jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Jie Zhu | Changcheng Ma | Jing He | Jingjing Lu | Zuoqi Hu
Source: MATEC Web of Conferences (article, 2018-01-01)
Field: Materials Science — Materials Chemistry

Effect of scaling on thermal properties and switching operation of phase change memory devices Phase change memory (PCM) is one of the most promising emerging non-volatile memory technologies. This paper simulates phase change memory devices (PCMDs) with careful attention to the scaling and its resulting impact on programming current during the switching operation, while Thomson heating within the phase change material and Peltier heating at the electrode interface are considered. The simulation results show that the device scaling has an influence on temperature distribution, volume of the molten region, heat diffusion and switching operation of PCMDs. The programming current decreases with smaller electrode size, greater thickness of phase change material and deeper isotropic scaling. The heat diffusion becomes more serious when the thickness of phase change materials decreases and the size of PCMD is isotropically scaled down. The scaling arguments also indicate that the impact of thermoelectric phenomena weakens with smaller dimensions due to the influence of programming current, heat diffusion and action area. This simulation provides useful insights to understand the switching operation of the PCMDs under the impact of thermoelectric effects. The process is instrumental for a complete understanding of device operation and hence provides valuable feedback for fine-tuning the device design so as to enhance its efficiency. Scaling ; Phase-change memory ; Thermoelectric effect ; Materials science ; Diffusion ; Isotropy ; Current (fluid) ; Phase-change material ; Phase (matter) ; Electrode ; Engineering physics ; Computer science ; Mechanics ; Phase change ; Electrical engineering ; Thermodynamics ; Nanotechnology ; Optics ; Engineering ; Physics Phase-change materials and chalcogenides ; Transition Metal Oxide Nanomaterials ; Advanced Memory and Neural Computing
Authors: Abhijit Dutta | Motiar Rahaman | Carina Morstein | Nicolas Schlegel | Peter Broekmann
Source: ECS Meeting Abstracts (article, 2018-04-13)
Field: Materials Science — Materials Chemistry

Morphology Matters: Additive-Assisted Metal Foam Deposition for the Electrochemical CO<sub>2</sub> Conversion High-surface area metal foam catalysts for the electrochemical CO 2 reduction reaction (ec-CO 2 RR) are deposited on planar model substrates and technical supports (e.g. 2D mesh or 3D sponges). The metal deposition is typically carried from acidified plating baths at particularly high current densities (e.g. -3 A/cm 2 ) where the metal deposition is superimposed on the hydrogen evolution reaction (HER). Gas bubbles formed on the support surface serve as geometrical template for the metal deposition leaving highly porous metal foams behind. 1,2 Pore density and the particular side-wall morphology of these foams can be fine-tuned not only by the current density, metal ion concentration in solution but also by the use of particular polymeric plating additives (e.g. polyethylene-imines, PVPs, polymerizates of imidazole and epichlorohydrin). The activity and product selectivity of the electrochemical reduction of CO 2 on Cu foam catalysts strongly depend on the resulting pore size distribution of the Cu catalyst. The maximum in the C-C coupling efficiency (FE C2 = 55%) observed for pore size dimensions in the range of 50 to 100 µm. Such morphology dependence of the ec-CO 2 RR product distribution will be discussed not only on the basis of the availability of certain reactive surface sites and facets but also on the basis of a temporal trapping of gaseous intermediates (in particular CO and C 2 H 4 ) inside the mesoporous catalyst material. Mild thermal annealing (300°C, 1h) of the Cu metal foams activates them for the production of C2 and C3 alcohols (ethanol, n-propanol). Identical location (IL) HR-SEM, HR-TEM, white-light interferometry and 3D optical microscopy are applied to probe morphological changes on different length scales that are induced by the foam activation (e.g. by thermal annealing) and the ec-CO 2 RR itself. This study indicates that the catalyst morphology might undergo drastic changes under operando conditions. [1] Shin, H. C.; Liu, M. L., Chem. Mater. 2004, 16 (25), 5460-5464. [2] Shin, H. C.; Dong, J.; Liu, M. L., Adv. Mater. 2004, 16 (3), 237-240. Catalysis ; Materials science ; Electrochemistry ; Metal ; Metal foam ; Chemical engineering ; Mesoporous material ; Epichlorohydrin ; Deposition (geology) ; Chemistry ; Composite material ; Electrode ; Organic chemistry ; Metallurgy Catalytic Processes in Materials Science ; Supercapacitor Materials and Fabrication ; Electrocatalysts for Energy Conversion
Authors: Kaveh Shervin | Khim Kharel | Michael Fitchette | Wei Wang | A. Freundlich
Source:  (article, 2018-06-01)
Field: Materials Science — Materials Chemistry

