Scientific Program

Conference Series Ltd invites all the participants across the globe to attend 4th International Conference on Physical and Theoretical Chemistry Dublin, Ireland.

Day 2 :

Physical Chemistry 2017 International Conference Keynote Speaker Wai-Yim Ching photo
Biography:

Dr. Wai-Yim Ching is a Distinguished Curators’ Professor of Physics at the University Missouri-Kansas City, USA. He leads the Electronic Structure Group (ESG) in the Department of Physics and Astronomy. His research focuses on condensed matter theory and computational materials science using first-principles methods. With more than 40 years of experience, he is an author or co-author of over 410 journal articles in diverse areas related to materials and with a Google Scholar Citation H-index 64.  He is an Academician of World Ceramic Academy, a Fellow of the American Ceramic Society and the American Physical Society. He is an Associate Editor of the Journal of the American Ceramic Society and is on the Editorial Board of Nature Scientific Reports.

Abstract:

Statement of the problem: Metal-organic frameworks (MOFs) materials have attracted immense attention from diverse disciplines of chemistry, physics, engineering, material sciences, biological and biomedical sciences. Zeolitic imidazolate framework (ZIF) is an important member of MOF with a network topologies analogous to silica. In the network, the corner-sharing SiO4 tetrahedra are replaced by MN4 tetrahedra (M = metal, Zn in this work) linked by imidazolate (IM) (C3N2H3)-anions. The chemically tunable porosities of ZIFs are pivotal for many of their potential application. There exist a large number of crystalline ZIFs with well-defined zeolite structures, the emerging category of non-crystalline or amorphous ZIF (a-ZIF) is of particular interest. The a-ZIF can be viewed as a model system for understanding the general features and properties of a novel hybrid inorganic/organic glass with no long range order (LRO) but with well-preserved short range order (SRO). We have recently constructed a large a-ZIF mode and studied its electronic structure, inter-atomic bonding and optical properties. In this talk I present further study of the deformation behavior of this interesting material by applying step-wise homogenous compression and extension with strains respectively up to -0.30 and +0.30. The data for stress vs strain at each step are fully analyzed including mechanical properties. It shows that a-ZIF is a super-soft materials with intricate properties that have not been seen before. The origin of this behavior is explained by detailed electronic structure and bonding investigation.  Conclusion and significance: Our investigation shows that a-ZIF belongs to a class of super-soft materials with some intricate properties previous unknown. Additional large-scale accurate simulations may reveal other properties for potential applications especially in the soft covalent organic framework (COF) materials.

 

Physical Chemistry 2017 International Conference Keynote Speaker Werner Paulus photo
Biography:

Werner Paulus is exploring low temperature oxygen diffusion mechanisms in transition metal oxides. Oxygen doping, via topotactic reaction mechanisms while proceeding at ambient temperature is a powerful tool to access structural and electronic complexity in a controlled way. It also allows to better explore the underlying diffusion mechanisms on an atomic scale, having huge importance in solid state ionics, e.g. for the optimisation of battery materials, fuel cell membranes/electrolytes or sensors. Research activities cover synthesis methods from powder to large single crystals and to explore oxygen intercalation reactions in especially dedicated electrochemical cells on single crystals and polycrystalline electrodes by neutron and X-ray diffraction (synchrotron & laboratory), spectroscopy (XAFS, Raman, INS, IXS, NMR) combined with 18O/16O oxygen isotope exchange reactions and sophisticated data analysis (Maximum Entropy, twinning).

Abstract:

Since more than two decades, Transition Metal Oxides with strongly correlated electrons are intensively studied due their interesting physical properties. This includes colossal magnetoresistance (CMR) where huge variations in resistance are achieved just by small changes in the applied magnetic field, or high temperature superconductivity (HTC) to name two of them [3-6]. These materials are characterized by the existence of several competing states such as charge, spin and orbital ordering, interacting in a synergetic way and leading to fairly complex phase diagrams. Thereby the physical properties can be tuned in a wide range via hole doping, e.g. by cation substitution as is the case for RE2-xSrxMO4.

An alternative way of hole doping presents oxygen intercalation, generally proceeding at ambient temperature via a topotactic oxygen uptake along shallow potential diffusion pathways. Contrary to the cation substitution, requiring high reaction temperatures, oxygen intercalation reactions allow the controlled synthesis of strongly correlated oxides far away from thermodynamic equilibrium, essentially resulting in kinetically stabilized and thus metastable phases.

Low temperature reactivity of solids may thus be used as a concept, to investigate the limits of available structural and electronic complexity in transition metal oxides. The reaction pathway to insert oxygen at low temperatures in solid oxides becomes a decisive parameter to tune correlations, leading to extremely complex phase relations as physical and structural properties are not only depending on the overall stoichiometry, but decisively on the sample history. Taking these oxides as oxygen ‘sponges’ operating at low reaction temperatures down to ambient, structural and electronic correlation lengths could then be influenced by the reaction conditions and kinetics. We here discuss here the challenges, low temperature solid state reactivity implies for the synthesis of new complex oxides but equally the current understanding of the relying oxygen diffusion mechanisms, having a huge fundamental and technological interest.

Pr2NiO4.25: Representations of the NiO6 isosurfaces (left) for indicate the anharmonic double potential of the apical oxygen atoms present at 673 K, obtained from single crystal neutron diffraction and Maximum Entropy Analysis. The large anisotropic displacements of the apical oxygen atoms along [110] directly point towards the interstitial oxygen sites, forming a shallow oxygen diffusion pathway which is dynamically activated.

Physical Chemistry 2017 International Conference Keynote Speaker Per Jensen photo
Biography:

Per Jensen is professor of theoretical chemistry at the University of Wuppertal, Germany. His research interests lie in the border area between high-resolution molecular spectroscopy and quantum chemistry. He develops and applies methods for the accurate simulation of rotation-vibration spectra of small molecules, mostly of astrochemical and/or atmospheric interest. He is particularly interested in the application of molecular symmetry to facilitate the solution of nuclear-motion problems. Recently, he has worked extensively on interactions between electronic states (the Renner effect), the characterization of rovibrational energy clusters at high rotational excitation, and extremely flexible (structureless) molecules. He is author or co-author of about 200 publications.

Abstract:

Traditionally, molecules are theoretically described as near-static structures rotating in space. Vibrational motion causing small structural deformations induces a perturbative treatment of the rotation-vibration interaction. This treatment fails in highly flexible molecules, where all vibrational motions have amplitudes comparable in size to the linear dimensions of the molecule. An example is protonated methane (CH5+). For these molecules, customary theory fails to simulate reliably even the low-energy spectrum. Within the traditional view of rotation and vibration being near-separable, rotational and vibrational wavefunctions are symmetry classified separately in the molecular symmetry (MS) group. All MS groups discussed so far are isomorphic to subgroups of the special orthogonal group in three dimensions SO(3). This leads to a group theoretical foundation of the technique of equivalent rotations. The group G240 (the MS group of protonated methane) represents, to the best of our knowledge, the first example of an MS group which is not isomorphic to a subgroup of SO(3). Because of this, a separate symmetry classification of vibrational and rotational wavefunctions becomes impossible in this MS group, consistent with the fact that a decoupling of vibrational and rotational motion is impossible. The talk will discuss the consequences of this and propose an alternative description making use of the fact that G240 and SO(3) are both subgroups of the group SO(5) of rotations in five-dimensional space. We take SO(5) to be a near-symmetry group for CH5+ and develop a theoretical model that successfully explains recent experimental observations of rotation-vibration transitions in cold CH5+. Two of the vibrational degrees of freedom are essentially free and, in an initial approximation, these vibrations are combined with the “usual” rotation in 3D space with the resulting motion being viewed as free rotation in 5D space, consistent with the symmetry group SO(5).

Figure 1: The effect of the proton permutation (15432) on a CH5+ ion. It rotates the quantization axis z and so the customary technique of equivalent rotations cannot be applied.

  • Photochemistry | Solid-state Chemistry | Spectroscopy | Surface Science | Quantum Chemistry | Thermochemistry | Biophysical Chemistry
Location: Dublin, Ireland
Speaker
Biography:

Hideaki Shirota received his Ph.D. from the Graduate University for Advanced Studies in 1998.  His academic career started as a Research Associate at the University of Tokyo in 1996 in advance of receiving his Ph.D.  He then worked at the State University of New Jersey, Rutgers and the University of Tokyo as a Postdoctoral Associate and a Research Associate.  In 2006, he joined Chiba University, as an Associate Professor of chemistry.  His current research interests include molecular spectroscopy, laser spectroscopy, time-resolved spectroscopy, molecular dynamics in condensed phases, reaction dynamics in solutions, and solution chemistry.

