Events: Fysik events at Chalmers University of TechnologyFri, 21 Sep 2018 11:30:58 +0200 Physics Colloquium: How Nature makes Gold<p>PJ, lecture hall,</p><p>Colloquium by Karlheinz Langanke, Darmstadt University​, Germany</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">Where does Nature produce heavy elements like gold or platinum? To answer this question requires interdisciplinary research in astronomical </span><span style="background-color:initial">observation, astrophysical modelling and nuclear physics research.</span></div> <div> </div> <div>The talk will discuss the general understanding of the origin of the elements in the Universe and highlight how the recent observation of <span style="background-color:initial">merging neutron stars helps to answer this question.</span></div> <div> </div> <div>Decisive progress towards solving this puzzle is also expected from Europe's next-generation large-scale accelerator complex, the Facility <span style="background-color:initial">f</span><span style="background-color:initial">or Antiproton and Ion Research, which is currently under construction in Darmstadt and will allow to experimentally study many of the exotic </span><span style="background-color:initial">nuclear physics processes involved in Nature's main sites for element production.</span></div> seminar: Mikael Valter<p>Kollektorn, lecture room,</p><p>​ Title: Electrooxidation of glycerol and methanol on gold.</p><h4 class="chalmersElement-H4">Abstract:</h4> <div><span style="background-color:initial">Burning of fossil fuels leads to excess CO<sub>2</sub> in the atmosphere, causing global warming, threatening civilisation and ecosystems worldwide. As a step in making the society fossil-independent, we need to replace oil, coal, and gas in the transportation sector with fuels originating from sustainable energy. Biodiesel is one such option, from which we get glycerol as a byproduct. With the help of electrooxidation, we can use glycerol as a feedstock to extract hydrogen gas, which may be for upgrading biofuels or used in proton exchange membrane (PEM) fuel cells. Methanol is another possible fuel in so called direct methanol fuel cells (DMFC), which raises the interest for studying methanol electrooxidation.</span></div> <div> </div> <div><br /></div> <div> </div> <div>In this work, we study glycerol and methanol electrooxidation on gold. We use density functional theory, and verification by cyclic voltammetry, to study thermodynamics of reaction conditions and mechanisms for the electrooxidation mechanisms. Long range dispersion (van der Waals), which have been neglected in computations until recently, is investigated by assessing van der Waals exchange-correlation functionals. Furthermore, microsolvent effects are investigated by inclusion of explicit water molecules.</div> <div> </div> seminar: 2D materials beyond graphene<p>Palmstedtsalen, Campus Johanneberg</p><p>​Welcome to an initiative seminar on 2D materials beyond graphene, arranged by the Excellence initiative and Graphene Centre Chalmers.</p>​<div><span style="background-color:initial">The continuing trend to miniaturization of devices in modern technology faces fundamental physical limits of applied materials. The search for novel structures with new functionalities has brought </span><span style="background-color:initial">atomically thin two-dimensional (2D) nanomaterials</span><span style="background-color:initial"> </span><span style="background-color:initial">into the focus of current research. They represent a new class of materials that are characterized by a wide range of exceptional optical, electronic, mechanical, chemical, and thermal properties suggesting technological application in </span><span style="background-color:initial">next-generation flexible and transparent nanoelectronic devices</span><span style="background-color:initial">.</span></div> will receive the Nobel Prize in Physics 2018?<p>Kollektorn, lecture room,</p><p>​Let&#39;s find out together! Forum för tekniska fysiker (forum for engineering physicists) invites all of you to a sparkling new presentation of the Nobel Prize in Physics.</p><div>Together we will follow the live broadcast of the Royal Swedish Academy of Sciences announcement of the Nobel Prize in Physics. This will take place no earlier than 11.45. After the Academy's decision we will learn a bit more about the laureate/laureates and hopefully, we can listen to a live interview in connection with the press conference.</div> <br /><div>Welcome to attend the event!</div> <div><br /></div> <div><a href=""><img class="ms-asset-icon ms-rtePosition-4" src="/_layouts/images/icgen.gif" alt="" />To the homepage of Forum för tekniska fysiker. </a> <br /></div> <br /> seminar: David Albinsson<p>PJ, lecture hall,</p><p>​Title: Combining Nanoplasmonics and Nanofluidics for Single Particle Catalysis.