jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Xin Liu | Tina Monzavi | Ivan Gitsov
Source: Polymers (article, 2019-03-21)
Field: Chemistry — Organic Chemistry

Controlled ATRP Synthesis of Novel Linear-Dendritic Block Copolymers and Their Directed Self-Assembly in Breath Figure Arrays Herein, we report the formation and characterization of novel amphiphilic linear-dendritic block copolymers (LDBCs) composed of hydrophilic dendritic poly(ether-ester), PEE, blocks and hydrophobic linear poly(styrene), PSt. The LDBCs are synthesized via controlled atom transfer radical polymerization (ATRP) initiated by a PEE macroinitiator. The copolymers formed have narrow molecular mass distributions and are designated as LGn-PSt M<sub>n</sub>, in which LG represents the PEE fragment, n denotes the generation of the dendron (<i>n</i> = 1⁻3), and M<sub>n</sub> refers to the average molecular mass of the LDBC (<i>M</i><sub>n</sub> = 3.5⁻68 kDa). The obtained LDBCs are utilized to fabricate honeycomb films by a static "breath figure" (BF) technique. The copolymer composition strongly affects the film morphology. LDBCs bearing acetonide dendron end groups produce honeycomb films when the PEE fraction is lower than 20%. Pore uniformity increases as the PEE content decreases. For LDBCs with hydroxyl end groups, only the first generation LDBCs yield BF films, but with a significantly smaller pore size (0.23 μm vs. 1⁻2 μm, respectively). Although higher generation LDBCs with free hydroxyl end groups fail to generate honeycomb films by themselves, the use of a cosolvent or addition of homo PSt leads to BF films with a controllable pore size (3.7⁻0.42 μm), depending on the LDBC content. Palladium complexes within the two triazole groups in each of the dendron's branching moieties can also fine-tune the morphology of the BF films. Copolymer ; Dendrimer ; Atom-transfer radical-polymerization ; Polymer chemistry ; Branching (polymer chemistry) ; Styrene ; Materials science ; Amphiphile ; Self-assembly ; Polymer ; Nanotechnology Advanced Polymer Synthesis and Characterization ; Dendrimers and Hyperbranched Polymers ; Block Copolymer Self-Assembly
Authors: Sjoerd J. Rijpkema | B. Jelle Toebes | Marijn N. Maas | Noël de Kler | Daniela A. Wilson
Source: Israel Journal of Chemistry (article, 2019-06-28)
Field: Chemistry — Organic Chemistry

Designing Molecular Building Blocks for Functional Polymersomes Abstract In recent years various polymeric vesicles have been reported that show promising results for drug delivery applications, nanomotors and/or nanoreactors. These polymeric vesicles can be assembled from many different materials and various coupling reactions have been applied for functionalization of the vesicles. However, the designs reported are still rather simple, as it is challenging to mimic biological complex systems. In this review we focus on the properties of widely used hydrophobic polymers to better understand polymersome properties for various applications. Examples are shown of how researchers have used and modulated block‐copolymers and their properties to their advantage. Furthermore, an overview of possible end group functionalizations of nanoparticles is reported, giving insight in recent developments of smart nanoparticles for biomedical applications. Chemistry ; Polymersome ; Nanotechnology ; Computational biology ; Organic chemistry ; Polymer ; Copolymer ; Amphiphile Advanced Polymer Synthesis and Characterization ; biodegradable polymer synthesis and properties ; Innovative Microfluidic and Catalytic Techniques Innovation
Authors: Daniel M. Knoll | Christoph Zippel | Zahid Hassan | Martin Nieger | Patrick Weis | Manfred M. Kappes | Stefan Bräse
Source: Dalton Transactions (article, 2019-01-01)
Field: Chemistry — Organic Chemistry

A highly stable, Au/Ru heterobimetallic photoredox catalyst with a [2.2]paracyclophane backbone We report the synthesis and catalytic application of a highly stable distance-defined Au/Ru heterobimetallic complex. [2.2]Paracyclophane serves as a backbone, holding the two metal centers in a spatial orientation and metal-metal fixed distance. The Au/Ru heterobimetallic complex is highly stable, easily accessible and exhibits promising catalytic activity in a visible-light mediated dual Au/Ru Meyer-Schuster rearrangement. Catalysis ; Chemistry ; Photochemistry ; Polymer chemistry ; Materials science ; Organic chemistry Catalytic C–H Functionalization Methods ; Radical Photochemical Reactions ; Synthesis and Properties of Aromatic Compounds
Authors: Vithyasaahar Sethumadhavan | Sam Rudd | Eliza Switalska | Kamil Zuber | Peter R. Teasdale | Drew Evans
Source: BMC Materials (article, 2019-11-21)
Field: Materials Science — Polymers and Plastics

