jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Sanju Gupta | Romney Meek | Brendan Evans | Nicholas Dimakis
Source: Journal of Applied Physics (article, 2018-09-26)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Graphene-based “hybrid” aerogels with carbon nanotubes: Mesoporous network–functionality promoted defect density and electrochemical activity correlations Electrochemical activity of graphene and graphene-based “hybrid” nanomaterials is crucial for energy and water sustainability applications, which requires fine tuning over combined geometric and electronic structures. We demonstrate that precise control of defects, porosity, and topological interconnectedness, invoked in hydrothermally synthesized graphene aerogel integrated with multi-walled carbon nanotubes, promotes finely tuned morphology, structure, defect number density, hierarchical mesoporosity, and conductivity and enhances the electrochemical heterogeneous electron transfer rate (kET). We prepared a range of graphene-based “hybrid” scaffolds (or monolithic aerogels) and their nitrogenated equivalents with varying graphene–carbon nanotube compositions using two synthetic schemes known as approaches 1 and 2. This study allows us to correlate quantitatively between number defect density (via Raman spectroscopy; RS) and heterogeneous electron transfer rate (via scanning electrochemical microscopy). RS provided microscale structural characterization revealing localized lattice vibrations. The first- and second-order Raman bands were analyzed in terms of band position, intensity ratio, and integrated intensity determining structural disorder, in-plane cluster size, inter-defect distance, and number defect density. The role of oxygenated (carbonyl; C═O, carboxyl; —COOH) and nitrogenated (pryridinic-N and graphitic/pyrrolic-N) functionalities and bonding configurations besides mesoporosity is emphasized for understanding the role of surface chemistry in regionally improved physicochemical (electroactivity and catalytic) properties. The defect-induced increase in finite electronic density of states (DOS) near Fermi level calculated using density functional theory under hydration helped in establishing moderate defect density for enhanced heterogeneous electron transfer rate as a critical onset such that the carbon system is electroactive while maintaining integral sp2 C structural network. Moreover, the defect sites allow sufficient overlap between DOS for graphene-based aerogels and redox probe wavefunctions, which emphasizes the experimental correlation establishments. Graphene ; Materials science ; Density functional theory ; Carbon nanotube ; Fermi level ; Raman spectroscopy ; Aerogel ; Mesoporous material ; Nanotechnology ; Electron transfer ; Nanomaterials ; Chemical physics ; Chemical engineering ; Chemistry ; Computational chemistry ; Catalysis ; Electron ; Physical chemistry ; Organic chemistry Supercapacitor Materials and Fabrication ; Advancements in Battery Materials ; Electrocatalysts for Energy Conversion
Authors: E. Mahmoudpour | Shahrokh Hosseini-Hashemi | S. Ali Faghidian
Source: Microsystem Technologies (article, 2018-11-07)
Field: Materials Science — Materials Chemistry

Nonlinear resonant behaviors of embedded thick FG double layered nanoplates via nonlocal strain gradient theory Nonlinear system ; Galerkin method ; Vibration ; Dimensionless quantity ; Materials science ; Mathematical analysis ; Length scale ; Mechanics ; Amplitude ; Harmonic balance ; Physics ; Classical mechanics ; Mathematics ; Optics ; Acoustics Nonlocal and gradient elasticity in micro/nano structures ; Composite Structure Analysis and Optimization ; Thermoelastic and Magnetoelastic Phenomena
Authors: Álvaro González García | Alessandro Ianiro | Remco Tuinier
Source: ACS Omega (article, 2018-12-21)
Field: Chemistry — Organic Chemistry

On the Colloidal Stability of Spherical Copolymeric Micelles Using self-consistent field (SCF) calculations, we systematically quantify the pair interactions between spherical diblock copolymer micelles following a bottom-up approach. From the equilibrium properties of self-assembling micelles at different separation distances, a simple yet insightful pair interaction can be extracted. The SCF results match with an analytical model based upon closed expressions for the free energy change per diblock copolymer in the micelle. To gain insights into the colloidal stability of dilute micelle suspensions, the second virial coefficient normalized by the undistorted micelle volume (<i>B</i> <sub>2</sub> <sup>*</sup>) is evaluated. For stable micelles (<i>B</i> <sub>2</sub> <sup>*</sup> ≳ -6), we find a weak dependence of <i>B</i> <sub>2</sub> <sup>*</sup> on solvophilic block length for varying core-forming block properties (core solvation and block length). The micelle suspension gets unstable (<i>B</i> <sub>2</sub> <sup>*</sup> ≲ -6) when the corona-forming block crosses Θ-solvent conditions toward poor solvency. In contrast with what is expected from models where the soft nature of the micelle is not taken into account, increasing the effective grafting density of solvophilic tails from the core then leads to colloidal destabilization of the micelle suspension. Micelle ; Copolymer ; Colloid ; Solvation ; Chemical physics ; Materials science ; Solvophobic ; Chemical engineering ; Chemistry ; Solvent ; Aqueous solution ; Physical chemistry ; Organic chemistry ; Polymer Surfactants and Colloidal Systems ; Polymer Surface Interaction Studies ; Block Copolymer Self-Assembly
Authors: Cristina Giovannoli | Cinzia Passini | Fabio Di Nardo | Laura Anfossi | Claudio Baggiani | Ian A. Nicholls
Source: Polymers (article, 2018-02-15)
Field: Chemistry — Analytical Chemistry