</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">Nanoparticles are, due to their large exposed surface area, widely used in the field of </span><span style="background-color:initial">heterogeneous catalysis where they accelerate and steer chemical reactions. Although </span><span style="background-color:initial">catalysis has been known about for centuries, the scrutiny of catalysts under realistic </span><span style="background-color:initial">application conditions is still a major challenge. This difficulty originates from the fact </span><span style="background-color:initial">that real catalyst materials are very complex, often consisting of large ensembles of </span><span style="background-color:initial">nanoparticles that all are unique. Furthermore, the typically used macroscopic reactors in </span><span style="background-color:initial">catalysis studies gives rise to locally, at the level of the active site, ill-defined reactant </span><span style="background-color:initial">concentrations and diffusion limitations.</span></div> <div> </div> <div>To overcome these limitations, on one hand, techniques are being developed that are <span style="background-color:initial">sensitive enough to probe individual catalytic particles and that at the same time can </span><span style="background-color:initial">operate under realistic reaction conditions. On the other hand, strategies to more carefully </span><span style="background-color:initial">control the amount and structure of catalyst material, as well as to precisely control mass </span><span style="background-color:initial">transport to and from the active catalyst, are being investigated by scaling down the size </span><span style="background-color:initial">of </span><span style="background-color:initial">the used chemical reactor. To further push the limit of downsizing, in this thesis, I </span><span style="background-color:initial">present a miniaturized reactor platform based on nanofluidic channels that have been </span><span style="background-color:initial">carefully decorated with catalytic nanoparticles, and that is integrated with plasmonic </span><span style="background-color:initial">nanospectroscopy readout. This optical technique relies on the nanoscale phenomenon </span><span style="background-color:initial">known as the Localized Surface Plasmon Resonance (LSPR) and enables the study of </span><span style="background-color:initial">individual metal nanoparticles in operando by means of dark-field scattering </span><span style="background-color:initial">spectroscopy.</span></div> <div> </div> <div>As the first step in this development, we constructed a nanofluidic device with integrated <span style="background-color:initial">plasmonic nanoparticles to detect minute changes in the liquid flowing through the </span><span style="background-color:initial">channels, as well as molecules binding to the nanoparticles. As the second step, we </span><span style="background-color:initial">developed the nanofluidic system with an integrated heater and to facilitate gas flow </span><span style="background-color:initial">through the nanochannels with the possibility to connect to a mass spectrometer for online </span><span style="background-color:initial">product analysis. This system was then successfully used to correlate activity with</span></div> <div> </div> <div>surface and bulk oxidation state changes taking place on individual catalytic Cu and Pt <span style="background-color:initial">nanoparticles during CO oxidation, measured by means of plasmonic nanospectroscopy. </span><span style="background-color:initial">To this end, in a separate study, I also employed the plasmonic approach to study the </span><span style="background-color:initial">oxidation process of Cu nanoparticles both experimentally and by electrodynamics </span><span style="background-color:initial">simulations.