Abstract:

Ionic liquids (ILs) are liquid state salts at room temperature.  ILs possess unique features, such as low melting points, negligible vapor pressure at ambient temperature and pressure, and so on. In fact, such unique properties are largely responsible for their complex intermolecular interactions. Because the intermolecular vibrations probe the microscopic structure and intermolecular interactions in condensed phases, it is essential to study their intermolecular vibrations.  Femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES) observes the molecular motions in the low-frequency region (ca. 0.3–700 cm-1) where the intermolecular vibrational bands in most condensed phases appear.  Thus, fs-RIKES is a useful spectroscopic technique to study ILs. So far, we have reported several specific topics on the low-frequency spectral features of ILs: (i) heavy atom substitution effect, (ii) comparison between dicationic and monocationic ILs, and (iii) understanding the general spectral features of aromatic cation based ILs on the basis of 40 samples. In this talk, I will show the results of the temperature dependence of the low-frequency spectra of ILs that we are currently studying. Figure 1 shows the low-frequency spectra of bis(trifluoromethylsulfonyl)amide ([NTf2]-) salts of (a) 1-butyl-3-methylimidazolium cation ([C4MIm]+) and (b) 1-butyl-1-methylpyrrolidinium cation ([Pyrr14]+) at various temperatures. We can see the clear difference between the two, and the difference will be discussed in detail.

Figure 1. Temperature dependent low-frequency spectra of bis(trifluoromethylsulfonyl)amide ([NTf2]-) salts of (a) 1-butyl-3-methylimidazolium cation ([C4MIm]+) and (b) 1-butyl-1-methylpyrrolidinium cation ([Pyrr14]+).

Speaker
Biography:

Wen-Hsien Li is a Full Professor of the Physics Department, National Central University, Taiwan. He has been the Director since the Center for Neutron Beam Applications of National Central University was found in 2006. He contributed very heavily to the birth of Taiwan Neutron Science Society (TWNSS) and Center for Neutron Beam Applications of National Central University. Wen-Hsien’s current research is focused in quantum nanoparticle and multiferroic, using neutron scattering, Raman scattering, and other techniques to elucidate the interplay between the superconducting and magnetic degrees-of-freedom of these systems.

Abstract:

Fruitful magnetic behaviors, such as light-induced magnetism, metastable ferrimagnetism, negative magnetization, spin crossover and spin delocalization have been identified in the hexacyanoferrate polynuclear complexes known as Prussian blue (PB) and its analogues (PBA). The PBA’s are composed of alternately stacked MN6 and M¢C6 octahedra along the three crystallographic axes, where M and M¢ can be divalent or trivalent transition metal ions. The flexibility to accommodate either divalent or trivalent ions at the M and M¢ sites has led to a large family of analogues and applications.  For example, the structure builds up three-dimensional open channels to accommodate weakly bonded ions able to migrate through the channels and the framework has been exploited as electrode materials for secondary batteries, providing housing for ions to leave the framework during charging and reenter during discharging. In the present studies, different magnetic phases have been identified in nano-sized core/shell PBA cubes, with a 250 nm Rb-Co-Fe phase (Rb0.48Co[Fe(CN)6]0.75[(H2O)6]0.25·0.34H2O) in the core coated by a 45 nm K-Ni-Cr phase (K0.36Ni[Cr(CN)6]0.74[(H2O)6]0.26·0.11H2O) on the shell. Three separate characteristic temperatures at 86, 69, and 67 K are associated with magnetic phases in the K-Ni-Cr shell. Two magnetic exchange paths are identified. One propagates along the three crystallographic axis directions. The other propagates along the [110] crystallographic direction for the associated Ni-Ni interactions, but Cr-Cr interactions. The severe Cr-deficiency and the appearance of direct Ni-Ni exchange are used to understand the appearance of two separate transitions associated with magnetic ordering. A weak moment develops in the core at low temperature, corresponding to separate ordering of the Co-Fe PBA network.

Speaker
Biography:

Malgorzata Bayda received her Ph.D. in chemistry from the Adam Mickiewicz University, Poznan, Poland (2009) working under supervision of Prof. Bronislaw Marciniak. She had 4 external positions: short-term research positions at Radiation Laboratory, University of Notre Dame, USA working with Dr. Gordon L. Hug (2008, 2015) and postdoctoral associate positions in Professor Jack Saltiel’s research laboratory at the Florida State University, USA (2010-2011, 2012). Since 2009 she works as assistant professor (teaching and research) at AMU. She has her expertise in photophysics and photochemistry of organosilicon compounds using steady-state and time-resolved absorption and emission spectroscopy. Her earlier work was focused on a cis/trans photoisomerization of p-phenylene-silylene-vinylene polymers. Recently, her scientific interest turned toward searching for an attractive organosilicon light-emitting materials. To improve performance of such materials through rational molecular design she investigates excited-state processes between silylene-bridged chromophores focussing on a role of silicon atom in these processes.

Abstract:

There are still few examples of materials emitting blue and green light. Coming forward to meet these needs we proposed silicon-bridged chromophores as sources for blue-green emission. Although the individual chromophores chosen (N-isopropylcarbazole (CBL) and 1,4-divinylbenzene (DVB)) emit in the UV range, linking them through the silylene bridge ‘switches on’ the coloured emission which originates from an intramolecular charge transfer reaction (ICT). This phenomenon was observed not only for the polymer but also for its bichromophoric model compound representing the repeating unit of the polymer. This finding indicates that the ICT occurs between adjacent chromophores through the silylene bridge. If so, it was justified to use a model to describe in detail excited-state processes in this kind of substances to give rise to rational molecular design of new light-emitting materials. The questions raised in this work are: what are the nuclear motions essential to intramolecular charge transfer?  Is the ICT process solvent-controlled or is the driving force some geometric change of a solute in the excited state? To answer these questions, we studied ICT on a model compound. We found that in nonpolar solvents, emission arises from the local excited state (LE) of carbazole whereas in more polar solvents dual emission was detected (LE+ICT). The CT character of the additional emission band was concluded from the linear dependence of the fluorescence maxima on solvent polarity. Electron transfer from CBL to DVB resulted in a large excited-state dipole moment (37.3 D) as determined from a solvatochromic plot and DFT calculations. Steady-state and picosecond time-resolved fluorescence experiments performed in butyronitrile (293-173 K) showed that the ICT excited state arises from the LE state of carbazole. These results were analyzed and found to consistent with an adiabatic version of Marcus theory including solvent relaxation.

Speaker
Biography:

Dr. Lei Zhu is a Research Scientist at the Wadsworth Center, New York State Department of Health, and a professor in the Department of Environmental Health Sciences at SUNY-Albany.  Dr. Zhu’s research program has been designed to investigate and understand what controls the atmosphere’s energy balance and how chemical reactions impact composition, pollutant and oxidant formation in the earth’s environment.  Her research interests include kinetics and photochemistry of homogeneous and heterogeneous atmospheric reactions, atmospheric application of cavity ring-down spectroscopy and its variants, and atmospheric application of time-resolved FT-IR.

Abstract:

Statement of the Problem: The significantly elevated daytime nitrous acid (HONO) concentrations compared to those predicted based on the photochemical stationary state between HONO sources and sinks leads to postulate that HONO is produced by photochemical sources.  One proposed HONO source is gas phase photolysis of 2-nitrophenol (o-C6H4(NO2)OH) over the 300-500 nm region.  2-Nitrophenol is also an important component of “brown carbon” in the atmosphere.  The concentration of 2-nitrophenol is expected to be high in polluted areas where there are increased emissions of aromatic hydrocarbons.  To assess the air quality impacts of pollutant emissions, it is important to determine oxidant formation potential of the emitted species.  Although photodissociation dynamics studies of 2-nitrophenol have reported OH formation at photolysis wavelengths of 266 nm, 355 nm, and over the 361-390 nm range, and HONO was observed as a product from 2-nitrophenol photolysis in a smog chamber, the lack of quantitative absorption cross section and product quantum yield information has prevented quantitative assessment of the extent of oxidant formation from 2-nitrophenol photolysis in the atmosphere.  The purpose of this study is to determine quantitatively the gas phase absorption cross sections of 2-nitrophenol over the 295-400 nm range, to investigate the HONO and OH formation channels following the 308 and 351 nm photolysis of 2-nitrophenol, and to obtain the OH and the HONO quantum yields.  We have estimated the atmospheric oxidant formation rate constants following the gas phase photolysis of 2-nitrophenol using 2-nitrophenol near UV absorption cross sections, and OH and HONO formation quantum yields obtained from this study. Conclusion & Significance: Gas phase photolysis rate constant of 2-nitrophenol is about twice that of NO2 and the sum of OH and HONO formation quantum yields are about unity at 308 nm and 351 nm.  OH formation rate constant is fast from the gas phase photolysis of 2-nitrophenol.  Recommendations are made to include gas phase 2-nitrophenol photolysis as a significant missing source of OH in the modeling of the chemistry of the polluted atmosphere.

Speaker
Biography:

Youngmin You is Associate Professor of the Division of Chemical Engineering and Materials Science at Ewha Womans University. He earned his bachelor and master degrees in Chemical Engineering from Seoul National University in 1997 and 2003, respectively. He continued graduate study in Department of Materials Science and Engineering at the same university, and obtained his Ph.D. degree in 2007. He started his independent carrier as an assistant professor at Kyung Hee University in 2013, and moved to Ewha Womans University in 2015. Prof. You focuses on the development of novel molecules and photoelectrofunctions. His current research interests include luminescent molecules for exciton harvesting and circularly polarized emission, photoredox catalysis, and photoluminescent bioprobes. He published 54 papers, including six review articles.