Affinity Capillary Electrochromatography of Molecularly Imprinted Thin Layers Grafted onto Silica Capillaries Using a Surface-Bound Azo-Initiator and Living Polymerization Molecularly imprinted thin layers were prepared in silica capillaries by using two different surface polymerization strategies, the first using 4,4'-azobis(4-cyanovaleric acid) as a surface-coupled radical initiator, and the second, S-carboxypropyl-S'-benzyltrithiocarbonate as a reversible addition-fragmentation chain transfer (RAFT) agent in combination with 2,2'-azobisisobutyronitrile as a free radical initiator. The ability to generate imprinted thin layers was tested on two different polymerization systems: (i) a 4-vinylpyridine/ethylene dimethacrylate (4VP-EDMA) in methanol-water solution with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) as a template; and (ii) methacrylic acid/ethylene dimethacrylate (MAA-EDMA) in a chloroform solution with warfarin as the template molecule. The binding properties of the imprinted capillaries were studied and compared with those of the corresponding non-imprinted polymer coated capillaries by injecting the template molecule and by measuring its migration times relative to a neutral and non-retained marker. The role of running buffer hydrophobicity on recognition was investigated by studying the influence of varying buffer acetonitrile concentration. The 2,4,5-T-imprinted capillary showed molecular recognition based on a reversed phase mechanism, with a decrease of the template recognition in the presence of higher acetonitrile content; whereas warfarin-imprinted capillaries showed a bell-shaped trend upon varying the acetonitrile percentage, illustrating different mechanisms underlying imprinted polymer-ligand recognition. Importantly, the results demonstrated the validity of affinity capillary electrochromatography (CEC) to screen the binding properties of imprinted layers. Capillary electrochromatography ; Electrochromatography ; Molecularly imprinted polymer ; Polymerization ; Chemistry ; Chemical engineering ; Polymer chemistry ; Materials science ; Chromatography ; Capillary electrophoresis ; Polymer ; Organic chemistry ; Catalysis ; Selectivity Analytical chemistry methods development ; Microfluidic and Capillary Electrophoresis Applications ; Analytical Chemistry and Chromatography
Authors: Mahboobeh Shahbazi | Henrietta E. Cathey | Natalia Danilova | Ian D.R. Mackinnon
Source: Materials (article, 2018-07-22)
Field: Materials Science — Materials Chemistry

Single Step Process for Crystalline Ni-B Compounds Crystalline Ni₂B, Ni₃B, and Ni₄B₃ are synthesized by a single-step method using autogenous pressure from the reaction of NaBH₄ and Ni precursors. The effect of reaction temperature, pressure, time, and starting materials on the composition of synthesized products, particle morphologies, and magnetic properties is demonstrated. High yields of Ni₂B (>98%) are achieved at 2.3⁻3.4 MPa and ~670 °C over five hours. Crystalline Ni₃B or Ni₄B₃ form in conjunction with Ni₂B at higher temperature or higher autogenous pressure in proportions influenced by the ratios of initial reactants. For the same starting ratios of reactants, a longer reaction time or higher pressure shifts equilibria to lower yields of Ni₂B. Using this approach, yields of ~88% Ni₄B₃ (single phase orthorhombic) and ~72% Ni₃B are obtained for conditions 1.9 MPa < P<sub>max</sub> < 4.9 MPa and 670 °C < T<sub>max</sub> < 725 °C. Gas-solid reaction is the dominant transformation mechanism that results in formation of Ni₂B at lower temperatures than conventional solid-state methods. Orthorhombic crystal system ; Materials science ; Solid-state ; Phase (matter) ; Reaction mechanism ; Particle size ; Analytical Chemistry (journal) ; Physical chemistry ; Chemistry ; Crystallography ; Crystal structure ; Catalysis ; Organic chemistry Hydrogen Storage and Materials ; MXene and MAX Phase Materials ; Ammonia Synthesis and Nitrogen Reduction
Authors: Bastian Ebeling | Khaled Belal | François Stoffelbach | Patrice Woisel | Muriel Lansalot | Franck D’Agosto
Source: Macromolecular Rapid Communications (article, 2018-09-10)
Field: Chemistry — Organic Chemistry