</span></div> seminar: Cecilia Fager<p>PJ, lecture hall,</p><p>​ Title: 3D Reconstruction of Porous and Poorly Conductive Soft Materials using FIB-SEM Tomography</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">Focused ion beam combined with scanning electron microscope (FIB-SEM) is a powerful tool that can be utilised to reveal the internal microstructure of materials. It basically uses ions to make cross-sections with high precision and electrons to image the cross-section surface with high spatial resolution. In addition to revealing the internal microstructure, FIB-SEM can be used to perform a sequential slice and image procedure which, after some data processing, can result in a 3D reconstruction of the microstructure, also denoted as FIB-SEM tomography. Focused ion beam tomography is a well-established procedure since 1987. It has been successfully applied to a variety of well conductive materials. However, to perform FIB-SEM tomography on ion and electron beam sensitive as well as poorly conductive soft materials is still challenging. Some of the common challenges are cross-sectioning artefacts, shadowingeffects and charging. The presence of pores adds additional challenges. Fully dense materials provide a planar cross-section while pores expose surface area beneath the planar cross-section surface as well. The sub-surface pore information and the varying intensity from the sub-surface areas give rise to intensity overlaps which complicates the data processing. Several solutions to overcome these challenges have been reported. Examples are milling and imaging at low beam energies and specimen preparations. However, the ultimate aim is to examine porous and poorly conductive soft materials as close to their original state to avoid introduction of artefacts.  <br /><br /></span></div> <div> </div> <div>The aim of this work was to develop a general protocol for optimisation of FIB-SEM tomography parameters for porous and poorly conductive soft materials. The optimised parameters include the energies and currents of the ion and electron beams, reduction of shadowing-effects, choice of electron detector and selection of method for charge neutralisation. In addition, a new self-learning binarisation algorithm is introduced to enable an automatic separation between pores and matrix. The binary data have been used to visualise the interconnectivity in 3D of individual pore paths through phase separated polymer films. The optimised protocol for FIB-SEM tomography is applicable to a variety of porous and poorly conductive soft materials.   <br /> </div> <div> </div> <div>The porous and poorly conductive soft materials in these studies were leached phase separated polymer films intended for controlled drug release coatings in pharmaceuticals. The porous microstructure within the films acts as transport path for the drug. In this work, the complex microstructure has been visualised in 3D. In addition, 3D visualisation of the shortest, intermediate and longest paths through the films, based upon tortuosity calculations, have been performed as well.  </div> seminar: Gustav Åvall<p>Nexus 4030, meeting room, Fysik, Origo</p><p>​ Title: Modelling of Battery Electrolyte Interactions</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">The rechargeable lithium-ion battery (LIB), powering our portable electronics, has transformed our everyday lives. Even though the success of the LIB there is a need for next generation batteries, due to a lack of abundant lithium and a need for greater performance and sustainable chemistries, in order to move towards a sustainable society with applications such as hybrid and electrical vehicles (EVs) and large scale energy storage for solar and wind power. Therefore, there is a large interest in various next generation batteries, such as sodium-ion, Li-S, and Li-air batteries.</span></div> <div> </div> <div><br /></div> <div> </div> <div>In this thesis the structure of Li+ and Na+ solvation shells, as functions of salt concentrations, is studied using a semi-empirical method. Overall, this shows that: i) The first solvation shell of the Na-ion is larger and more disordered than the Li-ion first solvation shell, ii) The coordination number (CN) remain quite constant as a function of concentration, while the disorder, as measured by the variance of the CN, increases with concentration, and iii) The choice of solvent influences the disorder. Moreover, the interaction of O<sub>2</sub> with several anions is computed, showing a correlation between the interaction energy and the O<sub>2</sub> solubility, with application to Li-air batteries. Finally, a novel approach employing ab initio molecular dynamics to study solvation shell dynamics is presented. </div> Maja Feierabend<p>Nexus 4030, meeting room, Fysik, Origo</p><p>​Title: Out of the Dark and into the Light _ Microscopic Analysis of Bright, Dark and Trapped Excitons.</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">Atomically thin transition metal dichalcogenides (TMDs) have been in the focus of current research due to their efficient light-matter interaction, as well as the remarkably strong Coulomb interaction that leads to tightly bound excitons. Due to their unique band structure, TMDs show a variety of optically accessible bright and inaccessible dark excitons. Moreover, due to their optimal surface-to-volume ratio, these materials are very sensitive to changes in their surroundings, which opens up the possibility of externally tailoring their optical properties.