property of osteoconductivity. Field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and tensile tester were employed to investigate the mechanical properties of PHBV, PHBV-nHA, PHBV/PAA and PHBV/PAA-nHA nanofibers. Human fetal osteoblast cells were cultured on these scaffolds for evaluating the cell proliferation and mineralization. Morphological evaluation on firmed the fiber diameters of PHBV and PHBV/PAA as 447±69 nm and 368±124 nm, respectively. There was no obvious changes about the diameters after depositing nHA. However, the surface of the scaffold transformed from hydrophobic to hydrophilic after the deposition of nHA with water contact angles of 129.4°?114.2°?82.8° and 51.7° for PHBV, PHBV/PAA, PHBV/PAA-nHA and PHBV/PAA-nHA nanofibers. Initial adhesion of hFOB is especially critical for long-term stability and mineralization of the cells; thus, the capacity for nanofiber scaffolds to support hFOB adhesion and proliferation was evaluated using cell proliferation assay at day 5, 10 and 15. It was obvious that the cells on all of the scaffolds kept increasing during the process of culture. Especially, cells on PHBV-nHA scaffold had 35.10% higher proliferation than that on pure PHBV scaffold. Comparing with PHBV/PAA nanofibers, cell on PHBV/PAA-nHA nanofibers had a higher proliferation of 26.68%. The biological advantages of adding nHA are crucial since it is the major inorganic component of the bone matrix and it has specific affinity towards many adhesive proteins. The CMFDA (5-chloromethylfluorescein diacetate) images on day 15 showed that the cells on nanofiber scaffolds formed noticeably more colonies than that on control surfaces, owing to the favorable nanofibrous architecture which promoted cellular activities. Evidence suggesting cellular infiltration was observed via FE-SEM, multi-layers of cells on all scaffolds with mineral particles on the surface indicate confluent cell growth with cell-secreted mineralization. By day 15, high mineralization was observed with fused cells forming a thick layer on the surface of the scaffolds along with the cell ECM deposits. Notably, PHBV/PAA-nHA scaffolds were apparently in favor of producing more mineral nodules and appeared to aggregate and coalesce into large mineral clumps compared to other scaffolds. nHA initiated an increase in osteoblast adhesion, osteo-integration and deposition of calcium containing minerals on the surface of the scaffolds, thus enhancing new bone formation. Nanofibrous scaffolds contained nHA had the ability to accelerate the growth and maturity of hFOB cells. The observed results proved that the PHBV/PAA-nHA scaffolds promoted greater osteogenic mineralization of hFOB as evident from the enzyme activity and mineralization profiles for bone tissue engineering.

Resume : We describe the use of a layer-by-layer hierarchical nanostructure to exploit the synergy of different lanthanide ions for converting single wavelength excitation into emissions spanning the whole spectral region. By lining up a set of lanthanide ions with matched energy levels in a core–shell nanostructure, we demonstrate well-defined cascades of energy transfer that gives access to optical emissions from a large collection of lanthanide ions (Tb3+, Eu3+, Dy3+, Sm3+, Nd3+, Yb3+, and Er3+) after excitation into a common sensitizer of Ce3+ featuring a broad absorption. Through optimization of the nanoparticle structure and surface coating, high quantum yields of up to 90% are achieved. Our results highlight that the controlled energy cascades at nanometer scale provide new opportunities for applications such as fighting against counterfeiting and sensing small molecules.