Abstract:

Spin statics of excitons is the key factor that determines the efficiency for interconversion between photon and electron. For example, internal quantum yields of electrofluorescence devices are limited by 25% in the absence of processes that aid intersystem crossing. Charge collection efficiencies in photovoltaic devices are also intimately associated with spin distributions. Efforts have, thus, been paid to develop the materials that overcome the spin selection rule. Notable examples include organometallic complexes of Ir(III) or Pt(II) which exhibit strong spin-orbit coupling. Of recent interest are dipolar organic molecules and coordination compounds of Cu(I). These compounds possess charge-separated excited states with small exchange energies. This electronic structure allows for thermally activated reverse intersystem crossing, leading to exciton-harvested fluorescence emission. Our group was intrigued by the key role of the excitonic spin states in electroluminescence devices. We investigated the fluorescence properties of chromophores bearing n-p* transitions. Although n-p* molecules can serve as electroluminescent materials because of the harvesting of singlet and triplet excitons through El-Sayed-rule-allowed reverse intersystem crossing, the weak fluorescence emissions of such molecules have prevented applications into devices. To enable systematic studies, we prepared a series of electron-deficient coumarin compounds having aryl substituents with different band gap energies. We observed two orders of magnitude improvement in fluorescence quantum yields upon facilitating intra- and intermolecular electron transfer to the coumarins. Special focus has been paid to understand the electron-transfer processes and the molecular factors that controlled the kinetic steps. The mechanistic studies revealed that judicious control over excited-state potentials was crucial to achieving efficient fluorescence.

Speaker
Biography:

Dr. Anjan Chattopadhyay is an Associate Professor in the Department of Chemistry, BITS-Pilani, K.K.Birla Goa Campus, India. He works on computational photochemistry of organic molecules which include nitrones, iminium ions and push-pull polyene systems. His area of research interest also includes the study of van der Waals systems and solvent effects on the molecular rotors. In recent years his research group has been actively involved in exploring the photochemical reaction paths of different categories of nitrone systems. He has collaborations with the experimental chemists working in the field of organic and inorganic chemistry.

Abstract:

In recent times, we have computationally explored the photochemistry of several conjugated nitrone systems which include the chemopreventive retinyl nitrones, fluorescent naphthyl nitrones and small open-chain nitrones with phenyl substitutions at the C-terminal positions. In the latter category, we have studied the α-styryl N-methylnitrone and the 3,3-diphenylethylene N-methylnitrone, both synthesized and characterized by our group. Results based on high-level computational investigations on the photo-excited states of these two conjugated N-methylnitrone systems have justified their experimentally observed photochemical features. The UV peaks gradually developed near 260 nm has been theoretically predicted to appear from the oxaziridine. Analysis of the IR peaks has also indicated this terminal heterocyclic species as the photoproduct. Photo-excitation of the planar α-styryl N-methylnitrone is found to populate the first excited singlet state through allowed S0-S1 transition of roughly 7 Debye transition moment value. This is subsequently followed by a reaction path leading towards the lowest-energy conical intersection (S0/S1) with a terminal CNO-kinked geometry (27-30 kcal/mol below the relaxed S1 state). Following the gradient difference vectors of this conical intersection, an oxaziridine structure was located around 14 kcal/ mol above the ground state. In contrast, the photo-excitation of the non-planar 3,3-diphenylethylene N-methylnitrone leads to two strongly allowed singlet-singlet transitions (S0-S1 and S0-S2). The initially photo-excited S2 state relaxes to the S1 state which is further followed by oxaziridine formation through the terminally twisted conical intersection. However, the S0–S1 transition in this nitrone is found to follow another route by transfer of huge amount of non-bonding electron cloud of oxygen to the π* orbital, and thus forming a stable excited state geometry with an elongated N-O bond which gets involved in a sloped conical intersection with the ground state; this can be related to the experimentally observed slow decay of the longer wavelength UV peak of this nitrone.

 

Speaker
Biography:

Akira Chikamatsu holds a Ph.D. from the University of Tokyo in 2008, and currently works on the University of Tokyo as an assistant professor. He is an expert in solid-state chemistry and physics, thin-film growth, and electron spectroscopy. He developed new thin-film growth techniques of mixed-anion transition metal oxides, and succeeded in creating some new materials by these methods. His current research interests in searching for new functionalities and new phenomena in mixed-anion transition metal oxides by using layer-by-layer thin film growth and topotactic reaction technologies.

Abstract:

Transition metal oxides exhibit fascinating physical and chemical properties, including superconductivity, colossal magnetoresistance, ferroelectricity, and photocatalytic abilities. Since these properties are strongly affected by bonding interactions between the d orbital of transition metal cations and the p orbital of oxide anions, moderate replacement of O2- by H- or F- can drastically change the characters. One of the most excellent methods to obtain oxyhydrides and oxyfluorides is topotactic synthesis using reagents, where guest species can be introduced into a host crystalline structure without destroying the initial crystalline matrix. For example, insulating BaTiO3 changes into oxide hydride BaTiO2.4H0.6 with metallic nature by CaH2 treatment [1], and bulk crystal of SrFeO3-δ changes into SrFeO2F by annealing with poly-CH2CF2 (PVDF) at 400°C [2]. Though this method has mainly been applied to powder bulk samples, the reaction on thin-film samples is expected to have several advantages over bulk: considerably higher reactivity owing to the larger surface area/volume ratio, stabilization of the crystal framework by epitaxial effect, and modification of physical properties by epitaxial strain. In this study, we examined four types of topotactic reactions for various transition-metal oxide epitaxial thin films, i.e., hydridation and strong reduction using CaH2, fluorination using PVDF, and strong oxidation using NaClO solution, as schematically illustrated in Figure 1. Furthermore, we found interesting electronic properties in the obtained mixed-anion oxide thin films, such as ferromagnetic metal to antiferromagnetic insulator transition. These reactions will be useful for designing and synthesizing novel mixed-anion compounds in epitaxial thin film form.

 

Speaker
Biography:

Arnaud Caron is a materials scientist with expertise in the multi-scale mechanical behavior of materials, surfaces and micro-components. Since 2015 Arnaud Caron is Assistant Professor in the School of Energy, Materials and Chemical Engineering at KoreaTech – Korea University of Technology and Education, Republic of Korea. Arnaud Caron obtained his engineering degree in Materials Science in 2004 from the University of Saarland, Germany and was awarded with the Schiebold Medal. In 2009, he earned his doctoral degree in Materials Science from the University of Saarland, Germany. From 2007 to 2015 Arnaud Caron worked as a research associate at the Institute of Micro- and Nanomaterials of the University of Ulm, Germany, the WPI-Advanced Institute of Materials Research at the Tohoku University, Japan and the Leibniz – Institute for New Materials, Germany.

Abstract:

In this work, we apply atomic force microscopy / spectroscopy (AFM/S) and friction force microscopy (FFM) in immersed conditions to probe the structure of water at the interface of highly oriented pyrolytic graphite (HOPG) and AFM tips with different metallic coatings. While AFS measurements allow the observation of the layering of water molecules as a function of the distance from the HOPG surface, FFM measurements and the occurrence of molecular scale stick-slip give provide new insights in the two-dimensional distribution of interfacial water molecules. The layering of water is found to be significantly affected by the chemistry of the AFM tip approaching the HOPG surface. Beside the periodicity of the graphitic honeycomb structure, statistical analysis of the stick slip friction behavior reveals characteristic structural lengths that also depends on the chemistry of the AFM-tip sliding on HOPG. We discuss these observations based on the conformation of different ice structures at the interfaces between an HOPG surface and different counter bodies.

Manfred Martin

RWTH Aachen University, Germany

Title: Anion and Cation Diffusion in Complex Oxides
Speaker
Biography:

Manfred Martin is Professor and Head of the Institute of Physical Chemistry of RWTH Aachen University, Germany. At Seoul National University, Korea he was WCU Professor and is now Adjunct Professor. He has more than 30 years of experience in education and research of physical chemistry of solids as well as service at department, faculty and university level. His current research focusses on materials for energy conversion, resistive switching, solid-state reactions, secondary ion mass spectrometry, and computer simulations as well. Professor Manfred Martin has published >200 scientific papers in international, refereed journals. He received the Carl-Wagner Award and has been elected as member of the Royal Society of Chemistry. He has supervised more than 50 Ph.D. students and more than 20 postdoctoral fellows.

Abstract:

Oxygen diffusion in complex oxide materials is of great importance for applications, e.g. in fuel cells (oxygen ion conductivity) or oxygen permeation membranes (ambipolar diffusion of oxygen). For heavily doped oxides, such as doped zirconia, ceria or lanthanum gallate, we give a qualitative and quantitative explanation of the observed maximum of the conductivity as a function of the dopant fraction by combining DFT calculations of energies and entropies with Kinetic Monte Simulations of the oxygen ion conductivity.

Concerning cation diffusion in complex oxides we report our recent findings in perovskites, with a special focus on doped lanthanum gallates, barium titanate, and BSCF. Our experimental results indicate that the cation diffusion mechanisms are more complicated than simple vacancy mechanisms. We show that the experimental observations can be explained well by A- and B-site cation vacancies that are strongly bound in defect clusters and perform a highly correlated motion.

