jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Polina A. Zezyulina | Dmitry A. Petrov | Konstantin N. Rozanov | Д.А. Винник | Sergey S. Maklakov | В.Е. Живулин | A.Yu. Starikov | D. P. Sherstyuk | Santiranjan Shannigrahi
Source: Coatings (article, 2020-08-14)
Field: Materials Science — Materials Chemistry

Study of the Static and Microwave Magnetic Properties of Nanostructured BaFe12−xTixO19 The effect of Ti substitution on the microwave and magnetostatic properties of nanostructured hexagonal BaFe12−xTixO19 ferrite composites is studied. The microwave permeability is measured in the frequency range of 0.1–22 GHz by a coaxial technique. An analysis of the magnetostatic data is made by the law of approach to saturation. The ferrimagnetic resonance frequencies calculated from the magnetostatic data are consistent with those obtained from the microwave measurements. The natural ferrimagnetic resonance frequencies are located in the frequency range of 15 to 22 GHz, depending on the substitution level x. An increase in the amount of substitution elements results in a low-frequency shift of the ferrimagnetic resonance frequency for samples with x &lt; 1. With x rising from 1 to 2.5, the resonance frequency increases. The results of the study demonstrate that the tailored optimization of the nano-structure of a functional material is a robust tool to fine-tune its microwave magnetic properties. The ferrites under study are promising materials to be applied as functional coatings intended to control electromagnetic interference in microwave devices. Ferrimagnetism ; Microwave ; Ferromagnetic resonance ; Materials science ; Ferrite (magnet) ; Barium ferrite ; Resonance (particle physics) ; Condensed matter physics ; Nuclear magnetic resonance ; Magnetization ; Composite material ; Magnetic field ; Physics ; Telecommunications ; Atomic physics ; Computer science Magnetic Properties and Synthesis of Ferrites ; Electromagnetic wave absorption materials ; Magneto-Optical Properties and Applications
Authors: Luuk Kortekaas | Jorn D. Steen | Daniël R. Duijnstee | Denis Jacquemin | Wesley R. Browne
Source: The Journal of Physical Chemistry A (article, 2020-07-21)
Field: Materials Science — Materials Chemistry