Resume : Metal nanowires are building blocks for realizing new devices with applications in optoelectronics, spintronics, biosensing and medicine, as well as in catalysis, motors, and drug delivery [1-4]. Metal nanowires also enable fundamental studies of ballistic transport and of the effect of dimensionality on phenomena such as spin and orbital momentum and magnetic anisotropy [5,6]. However high quality, high density single crystalline materials have been surprisingly difficult to fabricate. Here we report a versatile, template-free method for fabrication of single crystalline metal and metal alloy nanowires (Co, Ni, NiCo, CoFe, and NiFe) by reduction of metal nitride precursors formed in situ by reaction of metal salts with a nitrogen source. Currently, template electrodeposition is the most commonly used method for producing uniform, high-density metal nanowires. Recent advances in the electrodeposition technique have made it possible to fabricate single crystalline nanowires from ferromagnetic, high melting temperature, metals Co, Fe and Ni and their alloys, with control over crystal structure and composition [7,8]. However the multi-step technique is cumbersome and subject to surface roughening, high concentrations of stacking faults, fracturing of high aspect ratio structures, and contamination due to post-deposition template removal processes [9]. Whilst template-free self-assembly of single-crystal cobalt and nickel nanowires has been achieved, low yields and substrate limitations have limited applications of epitaxially-grown nanowires, while solvothermal growth methods typically produce aggregates of low aspect ratio nanowires [10,11]. To date, no general method of template-free self-assembly of binary or ternary metal alloy nanowires has been reported. Here we report a versatile and scalable fabrication technique for single crystalline metal and metal alloy nanowires (eg. Co, Ni, NiCo, CoFe, and NiFe)[12]. The method employs reduction of metal nitride precursors formed in situ by reaction of metal salts with a nitrogen source. Nanowires may be grown using gas-phase, solution-phase or a combination of gas- and solution-phase precursors. We also examine the roles of the reactants and intermediate metal phases in the uniaxial growth mechanism. Thiol reduction of the metal nitrides to the metallic phase at 550-600˚C results in nanowire growth. In this process, sulfur acts as a uniaxial structure-directing agent, passivating the surface of the growing nanowires and preventing radial growth. The robustness and versatility of the method is demonstrated by achieving nanowire growth from gas-phase, solution-phase or a combination of gas- and solution-phase precursors. The fabrication method is suited to large-area CVD on a wide range of solid substrates. [1] H. Wu, D.S. Kong, Z.C. Ruan, P.C. Hsu, S. Wang, Z.F. Yu, T.J. Carney, L.B. Hu, S.H. Fan, Y. Cui, Nature Nanotechnology 8 (2013) 421. [2] U. Yogeswaran, S.-M. Chen, Sensors 8 (2008) 290. [3] S.A. Wolf, D.D. Awschalom, R.A. Buhrman, J.M. Daughton, S. von Molnar, M.L. Roukes, A.Y. Chtchelkanova, D.M. Treger, Science 294 (2001) 1488. [4] Y. Imura, K. Tsujimoto, C. Morita, T. Kawai, Langmuir 30 (2014) 5026. [5] F. Garcia-Sanchez, H. Szambolics, A.P. Mihai, L. Vila, A. Marty, J.P. Attane, J.C. Toussaint, L.D. Buda-Prejbeanu, Physical Review B 81 (2010) 134408. [6] R. Skomski, H. Zeng, M. Zheng, D.J. Sellmyer, Physical Review B 62 (2000) 3900. [7] H. Pan, B.H. Liu, J.B. Yi, C. Poh, S. Lim, J. Ding, Y.P. Feng, C.H.A. Huan, J.Y. Lin, J. Phys. Chem. B 109 (2005) 3094. [8] R.M. Metzger, V.V. Konovalov, M. Sun, T. Xu, G. Zangari, B. Xu, M. Benakli, W.D. Doyle, Ieee Transactions on Magnetics 36 (2000) 30. [9] G. Cao, D. Liu, Advances in Colloid and Interface Science 136 (2008) 45. [10] S.-i. Kim, H. Yoon, H. Lee, S. Lee, Y. Jo, S. Lee, J. Choo, B. Kim, Journal of Materials Chemistry C 3 (2015) 100. [11] Y. Soumare, C. Garcia, T. Maurer, G. Chaboussant, F. Ott, F. Fievet, J.Y. Piquemal, G. Viau, Adv. Funct. Mater. 19 (2009) 1971. [12] J. Scott, D. Totonjian, A. Martin, T.T. Tran, J. Fang, M. Toth, A. McDonagh, I. Aharonovich, C. Lobo, Nanoscale (2016).