Speaker
Biography:

The research interests of Ulrich Wedig are located at the borderline between solid state chemistry and physics, between theory and experiment. Having a sound background in quantum chemistry, he collaborates with experimenters in order to elaborate a deeper understanding of the behaviour and properties of molecular and solid state systems. Special emphasis is put on the relation between quantum chemical data and chemical concepts, bridging the gap between more or less rigorous ab initio calculations and a local description of bonds in chemistry.

Abstract:

The Tetrelphosphide Ag6Ge10P12 is the prototype of a class of compounds which is known since the mid of the 1970s. In the subsequent years, various experimental results were published. However, due to a lack of accurate quantum chemical investigations, the interpretation of the data was not unambiguous at this time. After three decades of silence, these compounds attracted attention again, due to the promising thermoelectric performance. The figure of merit (zT) of pristine Ag6Ge10P12 is already 0.6 at 700K, leaving room for improvements in this class of compounds. Reason for this relatively large zT value is the small thermal conductivity, k < 1 W·m-1·K-1, which is related to the exceptional bonding characteristics. According to recent density functional calculation and a thorough bonding analysis, the crystal structure consists of a zinc blende like arrangement of germanium and phosphorus atoms with large voids. This covalent framework incloses subvalent silver octahedra. Four of the faces of the Ag64+ clusters are capped by another germanium atom, respectively. The atoms within the voids are weakly bound. Concerning the bonding types, there exists a hierarchy with a wide range of bond strength, giving rise to local, low-frequency phonon modes which lead to the reduced lattice contribution to the thermal conductivity. The electronic as well as the dynamic properties of the compound can be modified by substituting elements at the various tetrel sites in the crystal. The covalent framework becomes more rigid when replacing germanium by silicon. Taking tin as capping atoms of the silver octahedral results in a blue shift of the low-lying frequencies and a smaller band gap. By these controlled modifications, new insight can be gained into the complex interplay of electrical and thermal transport properties in thermoelectric materials.

Speaker
Biography:

Nadia Djaker is an assistant-professor in a medical faculty in Paris 13 university. Teaching optical techniques for biological media characterization in Master and PhD levels. Her research expertise involves optical linear (fluorescence, Raman) and nonlinear (SHG,CARS) spectroscopy techniques. Recently, she has developed a project on nanoparticles toxicity, especially in nanoparticles and biological media interactions study by correlation spectroscopy with a collaboration of several national and international research teams. Her project is on the border between fundamental and applied research directly related to the clinical diagnosis of the toxicity of nanoparticles and therefore to public health.

Abstract:

Gold nanoparticles (GNP) are widely used in many fields, such as analytical chemistry, catalysis and biomedical applications. The geometrical and optical characterization of these GNP is an inevitable step before any practical application. For example, plasmonic properties such as absorption and scattering and electromagnetic field enhancement have been explored for different type of GNP, with several techniques, like UV-Vis spectroscopy, surface enhanced Raman scattering (SERS) or correlation spectroscopy. Geometrical properties such as size and shape were mostly explored by electronic microscopy and have a strong influence on their optical properties. In addition, other properties like the surface area and volume are very important before GNP functionalization, especially for branched nanoparticles such as nanostars, nanoflowers or nanourchins.

Recently, scattering correlation spectroscopy (SCS) is one of the most used techniques for GNP characterization. As fluorescence correlation spectroscopy, the SCS technique is based on the analysis of intensity fluctuations within a well-defined confocal volume (~ 1 fL). The correlation curve is directly related to the hydrodynamic radius of molecules or nanoparticles, to their diffusion coefficient, concentration and shape. The SCS is very sensitive to GNP morphology and brightness since the scattering intensity depends on the GNP volume.

SCS technique will be presented to characterize the hydrodynamic sizes of  different shapes of GNP (spheres, urchins and flowers), with different surface chemistries (PEG, thiophenol) and different sizes (20-80 nm) at very low concentrations (~pM) and with very high precision (~0.2 nm). We explored the scattering  properties of these GNP at different wavelengths, close and far from their plasmon resonances. As predicted by Mie theory, we demonstrated that the increase in GNP size leads to the increase of the scattered intensity with the excitation power. In the case of nanoflowers, we observed a large increase of the  scattered signal due to their specific surface morphology. Such results make this type of nanoparticles a better candidate for both cell imaging and photothermal therapy.

 

Speaker
Biography:

Jolanda Spadavecchia is a senior researcher. Her research activities are focused on the realization of nanoparticles and biosensors. In particular, she is interested in the processes responsible for the bioconjugation of protein, macromolecules or DNA oligonucleotides onto gold nanoparticles and substrates for the creation of optical biosensors. She is currently involved in the synthesis of Polymeric nanoparticles and the development of Nano-hybrid materials for Nanomedicine. Actually she has an active collaboration with Berlin and Louvre Museum in order to establish the mechanism responsible of the AuNP formation at the surface of ancient ivory objects from different archaeological and historical contexts.

Abstract:

In this study, we report the synthesis, physico-chemical characterization and results of the biological behavior of doxorubicin-complex –gold COOH-terminated PEG-coated NPs (DOXO IN-PEG-AuNPs) before and after conjugation with antibody (anti-Kv11.1-pAb) to evaluate the influence of the nanocarrier and of the active targeting functionality on the anti-tumour efficacy of doxorubicin, with respect to its half-maximal effective concentration (EC50) and to drug-triggered changes in the cell cycle [1]. The anti-Kv11.1-pAb recognized specifically the Kv11.1 subunit of the hERG1 channel aberrantly expressed on the membrane of pancreatic cancer cells. The synthetic approach consist in four steps  (Figure 1): (1) Complexation between doxorubicin ( DOXO)  and tetrachouric acid ( HAuCl4 ) to form gold clusters; (2) adsorption of COOH-terminated PEG molecules (PEG) onto DOXO-Au complex; (3) reduction of metal ions in that vicinity, growth of gold particles and colloidal stabilization.(4) Bioconjugation of  anti-Kv11.1-pAb. Raman spectroscopy   were performed for the vibrational characterization of each step of the synthesis of doxorubicin-nanocarrier, distinguishing them from the free drug, protonated or not on the phenolic part of its chromophore. The calculated characterization DOXO IN-PEG-AuNPs vibrational bands show qualitative agreement with the experimental observations. Although preliminary, data gathered from this study have a considerable potential in the application of gold complexes with high stability, for the treatment of PDAC, a disease with a dismal prognosis and one of the main current burdens of today healthcare bill of industrialized countries. Further studies are still envisaged, focused on assessing the in vivo assessment toxicity, pharmacokinetics and dynamics on relevant.

Speaker
Biography:

Titus Adrian Beu is Professor of Theoretical and Computational Physics at the University Babeș-Bolyai from Cluj-Napoca, Romania. He has been actively involved in computational physics, material science, and chemical physics for more than 30 years. His research topics have evolved from Tokamak plasma and nuclear reactor calculations in the 1980s, collision theory and molecular cluster spectroscopy in the 1990s, to simulations of fullerenes, nanofluidic systems and biopolymers in recent years. The development of complex computer codes has been at the heart of all the research projects the author has conducted. In parallel, he taught courses in general programming techniques and advanced numerical methods, general simulation methods and advanced molecular dynamics.

Abstract:

Over more than a decade, cationic polymers have been validated as excellent gene delivery vectors, not in the least, due to their accessible chemistry, cost effectiveness, and controllable toxicity [1,2]. Polyethylenimine (PEI), in particular, is one of the most commonly employed synthetic polycations. The predominant electrostatic interactions between the positive amino groups of these polymers and the negative phosphate groups of DNA lead to condensed polyplexes, which protect DNA from degradation and are able to enter cells via endocytosis. The specific charge pattern of protonated PEI is widely considered to be responsible for the release of the polyplexes from the endosome (via proton sponge effect), and, finally, for the release of DNA from polyplexes (prior to being processed by the nucleus). Our investigations aim to provide a new, realistic molecular mechanics force field for PEI, to be used in detailed atomistic simulations of DNA-PEI condensation. Accordingly, we tackle two major issues: (1) we develop a new atomistic CHARMM force field for PEI of arbitrary length and protonation patterns, rigorously derived from high-quality ab initio calculations on model polymers, and (2) we perform molecular dynamics simulations, investigating the dynamic structuring of solvated PEI chains in dependence of their size and protonation state. We characterize the dynamic structuring in terms of gyration radius, end-to-end distance, persistence length, radial distribution functions, coordination numbers, and diffusion coefficients. Altogether, the developed force field [5] leads to more rigid PEI chains than other computational studies. Notably, the calculated diffusion coefficients are in excellent agreement with experimental data and validate the force field for the realistic modeling of the size and protonation behavior of linear PEI chains, whether individually or as part of polyplexes.

Figure 1: Protonated PEI tetramer used as model for the force field parametrization.