Noncommutative Switching of Double Spiropyrans The spiropyran family of photochromes are key components in molecular-based responsive materials and devices, e.g., as multiphotochromes, covalently coupled dyads, triads, etc. This attention is in no small part due to the change in properties that accompany the switch between spiropyran and merocyanine forms. Although the spiropyran is a single structural isomer, the merocyanine form represents a family of isomers (<i>TTT</i>, <i>TTC</i>, <i>CCT</i>, etc.) and protonation states. Combining two spiropyrans into one compound increases the number of possible structures dramatically and the interaction between the units determines, which are impeded due to intramolecular quenching of excited states. Here, we show that the coupling of two spiropyran photochromes through their phenol units yields favorable interactions (crosstalk) between the components that provides access to species inaccessible with the component monospiropyran alone. Specifically, the ring opening of one spiropyran unit, which is thermally stable at -30 °C, prevents ring opening of the second spiropyran unit. Furthermore, whereas protonated <i>E</i>- and <i>Z</i>-monomerocyanines were previously shown to undergo thermal- and photo-equilibration, the corresponding protonated <i>E</i>- and <i>Z</i>- bimerocyanines are thermally stable and show one-way photoisomerization from the <i>Z</i>,<i>Z</i>- to an emissive <i>E</i>,<i>E</i>-bimerocyanine form. Subsequent deprotonation at room temperature resets the system to the bispiro ring-closed form, but deprotonation at -30 °C yields the otherwise inaccessible bimerocyanine form. This form is photochemically inert but undergoes a two-step thermal relaxation via the merocyanine-spiropyran form, showing that the connection at the phenol units provides sufficient intramolecular interaction to fine-tune the complex isomerization pathways of spiropyrans and demonstrating noncommutability in photo- and pH-regulated multistep isomerization pathways. Spiropyran ; Merocyanine ; Protonation ; Chemistry ; Photochemistry ; Intramolecular force ; Photoisomerization ; Deprotonation ; Photochromism ; Isomerization ; Stereochemistry ; Organic chemistry Photochromic and Fluorescence Chemistry ; Photoreceptor and optogenetics research ; Neurobiology and Insect Physiology Research
Authors: Atsushi Kashiro | Wakana Kohno | Takayuki Ishida
Source: Inorganic Chemistry (article, 2020-07-09)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Odd–Even Effect on the Spin-Crossover Temperature in Iron(II) Complex Series Involving an Alkylated or Acyloxylated Tripodal Ligand In the context of magneto-structural study, a relatively short alkyl group was introduced to anionic spin-crossover (SCO) building blocks based on [Fe(py<sub>3</sub>CR)(NCS)<sub>3</sub>]<sup>-</sup>, where py<sub>3</sub>CR stands for tris(2-pyridyl)methyl derivatives. The linear alkyl and acyloxyl derivatives of Me<sub>4</sub>N[Fe(py<sub>3</sub>CR)(NCS)<sub>3</sub>] with R = C<sub><i>n</i></sub>H<sub>2<i>n</i>+1</sub> (<i>n</i> = 1-7) and C<sub><i>n</i></sub>H<sub>2<i>n</i>+1</sub>CO<sub>2</sub> (<i>n</i> = 1-6) were synthesized, and the magnetic study revealed that all the compounds investigated here exhibited SCO. The SCO temperature (<i>T</i><sub>1/2</sub>) varied in 289-338 K for the alkylated compounds, and those of the acyloxylated ones were lower with a narrower variation width (<i>T</i><sub>1/2</sub> = 216-226 K). The crystal structures of the former with <i>n</i> = 3, 4, and 5 and the latter with <i>n</i> = 1, 4, 5, and 6 were determined, and various molecular arrangements were characterized. There is no structural evidence for a molecular fastener effect. The plots on <i>T</i><sub>1/2</sub> against <i>n</i> displayed a pronounced odd-even effect; the SCO temperatures of the homologues with even <i>n</i> are relatively higher than those of the homologues with odd <i>n</i>. The odd-even effect on <i>T</i><sub>1/2</sub> may be related with the entropy difference across the SCO, rather than crystal field modification or intermolecular interaction. The present work will help molecular design to fine-tune <i>T</i><sub>1/2</sub> by means of simple chemical modification like alkylation and acyloxylation. Chemistry ; Alkylation ; Spin crossover ; Alkyl ; Context (archaeology) ; Crystal structure ; Ligand (biochemistry) ; Tripodal ligand ; Stereochemistry ; Crystallography ; Intermolecular force ; Pincer movement ; Medicinal chemistry ; Molecule ; Organic chemistry ; Catalysis Magnetism in coordination complexes ; Lanthanide and Transition Metal Complexes ; Metal-Catalyzed Oxygenation Mechanisms
Authors: Jianbo Zhao | Haifeng Yuan | Jiangcun Li | Wanzhen Bing | Weichuang Yang | Yingfan Liu | Junli Chen | Chengzhen Wei | Liming Zhou | Shaoming Fang
Source: ACS Omega (article, 2020-03-18)
Field: Chemistry — Organic Chemistry

Effects of Preparation Parameters of NiAl Oxide-Supported Au Catalysts on Nitro Compounds Chemoselective Hydrogenation Effects of preparation parameters of NiAl oxide-supported Au nanocatalysts on their performance in the chemoselective hydrogenation of nitro compounds were investigated. The deposition-precipitation method, low Au loading, and low Ni/Al molar ratio of the support contributed to the generation of small-sized Au nanoparticles. High catalytic properties were related to the small sizes of Au particles and appropriate basicity of supports. Accordingly, the 0.43% Au/NiAlO-2-500 (the Ni/Al molar ratio of the support = 2) showed high activity and excellent selectivity for nitro hydrogenation. It also showed good versatility for other nitro compounds and good recyclability. Interestingly, for the first time, this Au catalyst switched its selectivity to vinyl hydrogenation by mere regulation of the composition of the support (the Ni/Al molar ratio of the support = 4). The observed shift in selectivity was ascribed to the different adsorption behaviors of the nitro and vinyl group on Au nanocatalysts. It provides a novel and facile strategy to construct Au nanocatalysts with high activity and switchable selectivity for hydrogenation of nitro compounds by the fine tuning of preparation parameters. Nanomaterial-based catalyst ; Selectivity ; Catalysis ; Nitro ; Nanoparticle ; Materials science ; Nial ; Molar ratio ; Inorganic chemistry ; Chemistry ; Chemical engineering ; Organic chemistry ; Nanotechnology ; Intermetallic ; Alloy Nanomaterials for catalytic reactions ; Catalytic Processes in Materials Science ; Copper-based nanomaterials and applications
Authors: M. A. Gokul | Vrinda Narayanan | Atikur Rahman
Source: Nanotechnology (article, 2020-06-22)
Field: Materials Science — Materials Chemistry