Resume : Radionuclide diffusion ability of some natural materials is studied here. The natural radionuclide easily measured is the radon-222. Being a gas, an annealing at various temperatures between 100 and 900°C makes possible to follow at the same time its behavior and transport in porous natural material as phosphate, fossilized teeth, clay. Radioactivity is studied in various crystalline structures like natural apatite (phosphate, fossilized teeth) and its by-product (phosphogypsum). Uranium and radium contents and radon emanation power are determined by gamma spectrometry. Less than 30% of total radon formed in the sample is evacuated naturally from the samples (at room temperature); then the remainder represents the natural radon retention power. That means, up to 70 % is confined in the solid matrix of sample. The heat treatment effect on radon emanation power is examined between room temperature and 900°C and conduct to put in evidence two effects: an immediate effect (IE) and a long term effect (LTF). - In the immediate effect (Radon exhalation), a brutal evacuation of radon took place at 600°C while it stabilized at a maximum at temperature higher than 800°C. - In the long term effect (Radon retention improvement), the radon emanation is reduced in the samples annealed at various temperatures (after cooling at room temperature and after radon reconstitution in the sample), and decrease with increasing temperature. It is the lower in the samples annealed at temperature higher than 800°C, the radon retention is maximum (more than 90%) in these samples. Dry gel silica-iron, an amorphous sample, show that the structure has a considerable effect on radon diffusion. For this sample, the radon exhalation is total at 100°C. A linear correlation between the radon emanation and the structure/microstructure is deduced relatively to the both heat effects.

Resume : Formation of intended nano- and micro-structures with regular building blocks has attracted much attention due to the potential applications in the fields of optic, electronic and catalysis. Herein, we report a novel strategy to spontaneously grow three-dimensional (3D) hierarchical cabbage-like microparticles (CLMPs) constructed by individual Au nanoplates. By reducing gold precursor to gold atoms, N-(3-amidino)-aniline (NAAN) itself was oxidized to form poly (N-(3-amidino)-aniline) (PNAAN), which specifically binds on Au {111} facet as capping agent and led to the formation of gold nanoplates. Due to the incomplete coverage of Au {111} facet, new gold nanoplate growth sites were spontaneously generated from the crystal plane of existing Au nanoplates for the growth of other nanoplates. This process continued until the nanoplate density reached its maximum range, eventually resulting in CLMPs with well-controlled structures. It opens a new avenue to utilize the imperfection during nanoparticle (NP) growth for the construction of microstructures. The individual CLMP shows excellent surface-enhance Raman scattering (SERS) performance with high enhancement factor (EF) and good reproducibility as it integrates the SERS enhancement effects of individual Au nanoplates and the nanogaps formed by the uniform and hierarchical structures.

Resume : In this paper, quantum correction in the inversion layer charge density calculation was investigated. This study is carried out for one-dimensional Metal-Insulator-Semiconductor (MIS) structure with (100) oriented P-type silicon as substrate. The purpose of this paper is to point out the differences between the semi-classical and quantum-mechanical charge description at the interface Al2O3/Si. And identify some electronic properties of our MIS device using different thickness of the high-K oxide and diverse temperature with different carrier statics (Fermi-Dirac statics and Boltzmann statics). In particular, capacitance voltage (C-V), Sheet electron density, relative position of the subband energies and their wave functions are performed to examine qualitatively and quantitatively the electron states and charging mechanisms in our device.

Resume : The WPI Program was initiated in 2007 as a Japanese version of “Research Excellence Initiative (REI)” under the following 4 ambitious missions: - Top-quality science, - Internationalization, - Interdisciplinary researches and - Reform of existing systems. Under these missions, 9 WPI centers are now operating in the research fields of biomedical sciences, materials science and origins of universe, earth and life. Those in materials science are: - AIMR on mathematical materials science at Tohoku University - iCeMS on cell-inspired materials at Kyoto University - MANA on nanotechnology at National Institute for Materials Science. - I2CNER on carbon neutral energy at Kyushu University. These centers are now organizing a joint symposium on the occasion of E-MRS2016 In FY2017, the first 10-year support to AIMR, iCeMS and MANA will be terminated, but the government will continue to support their international activities such as satellite laboratory, employment of foreign PIs and postdocs and organization international events etc. under the program of “WPI Association”. The WPI program itself will sustain by creating new centers. We hope that WPI centers will continuously serve as a hub of global brain circulation.

Resume : Brief introduction of the four WPI Institutes, i.e., MANA, AIMR, iCeMS and I2CNER will be given by the Directors of respective Institutes.