Speaker
Biography:

Shigeharu Kittaka has his expertise in surface chemistry of metal oxide-water systems: electrification of metal oxides in water, fine spherical particle formation and surface structure, layer structure of V2O5·nH2O by intercalation of water and organic molecules and electrical properties, phase changes of molecular liquids: water, ammonia, alcohol etc. Employed methodologies are electro-kinetic measurements, gas adsorption, FTIR, differential scanning calorimetry, adiabatic calorimetry, neutron scattering, electron microscopy, XRD analysis etc.

Abstract:

The nature of super-cooled water in confinement is an important subject that involves many aspects of natural sciences. Strong hydrogen bonds lead to the formation of structured collective entities in liquid water, finally resulting in crystallization of ice. Since the development of synthetic methods of well-defined porous silicas of various sizes, cylindrical, spherical, etc., experimental and theoretical analysis of pore water has significantly developed. The present interest is to find how the collective entities of water grow in fine pores of different shapes and what dynamic motions are there. Neutron spin echo (NSE) measurements were conducted on heavy water confined in cylindrically porous MCM-41 and spherically porous SBA-16 in the temperature range 210–290 K. Deuterium has a nuclear spin of 1 and thus has a highly coherent scattering cross-section that is convenient for the study of the dynamics of collective entities of heavy water. In the spherical pores of SBA-16, the translational motion of heavy water was strongly inhibited, even at 290 K. Rotational motion, however, was observed clearly in the temperature range 230–290 K and was analysed by the Vogel–Fulcher–Tammann relation. The relaxation time of the rotational motion of heavy water increased with a decrease in temperature. For heavy water in the cylindrically porous MCM-41, the relaxation time increased with reducing the temperature, as in SBA-16, but much more sharply. The larger value for the former is ascribed to the linear growth of hydrogen bonds in the cylindrical pores. In contrast, in the spherical space of SBA-16, spherical growth of heavy water clusters could permit a faster dynamic rotational motion. NSE measurements of light water in SBA-16 showed the translational diffusion of discrete water molecules there, indicative of the occurrence of breaking and recombination of hydrogen bonds in the collective entities.

Speaker
Biography:

Werner Lottermoser, solid state physicist, has completed his thesis work about neutron diffraction and magnetism of special silicates at CNRS, CENG and ILL Grenoble, France, and University of Frankfurt, Germany. He obtained university lecturing qualfication and professorship due to a study on Single Crystal Mössbauer Spectroscopy at Salzburg University, Austria, and was working in different scientific projects granted by the Austrian Fund of Scientic Research (FWF). Together with his working group he developed a software to combine the results of SCMBS, X-ray/synchrotron and neutron diffractometry to the common benefit of nanoscience. This rather new method is called "Difference Electron Nanoscopy (DEN) and allows to get uncompared quasi-3D views of the electronic distribution within the crystal unit cell and is described in a book (s. above), which has recently appeared. Consequently he is now working on sub-nanometric imaging, nanomaterials and materials for industrial applications.

Abstract:

Statement of the Problem: The admixture of 3d transition metals to particles and ceramic structures of non-reducible metal oxides has given rise to a variety of functionalities used in industrial applications. However, it is not easy to control  the impurity localization and  the nanomaterials' functional properties.

Methodology & Theoretical Orientation: Powders of Fe-Mg-O nanocomposite particles have been grown using a novel chemical vapor synthesis approach which involves metalorganic precursor decomposition inside the combustion flame. After annealing in controlled gas atmosphere composition distribution functions, structure and phase stability of the obtained magnesiowüstite nanoparticles were measured with a combination of methods.

Findings: 57-Mössbauer spectroscopy measurements revealed that - depending on Fe loading and annealing temperature - either metastable and superparamagnetic solid solutions of FeIII ions in periclase MgO or phase separated mixtures of MgO and antiferromagnetic magnesioferrite MgFe2O4 nanoparticles can be obtained.

Conclusion & Significance: The combination of the present hybrid combustion technique with annealing protocols emphasize the great potential of vapor phase grown non-equilibrium solids: Applying this method, phase separation, disproportionation and the appearance of magnetic properties can be tuned intentionally. Different from their bulk counterpart, MgFe2O4 nanoparticles with identical composition and structure are superparamagnetic and are promising material components for Magnetic Resonance Imaging (MRI), as high density information storage materials or for magnetocaloric refrigeration.

Speaker
Biography:

Dr. Masaharu Oshima is now a project researcher of Institute for Solid State Physics (ISSP), the University of Tokyo. He got his Bachelor degree in Dpt. of Industrial Chemistry, the University of Tokyo in 1972, and got his Doctor of Engineering degree at the University of Tokyo in 1984. After he started his experience at Stanford University in 1981-82, he is continuing synchrotron radiation science for semiconductors, magnetic materials and catalysts for more than 35 years. He became a professor at Dpt. of Applied Chemistry, the University of Tokyo in 1995. He was the President of the Japanese Society for Synchrotron Radiation Research (JSSRR) in 2009-2011, and the President of the Surface Science Society of Japan (SSSJ) in 2013-2015. He had received many Research Awards including ECS Best Paper Award in 2010 and Ministry of Education, Science and Technology (MEXT) Award in 2014.

Abstract:

In order to clarify the effect of water adsorption on fuel cell cathode catalysis surface, we have investigated electronic structure of Pt and Pt-Co nano-particles with O2 adsorption and O2/H2O co-adsorption by in situ hard X-ray photoelectron spectroscopy (HAXPES) together with in situ high resolution fluorescence detected x-ray absorption (HERFD-XAS). The valence band (mainly Pt 5d) and Pt 4f spectra were successfully obtained under up to 1 mbar with an ambient cell for the first time by in situ HAXPES. Both valence band and Pt 4f spectra show that O2/H2O co-adsorption hindered oxygen adsorption. Based on our first principles calculation of valence band density-of-states (DOS) we have found that H2O molecules may occupy the oxygen adsorption sites on Pt surface more easily than oxygen, resulting in hindering the successive oxygen adsorption.

However, under the more realistic condition at atmospheric pressure the formation of higher oxidation states of Pt in Pt L3-edge absorption spectra was enhanced by water adsorption, which was obtained by high resolution (Pt M5 FWHM about 2.5 eV) in situ HERFD-XAS. These changes in white line cannot be observed by conventional XAFS spectra due to large life-time broadening of Pt L3 (FWHM about 5.2 eV). At 1 bar more frequent attack by oxygen molecules onto water-adsorbed Pt surface may occur, resulting in the formation of hydrated hydroxyl intermediates and higher oxidation states. This enhanced oxygen adsorption is more clearly observed for Pt than Pt3Co nano-particles, probably because Pt nano-particles with stronger Pt-O bonding than Pt-Co nano-particles may further stabilize Pt-O bonding by additionally adsorbed water leading to less water effect on oxygen adsorption on Pt-Co. These results would be helpful to understand the reason why Pt-Co nano particles show higher ORR activity than Pt nano particles.

Figure 1. (a) Valence band spectra under in situ/ex situ reductions, (b) Calculated projected Pt d-pDOSs of bare Pt(111) surface with various adsorbates, (c) experimental difference spectra of ex situ reduced, H2O, and O2 adsorbed condition (solid lines) obtained by subtracting the in situ reduced spectrum, together with calculated difference spectra of H2O and O2 adsorption (dashed lines).

R. Marshall Wilson

Bowling Green State University, USA

Title: Pyridinium Salts as Photoinduced Electron Traps
Speaker
Biography:

R. Marshall Wilson is a Research Professor in Chemistry Department at Bowling Green State University, USA. He was awarded Ph.D., in the year 1965 from Massachusetts Institute of Technology. His research interests are directed towards photochemical application of lasers, primarily argon ion lasers, and fall into two broad categories: the laser synthesis of new materials and the development of reagents for the photochemical manipulation of biological systems.

Abstract:

When two or more Pyridinium salts are held face-to-face to each other they will share electrons equally between the rings. Calculations show this distribution of the trapped electron for the dimethyl 1,2-(di-4-pyridinium) ethane and the tetramethyl 1,1,2,2-(tetra-4-pyridinium) ethane as shown below. The electron trapping properties as characterized in ultrafast transient absorption spectroscopy and theoretical calculations for a variety of polypyridinium salts will be discussed.

Speaker
Biography:

Tim Wright has been working in the field of spectroscopy covering electronic and photoelectron spectroscopy since 1988. He has used both conventional and laser-based methods. Interests have covered hydrogen-bonded complexes, metal-rare gas complexes, NO-containing complexes and more recently trying to systematize the vibrational labelling in substituted benzenes. His work has always been underpinned by appropriate quantum chemical calculations and these often provide the foothold that allows the assignment of the spectra. Recent focus has been on understanding couplings between vibrations, torsional and vibration-torsions in simple molecules that contain the key features of nucleic acid bases: these interaction underpin intramolecular vibrational redistribution (IVR) and impact on photostability and chemical control.