</span></div> <div> </div> <div>The aim of this thesis is to present different strategies to control the optical fingerprint of TMD monolayers via molecules, strain and impurities. Based on a fully quantum-mechanical approach, we show that the coupling of excitons to high-dipole molecules can activate dark excitonic states, resulting in an additional and well-pronounced peak in the optical spectra. </div> <div> </div> <div>Moreover, we find that these dark excitonic states are very sensitive to strain, leading to crucial energy shifts and intensity changes of the dark exciton signature. Our findings reveal the potential for optical sensing of strain through activation of dark excitons. </div> <div> </div> <div>Finally, we investigate the possibility of local impurities to trap excitons resulting in localized states.</div> <div> </div> <div>We study the formation, excitonic binding energies and wave functions of localized excitonic states, all of which depend on the trapping potential. With this, we are able to calculate the photoluminescence signal and investigate the possibility of single-photon emission.</div> Nanogap Devices and Applications<p>PJ, lecture hall,</p><p>Surface-enhanced spectroscopies, sub-volt dielectrophoresis, single-molecule optical trapping ​ Seminar by Dr. Sang-Hyun Oh, University of Minnesota, USA</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">​​Nanometer-scale gaps in metals are one of key building blocks for plasmonics and nano-optics. I will present new approaches to (1) manufacture sub-10-nm gaps with uniformity and high throughput; (2) use nanogap electrodes for rapid sample concentration via sub-volt dielectrophoresis; and (3) use a resonant annular nanogap device for optical trapping of single protein molecule. In our scheme, the width of vertically oriented nanogap structure is precisely defined by the thickness of oxide films grown by atomic layer deposition (ALD). By scaling the gap size toward single-nanometer regime, we can perform low-voltage dielectrophoresis trapping of nanoparticles and biomolecules, followed by surface-enhanced spectroscopic detection. With a ring-shaped coaxial nanoaperture, we can generate strong optical resonances that can be tuned from visible to mid-infrared frequencies. We show applications of resonant coaxial nanoapertures for mid-infrared spectroscopy and single-molecule optical trapping. </span></div> <div> </div> Physics Colloquium by Gunnar Westberg<p>PJ, lecture hall,</p><p>​Colloquium by Gunnar Westberg, ICAN (Int. Campain to Abolish Nuclear Weapons).</p> Principles Monte Carlo Simulations of Adsorption and Reaction Equilibria<p>PJ, lecture hall,</p><p>S​eminar by J. Ilja Siepmann, University of Minnesota, USA</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">Nanoporous materials, such as zeolites and metal-organic frameworks, play numerous important roles in modern oil and gas refineries and have the potential to advance the production of fuels and chemical feedstocks from renewable resources. This talk will highlight recent developments enabling first principles Monte Carlo (FPMC) simulations for which the potential energy is calculated on-the-fly using Kohn-Sham density functional theory. Applications of FPMC to the prediction of (a) adsorption isotherms for gas molecules in metal-organic frameworks with under-coordinated metal nodes and (b) reaction equilibria in cation-exchanged zeolites. Emphasis will be given to simulation methodologies and microscopic-level origins of the observed thermodynamic behavior.</span></div> ​ seminar: Silver Jõemetsa<p>PJ, lecture hall,</p><p>​Title: Towards the Characterization of Biological Nanoparticles</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div><span style="background-color:initial">Lipids are integral to all forms of life. Both cells and the majority of particles involved with living systems are enveloped by a lipid membrane, which protects their content from the external environment while simultaneously controlling molecular transport using membrane-embedded proteins. A subset of these particles are known as biological nanoparticles (BNPs), including extracellular vesicles, exosomes and viruses. BNPs are known to transfer genetic material during cellular communication, but many aspects of the mechanisms regulating their various functions remain unknown. Progress within this scientific discipline is hampered by their small size (between 50 and 200 nm in diameter) and significant biomolecular heterogeneity, making both quantitative nanoparticle analytics and functional characterization, highly demanding tasks.