Ge Thin Films on Glass by Al-Induced Crystallization as Low-Cost Substrates for III-V Photovoltaics We have looked experimentally into a low temperature (<;400C) Al induced crystallization of amorphous Ge layers deposited at room temperature on Al coated glass. We show the critical role of layer thicknesses, specifically Al, in controlling the crystalline orientation and subsequently demonstrate that by fine tuning the annealing temperature and its duration as well as the thickness of the Al layer and its native oxide it is possible to drive the a-Ge to yield cubic (110) and (111) dominated polycrystalline films or a rhombohedric (100) Ge with a c-plane perpendicular to the interface offering an interesting option toward tuning of the Ge lattice constant to ~0.593 nm (instead of 0.565nm for c-Ge), closely matched to the lattice of InP and related materials. We also report possibility of extracting strong Photoluminescence emission in the vicinity of the expected band gap of Ge. Currently, the stage of epitaxial GaAs growth on Ge thin films are ongoing and the results will be presented at the conference. Materials science ; Amorphous solid ; Annealing (glass) ; Crystallization ; Crystallite ; Photoluminescence ; Epitaxy ; Thin film ; Optoelectronics ; Lattice constant ; Photovoltaics ; Band gap ; Oxide ; Diffraction ; Layer (electronics) ; Crystallography ; Composite material ; Chemical engineering ; Photovoltaic system ; Nanotechnology ; Optics ; Metallurgy ; Chemistry ; Electrical engineering Silicon Nanostructures and Photoluminescence ; Thin-Film Transistor Technologies ; Photonic and Optical Devices
Authors: K Rogers
Source: Microreviews in Cell and Molecular Biology (article, 2018-05-12)
Field: Materials Science — Biomaterials

Stem Cell Research with Dr. Yolanda Vasquez Dr. Vasquez is an assistant professor of Chemistry at Oklahoma State University and is heavily involved in the research on stem cells at the University. Her recent research in the topic contributed to the paper “Fine-tuning the degree of stem cell polarization and alignment on arrays of high-aspect ratio nanopillars”. The broad scope of the paper was looking at how there are lots of factors that influence the ability of stem cells to differentiate, and the surface with which they interact is one of them. Mesenchymal stem cells are the specific type of stem cells that their study looked at. Regular stem cells can differentiate into any type of cell, but with the mesenchymal stem cells, they are limited to number of cells they can differentiate into. They can differentiate into at most 10 types of cells, the main cells being bone cartilage and fat. As previously stated, the surface that the stem cell interacts with, can help determine what type of cell it differentiates into. This has great applications in medicine as stem cells are used to regenerate tissue, and the surface on which it is bound must be thoroughly studied or else the stem cells might differentiate into something that is not desired. Stem cell ; Mesenchymal stem cell ; Cell biology ; Cell type ; Adult stem cell ; Stem cell transplantation for articular cartilage repair ; Endothelial stem cell ; Biology ; Cell ; Chemistry ; Biochemistry ; In vitro Electrospun Nanofibers in Biomedical Applications
Authors: Dao Zhang | Yu Ping Zhang | Wen D. Song | Liang Chen | Guanjun Wang | Kai‐An Wang | Jidong Yang | Yu Chen | Cheng Jiao
Source:  (article, 2018-11-05)
Field: Materials Science — Materials Chemistry