Resume : Storage of renewable energy becomes more important with increasing contribution of renewable energy to the energy demand. Energy storage for mobility and seasonal storage are the two major challenges, because of the high energy density required and the large amount of stored energy. The technical solution is to produce hydrogen from renewable electricity and use the hydrogen to reduce CO2 from the atmosphere in order to synthesize liquid hydrocarbons. This requires large scale electrolyzers, hydrogen storage, adsorption of CO2 and finally a well controlled reaction of H2 and CO2 to a specific product, e.g. octane. The storage of liquid hydrocarbons is a well established technology. The challenges and the solutions for the realization of the technical process will be discussed and an example of the realization of the whole energy conversion chain will be presented. Fig. Schematic representation of the closed materials cycle, where hydrogen is produced from renewable energy and used together with CO2 from the atmosphere to synthesize hydrocarbons as CO2 neutral energy carriers.

Resume : Complex hydrides exhibit various energy-related functions; such as high-density hydrogen storage and microwave absorption for future fuel cell technologies, as well as lithium/sodium super-ionic conduction for rechargeable battery devices. The presenter will introduce some recent researches; on the synthesis of new high-density hydrides with CrH7 pentagonal-bipyramidal anion [Angew. Chem. Int. Ed. (2015)]; on the super-ionic conduction in BnHn-type hydrides with large cage-like units [Adv. Mater. (2014), Energy Environ. Sci. (2015)]; and also on the development of new all-solid-state rechargeable battery devices including lithium-sulfur (Li-S) battery using complex hydride electrolytes [Appl. Phys. Lett. (2014), Chem. Comm. (2015)].

Resume : Crystalline Si solar cell efficiency increase in the past years has been coupled with a decrease in wafer thickness, since one of the main cost driver of this technology is the amount of silicon consumed per Watt-peak. However, to pursue this tendency, and avoid fragile wafers, very thin c-Si films transferred on glass is an interesting option. Because of optical losses related to the material reduction, the light management schemes of thin c-Si solar cells providing more efficient optical absorption is essential. The recent development of Nanophotonics has triggered the emergence of novel concepts for light management. Light trapping schemes based on Photonic Crystals (PCs) and pyramidal nanostructuration are considered. The goal is to integrate such structures into ultra-thin film silicon (1-10 µm) solar cells, with a view to improve their conversion efficiency. A PCs assisted ultra-thin film c-Si solar cell is designed and optimized by using the Finite Different Time Domain (FDTD) approach to calculate the Jsc. An increase over 50% can be achieved for the absorption (compared with a flat structure), as integrated over the whole spectral range, by combining Slow Bloch modes, Structural antireflection and Fabry-Perot modes. To fabricate such solar cells, we developed a process based on Laser Holographic Lithography, RIE and ICP etching. Absorption measurements are in good agreement with theoretical simulations. Moreover, the integrated absorption is tolerant with regard to the sunlight angle of incidence. These are first steps towards the development of a future generation of PC and diffraction grating assisted solar cells. Simul elec, div disorientation crystalline more advanced shapes nanostructures

Resume : Energy and water are key geopolitical issues. Separately the issues are well known; The search for new sources of energy, that have less impact on environmental climate change; Equally, identifying ways to mitigate the effects of rapid consumption and pollution of a diminishing resource, potable fresh water. Less well known is the connectivity of these two issues, which is simply related to the fact that it requires energy to generate clean water, and a significant amount of fresh water is required for non-drinking purposes. I will be discussing the possibilities, and practicalities of future membrane technologies to address both the issue of water and energy-related emissions, giving a broad overview of the basics of the field of membrane technology whilst highlighting recent work in our own group, in the development of high performance polymeric and nanocomposite membranes.