Abstract:

We initially present vibrationally-resolved electronic spectra obtained using resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The spectra are obtained from jet-cooled seeded expansion using lasers. The spectra exhibit many bands, identifying the energetic positions of vibrational levels in the S1 electronic state; a number of these are found to arise from overlapped and/or interacting vibrational levels. By fixing one laser at the energy of one of those levels, we then ionize the electronically-excited molecule and record zero-kinetic-energy (ZEKE) spectra, whose assignment allows the deduction of the make-up of the intermediate S1 vibrational levels. In many cases we can identify the so-called zero-order states (ZOSs) which have coupled to give the resultant eigenstate; this coupling occurs as a result of Fermi resonance. As well as “pure” vibrations, we find that these ZOSs may be torsional levels or vibration-torsion (vibtor) levels. The coupling of the ZOSs leads to levels whose motions are more delocalized across the molecule. This has implications for photostability and chemical control. Assignment of the spectra is aided by recording ZEKE spectra at different energies through a REMPI feature that corresponds to coupled ZOSs. In this way, we can see activity move in and out of resonance through the feature. By plotting these spectra together we obtain a “two-dimensional” ZEKE spectrum. Quantum chemical calculations are used to aid in the assignments. The treatment of the torsional levels requires the use of molecular symmetry groups: G12 for toluene and para-fluorotoluene; G72 for para-xylene.

Speaker
Biography:

Slavica Stankic has her expertise in synthesis and surface characterization of pure and multi metal oxide nanoparticles. After some years of experience in well-known international institutions for nanomaterials research (TU Vienna, Austria; INSP-CNRS, Paris, France) she has established new pathways for determining reactivity of surface sites or improving surface doping. Beside fundamental studies – that involved photo-induced processes on oxide surfaces with a strong focus on the effects of particles size, shape and/or surface termination – she furthermore developed an interdisciplinary-based research project. Herein, metal oxide nanoparticles are used as model systems for studying their interaction with living organisms with a goal to assess their potential for medical applications as an alternative to existing antibiotics.

Abstract:

The ubiquity of oxides in dispersed form has prompted research strategies in two directions: understanding the existing materials by means of appropriate reference systems and tailoring the desired properties through innovative syntheses. In this talk I will show on examples of two prototype oxides, ZnO and MgO, to which extent they can be used as model systems for probing surface reactivity.

When studied in parallel with DFT calculations, surface hydroxylation, provided either by adsorbing H2O or H2, turned to be a win-win combination for a precise surface site identification.  In that manner, we have demonstrated that ZnO nanopowders behave as multi-facet single crystals involving (10-10), (11-20), (0001) and (000-1) surfaces with the polar orientations corresponding to 25% of the total surface area [2]. Moreover, we were able to report on water structures on ZnO(11-20) for the first time. Similarly, combining DFT and H2-Infrared spectroscopy on MgO nanocubes, we proposed a model in which multisite dissociation of hydrogen is suggested to occur on mono- and di-atomic steps at (001) MgO surface [2].

Nanoparticles of a well-defined size, shape, and surface termination are required for studying the reactions occurring over their surface. A strong emphasis in our work is, therefore, given to govern the synthesis pathways when producing desired nanoparticles, either in pure or doped form. Accordingly, an example of ruling the particles surface termination by controlling synthesis parameters will be presented in this talk [3].

Finally, I will also show how the interactions between water and nanoparticles surface can be used for studying particles dissolution as a function of their size [4]. This is especially important in case of mixed form of ZnO and MgO (ZnMgO) [5] which, as I will be demonstrating in short, exhibits a promising potential for medical applications as an alternative to existing antibiotics [3,5,6].

 

Speaker
Biography:

Yannick Carissan is Assistant Pr. at Aix-Marsielle University. He is an expert in theoretical chemistry and focuses on the interaction between research and teaching. His model based on chemically relevant concepts is an attempt to fill the gap between empirical methods and ab-initio full electron quantum chemistry calculations. He is also a main author of the hulis program (http://www.hulis.free.fr), which uses empirical methods and graph theory to give insights into chemical problems.

Abstract:

Atomic pseudo potentials were primarily used to replace core electrons in quantum chemistry calculations. Since 2013 (Drujon and Carissan, JCC 34(1):49-59), we decided to use pseudo potentials to model core and valence electrons for hybridized atoms. In this work, we focus on the sp2 carbon atom.

We decided to begin with a pseudo-carbon, and used the CH3 radical as a reference to which we tried to optimise the model. Starting with a 'pseudo-carbon' with a charge of one, and one electron, we were able to use potentials to force the occupation of specific orbitals, and to manipulate the energy levels of these orbitals. In practice, the only way to make the s potentials affect the orbitals was not to place them on the molecular plane itself, thus we ended up with a scheme that had potentials above and below the plane. After confirming the model worked on the ethene molecule, we were able to reproduce to good accuracy characteristics such as ionisation and excitation energies across a range of molecules including chain alkenes and aromatic, cyclic compounds.

Unlike in previous attempts, we are now able to extract atom based pseudo potentials: no bond centered potential is now required making the scope of use of these potentials extremely large.

In order to be useful, these potentials must be able to replicate their results across other systems. Testing them with some of the systems used in Carissan & Drujon, we have met with success. A single set of optimised potentials give results within ~0.5eV of reference calculations over HF, DFT and TD-DFT calculations.

Speaker
Biography:

Corentin BOILLEAU has his expertise in electronic structures and magnetic properties. He built his professional experience by first realizing his thesis in Toulouse under the supervision of Nathalie GUIHERY and Nicolas SUAUD, studying molecular magnetism through ab initio calculations. After his PhD, He joined for 2 years Vincenzo BARONE's laboratory in Pisa to participate to the development of BALOO, a post hartree fock method. Then, Corentin BOILLEAU joined Karine COSTUAS in Rennes for one in order to study ruthenium based compounds using DFT methods and model Hamiltonians. Today, he works at the Institute of Physics in Warsaw where he obtained a grant for 3 years to carry out a study on multifunctional compounds allowing a modulation of their magnetic properties.

Abstract:

Due to the slowdown of the information technology development, a great challenge of present-day applied science is to develop new electronic devices at the molecular scale. Indeed, molecular spintronic offers great potential multifunctional molecules performing new properties or operations unreachable by conventional semi-conductor technology. This project takes place in this quest of tomorrow's technologies conquest in the new field of Molecular Spintronic. The goal is to provide multifunctional compounds made from bricks with remarkable properties, for storage or manipulation of information across a single molecule. This work use an uncommon strategy based on redox properties of Ruthenium compounds associated with magnetic centers in order to obtain a device allowing a modulation of the magnetic properties. The aim is to study the inter-molecular interactions, to understand the interplay of the components in view of obtaining their synergistic working mode.

Considering the crucial role of the electronic correlation in magnetic systems and the strong geometrical and electronic coupling existing between the different functional elements, modelling of such systems is a tough task. A correct description of these systems requires to take into account the couplings between the subunits. The nature of the interactions studied, the presence of transition metals and the need for investigation of both ground and excited states suggest the use of Post Hartree Fock methods. But, considering their computational cost and the size of our systems, they are here prohibited. Therefore, the use of DFT with hybrid functionals is suitable. Standard and Broken Symmetry calculations have been performed to determine the magnetic coupling.

The supramolecular assembly proposed present efficient switching properties allowing the realization of logical functions. Depending on their composition, shape, physical and chemical properties they can be used as data processing devices (molecular wires, transistors, circuits) as information storage devices (molecular switchers) or as molecular machines.

Speaker
Biography:

Fabio Negreiros Ribeiro has his expertise in computational physics applied in condensed matter physics. His main areas of research are Surface Physics, heterogeneous catalysis and reactivity of metal and oxides surfaces in catalysis. He uses in hist study, most of the time, the open source CP2K and QE packages to provide a characterization at the DFT level, but he has also experience with semi-empirical potentials. He has also developed scripts that apply global optimization techniques at the DFT level, calling both CP2K/QE packages.

Abstract:

Statement of the Problem: A great deal of attention has been devoted to the study of photocatalytic effects on the interface between insulating oxide materials and water. It has been widely demonstrated, for a variety of materials, that water splitting can occur at these surfaces under certain specific conditions. The choice of the best material includes a balance between cost and performance. Among the desired properties, we need a specific band gap and band offset in order for the oxidation and reduction energies of water to be placed inside the band gap. There has been considerable interest in hematite, owing to its low cost and good photocatalytic activity. A considerable amount of theoretical and experimental works characterizing this structure can be found in the literature. The interaction of hematite with water is, therefore, of great interest for both academic and industrial purposes. Methodology & Theoretical Orientation: We performed DFT+U calculations to study the interaction of water with the Fe2O3(0001) surface. Using the CP2K and QE open source softwares, we determined the most stable configurations of a single water molecule adsorbed on the pristine oxygen-terminated surface, and how adding more water changes this interaction. Surface oxygen and iron vacancies were also considered at different charge states. Findings: Ab-initio molecular dynamics simulations at room temperature reveal that water spontaneously dissociates (H2O→H+OH-) at the interface, covering more than 50% of the surface with hydroxyls. Furthermore, in oxygen rich conditions, surface iron vacancies are found to be more stable than the pristine surface as long as the electronic chemical potential is 1eV higher than the Fermi energy. Iron vacancies also increase the water dissociation rate at the interface.