Modulating flow near substrate surface to grow clean and large-area monolayer MoS <sub>2</sub> Chemical vapour deposition (CVD) is one of the most promising methods to synthesize monolayers of 2D materials like transition metal dichalcogenides (TMDs) over a large area with high film quality. Among many parameters that determine the growth of 2D materials, flow of precursor near the surface is one of the most sensitive conditions. In this study, we show how subtle changes in the flow near the substrate surface can affect the quality and coverage of the MoS<sub>2</sub> monolayer. We fine tune the flow of the carrier gas near the substrate under two extreme conditions to grow large area and clean monolayer. In the first study, we grew several centimetres long continuous monolayer under the condition, which generally produces monolayers of few tens of micrometres in size without tuning the flow on the substrate surface. In the second case, we got monolayer MoS<sub>2</sub> under the conditions meant for the formation of bulk MoS<sub>2</sub>.We achieved this by placing blockades on the substrate surface which helped in modifying the flow near them. Through simulation, we showed how the flow is affected near these blockades and used it as a guiding rule to grow patterned continuous MoS<sub>2</sub> monolayers. Detailed electrical and optical measurements were done to determine the quality of the as-grown samples. Our studies provide a way to obtain clean, large area monolayer of desired pattern by tuning the flow of precursor on the vicinity of the substrate surface even when the growth conditions in CVD are far from optimum. Monolayer ; Materials science ; Substrate (aquarium) ; Chemical vapor deposition ; Flow (mathematics) ; Deposition (geology) ; Transition metal ; Nanotechnology ; Chemical engineering ; Optoelectronics ; Chemistry ; Catalysis ; Organic chemistry ; Mechanics ; Geology 2D Materials and Applications ; MXene and MAX Phase Materials ; Graphene research and applications
Authors: Enlai Gao | Chunbo Zhang | Ke Zhou | Ning Wei
Source: ACS Applied Nano Materials (article, 2020-11-09)
Field: Materials Science — Materials Chemistry

Computational Study on Strain-Engineered Graphene Nanopores for Selective Gas Separation Precise fine-tuning of gas transport across nanopores is highly desirable in numerous industrial applications. In this work, we perform a computational study to investigate the strain engineering of gas permeation across the nanopores in graphene. First, we optimize the geometries of nanoporous graphene under uniaxial and biaxial strains using first-principles calculations and thus compute the potential energy barriers for gases (He, H2, O2, CO, CO2, and N2) across these nanopores. Afterward, the capability of the strain-engineered nanopores for selective gas separation is accessed based on the computations and transition state theory. Our calculations demonstrate that the strain-engineered nanopores exhibit remarkably improved permeance while maintaining significant selectivity for gas separation, yielding as high as 34 orders of magnitude increase in the gas transport rate. Finally, the underlying mechanism of the mechanosensitive nanopores for selective gas separation gas is revealed by providing insight into the atomic and electronic structures. Our findings shed light on strain engineering permeance and selectivity of nanopores in two-dimensional materials. Permeance ; Nanopore ; Graphene ; Nanoporous ; Materials science ; Gas separation ; Nanotechnology ; Work (physics) ; Permeation ; Chemical physics ; Membrane ; Chemistry ; Thermodynamics ; Physics Graphene research and applications ; Nanopore and Nanochannel Transport Studies ; Membrane Separation and Gas Transport
Authors: Samir Kumar Sarkar | Shilpa Eshwar Rao | Pakkirisamy Thilagar
Source: The Journal of Physical Chemistry B (article, 2020-09-25)
Field: Materials Science — Materials Chemistry