Polymer Nanospheres with Hydrophobic Surface Groups as Supramolecular Building Blocks Produced by Aqueous PISA A robust and straightforward synthesis of waterborne polymer nanospheres bearing the supramolecular association unit dialkoxynapthalene at their surface is presented using polymerization-induced self-assembly (PISA). A RAFT agent bearing this unit is first employed to produce poly(acrylic acid) chains, which are then chain-extended with styrene (S) to spontaneously form the nano-objects via RAFT aqueous emulsion polymerization. The particular challenge posed by the dialkoxynapthalene hydrophobicity can be overcome by the use of PISA and the deprotonation of the poly(acrylic acid). At pH = 7, very homogeneous latexes are obtained. The particle diameters can be tuned from 36 to 105 nm (with a narrow particle size distribution) by varying the molar mass of the PS block. The surface accessibility of the dialkoxynapthalene moieties is demonstrated by complexation with the complementary host cyclobis(paraquat-p-phenylene) (CBPQT<sup>4+</sup> · Cl<sup>-</sup> ), highlighting the potential of the nanospheres to act as building blocks for responsive supramolecular structures. Polymer chemistry ; Supramolecular chemistry ; Polymerization ; Acrylic acid ; Chemistry ; Emulsion polymerization ; Polymer ; Molar mass ; Supramolecular polymers ; Aqueous solution ; Copolymer ; Reversible addition−fragmentation chain-transfer polymerization ; Raft ; Chemical engineering ; Radical polymerization ; Organic chemistry ; Molecule Advanced Polymer Synthesis and Characterization ; Supramolecular Chemistry and Complexes ; Luminescence and Fluorescent Materials
Authors: Stefan W. Tabernig | Benjamin Daiber | Tianyi Wang | Bruno Ehrler
Source: Journal of Photonics for Energy (article, 2018-05-10)
Field: Materials Science — Materials Chemistry

Enhancing silicon solar cells with singlet fission: the case for Förster resonant energy transfer using a quantum dot intermediate One way for solar cell efficiencies to overcome the Shockley–Queisser limit is downconversion of high-energy photons using singlet fission (SF) in polyacenes like tetracene (Tc). SF enables generation of multiple excitons from the high-energy photons, which can be harvested in combination with Si. In this work, we investigate the use of lead sulfide quantum dots (PbS QDs) with a band gap close to Si as an interlayer that allows Förster resonant energy transfer (FRET) from Tc to Si, a process that would be spin-forbidden without the intermediate QD step. We investigate how the conventional FRET model, most commonly applied to the description of molecular interactions, can be modified to describe the geometry of QDs between Tc and Si and how the distance between QD and Si, and the QD bandgap affects the FRET efficiency. By extending the acceptor dipole in the FRET model to a 2-D plane, and to the bulk, we see a relaxation of the distance dependence of transfer. Our results indicate that FRET efficiencies from PbS QDs to Si well above 50% are possible at very short but possibly realistic distances of around 1 nm, even for QDs with relatively low photoluminescence quantum yield. Quantum dot ; Förster resonance energy transfer ; Singlet fission ; Resonant inductive coupling ; Photoluminescence ; Photon ; Band gap ; Optoelectronics ; Molecular physics ; Exciton ; Acceptor ; Materials science ; Singlet state ; Atomic physics ; Physics ; Energy transfer ; Fluorescence ; Optics ; Condensed matter physics ; Excited state Quantum Dots Synthesis And Properties ; Molecular Junctions and Nanostructures ; Semiconductor Quantum Structures and Devices
Authors: Michal Jurı́ček
Source: CHIMIA International Journal for Chemistry (article, 2018-05-23)
Field: Chemistry — Organic Chemistry