 

Torsten Kreer

The Leibniz Institute for Polymer Research, Germany

Title: Polymer-brush lubrication
Speaker
Biography:

Dr. Torsten Kreer studied physics at the University of Mainz, Germany, and received his PhD in 2002. Later, he moved to the Institute Charles Sadron in Strasbourg, France, for a post-doctoral stay funded by the German Science Foundation. Since 2011, Torsten Kreer is a researcher and leader of the ‘‘Non-equilibrium properties of polymers’’ group within the Institute ‘‘Theorie der Polymere’’ at the IPF Dresden, Germany. He received several grants from the European Science Foundation (ESF-STIPOMAT programme) and the German Science Foundation. Apart from polymer brushes and their non-equilibrium properties, his main research interests cover polymers, colloids and their mixtures.

Abstract:

Polymer-brush bilayers [1], which consist of two opposing, polymer-brush covered surfaces, represent model systems for the investigation of lubrication mechanisms as they are believed to appear in synovial joints. Using scaling theory, I derive analytical expressions for compressive [2] and shear forces [3], which are essential for the minimization of the kinetic friction coefficient. The theory is compared to numerical data and data from the Surface-Forces-Apparatus (SFA) and the Atomic Force Microscope (AFM).

As a further step, I discuss bilayers in highly non-stationary shear motion, such as the invertion of shear direction. Here, I show how data from molecular dynamics (MD) simulations coincide with the scaling theory [4].

Once established for electrically inert bilayers, the approach is extended to polyelectrolyte bilayers [5] and bilayers with macromolecular inclusions [4]. By means of data from MD simulations, I demonstrate that such modifications do not improve the lubricity of the bilayer in stationary shear motion, but are of great importance with respect to highly non-stationary processes, which typically appear in synovial joints.

Speaker
Biography:

Nadia Dozova obtained her PhD in Physical Chemistry at Université Pierre et Marie Curie in 2006. She is an Assistant professor in the PASTEUR lab (Université Pierre et Marie Curie, École Normale supérieure, CNRS) since 2009. Her current research interests focus on ultrafast spectroscopy (broadband transient absorption, fluorescence up-conversion). She is interested in photoinduced processes in supramolecular constructs and photoactive proteins.

Abstract:

The photophysical properties of two highly symmetrical quadrupolar chromophores were studied by both steady-state and transient absorption spectroscopy. Their excited-state behavior is dominated by the solvent-induced Stokes shift of the stimulated-emission band. The origin of this shift is attributed to symmetry breaking that confers a non-vanishing dipole moment to the excited state of both compounds. This dipole moment is large and constant in DMSO, whereas symmetry breaking appears significantly slower and leading to smaller excited-state dipole in toluene. Time-dependant increase of the excited-state dipole moment induced by weak solvation is proposed to explain the results in toluene.

Valery N. Volodin

"Institute of Metallurgy and Ore Benefication" Joint-stock company, Kazakhstan

Title: Phase equilibrium of the melt-vapor in the tellurium-sulfur system
Speaker
Biography:

Valery N. Volodin is engaged in the development of distillation technologies for separation of chalcogenide melts and metal refining in vacuum. His fields of interest include thermodynamics and vapor-liquid equilibrium. The partial pressure of the vapor components is used as the basis for determining the boundaries of the liquid-vapor phase transition for high-temperature melts. Due to the impossibility of boiling of metallic and chalcogenide melts, due to the high specific density of their constituents as the boiling point, a temperature is assumed at which the sum of the partial pressures is equal to atmospheric and the composition of the vapor phase is equal to the fraction of the partial pressure in the total pressure. The limits of the coexistence of liquid alloys and the vapor phase thus found allow one to obtain information about the possibility of distillation separation of melts into components or lack thereof, technological difficulties, the number of distillation-condensation cycles, and are demanded by process engineers for the development of new processes.

Abstract:

Statement of the problem: in the distillation technologies of chalcogen purification, there is a problem of isolating one of the elements in pure form in the presence of the other two. Earlier, our studies of binary selenium-sulfur and tellurium-selenium systems revealed that the cause of the difficulties is the narrow field of coexistence of the melt and vapor in the first case and the presence of an azeotropic mixture in the second. A similar study of the tellurium-sulfur system in the sources of information was not found. The aim of the study was to construct the boundaries of the phase transition of the melt-vapor of the tellurium-sulfur system. Methodology: The boundaries of the field of coexistence of the melt and vapor are determined on the basis of the partial pressure of sulfur and tellurium vapor determined by the boiling point method and integration of the Gibbs-Duhem equation. The temperature of boiling of a melt of a certain composition was assumed to be the temperature at which the sum of the partial pressures of sulfur and tellurium is equal to atmospheric pressure. The composition of the vapor phase is defined as the ratio of the partial pressure of the component to the total pressure at the boiling point. Conclusions: As a result of the investigation, the fields of coexistence of the melt and vapor at atmospheric pressure and in a vacuum of 2000 and 100 Pa (the last shaded) are plotted on the existing diagram of the tellurium-sulfur state (Fig. 1).

The boundaries of the melt-vapor phase transition indicate the possibility of a fairly complete separation of the tellurium-sulfur system into elements by a single distillation. Lowering the pressure to the forequacuum shifts the boiling point and most of the field (M + P) to the two-phase region of coexistence of solid sulfur solutions in tellurium (Te) and the melt. That is, in vacuum, the evaporation of sulfur will be accompanied by crystallization (Te) with its accumulation in the bottom residue with a decrease in the concentration of S in the melt to ~ 86.7 at % (61.9 mass%) (determined graphically) at a pressure of 2000 Pa and up to ~ 93.3 at. % (77.8 wt%) at 100 Pa.

Thus, distillation purification of sulfur from tellurium does not present technological difficulties, the vapor phase is almost completely represented by sulfur, tellurium will concentrate in the bottom residue.

Speaker
Biography:

Joshua Hammons has expertise in small angle scattering and electrochemical techniques. Specific to small angle scattering, much of his work is devoted to removing model ambiguity by simultaneously performing other measurements or by changing the sample geometry. This approach is applied to nanoparticle stability, assembly and synthesis in deep eutectic solvents where complex inhomogeneities are observed. These solutions are a unique scattering system, as they contain very soft perturbations that can be induced by surface charging and/or adsorption. In the presence of nanoparticles, the deep eutectic solvent is significantly perturbed far from the particle surface. Other research interests include nano-second small angle scattering to study rapidly evolving systems, such as high explosives and nanoscale kinetics.

Abstract:

Deep eutectic solvents are two component solutions that are:  cost-effective, environmentally safe (some) and easy to synthesize. These solutions have a high concentration of ions, as well as a complex hydrogen bond network that results in unique physio-chemical properties. Many different nanoparticle assemblies have been achieved with DESs. Given the wide range of DESs that are known and the many more that have not been realized, it may be possible to tune the DES to achieve a particle assembly. In this work, nanoparticle, assembly and particle-solvent interactions are studied using small angle X-ray scattering as the primary technique. The high flux of X-rays that were provided by synchrotron sources allowed for these systems to be studied in-situ. From SAXS experiments, particle aggregation and assembly is observed immediately following nucleation by electrodeposition. The aggregation time is slow and occurs over several minutes. In some cases, particle assembly can occur in place of aggregation by changing the DES composition. In most cases, there are measurable deviations in the DES species concentration that extend far from the particle surface. The in-situ SAXS measurements reveal that these phenomena also depend on the DES and the nanoparticles. The extended perturbations are also observed in colloidal systems, where deviations exist hundreds of nanometers from the particle surface. These results demonstrate how DESs are unique as they are applied toward nanoparticle assembly and synthesis and how they differ from aqueous solutions and room temperature ionic liquids.

Speaker
Biography:

Ankita is a young nuclear safety researcher focused on challenges that sodium cooled reactor technology still offers. Her research lies primarily in the field of sodium fire aerosols produced in a severe accident.
After finishing her master studies specializing in Nuclear Engineering at Ecole des Mines de Nantes, France, she started her professional career as researcher in the French national institute for nuclear safety (IRSN). In the laboratory, where she has a doctoral researcher position, she is simulating and modeling interactions between sodium fire aerosols with iodine species in case of a severe accident in an SFR for a computer code which would be used to simulate severe accidents.

Abstract:

Within the framework of Generation IV nuclear reactor safety assessment, the objective of this research work is to investigate the radiological and chemical source term in case of a core disruptive accident in case of a sodium-cooled fast nuclear reactor. This work investigates the interactions between sodium aerosols, formed after primary system sodium ejection in the containment, and gaseous iodine.
Understanding the complex behaviour of surface reaction requires detailed knowledge of both macroscopic and microscopic processes that take place. To link these processes we followed a combined theoretical and experimental approach.
Firstly, methods to theoretically understand the thermodynamics of the heterogeneous reaction between sodium carbonate aerosols and fission products: I2, NaI and HI are proposed. Ab-initio, density functional theory (DFT) calculations using Vienna ab-initio simulation package are carried out.
Secondly, interactions between (I2)g and Na2CO3 were investigated experimentally. (I2)g was generated by heating permeation tubes containing (I2)s, and, passing it through a reaction chamber containing Na2CO3 sorbent. The concentration of unreacted iodine was then measured at the exit of reaction chamber.
DFT calculations show that for defect-free surfaces of Ƴ- Na2CO3 phase, the (001) facet is the most stable. This ideal surface reacts very strongly with HI and NaI, at T<300°C, a low partial pressure of these species (10-7 bar) is sufficient for achieving a surface coverage greater than 50%. However, I2 (g) would react weakly with this surface: to have a surface coverage of 10%, a high partial pressure of iodine is required (10-2 bar).
Experimental investigations suggest a stronger reactivity of iodine with exposed Na2CO3 sorbent, at T<100°C; a partial pressure limited to 10-6 bar is sufficient to obtain 10% surface coverage.
Both theoretical and experimental approaches indicate very low gas phase capture of I2 (g) by Na2CO3.
In summary we aim to combine computational and experimental studies to increase our understanding of complex surface adsorption phenomena.