Resume : Metal-Organic Frameworks (MOFs), also called Porous Coordination Polymers (PCPs) are (soft) crystalline coordination network materials composed of metal ion nodes connected by organic linkers, leading to a wide range of topologies and offering virtually unlimited opportunities for compositional modification and physical-chemical structure/property control. One fascinating aspect has been the use of intact MOFs as novel kind of host matrices for embedding nanoparticles to yield hybrid functionality.1 Also, by sacrificing the selected MOFs as precursors, one may directly obtain supported nanocatalysts of unique microstructures controlled by the MOF properties and by the pyrolysis protocols.2 We will present and discuss three typical examples: (i) The integration of preformed bimetallic (core/shell) and surfactant stabilized Pt/Pd and Ru/Pt nanoparticles inside UiO-66 for shape selective hydrogenation catalysis.3 (ii) Fabrication of Au/TiO2 photocatalysts for CO2 reduction in the presence of H2O based on oxidative conversion of NH2-MIL-125(Ti) pre-loaded with Au Nanoparticles.4 (iii) ZIF-67 derived Co/Co3O4 nanostructures encapsulated in Nitrogen-doped CNT as bi-functional electrode material for ORR and OER.5 References 1 C. Rösler, R. A. Fischer, „Metal–organic frameworks as hosts for Nanoparticles“, CrystEngComm 2015, 17, 199-217. 2 J. K. Sun, Q. Xu, "Functional materials derived from open framework templates/precursors: synthesis and applications",Energy Environ. Sci. 2014, 7, 2071-2100. 3 I. Luz, C. Rösler, K. Epp, F. X. Llabrés i Xamena, R. A. Fischer, Eur. J. Inorg. Chem. 2015, 3094-3912 4 K. Khaletskaya, A. Pougin, R. Medishetty, C. Rösler, C. Wiktor, J. Strunk, R. A. Fischer, “Fabrication of Gold/Titania Photocatalyst for CO2 Reduction based on pyrolytic Conversion of the Metal-Organic Framework NH2-MIL-125(Ti) loaded with Gold Nanoparticles“, Chem. Mater. 2015, 27, 7248–7257 5 A.Aijaz, J. Masa, C. Rösler, W. Xia, P. Weide, A. Botz, R. A. Fischer, W. Schuhmann, M. Muhler, „Co@Co3O4 Encapsulated in CNT-Grafted Nitrogen-Doped Carbon-Polyhedra as Advanced Bifunctional Oxygen Electrode,“ Angew. Chem. Int. Ed. 2016, 55, asap (10.1002/anie.201509382).

Resume : The energy related materials and processes leading to carbon neutral society based on renewable energy sources are in the central scope of materials science in the past decade. The recent advances in the miniaturization, device fabrication, and nanotechnology allowed for breakthroughs in fuel cell technologies, artificial photosynthesis, solar energy harvesting, bio-mimetic, etc. Combined with modern spectroscopy techniques, i.e., STM, LEIS, TEM, AFM, the computational materials science is a powerful tool to elucidate the dynamics of atomistic to large scale processes within the bulk materials, on the materials’ surfaces and interfaces. Its predictive power can provide novel control techniques to nanoscale processes which are often hard to access with experimental methods. In this work is demonstrated the guiding role of computational materials science in tree important energy related fields. First is the stabilization of metal nanoparticles on surfaces through control of the surface curvature for use in the nanoparticle catalysis. Second, we demonstrate the synergy of theoretical chemistry and LEIS spectroscopy in the design of novel SOFC electrode materials and third, we provide ways to mitigate the hydrogen embrittlement of steels by controlling the surface reaction of hydrogen dissociation through precise impurity level control. Finally, we demonstrate the practical outcomes of the computationally assisted materials research and the applications in the fields of carbon-neutral energy.

Resume : Phosphoric acid-doped polybenzimidazoles (PA-doped PBIs) have been considered as the most promising substitutive polyelectrolytes and the PEFC employing PA-doped PBIs not only in PEM but also in the catalyst layers (Cat-L) have been developed for high temperature operation. However, recent studies have revealed that leaching of liquid PA from PEM and Cat-L causes inhomogeneous PA distribution that results in deterioration of PEFC performance during long-term operation. In this study, in order to prevent acid leaching from the high temperature PEFC system, we used poly(vinylphosphonic acid) (PVPA) in place of PA because PVPA is a polymeric acid and is stably bound to the PBIs via multipoint acid-base reactions. We fabricated a novel electrocatalyst for Cat-L assembled with carbon nanotubes (CNTs), PVPA-doped PBI and platinum (Pt) nanoparticles as an electron-conducting supporting material, electrolyte and metal catalyst, respectively. Bottom-up assembly of nanometer-thick PVPA-doped PBI layer around CNTs is expected to serve as an effective proton conduction pathway via the Grotthuss mechanism. We tested the durability of the PVPA-doped MEA by following the protocol proposed by the Fuel Cell Commercialization Conference of Japan (FCCJ). As a comparison, the durability of a PA-non-doped MEA was tested. Dramatic drop of the cell voltage was observed for PA-non-doped MEA, while PVPA-doped MEA only showed slight decrease.