The Three C's of Cethrene Molecules that contain one or more unpaired electrons delocalized within a π-conjugated backbone are promising candidates for applications in spin electronics or simply 'spintronics'. Our group develops functional organic materials based on π-conjugated hydrocarbon molecules, where the electrons are unpaired either in the ground state or in the excited state that is low in energy and can be populated thermally. We aim to learn how to introduce and control a multitude of properties, namely, optical, chiroptical, magnetic, and conductive, in a bulk material made of these molecules, by manipulating spin interactions between the unpaired electrons. The first model system that was developed in our group is a hydrocarbon named cethrene, which has a diradicaloid singlet ground state and a low-lying triplet excited state. In this article, the structural parameters and their impact on the properties and reactivity of cethrene are discussed within the realm of the three C's that symbolize cethrene's C-shape, chirality, and chameleonic reactivity. Unpaired electron ; Delocalized electron ; Excited state ; Ground state ; Conjugated system ; Spintronics ; Chemical physics ; Molecule ; Electron ; Singlet state ; Reactivity (psychology) ; Chirality (physics) ; Chemistry ; Materials science ; Physics ; Atomic physics ; Condensed matter physics ; Ferromagnetism ; Organic chemistry ; Symmetry breaking ; Quantum mechanics ; Polymer Synthesis and Properties of Aromatic Compounds ; Advanced Chemical Physics Studies ; Fullerene Chemistry and Applications
Authors: Han Wang | Duo Zhang | Mengwei Cao | Carsten Bolm
Source: Synthesis (article, 2018-09-19)
Field: Chemistry — Organic Chemistry

Electrophilic Sulfoximidations of Thiols by Hypervalent Iodine Reagents A new electrophilic sulfoximidation of thiols has been developed. Using sodium hydride as a base, the treatment of sulfoximidoyl-containing hypervalent iodine(III) reagents with thiols affords the corresponding N-sulfenylsulfoximines (N-thiosulfoximines) in good to excellent yields. A plausible mechanism is proposed. Hypervalent molecule ; Chemistry ; Electrophile ; Iodine ; Reagent ; Sodium hydride ; Combinatorial chemistry ; Hydride ; Base (topology) ; Electrophilic addition ; Iodine compounds ; Organic chemistry ; Metal ; Catalysis Synthesis and Catalytic Reactions ; Oxidative Organic Chemistry Reactions ; Catalytic C–H Functionalization Methods
Authors: Arthur B. Porto | Glaura G. Silva | Hélio dos Santos | Luiz Fernando Cappa de Oliveira
Source: Journal of the Brazilian Chemical Society (article, 2018-01-01)
Field: Materials Science — Materials Chemistry

Oxidation of Single-Walled Carbon Nanotubes under Controlled Chemical Conditions Single-walled carbon nanotubes are oxidized in the presence of H 2 SO 4 /HNO 3 mixtures containing distinct concentrations of the nitronium ion, [NO 2 + ]. The spectroscopic analyses of the final samples suggest a higher structural disorder in the oxidized systems with increasing [NO 2 + ]. This is due to a considerable oxygen amount on the tube surface, reaching up to 30%, depending on the reaction time and [NO 2 + ]. Interestingly, if long reaction time is considered, the oxygen amount on the tube surface is maximum for low [NO 2 + ] and reduces slightly for larger [NO 2 + ]. On the other hand, the oxidation process occurs gradually at 4 h, allowing a fine control of the oxidation process. Therefore, if fine tuning of the oxidation degree is desirable, the reaction must be conducted during short time (4 h) using increasing [NO 2 + ] as those obtained from 2:1, 2.5:1 and 3:1 H 2 SO 4 /HNO 3 acid mixtures to produce increasing content of functionalization. Carbon nanotube ; Oxidation process ; Oxygen ; Surface modification ; Chemical engineering ; Carbon fibers ; Chemistry ; Materials science ; Inorganic chemistry ; Nanotechnology ; Organic chemistry ; Physical chemistry ; Composite material Carbon Nanotubes in Composites ; Graphene research and applications ; Catalytic Processes in Materials Science
Authors: Andreas Hänsel | Martijn J. R. Heck
Source: Sensors (article, 2018-08-31)
Field: Chemistry — Spectroscopy