 

Surendra B. Anantharaman

Swiss Federal Laboratories for Materials Science and Technology (Empa), Switzerland

Title: Strongly red-shifted photoluminescence band induced by molecular twisting in cyanine (cy3) dye films
Speaker
Biography:

Surendra Anantharaman has his expertise in growth and optical characterization of organic dye films. With Bachelors in Physics (Anna University, India), he did his Masters in Materials Science, and M.S (By Research) from Indian Institute of Technology Madras, India. His Master’s thesis was on ‘Electrolyte Materials for Intermediate Temperature Solid Oxide Fuel Cells’. His area of research interest lies in oxides, nitrides and organic molecules focusing on energy harvesting applications. After working as an Engineer in Taiwan Semiconductor Manufacturing Company (TSMC), Taiwan he joined as Ph.D Student at École Polytechnique Fédérale de Lausanne (EPFL) in 2015 under the guidance of Prof. Dr. Frank Nüesch and Dr. Jakob Heier. As a Ph.D student, he is working on understanding the growth of organic crystals and its methodology from the morphology and surface-molecule interactions in the Laboratory for Functional Polymers at Swiss Federal Laboratories for Materials Science and Technology (Empa) Dübendorf, Switzerland.

Abstract:

Cyanine dye molecules, used as monomers or in aggregate form, find interesting applications in opto-electronic devices. Among the various aggregate species incorporating organic dyes, centrosymmetric dimers are known as non-luminescent. They can act as exciton quenchers due to a low energy optically forbidden excited state.  In this study, however, we show that a dimer species in thin films exhibits efficient and strongly red-shifted photoluminescence [1]. When the films were excited, a monomer emission at 590 nm along with a second emission peak at 680 nm was observed. Temperature dependent fluorescence were studied for cyanine films. The dimer emission increases with decreasing temperature due to reduced non-radiative process becoming less effective. A close relation between the dye concentration and the emission showed that a new emission at 680 nm corresponds to the dimer emission. Circular dichroism (CD) spectroscopy reveals that a fraction of the dimers exists in a twisted dimer configuration. Stable, long-lived and quenchable fluorescence with high quantum yield are attributed to this dimer emission. Organic light emitting electrochemical cells (OLECs) fabricated with this dye showed a higher luminance owing to the dimer emission [2].

 

Biography:

Wilke Dononelli has his expertise in quantum chemical modelling of catalytic reactions at surfaces. In 2010 he received his bachelor in mathematics and chemistry and graduated as a master of science in 2014. In 2014 he started his PhD in theoretical chemistry at the University of Oldenburg in Germany and will graduate by the end of 2017. He is experienced in density functional theory and high level ab initio calculations. In his role as a member of the research unit for Nanoporous Gold Catalysis (NAGOCAT FOR2213) his main focus lies on bridging from theoretical calculations to model experiments, where he improved his skills with contributions on more than 20 international conferences and meetings.   

Abstract:

Bulk gold has been known as an inert material without any specific catalytic activity for almost a century. But then in the 1970s Bond et al. presented small gold particles placed on a SiO2 support that could be used for the hydrogenation of alkenes and alkynes. Since this decade a lot of research has been done on nanostructured gold. This Au-based catalysts can be used for fuel cells, the synthesis of esters or the selective oxidation of alcohols.

The selectivity of gold to partial oxidation products is higher than the selectivity of other metal catalysts, so there is a high interest in this gold based catalysts. A problem of gold nanoparticles as catalyst is, that the efficiency increases if the average particle size is reduced, so in most cases the major part of the surface area of the supporting material is not used for the catalytic processes.

In addition to this supported forms of gold catalysts an unsupported form of gold, the nanoporous gold (np-Au), characterized by Zielasek et. al., has recently attracted considerable interest due to its potential use in catalysis. Compared to supported gold nanoparticles the complete entire surface of the material can be possibly usable as a catalytic material.

The most prominent example for the use of np-Au as a catalyst is the selective oxidation of methanol. Although this reactions has been investigated by several groups, the origin of the catalytic activity of np-Au has not been understood completely. The main remaining question that we try to answer is the nature of the active sites of the np-Au. Within DFT (density functional theory) calculations we describe the influence of residual silver atoms in the material and try to explain some possible pathways for the activation of oxygen, the most essential step of most of oxidative coupling reactions.

Speaker
Biography:

Blaž Winkler is a 3rd year joint phd. student of physics at the university of Nova Gorica, Slovenia, and optics/photonics at university Jean Monnet Saint-Etienne, France. His research combines state of the art numerical methods for structural, electronic and optical properties with established experimental procedures to understand the effect of excess oxygen on point defects in amorphous silicon dioxide (silica). Silica is material with wide range of application in modern technology like micro-processors, optical fibers and other high performance light guides. Results of his work within well established internation group is expected to lay foundation for new generation of such devices.

Abstract:

Interest for oxide glasses has been renewed mainly by increased needs for improved sensors (Tomashuk et al., J. Lightwave Technol. 2014) and oxide based resistive random access memories – OxRRAM (Mehonic et al. J. Appl. Phys. 2015). In both applications, oxygen and diffusing species or oxygen related defects are expected to play a key role.

This work aims at addressing the issue of the optical signature of peroxy bridges by using first-principles methods that combine Density Functional Theory (DFT), GW and the solution of a Bethe-Salpeter Equation (BSE) on a bulk amorphous SiO2 model. Results show that the presence of bridges induces broad and weak absorption bands between 3.2 and 7.5 eV. By analyzing the correlations between Si-O-O-Si dihedral angle distributions and the corresponding electronic structure, we show that weak and broad absorption origins from low overlap between O-2p states and the further spread of the signal caused by dihedral angle site-to-site disorder. Moreover, the energy difference between the two first optical transitions depends linearly on the energy difference between the two first occupied defect-induced electronic states, i.e. depends on the dihedral angle of the bridge. This behavior may form a basis for explanation of the longstanding controversy regarding the optical signature of peroxy bridges in amorphous SiO2. As the correlation is independent on the specific hosting hard material, the results apply whenever the dihedral angle of the bridge has some degree of freedom.

Figure 1: Energy variation of HOMO-1 and HOMO as a function of dihedral angle

Biography:

Arnar Hafliðason is a Ph.D. student from the University of Iceland. He finished his B.Sc. in chemistry from the University of Iceland, with emphasis on physical chemistry and inorganic chemistry. His Ph.D. project is in the field of physical chemistry with focus on photochemistry, Arnar has published three articles, with main emphasis on photodissociation, photoionization and state interaction.

Abstract:

Analysis of mass resolved spectra as well as velocity map images derived from resonance enhanced multiphoton ionization (REMPI) of HBr via resonance excitations to mixed Rydberg and valence (ion-pair) states allows characterization of the effect of a triplet-to-singlet1,5 and singlet-singlet2,3,4,5 state interaction on further photoexcitation and photo-ionization processes. The analysis makes use of rotational spectra line shifts, line intensity alterations, kinetic energy release spectra as well as angular distributions. Energy-level-dependent state mixing of the resonance excited states is quantified and photoexcitation processes, leading to H+ formation are characterized in terms of the states and fragmentation processes involved, depending on the state mixing

Figure 1. Schematic representation of the main channels involving excitation, fragmentation and ionization of the HBr molecule. “KERs arrows” indicate kinetic energy release of fragment species. Other arrows show excitation and ionization processes involved.

Speaker
Biography:

Markus Becker has his expertise in the development and improvement of sequentially deposited planar perovskite solar cells. One of the main focuses lies on the computational investigation of alternative absorber materials. Therefore, a contextual model has been built which allows the prescreening of possible three-dimensional perovskite phases. Combined with more elaborate DFT protocols, new combinations can be investigated considering the thermally enabled movement of the central cation. He has built this model after years of experience in research at the University of Oldenburg (Germany).

Abstract:

In the present work, steric sizes of molecular mono-ammonium cations were calculated by concerning free rotation of the electron density around the center of mass of the molecule. Thereby, structural optimizations were intensively investigated regarding the level of theory and basis sets. A thorough literature study about existing hybrid perovskite compounds revealed a high success rate of predicted stability criteria and 3D phase formation[4]. Furthermore, a case study including the smaller hydroxylammonium (HA+) replacing MA+, confirmed the key role of the cationic size on the structural stability and revealed negligible energy barriers associated with preferred molecular orientations in the cuboctahedron. The newly developed computational approach is well suited for high temperature phases, since it considers thermally enabled movements of the central cation and the associated averaging of inorganic deformations.