Resume : A large variety of colloidal nanocrystal sizes and shapes, as well as material compositions are nowadays available by wet chemical routes. The nanocrystals however cannot always simply be separated from their surrounding solvents environment, which can lead to a loss of the physical and chemical properties which can be disadvantageous for certain applications. The development of tailored assembly techniques is therefore an important branch of nanoscience. We will present recent developments of our group regarding macroscopic hydrogels and aerogels from tailor-made colloidal nanoparticles. Certain types of semiconductor aerogels, such as from CdSe/CdS seeded nanorods, will be demostrated to have physical properties (ultralong fluorescence lifetimes in combination with high quantum yields) differing from those of their bulk or building blocks counterparts.[1] Furthermore, the need to develop versatile aerogel fabrication routes is addressed by presenting one route to such lightweight and porous gel monoliths based on freezing and subsequent freeze-drying.[2] We will show that this technique works quasi independently from the material, shape and surface modification of the nanoparticle building blocks, and that the macroscopic shape of the resulting monoliths can be freely chosen. References [1] S. Sánchez-Paradinas, D. Dorfs, S. Friebe, A. Freytag, A. Wolf, N.C. Bigall Advanced Materials 2015, 27 (40), 6152–6156. [2] A. Freytag, S. Sánchez-Paradinas, S. Naskar, N. Wendt, M. Colombo, G. Pugliese, J. Poppe, C. Demirci, I. Kretschmer, D.W. Bahnemann, P. Behrens, N.C. Bigall Angewandte Chemie Int. Ed. 2015 DOI: 10.1002/anie.201508972.

Resume : Hydrogen deteriorates mechanical properties of advanced high strength steels through various factors: enhancement of dislocation motion, reduction in surface energy, promotion of vacancy formation, reduction in stacking fault energy, etc. When hydrogen embrittlement occurs, all of these factors are noticed only as negative effects. However, a reduction in stacking fault energy of austenitic steels is generally known to enhance work hardening, which improves tensile elongation. For instance, twinning-induced plasticity (TWIP) steels were recently designed by decreasing stacking fault energy to promote FCC deformation twinning in austenitic steels, which have drawn attention as a new class of high strength steels with excellent workability. Therefore, the hydrogen effect decreasing the stacking fault energy is expected to enhance work hardening through promotion of deformation twinning or suppression of dislocation cross-slip. Fe-30Mn-(6-x)Si-xAl (x = 0, 2, 3, 6) austenitic alloys with different stacking fault energy from 16 to 64 mJ·m-2 were prepared for tensile tests. Hydrogen charging was carried out by exposing to a hydrogen gas atmosphere at 543 K and at 10 MPa for 200 h. The Fe-30Mn-6Si and Fe-30Mn-4Si-2Al alloys, in which the deformation mode is ε-martensitic transformation, showed distinct deterioration of the elongations by hydrogen uptake due to premature fracture. The elongation and work hardening behavior of the Fe-30Mn-3Si-3Al alloy were not affected by hydrogen. In contrast to these results, and surprisingly, a positive hydrogen effect appeared on the elongation of the Fe-30Mn-6Al alloy, where deformation twinning was observed only in the specimen with hydrogen charging.