</span></div> <div> </div> <div>To overcome the challenges of BNP characterization, we constructed an approach to identify the mechanism by which lipid vesicles are spontaneously converted into a planar supported lipid bilayer (SLB) on glass surfaces (Paper I). Total internal reflection fluorescence (TIRF) microscopy was used to track and temporally resolve the rate of vesicle adsorption, the onset of supported lipid bilayer (SLB) formation and the kinetics of their growth into a continuous SLB, through the use of a small fraction (1/100) of labelled lipid vesicles. It was found that the SLB formation processes was initiated by the merger of multiple small SLB patches at appreciably high vesicle coverage. In addition, the subsequent growth of SLB patches was, for the first time, shown to occur via a gradual increase in the average front velocity. Paper II focuses on quantifying both the size and molecular content of different types of BNPs. This was accomplished by tethering BNPs of varying complexity, to a fluid SLB formed on the floor of a microfluidic channel. By moving the BNPs with an applied hydrodynamic shear flow and by determining both the Brownian and directed motion using single particle tracking analysis, it was possible to determine the hydrodynamic radii for each BNP. Furthermore, imaging the BNPs using TIRF or epi-microscopy, made it possible to simultaneously determine the extent of fluorescent label attachment, which was specifically used to address how the incorporation efficiency of the membrane-staining dye spDIO depends on the size of the BNP.</div> <div> </div> <div>The insights gained on the SLB formation processes and BNP characterization are fundamental for the future development and advancement of novel techniques aimed at probing the molecular interaction between BNPs and cellular membranes.<br /><br /></div> <div> </div> <div>Keywords: supported lipid bilayer, TIRF microscopy, diffusion, size determination, lipophilic dyes, microfluidics</div> <div> </div> <div>​<br /></div> Sustainability Day 2018<p>Campus Johanneberg, mostly at Chalmers conference centre, Student Union Building</p><p>​Chalmers Sustainability Day is back - Tuesday 23 October 2018. This year’s theme is Good Health and Well-being.</p>​ <br /><div><h5 class="chalmersElement-H5">The programme is launched!</h5> <div>Chalmers Sustainability day will offer an exciting and vast programme, open to all Chalmers employees and students. </div> <div> </div></div> <div>Programme and registration: <a href="/en/about-chalmers/Chalmers-for-a-sustainable-future/sustainability-day2018/Pages/default.aspx">Chalmers Sustainability Day 2018</a></div> <br /><br /> Lin: Materials Science<p>KC, lecture hall, Chemistry building</p><p>​Title: Understanding the interactions between vibrational modes and excited state relaxation in garnet structured phosphors.                  ​</p><strong>​Abstract:</strong> To be announced​ Physics Colloquium by Brian Andersen<p>PJ, lecture hall,</p><p>Title: New Clues to the Mechanism of Unconventional Superconductivity from Spectroscopy and Theory of Iron-based Superconductors</p><h4 class="chalmersElement-H4">​Abstract: </h4> <div><span style="background-color:initial">Ir</span><span style="background-color:initial">on-based superconductors have been extensively studied both experimentally and theoretically over the last decade, with great progress in our understanding of these materials. Recent focus on FeSe has been centered on the connection between nematicity and superconductivity, and the possibility of enhancing Tc in monolayers on STO, or by pressure. In this talk, I will give and overview of recent developments and focus on recent scanning tunneling experiments mapping out the detailed spectroscopic features of FeSe by the group of J. C. Seamus Davis at Cornell University. I will explain the recent evidence for orbital selective superconducting pairing, and the direct detection of orbital selective quasiparticles by quasi-particle interference. This highlights the correlated nature of FeSe, more specifically its Hund’s metal nature with coexisting orbital-dependent coherent and incoherent low-energy states. I then proceed to discuss the theoretical modelling of these phenomena and the implications for our understanding of the origin of superconductivity in FeSe in particular, and in the iron-based superconductors in general.</span></div> ​ Olsson: Physics<p>PJ, lecture hall,</p><p>​ Title: The Stabilizing Role of Sugars for the Stabilization of Proteins.</p><strong>A​bstract:</strong> To be annonunced​ Physics Colloquium<p>PJ, lecture hall,</p><p>​​ Lecturer: To be announced​</p> Physics Colloquium<p></p><p>Colloquium by the Nobel Prize Laureate Takaaki Kajita​.</p>