Molecular Conformational Effect on Optical Properties and Fluoride Induced Color Changes in Triarylborane–Vinylbithiophene–BODIPY Conjugates Three new triads [bis(mesityl)boryl (Mes<sub>2</sub>B)-vinylbithiophene-BODIPY] bearing zero (<b>1</b>), two (<b>2</b>), and four (<b>3</b>) methyl groups on the BODIPY core are synthesized, and their optical properties are reported. The vinyl linker between the thiophene rings in the spacer moiety improved the electronic communication between the boryl and BODIPY units. It displayed a bathochromic shift in the absorption and emission spectra compared to the Mes<sub>2</sub>B-bithiophene-BODIPY triad reported elsewhere. These compounds exhibit intriguing multiple-emission features due to an incomplete energy transfer from donor borane to the acceptor BODIPY unit. These compounds' photoluminescence color can be conveniently fine-tuned by fluoride binding at the coordinatively unsaturated tricoordinate boron center. Triad <b>3</b>, with a rigid molecular structure, showed a sharp emission band, whereas triads <b>1</b> and <b>2</b>, with flexible molecular structures, displayed broad emission bands with a robust bathochromic shift, ascribed to their excited state structural reorganizations. These triads selectively bind fluoride ions and show colorimetric responses, which can be seen with an unaided eye. DFT computational studies were performed to rationalize the optical signatures of these compounds. BODIPY ; Fluoride ; Conjugate ; Conformational change ; Chemistry ; Biophysics ; Materials science ; Photochemistry ; Stereochemistry ; Fluorescence ; Optics ; Biology ; Physics ; Inorganic chemistry Luminescence and Fluorescent Materials ; Polydiacetylene-based materials and applications ; Photochromic and Fluorescence Chemistry
Authors: Daniel Sethio | João B. L. Martins | Latévi Max Lawson Daku | Hans Hagemann | Elfi Kraka
Source: The Journal of Physical Chemistry A (article, 2020-01-30)
Field: Chemistry — Inorganic Chemistry

Modified Density Functional Dispersion Correction for Inorganic Layered MFX Compounds (M = Ca, Sr, Ba, Pb and X = Cl, Br, I) MFX (M = Ca, Ba, Sr, Pb and X = Cl, Br, I) compounds have received considerable attention due to their technological application as X-ray detectors, pressure sensors, and optical data storage materials, when doped with rare-earth ions. MFX compounds belong to the class of layered materials with a tetragonal Matlockite crystal structure, characterized by weakly stacked double-halide layers along the crystallographic <i>c</i>-axis. These layers predominantly determine phase transitions, elastic, and mechanical properties. However, the correct description of the lattice parameter <i>c</i> is a challenge for most standard DFT functionals, which tend to overestimate the lattice parameter <i>c</i>. Because of the weak interactions between the halide layers, dispersion-corrected functionals seem to be a better choice. We investigated 11 different inorganic layered MFX compounds for which experimental data are available, with standard and dispersion-corrected functionals to assess their performance in reproducing the lattice parameter <i>c</i>, structural, and vibrational properties of the MFX compounds. Our results revealed that these functionals do not describe the weak interactions between the halide layers in a balanced way. Therefore, we modified Grimme's popular DFT-D2 dispersion correction scheme in two different ways by (i) replacing the dispersion coefficients and van der Waals radii with those of noble gas atoms or (ii) increasing the van der Waals radii of the MFX atoms up to 40%. Comparison with the available experimental data revealed that the latter approach applied to the PBE (Perdew-Burke-Ernzerhof)-D2 functional with 30% increased van der Waals radii, which we coined PBE-D2* (<i>S</i><sub>rvdw</sub> 1.30) is best suited to fine-tune the description of the weak interlayer interactions in MFX compounds, thus significantly improving the description of their structural, vibrational, and mechanical properties. Work is in progress applying this new, computationally inexpensive scheme to other inorganic layered compounds and periodic systems with weakly stacked layers. van der Waals force ; Tetragonal crystal system ; Density functional theory ; Halide ; Lattice energy ; Dispersion (optics) ; Lattice constant ; Lattice (music) ; London dispersion force ; Chemistry ; Crystal structure ; Van der Waals radius ; Ion ; Materials science ; Computational chemistry ; Crystallography ; Inorganic chemistry ; Physics ; Molecule ; Quantum mechanics Inorganic Fluorides and Related Compounds ; Luminescence Properties of Advanced Materials ; Crystal Structures and Properties
Authors: Krunoslav Juraić | Davor Gracin | Matija Čulo | Željko Rapljenović | Jasper R. Plaisier | Aden Hodžić | Zdravko Siketić | Luka Pavić | Mario Bohač
Source: Materials (article, 2020-11-17)
Field: Materials Science — Materials Chemistry