Improvement of color gamut in laser quantum dots backlight display A higher color gamut can bring more comfort to one’s watching experience; therefore, it is a key aspect when assessing the quality of the display. To improve the color gamut of a display, many techniques have been used. Although some techniques have been claimed to work, the overall quality of the color gamut of the display still does not satisfy many researchers. In this paper, we will consider several key factors that can affect the color gamut of the newly developed laser display system, including the center wavelength of the Quantum dot film, the efficiency of the Brightness Enhancement Film, and the quality of the color filter of the liquid crystal display panel. An improvement of nearly 45% can be achieved through fine tuning of the key factors when compared with our earlier models without finetuned ones. The average color gamut of the laser quantum dot backlight display system can reach up to 110% NTSC color gamut that yields vivid color results. Gamut ; Backlight ; Quantum dot ; Computer science ; LED display ; Laser ; Optoelectronics ; Computer graphics (images) ; Materials science ; Optics ; Liquid-crystal display ; Computer vision ; Physics Quantum Dots Synthesis And Properties ; Chalcogenide Semiconductor Thin Films ; Nonlinear Optical Materials Studies
Authors: Paolo Matteini | Martina Banchelli | Marella de Angelis | Roberto Pini | Cristiano D’Andrea
Source:  (article, 2018-02-13)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Plasmon-enhanced Raman detection of body-fluid components Plasmon-enhanced spectroscopies such as surface-enhanced Raman spectroscopy (SERS) concern the detection of enhanced optical responses of molecules in close proximity to plasmonic structures, which results in a strong increase in sensitivity. Recent advancements in nanofabrication methods have paved the way for a controlled design of tailor-made nanostructures with fine-tuning of their optical and surface properties. Among these, silver nanocubes (AgNCs) represent a convenient choice in SERS owing to intense electromagnetic fields localized at their extremities, which are further intensified in the gap regions between closely spaced nanoparticles. The integration of AgNCs assemblies within an optofluidic platform may confer potential for superior optical investigation due to a molecular enrichment on the plasmonic structures to collect an enhanced photonic response. We developed a novel sensing platform based on an optofluidic system involving assembled silver nanocubes of 50 nm in size for ultrasensitive SERS detection of biomolecules in wet conditions. The proposed system offers the perspective of advanced biochemical and biological characterizations of molecules as well as of effective detection of body fluid components and other molecules of biomedical interest in their own environment. Biomolecule ; Plasmon ; Nanotechnology ; Surface-enhanced Raman spectroscopy ; Materials science ; Raman spectroscopy ; Plasmonic nanoparticles ; Nanoparticle ; Nanolithography ; Photonics ; Nanostructure ; Surface plasmon ; Optoelectronics ; Raman scattering ; Fabrication ; Optics ; Physics Gold and Silver Nanoparticles Synthesis and Applications ; Biosensors and Analytical Detection ; Plasmonic and Surface Plasmon Research
Authors: Matthew J. Stark
Source: IRL - University of Missouri, St. Louis (University of Missouri–St. Louis) (article, 2018-01-01)
Field: Chemistry — Organic Chemistry

Cationic Ruthenium Complexes in Catalysis: The Activation of Propargylic Alcohols Through Electronically Tuned Complexes With increasing complexity of metal complexes, it is of worthwhile interest to pursue systematic examinations of ligand modifications to study their impact on the reactivity of a catalyst. To that end, this study aimed to understand the effect electron-withdrawing ligands conveyed to catalytic activity in the etherification of propargylic alcohols and related reactions. A number of half-sandwich ruthenium complexes bearing ligands with varying electron–withdrawing properties were synthesized and structurally characterized. Their electronic and structural properties were investigated utilizing X-ray crystallography, revealing that the series of complexes did not vary significantly in structure. The complexes were studied electronically with cyclic voltammetry, which discovered that the coordinated electron-withdrawing ligands resulted in complexes that were more difficult to oxidize and with possibly decreased electron density at the ruthenium center. All complexes showed catalytic activity in the etherification of propargylic alcohols and in the formation of oxygen-containing heterocycles from propargylic alcohols and diketones. Thermal instability offers an explanation as to why some catalyst systems do not perform very well at elevated temperatures. In a separate study, a more stable tridentate ligand was employed as an architecture for further study in this electronic fine-tuning methodology. A new ruthenium complex bearing a tridendate diacetylpyridine ligand was synthesized, characterized, and employed as catalyst in the coupling of carboxylic acids to terminal alkynes to form enol esters with good regioselectivity. Iron offers a number of advantages in transition metal catalysis, as it is inexpensive and relatively non-toxic. Based on preliminary findings from the Bauer laboratory, an in situ catalyst formed through oxidation of ferrocene boronic acid was found to be catalytically active in the etherification of propargylic acetates. Most interestingly, and opposed to all catalytic reactions performed for this study, the ferrocenium cation does not require elevated temperatures and performs well at room temperature. Ruthenium ; Cationic polymerization ; Catalysis ; Chemistry ; Photochemistry ; Combinatorial chemistry ; Polymer chemistry ; Organic chemistry Catalytic Alkyne Reactions ; Asymmetric Hydrogenation and Catalysis ; Catalytic Cross-Coupling Reactions
Authors: Jesús Rubén Rodríguez Núñez | S.G. Torres Badajoz | V. Peña Caballero | C.H. Herrera Méndez | Omar Surisadai Castillo Baltazar
Source: New Biotechnology (article, 2018-09-22)
Field: Chemistry — Organic Chemistry