Recent advances in ion sensing with conducting polymers Abstract Ions are present throughout our environment—from biological systems to agriculture and beyond. Many important processes and mechanisms are driven by their presence and their relative concentration. In order to study, understand and/or control these, it is important to know what ions are present and in what concentration—highlighting the importance of ion sensing. Materials that show specific ion interaction with a commensurate change in measurable properties are the key components of ion sensing. One such type are conducting polymers. Conducting polymers are referred to as ‘active’ because they show observable changes in their electrical and optical (and other) properties in response to changing levels of doping with ions. For example, p-type conducting polymers such as poly(3,4-ethylenedioxythiophene) and polypyrrole, can transition from semi-conducting to metallic in response to increasing levels of anions inserted into their structure. Under certain circumstances, conducting polymers also interact with cations—showing their utility in sensing. Herein, recent advances in conducting polymers will be reviewed in the context of sensing ions. The main scope of this review is to critically evaluate our current understanding of ion interactions with conducting polymers and explore how these novel materials can contribute to improving our ion-sensing capabilities. Conductive polymer ; Ion ; Nanotechnology ; Materials science ; Context (archaeology) ; Polymer ; Polypyrrole ; Scope (computer science) ; Chemical physics ; Computer science ; Chemistry ; Organic chemistry Conducting polymers and applications ; Analytical Chemistry and Sensors ; Electrochemical sensors and biosensors
Authors: Brenda Rosa | Marialaura Marchetti | Gianluca Paredi | Heinz Amenitsch | Nina Franko | Roberto Benoni | Barbara Giabbai | Maria Giovanna De Marino | Andrea Mozzarelli | Luca Ronda | Paola Storici | Barbara Campanini | Stefano Bettati
Source: International Journal of Molecular Sciences (article, 2019-10-21)
Field: Materials Science — Materials Chemistry

Combination of SAXS and Protein Painting Discloses the Three-Dimensional Organization of the Bacterial Cysteine Synthase Complex, a Potential Target for Enhancers of Antibiotic Action The formation of multienzymatic complexes allows for the fine tuning of many aspects of enzymatic functions, such as efficiency, localization, stability, and moonlighting. Here, we investigated, in solution, the structure of bacterial cysteine synthase (CS) complex. CS is formed by serine acetyltransferase (CysE) and <i>O</i>-acetylserine sulfhydrylase isozyme A (CysK), the enzymes that catalyze the last two steps of cysteine biosynthesis in bacteria. CysK and CysE have been proposed as potential targets for antibiotics, since cysteine and related metabolites are intimately linked to protection of bacterial cells against redox damage and to antibiotic resistance. We applied a combined approach of small-angle X-ray scattering (SAXS) spectroscopy and protein painting to obtain a model for the solution structure of CS. Protein painting allowed the identification of protein-protein interaction hotspots that were then used as constrains to model the CS quaternary assembly inside the SAXS envelope. We demonstrate that the active site entrance of CysK is involved in complex formation, as suggested by site-directed mutagenesis and functional studies. Furthermore, complex formation involves a conformational change in one CysK subunit that is likely transmitted through the dimer interface to the other subunit, with a regulatory effect. Finally, SAXS data indicate that only one active site of CysK is involved in direct interaction with CysE and unambiguously unveil the quaternary arrangement of CS. Cysteine ; Protein quaternary structure ; Protein subunit ; Small-angle X-ray scattering ; Active site ; Protein structure ; DHPS ; Biochemistry ; Enzyme ; Chemistry ; Mutagenesis ; Biology ; Mutation ; Scattering Enzyme Structure and Function ; Biochemical and Molecular Research ; Folate and B Vitamins Research
Authors: Ibón Alkorta | José Elguero | Manuel Yáñez | Otília Mó | M. Merced Montero‐Campillo
Source: Molecules (article, 2019-12-02)
Field: Chemistry — Physical and Theoretical Chemistry