Resume : The control and growth of semiconductor microstructures and nanostructures has driven the modern electronics industry. As device sizes shrink, an atomistic description of the structure of surfaces and interfaces in semiconductor nanostructures is becoming increasingly valuable. Moreover, this capability will give us the ability to model the properties of dopants in semiconductors, which control the electronic properties of the system and offer promising routes to quantum information implementations. I will describe the CONQUEST linear scaling[1] DFT code, developed by UCL and NIMS, which enables simulations of 100,000+ atoms with ab initio accuracy, and can use the largest supercomputers in the world with near-perfect efficiency[2]. I will describe applications of the code to two important areas of semiconductor nanostructures: the growth of three-dimensional “hut” clusters of Ge on Si(001)[3]; and the structure and properties of Ge/Si core-shell nanowires. These examples will show how large-scale DFT simulations offer unprecedented opportunities to model the exact structure of nanostructures being created experimentally. I will briefly mention new directions in the modeling, including ab initio molecular dynamics on systems with 32,000+ atoms[4]. References: 1) D. R. Bowler, T. Miyazaki,Rep. Prog. Phys. 75, 036503 (2012). 2) D. R. Bowler, T. Miyazaki,J. Phys.: Condens. Matter22, 074207 (2010). 3) M. Arita, S. Arapan, D. R. Bowler, T. Miyazaki, J. Adv. Simul. Sci. Eng.1, 87 (2014). 4) M. Arita, D. R. Bowler, T. Miyazaki, J. Chem. Theor. Comput.10, 5419 (2014).

Resume : Assembly of functional nanomaterials, in the same way that children play with building blocks, is one of the dreams of nanotechnology. In designing new materials with novel functionalities, we focus on two-dimensional (2D) oxide nanosheets (such as Ti1-O2, Ti1-xCoxO2, MnO2, perovskites), which are obtained by delaminating a layered compound into its single layers through soft-chemical procedures. 2D nanosheets, which possess atomic or molecular thickness, have increasingly attracted fundamental research interest because of their potential to be used as conductors, semiconductors, insulators, and even ferromagnets, depending on their chemical composition and how their atoms are arranged. Another attractive aspect of oxide nanosheets is that nanosheets can be organized into various nanoarchitectures by using solution-based layer-by-layer assembly. It is even possible to tailor superlattice assemblies, incorporating into the nanosheet galleries with a wide range of materials such as organic molecules, polymers, and inorganic/metal nanoparticles. Sophisticated functionalities or nanodevices can be designed through the selection of nanosheets and combining materials, and precise control over their arrangement at the molecular scale. We utilized oxide nanosheets as building blocks in the LEGO-like assembly, and successfully developed various functional nanodevices such as all nanosheet FETs, artificial ferroelectrics, spinelectronic devices, magneto-plasmonicmetamaterials, Li-ion batteries, etc. Our work is a proof-of-concept, showing that new nanodevices can be made from nanosheet architectonics.

Resume : Not only fabrication scale for the conventional semiconductor devices such as a field effect transistor, but also the physical operating is being reached limit in near future. One possible way to overcome these technological and physical limits is to achieve breakthroughs in device materials and　device-operation principle using nanotechnology. A nanoionics device, which is operated by controlling the local ion migration instead of electron and hole migration, is one of promising nanodevices . Recently,　we have found nanoionic phenomena that originate in physical or chemical action caused by local ionic migration near hetero-interfaces using ion conductors, and, as a result, created nanoinonic devices using these phenomena. For instance, the nanoionic devices with unique functionalities that cannot be obtained in conventional semiconductor devices, such as an a brain type device, an all solid electric double layer transistor, a multifunctionality on-demand device, and a superconducting device that can modulate the transition temperature are developed. In this presentation, recent interesting results of the solid state ionic field in the development research into next generation's electronic　information communication nanodevices will be introduced.

Resume : Molecular electronics started with the idea that a molecule sandwiched between electrodes may behave as a rectifying device. Since then, a number of studies have been reported that a molecule can rectify. Recently, C.A. Nijhuis et al has reported a SAMs molecular diode with high, robust, rectification ratios of 1.1 103. In this work, we develop a new strategy to build hybrid devices with specific electronic properties. The organic layer assembled between electrodes is fabricated by electro-generated radical grafting process using diazonium reduction. That makes it possible for the direct evaporation of various metals on the grafted organic layer in order to fabricate the top electrode through full CMOS compatible process. Metal/molecules/metal junctions based on oligo(BTB) [BTB = 1-(2-bisthienyl)benzene] layers show giant rectification from 103 to 4 103. The influences of various molecules as well as electrodes have been investigated. A possible electronic transport mechanism will be discussed to explain the rectifying behavior in agreement with the electrochemical behavior.