Hydrogels of chitosan as bioadsorbents of Cr (VI) in aqueous systems Fabrication ; Materials science ; Vinyl alcohol ; Aqueous solution ; Chemical engineering ; Nanoparticle ; Emulsion ; Catalysis ; Polymer ; Nanotechnology ; Chemistry ; Composite material ; Organic chemistry Nanomaterials for catalytic reactions ; Supercapacitor Materials and Fabrication ; Electrospun Nanofibers in Biomedical Applications
Authors: Sebastian Brückner | Oliver Supplie | Anja Dobrich | Peter Kleinschmidt | Thomas Hannappel
Source: physica status solidi (b) (article, 2018-04-01)
Field: Materials Science — Surfaces, Coatings and Films

Control Over Dimer Orientations on Vicinal Si(100) Surfaces in Hydrogen Ambient: Kinetics Versus Energetics (Phys. Status Solidi B 4/2018) In chemical vapor ambient, Si(100) surfaces and hydrogen can strongly interact with each other. As a result, energetic considerations cannot solely describe step and terrace formation sufficiently, as the formation of the equilibrium surface reconstruction can be counteracted by surface kinetics, in particular induced by hydrogen and driven by temperature. Combining optical in situ spectroscopy and in vacuo analysis, Brückner et al. (article no. 1700493) can confirm that high H2 pressures promote kinetically driven processes, while the impact of energetics increases with offcut magnitude. Suitable process routes, accordingly, strongly vary with the degree of misorientation. Dictated by the dominant driving force, monohydride terminated Si(100) surfaces with either “A-type” (1×2) or “B-type” (2×1) majority domains can be prepared both on low-offcut and vicinal surfaces. Optical fingerprints of these Si(100) surfaces thereby enable in situ control and process fine-tuning with regard to an atomic surface order which is suitable for subsequent nucleation and integration of III–V compound semiconductors for future high-performance optoelectronic devices. [Scheme of the Si(100) terrace kinetics (lower right corner) adapted from S. Brückner et al., New J. Phys. 2013, 15, 113049.] Vicinal ; Energetics ; Dimer ; Kinetics ; Hydrogen ; Chemistry ; Materials science ; Physics ; Thermodynamics ; Quantum mechanics Electron and X-Ray Spectroscopy Techniques ; Nuclear Physics and Applications ; Semiconductor materials and devices
Authors: Elena Chistè | A. Ghafarinazari | Marta Donini | Véronique Cremers | Jolien Dendooven | Christophe Detavernier | D. Benati | Marina Scarpa | Stefano Dusi | N. Daldosso
Source: Journal of Materials Chemistry (article, 2018-01-01)
Field: Materials Science — Materials Chemistry

TiO₂-coated luminescent porous silicon micro-particles as a promising system for nanomedicine Porous silicon (pSi) is a sponge-like material obtained by electrochemical etching of a crystalline silicon wafer. Due to quantum confinement effects, this material is photoluminescent and this is a fundamental property from the perspective of bioimaging applications. Limitations in nanomedicine to the use of photoluminescent pSi structures are mainly due to optical quenching in an aqueous environment and to the adverse effects of reactive groups introduced by etching procedures. In this work, we exploited an inorganic TiO₂ coating of pSi microparticles by Atomic Layer Deposition (ALD) that resulted in optical stability of pSi particles in a biological buffer (e.g. PBS). The use of a rotary reactor allows deposition of a uniform coating on the particles and enables a fine tuning of its thickness. The ALD parameters were optimized and the photoluminescence (PL) of pSi–TiO₂ microparticles was stabilized for more than three months without any significant effect on their morphology. The biocompatibility of the coated microparticles was evaluated by analyzing the release of cytokines and superoxide anion (O₂⁻) by human dendritic cells, which play an essential role in the regulation of inflammatory and immune responses. We demonstrated that the microparticles per se are unable to significantly damage or stimulate human dendritic cells and therefore are suitable candidates for nanomedicine applications. However, a synergistic effect of the microparticles with bacterial products, which are known to stimulate immune-response, was observed, indicating that a condition unfavorable to the use of inorganic nanomaterials in biological systems is the presence of infection diseases. These results, combined with the proved PL stability in biological buffers, open the way for the use of pSi–TiO₂ microparticles as promising materials in nanomedicine, but their ability to increase immune cell activation by other agonists should be considered and even exploited. Materials science ; Nanomedicine ; Photoluminescence ; Nanotechnology ; Nanomaterials ; Biocompatibility ; Porous silicon ; Coating ; Wafer ; Etching (microfabrication) ; Silicon ; Chemical engineering ; Nanoparticle ; Layer (electronics) ; Optoelectronics Silicon Nanostructures and Photoluminescence ; Anodic Oxide Films and Nanostructures ; Nanowire Synthesis and Applications
Authors: Zong‐Ying Liu | Jiun‐Wei Hu | Chi‐Lin Chen | Yi‐An Chen | Kew‐Yu Chen | Pi‐Tai Chou
Source: The Journal of Physical Chemistry (article, 2018-01-01)
Field: Chemistry — Physical and Theoretical Chemistry