Relativistic Effects on NMR Parameters of Halogen-Bonded Complexes Relativistic effects are found to be important for the estimation of NMR parameters in halogen-bonded complexes, mainly when they involve the heavier elements, iodine and astatine. A detailed study of 60 binary complexes formed between dihalogen molecules (XY with X, Y = F, Cl, Br, I and At) and four Lewis bases (NH<sub>3</sub>, H<sub>2</sub>O, PH<sub>3</sub> and SH<sub>2</sub>) was carried out at the MP2/aug-cc-pVTZ/aug-cc-pVTZ-PP computational level to show the extent of these effects. The NMR parameters (shielding and nuclear quadrupolar coupling constants) were computed using the relativistic Hamiltonian ZORA and compared to the values obtained with a non-relativistic Hamiltonian. The results show a mixture of the importance of the relativistic corrections as both the size of the halogen atom and the proximity of this atom to the basic site of the Lewis base increase. Halogen ; Relativistic quantum chemistry ; Hamiltonian (control theory) ; Chemistry ; Coupling constant ; Bromine ; Atom (system on chip) ; Lewis acids and bases ; Computational chemistry ; Physical chemistry ; Crystallography ; Atomic physics ; Physics ; Alkyl ; Quantum mechanics ; Organic chemistry ; Mathematics Crystallography and molecular interactions ; Solid-state spectroscopy and crystallography ; Advanced NMR Techniques and Applications
Authors: Ayham H. Abazid | Boris J. Nachtsheim
Source: Angewandte Chemie (article, 2019-10-10)
Field: Chemistry — Organic Chemistry

A Triazole‐Substituted Aryl Iodide with Omnipotent Reactivity in Enantioselective Oxidations Abstract A widely applicable triazole‐substituted chiral aryl iodide is described as catalyst for enantioselective oxidation reactions. The introduction of a substituent in ortho‐position to the iodide is key for its high reactivity and selectivity. Besides a robust and modular synthesis, the main advantage of this catalyst is the excellent performance in a plethora of mechanistically diverse enantioselective transformations, such as spirocyclizations, phenol dearomatizations, α‐oxygenations, and oxidative rearrangements. DFT‐calculations of in situ generated [hydroxy(tosyloxy)iodo]arene isomers give an initial rational for the observed reactivity. Enantioselective synthesis ; Reactivity (psychology) ; Substituent ; Chemistry ; Iodide ; Aryl ; Selectivity ; Combinatorial chemistry ; Catalysis ; Triazole ; Organic chemistry Oxidative Organic Chemistry Reactions ; Synthesis and Catalytic Reactions ; Catalytic C–H Functionalization Methods
Authors: Fatima Al-Zohbi | Johan Jacquemin | Fouad Ghamouss | Bruno Schmaltz | Mohamed Abarbri | Khalil Cherry | Mohamad Fadel Tabcheh | François Tran‐Van
Source: Journal of Power Sources (article, 2019-05-21)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Impact of the aqueous pyrrolidinium hydrogen sulfate electrolyte formulation on transport properties and electrochemical performances for polyaniline-based supercapacitor Supercapacitor ; Electrolyte ; Gravimetric analysis ; Polyaniline ; Electrochemistry ; Capacitance ; Ionic liquid ; Materials science ; Chemistry ; Aqueous solution ; Chemical engineering ; Inorganic chemistry ; Electrode ; Composite material ; Polymer ; Organic chemistry ; Physical chemistry Supercapacitor Materials and Fabrication ; Conducting polymers and applications ; Electrochemical sensors and biosensors
Authors: Leslie Labarre | Daniele Vigolo
Source: Microfluidics and Nanofluidics (article, 2019-11-08)
Field: Materials Science — Materials Chemistry