Origin of Mangetotransport Properties in APCVD Deposited Tin Oxide Thin Films Transparent conducting oxides (TCO) with high electrical conductivity and at the same time high transparency in the visible spectrum are an important class of materials widely used in many devices requiring a transparent contact such as light-emitting diodes, solar cells and display screens. Since the improvement of electrical conductivity usually leads to degradation of optical transparency, a fine-tuning sample preparation process and a better understanding of the correlation between structural and transport properties is necessary for optimizing the properties of TCO for use in such devices. Here we report a structural and magnetotransport study of tin oxide (SnO<sub>2</sub>), a well-known and commonly used TCO, prepared by a simple and relatively cheap Atmospheric Pressure Chemical Vapour Deposition (APCVD) method in the form of thin films deposited on soda-lime glass substrates. The thin films were deposited at two different temperatures (which were previously found to be close to optimum for our setup), 590 °C and 610 °C, and with (doped) or without (undoped) the addition of fluorine dopants. Scanning Electron Microscopy (SEM) and Grazing Incidence X-ray Diffraction (GIXRD) revealed the presence of inhomogeneity in the samples, on a bigger scale in form of grains (80-200 nm), and on a smaller scale in form of crystallites (10-25 nm). Charge carrier density and mobility extracted from DC resistivity and Hall effect measurements were in the ranges 1-3 × 10<sup>20</sup> cm<sup>-3</sup> and 10-20 cm<sup>2</sup>/Vs, which are typical values for SnO<sub>2</sub> films, and show a negligible temperature dependence from room temperature down to -269 °C. Such behaviour is ascribed to grain boundary scattering, with the interior of the grains degenerately doped (i.e., the Fermi level is situated well above the conduction band minimum) and with negligible electrostatic barriers at the grain boundaries (due to high dopant concentration). The observed difference for factor 2 in mobility among the thin-film SnO<sub>2</sub> samples most likely arises due to the difference in the preferred orientation of crystallites (texture coefficient). Materials science ; Tin oxide ; Thin film ; Crystallite ; Dopant ; Electrical resistivity and conductivity ; Doping ; Optoelectronics ; Transparent conducting film ; Electron mobility ; Analytical Chemistry (journal) ; Nanotechnology ; Metallurgy ZnO doping and properties ; Gas Sensing Nanomaterials and Sensors ; Copper-based nanomaterials and applications
Authors: Jonathan M. Skelton
Source: Journal of Physics Energy (article, 2020-02-20)
Field: Materials Science — Materials Chemistry

Lattice dynamics of Pnma Sn(S<sub>1–x</sub>Se<sub>x</sub>) solid solutions: energetics, phonon spectra and thermal transport Abstract Alloying is widely used as a means to fine-tune the properties of thermoelectric materials by reducing the lattice thermal conductivity. However, the effects of compositional variation on the lattice dynamics of alloy systems are not well understood, due in part to the difficulty of building realistic first-principles models of structurally-complex solid solutions. This work builds on our previous study of Sn n (S 1– x Se x ) m solid solutions (Gunn et al 2019 Chem. Mater. 31 3672) to explore the lattice dynamics of the Pnma Sn(S 1– x Se x ) system, which has been widely studied for potential thermoelectric applications. We find that the vibrational internal energy and entropy have a large quantitative impact on the mixing free energy and are likely to be particularly important in alloy systems with competing phases. The thermodynamically-averaged phonon dispersions and density of states curves show that alloying preserves the structure of the low-frequency bands of modes associated with the Sn sublattice but broadens the high-frequency chalcogen bands into a near-continuous spectrum at the 50/50 mixed composition. This results in a general reduction in the phonon mode group velocities and an increase in the number of energy-conserving scattering channels for heat-carrying low-frequency modes, which is consistent with the decrease in thermal conductivity observed in experimental measurements. Finally, we discuss some of the limitations of our first-principles modelling approach and propose methods to address these in future studies. Phonon ; Solid solution ; Thermoelectric effect ; Thermoelectric materials ; Thermal conductivity ; Lattice (music) ; Materials science ; Condensed matter physics ; Alloy ; Scattering ; Thermodynamics ; Spectral line ; Thermal ; Chemical physics ; Chemistry ; Physics ; Quantum mechanics Advanced Thermoelectric Materials and Devices ; Thermal properties of materials ; Machine Learning in Materials Science
Authors: Hassnain Asgar | Sönke Seifert | Ivan Kuzmenko | Michael H. Bartl | Greeshma Gadikota
Source: Materialia (article, 2020-06-10)
Field: Materials Science — Materials Chemistry

Mechanistic insights into the colloidal assembly of mesoporous silica using in-operando cross-scale X-ray scattering and spectroscopic measurements Small-angle X-ray scattering ; Materials science ; Mesoporous silica ; Mesoporous material ; Fourier transform infrared spectroscopy ; Chemical engineering ; Nucleation ; Scattering ; Colloidal silica ; Attenuated total reflection ; Polymerization ; Colloid ; Polymer ; Organic chemistry ; Nanotechnology ; Chemistry ; Catalysis ; Composite material ; Optics Mesoporous Materials and Catalysis ; Clay minerals and soil interactions ; Zeolite Catalysis and Synthesis