Correlation among Hydrogen Bond, Excited-State Intramolecular Proton-Transfer Kinetics and Thermodynamics for −OH Type Proton-Donor Molecules C A series of new molecules bearing alkyl-substitutes on the parent molecule 1-hydroxy-11H-benzo[b]fluoren-11-one (HBF) has been designed and synthesized, which possesses an intramolecular hydrogen bond (H-bond) between −OH proton donor and carbonyl proton acceptor. All studied molecules present an equilibrium type of excited-state intramolecular proton transfer (ESIPT) at 298 K. The alkyl-substitutions at various positions subtly alter the intramolecular H-bond strength, which then fine-tune the excited-state equilibrium and hence thermodynamics between normal and tautomer species. These, in combination with finite rates of ESIPT resolved by femtosecond fluorescence upconversion techniques, lead to the establishment of an empirical relationship among H-bond strengths, ESIPT kinetics, and thermodynamics for HBF series of molecules, in which the stronger H-bond is, the faster and more exergonic ESIPT is. The intensity ratio for normal versus proton-transfer tautomer emission can be systematically tuned, demonstrating the harness of −OH type ESIPT reaction via facile alkyl-substituent perturbation. Chemistry ; Exergonic reaction ; Intramolecular force ; Tautomer ; Hydrogen bond ; Photochemistry ; Molecule ; Alkyl ; Proton ; Excited state ; Substituent ; Stereochemistry ; Organic chemistry ; Catalysis Photochemistry and Electron Transfer Studies ; Metal-Catalyzed Oxygenation Mechanisms ; Radical Photochemical Reactions
Authors: Dirk M. Guldi
Source: ECS Meeting Abstracts (article, 2018-04-13)
Field: Chemistry — Electrochemistry

(Invited) Mediating Reductive Charge Shift Reactions in Electron Transport Chains We report the synthesis of a full-fledged family of covalent electron donor-acceptor 1 -acceptor 2 conjugates and their charge-transfer characterization by means of advanced photophysical assays. Both Zn(II)Porphyrins and Zn(II)Phthalocyanines were linked to different electron-transport chains of pairs of electron accepting C 60 and C 70 fullerenes. In this way, a fine-tuned redox gradient is established to power a unidirectional, long-range charge transport from the excited-state electron donor via a transient C 60 •- towards C 70 •- . This strategy helps minimize energy losses in the reductive, short-range charge shift from C 60 to C 70 . At the forefront of our investigations are excited-state dynamics deduced from femtosecond transient absorption spectroscopic measurements and subsequent computational deconvolution of the transient absorption spectra. These provide evidence for cascades of short-range charge-transfer processes, including reductive charge shift reactions between the two electron-accepting fullerenes, and for kinetics that are influenced by the nature and length of the respective spacer. Of key importance is the postulate of a mediating state in the charge-shift reaction at weak electronic couplings. Our results point to an intimate relationship between triplet-triplet energy transfer and charge transfer. Ultrafast laser spectroscopy ; Excited state ; Electron transfer ; Chemistry ; Electron acceptor ; Electron transport chain ; Acceptor ; Marcus theory ; Fullerene ; Charge (physics) ; Electron ; Electron donor ; Absorption spectroscopy ; Absorption (acoustics) ; Chemical physics ; Photochemistry ; Atomic physics ; Materials science ; Kinetics ; Spectroscopy ; Physics ; Catalysis ; Reaction rate constant Electrochemical Analysis and Applications