Microfluidics approach to investigate foam hysteretic behaviour Abstract Foam stability often refers to the foam left to evolve with time in static conditions. However, in everyday life, foams are submitted to numerous deformations. A feature of foam stability is represented by the foam’s ability to resist to the deformation and to recover its initial properties after deformation. The technique developed here allows for a qualitative evaluation of the property of foam recovery after a deformation in a flow-focusing microfluidic device. The foam hysteretic behaviour was evaluated by introducing the analogous of a standard three-step test in which the recovery of viscosity is commonly studied over three deformation stages. The foam behaviour is analysed over an induced cycle of ascendant and descendant deformation at the wall, well controlled by varying the gas pressure for a constant liquid pressure. Thus, the recovery of the two-row foam pattern used as reference is studied after a high deformation phase corresponding to the bamboo pattern and the level of hysteresis is measured qualitatively. The samples investigated comprise a range of Newtonian aqueous solutions containing 5 cmc (critical micellar concentration) of sodium dodecyl sulphate (SDS). A retardation effect was observed leading to hysteresis caused by the increase in viscosity. A higher surface elasticity produced a smaller but non-negligible hysteresis due to an excess in elastic energy caused by the increase of the duration of the bubble rearrangements. The present study has gone some way towards enhancing our understanding of the mechanisms triggering or enhancing foam hysteresis in a microchannel. The findings will be of interest to many industrial processes where foams are submitted to a series of deformation steps along the process line from food industrial applications to biological systems. Graphical abstract A schematic of the three-step test consisting in an ascending and descending pressure ramps obtained by varying the gas pressure for a constant liquid pressure. Materials science ; Hysteresis ; Viscosity ; Deformation (meteorology) ; Composite material ; Bubble ; Microfluidics ; Microchannel ; Enhanced oil recovery ; Newtonian fluid ; Viscoelasticity ; Rheology ; Mechanics ; Nanotechnology ; Chemical engineering Pickering emulsions and particle stabilization ; Innovative Microfluidic and Catalytic Techniques Innovation ; Enhanced Oil Recovery Techniques
Authors: Judith Martín‐de León | Victoria Bernardo | Ester Laguna‐Gutiérrez | Miguel Ángel Rodríguez‐Pérez
Source: Polymer International (article, 2019-09-16)
Field: Materials Science — Polymers and Plastics

Influence of the viscosity of poly(methyl methacrylate) on the cellular structure of nanocellular materials Abstract Three different grades of poly(methyl methacrylate) (PMMA) with different rheological properties are used for the production of nanocellular materials using gas dissolution foaming. The influences of both the viscosity of the different polymers and the processing parameters on the final cellular structure are studied using a wide range of saturation and foaming conditions. Foaming conditions affect similarly all cellular materials. It is found that an increase of the foaming temperature results in less dense nanocellular materials, with higher cell nucleation densities. In addition, it is demonstrated that a lower viscosity leads to cellular polymers with a lower relative density but larger cell sizes and smaller cell nucleation densities, these differences being more noticeable for the conditions in which low solubilities are reached. It is possible to produce nanocellular materials with relative densities of 0.24 combined with cell sizes of 75 nm and cell nucleation densities of 10 15 nuclei cm −3 using the PMMA with the lowest viscosity. In contrast, minimum cell sizes of around 14 nm and maximum cell nucleation densities of 3.5 × 10 16 nuclei cm −3 with relative densities of 0.4 are obtained with the most viscous one. © 2019 Society of Chemical Industry Nucleation ; Materials science ; Polymer ; Methyl methacrylate ; Viscosity ; Rheology ; Dissolution ; Chemical engineering ; Saturation (graph theory) ; Polymer chemistry ; Composite material ; Chemistry ; Copolymer ; Organic chemistry Polymer Foaming and Composites ; Injection Molding Process and Properties ; Rheology and Fluid Dynamics Studies
Authors: Merlin von Soosten | Dennis Valbjørn Christensen | Chang‐Beom Eom | Thomas Sand Jespersen | Yunzhong Chen | Nini Pryds
Source: PubMed (article, 2019-11-29)
Field: Materials Science — Materials Chemistry

On the emergence of conductivity at SrTiO<sub>3</sub>-based oxide interfaces - an in-situ study. Heterostructures and crystal interfaces play a major role in state-of-the-art semiconductor devices and play a central role in the field of oxide electronics. In oxides the link between the microscopic properties of the interfaces and bulk properties of the resulting heterostructures challenge our fundamental understanding. Insights on the early growth stage of interfaces and its influence on resulting physical properties are scarce - typically the information is inferred from post growth characterization. Here, we report on real time measurements of the transport properties of SrTiO<sub>3</sub>-based heterostructures at room temperature, while the heterostructure is forming. Surprisingly, we detect a conducting interface already at the initial growth stage, much earlier than the well-established critical thickness limit for observing conductivity ex-situ after sample growth. We investigate how the conductivity depends on various physical processes occurring during pulsed laser depositions, including light illumination, particle bombardment by the plasma plume, interactions with the atmosphere and oxygen migration from SrTiO<sub>3</sub> to the thin films of varying compositions. We conclude that the conductivity in these room-temperature grown interfaces stem from oxygen vacancies with a concentration determined primarily by a balance between vacancy formation through particle bombardment and interfacial redox reaction and vacancy annihilation through oxidation. Using this approach, we propose a new design tool to control the electrical properties of interfaces in real time during their formation. In situ ; Conductivity ; Oxide ; Materials science ; Computer science ; Chemistry ; Metallurgy ; Physical chemistry Electronic and Structural Properties of Oxides ; Magnetic and transport properties of perovskites and related materials ; Ferroelectric and Piezoelectric Materials
Authors: Zongliang Wang | Jun Chang | Huishan Yu | Cunwei Tian | Hao Zhang | Zhang Xiu-kun | Longfei Tang | Qinduan Zhang | Yiwen Feng
Source: Photonic Sensors (article, 2019-04-12)
Field: Chemistry — Spectroscopy