Feasibility of Telecom-Wavelength Photonic Integrated Circuits for Gas Sensors To be of commercial interest, gas sensors must optimise, among others, sensitivity, selectivity, longevity, cost and measurement speed. Using the example of ammonia, we establish that integrated optical sensors provide means to maintain the benefits of optical detection set-ups at, in principle, a lower cost and smaller footprint than currently available commercial products. Photonic integrated circuits (PICs) can be used in environmental and agricultural monitoring. The small footprint and great cost scaling of PICs allow for sensor networks with multiple devices. We show, that Indium Phosphide based commercial foundries reached the technological maturity to enable ammonia detection levels at less than 100 ppb. The current unavailability of portable, low cost ammonia sensors with such detection levels prevents emission monitoring, for example, in pig farms. The feasibility of these sensors is investigated by applying the common noise figures of the multiproject wafer platforms operating around 1550 nm to a model for an absorption measurement. The analysis is extended to other relevant gas species with absorption features near telecom-wavelengths. Footprint ; Sensitivity (control systems) ; Unavailability ; Electronic circuit ; Photonics ; Integrated circuit ; Telecommunications ; Computer science ; Electrical engineering ; Electronic engineering ; Engineering ; Materials science ; Optoelectronics ; Reliability engineering Spectroscopy and Laser Applications ; Photonic and Optical Devices ; Advanced Chemical Sensor Technologies
Authors: Chengfen Xing | Hu Zhang | Kewen Long | Yaning Xiao | Hanning Zhang | Zhijie Qiu | Dai He | Xingyu Liu | Yingli Zhang | Yi Long
Source: Crystals (article, 2018-08-18)
Field: Materials Science — Materials Chemistry

The Effect of Different Atomic Substitution at Mn Site on Magnetocaloric Effect in Ni50Mn35Co2Sn13 Alloy The effect of different atomic substitutions at Mn sites on the magnetic and magnetocaloric properties in Ni50Mn35Co2Sn13 alloy has been studied in detail. The substitution of Ni or Co for Mn atoms might lower the Mn content at Sn sites, which would reduce the d-d hybridization between Ni 3d eg states and the 3d states of excess Mn atoms at Sn sites, thus leading to the decrease of martensitic transformation temperature TM in Ni51Mn34Co2Sn13 and Ni50Mn34Co3Sn13 alloys. On the other hand, the substitution of Sn for Mn atoms in Ni50Mn34Co2Sn14 would enhance the p-d covalent hybridization between the main group element (Sn) and the transition metal element (Mn or Ni) due to the increase of Sn content, thus also reducing the TM by stabilizing the parent phase. Due to the reduction of TM, a magnetostructural martensitic transition from FM austenite to weak-magnetic martensite is realized in Ni51Mn34Co2Sn13 and Ni50Mn34Co2Sn14, resulting in a large magnetocaloric effect around room temperature. For a low field change of 3 T, the maximum ∆SM reaches as high as 30.9 J/kg K for Ni50Mn34Co2Sn14. A linear dependence of ΔSM upon μ0H has been found in Ni50Mn34Co2Sn14, and the origin of this linear relationship has been discussed by numerical analysis of Maxwell’s relation. Magnetic refrigeration ; Materials science ; Austenite ; Alloy ; Martensite ; Diffusionless transformation ; Crystallography ; Metal ; Transition metal ; Manganese ; Covalent bond ; Condensed matter physics ; Substitution (logic) ; Metallurgy ; Magnetic field ; Chemistry ; Magnetization ; Microstructure ; Physics Shape Memory Alloy Transformations ; Magnetic and transport properties of perovskites and related materials ; Magnetic Properties of Alloys
Authors: Ahmed Algellai | Marija M. Vuksanović | Nataša Tomić | Аleksandar Marinković | Marina Dojčinović | Tatjana Volkov‐Husović | Radmila Jančić Heinemann
Source: Hemijska industrija (article, 2018-01-01)
Field: Materials Science — Materials Chemistry

Improvement of cavitation resistance of composite films using functionalized alumina particles Composite films having the UV cured Bis-GMA (Bisphenol A glycidylmethacrylate)/TEGDMA (triethylene glycol dimethacrylate) as a matrix and the ferrous oxide doped alumina (Al2O3 Fe) based particles were prepared and subjected to cavitation. In order to improve the mechanical and adhesion properties of composites, four different surface modifications of filler particles were performed: 3-methacryloxypropyltrimethoxysilane (MEMO), vinyl-tris(2-methoxyethoxy)silane (VTMOEO), (3-aminopropyl)trimethoxysilane (APTMS) and biodiesel (BD). Composite films were made with 0.5, 1.5, and 3 wt.% of ferrous oxide doped alumina particles with each of the mentioned surface modifications. Composite films were prepared on brass substrates and exposed to cavitation erosion. The erosion was monitored using the mass loss while image analysis was used to observe surface defects. The composite film reinforced with Al2O3 Fe having VTMOEO as a surface modifier was the most resistant one in terms of mass loss, as well as the level of surface destruction. Results were compared to the same polymer matrix film and composite films prepared with fillers without surface modifications revealing that all composites with surface modified fillers exhibited some improvement in resistance to cavitation. Materials science ; Composite number ; Composite material ; Silane ; Ferrous ; Metallurgy Magnesium Oxide Properties and Applications ; Ultrasound and Cavitation Phenomena ; Materials Engineering and Processing