Multi-Component and Multi-Point Trace Gas Sensing in Wavelength Modulation Spectroscopy Based on Wavelength Stabilization Multi-component and multi-point trace gas sensing in the wavelength modulation spectroscopy is demonstrated based on the frequency-division multiplexing and time-division multiplexing technology. A reference photodetector is connected in series with a reference gas cell with the constant concentration to measure the second-harmonics peak of the components for wavelength stabilization in real time. The central wavelengths of the distributed feedback lasers are locked to the target gas absorption centers by the reference second-harmonics signal using a digital proportional-integral-derivative controller. The distributed feedback lasers with different wavelengths and modulation frequencies are injected into the gas cell to achieve multi-components gas measurement by the frequency-division multiplexing technology. In addition, multi-point trace gas sensing is achieved by the time-division multiplexing technology using a photoswitch and a relay unit. We use this scheme to detect methane (CH4) at 1650.9 nm and water vapor (H2O) at 1368.597 nm as a proof of principle with the gas cell path length of 10 cm. The minimum detection limits achieved for H2O and CH4 are 1.13 ppm and 11.85 ppm respectively, with three-point gas cell measurement; thus 10.5-fold and 10.1-fold improvements are achieved in comparison with the traditional wavelength modulation spectroscopy. Meanwhile, their excellent R-square values reach 0.9983 and 0.99564 for the concentration ranges of 500 ppm to 2000 ppm and 800 ppm to 2700 ppm, respectively. Trace gas ; Spectroscopy ; Optics ; Wavelength ; Modulation (music) ; Multiplexing ; Harmonics ; Materials science ; Physics ; Optoelectronics ; Electronic engineering ; Engineering Spectroscopy and Laser Applications ; Analytical Chemistry and Sensors ; Atmospheric Ozone and Climate
Authors: Morten H. Christensen | Jian Kang | Rafael M. Fernandes
Source: Physical review. B./Physical review. B (article, 2019-07-15)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Intertwined spin-orbital coupled orders in the iron-based superconductors The underdoped phase diagram of the iron-based superconductors exemplifies the complexity common to many correlated materials. Indeed, multiple ordered states that break different symmetries but display comparable transition temperatures are present. Here we argue that such a complexity can be understood within a simple unifying framework. This framework, built to respect the symmetries of the nonsymmorphic space group of the FeAs/Se layer, consists of primary magnetically ordered states and their vestigial phases that intertwine spin and orbital degrees of freedom. All vestigial phases have Ising-like and zero wave-vector order parameters, described in terms of composite spin order and exotic orbital-order patterns such as spin-orbital loop currents, staggered atomic spin-orbit coupling, and emergent Rashba- and Dresselhaus-type spin-orbit interactions. Moreover, they host unusual phenomena, such as the electronematic effect, by which electric fields act as transverse fields to the nematic order parameter, and the ferro-N\'eel effect, by which a uniform magnetic field induces N\'eel order. We discuss the experimental implications of our findings to iron-based superconductors and possible extensions to other correlated compounds with similar space groups. Condensed matter physics ; Homogeneous space ; Superconductivity ; Phase diagram ; Physics ; Spin (aerodynamics) ; Coupling (piping) ; Order (exchange) ; Space (punctuation) ; Degrees of freedom (physics and chemistry) ; Quantum mechanics ; Phase (matter) ; Materials science ; Mathematics ; Geometry Iron-based superconductors research ; Corporate Taxation and Avoidance ; Rare-earth and actinide compounds
Authors: Habiba Lais | Premesh Shehan Lowe | Tat‐Hean Gan | L.C. Wrobel
Source: Ultrasonics Sonochemistry (article, 2019-04-03)
Field: Materials Science — Materials Chemistry

Numerical investigation of design parameters for optimization of the in-situ ultrasonic fouling removal technique for pipelines Fouling ; Ultrasonic sensor ; Pipeline transport ; In situ ; Materials science ; Environmental science ; Process engineering ; Chemistry ; Engineering ; Environmental engineering ; Acoustics Material Properties and Failure Mechanisms ; Coal Combustion and Slurry Processing ; Ultrasound and Cavitation Phenomena