jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: S. Suresh Bagavathy | A. Ramesh | Anand Krishnasamy | Senthur Pandian
Source: SAE technical papers on CD-ROM/SAE technical paper series (article, 2019-01-09)
Field: Materials Science — Materials Chemistry

Parametric Investigations on the Performance of Diesel Oxidation Catalyst in a Light Duty Diesel Engine - An Experimental and Modelling Study &lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;In order to comply with the stringent future emission mandates of automotive diesel engines it is essential to deploy a suitable combination of after treatment devices like diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and DeNox converter (Lean NOx Trap (LNT) or Selective Catalytic reduction (SCR) system). Since arriving at a suitable strategy through experiments will involve deploying a lot of resources, development of well-tuned simulation models that can reduce time and cost is important. In the first phase of this study experiments were conducted on a single cylinder light duty diesel engine fitted with a diesel oxidation catalyst (DOC) at thirteen steady state mode points identified in the NEDC (New European Driving cycle) cycle. Inlet and exit pressures and temperatures, exhaust emission concentrations and catalyst bed temperature were measured. A one dimensional simulation model was developed in the commercial software AVL BOOST. Eight of the experimental data sets from the 13 modes were taken for fine tuning the chemical kinetic rate parameters and friction factor of the model. The prediction of the model was validated at the remaining five experimental data points keeping the kinetic and friction parameters the same. The model could predict the conversion efficiency and pressure drop across the DOC within 1.5%. The influence of the length and diameter of the DOC was studied using the model which indicated that increasing the diameter is more effective than increasing the length based on the conversion efficiency and pressure drop. It was also found that increasing the diameter will enable the reduction in the DOC volume without any sacrifice in the conversion efficiency while the pressure drop can also be reduced simultaneously. The developed model can be used to size the DOC based given the requirements of space and conversion efficiency.&lt;/div&gt;&lt;/div&gt; Diesel fuel ; Diesel engine ; Automotive engineering ; Parametric statistics ; Diesel particulate filter ; Catalysis ; Computer science ; Environmental science ; Engineering ; Chemistry ; Mathematics Catalytic Processes in Materials Science ; Biodiesel Production and Applications ; Catalysis and Oxidation Reactions
Authors: M. Heuken | Annika Grundmann | H. Kalisch | Andrei Vescan
Source:  (article, 2019-03-04)
Field: Materials Science — Materials Chemistry

Hydride-free MOCVD of 2D MoS2 and 2D WS2 for optoelectronic applications (Conference Presentation) The 2D transition metal dichalcogenides MoS2 and WS2 have attracted great interest due to their unique (opto)electronic properties. For their fabrication on an industrial scale, high-productivity MOCVD systems are most suitable because of precisely controlled precursor fluxes, advanced temperature control and superior homogeneity. Here, we report on the development of an MOCVD process for 2D WS2 and 2D MoS2 on sapphire (0001) substrates in a commercial AIXTRON planetary hot-wall reactor in 10 × 2" configuration. Molybdenum hexacarbonyl (MCO), tungsten hexacarbonyl (WCO) and di-tert-butyl sulfide (DTBS) are used as sources, respectively. A one-step process was developed to control nucleation and lateral growth of both 2D materials at 30 hPa total pressure in an N2 atmosphere. It was found that a fine-tuned S-to-metal ratio can inhibit the parasitic deposition of carbon contaminations. Investigations of the influence of deposition temperature on lateral growth of WS2 confirm previous findings for MoS2. The optimum growth temperature for MoS2 and WS2 is 845 °C. WS2 deposition experiments show that in order to achieve a fully coalesced 2D film, it is necessary to supply a sufficient amount of WCO, the limiting species during WS2 growth. Increasing the WCO flow from 1 nmol/min to 20 nmol/min raises the total substrate coverage from 2.5 % to >50 % in 10 h processes. Extending gradually the growth time to 20 h results in deposition of fully coalesced WS2 samples without carbon contaminations and only sparse bilayer nucleation. Moreover, the fully coalesced WS2 samples exhibit strong PL signals. Metalorganic vapour phase epitaxy ; Nucleation ; Materials science ; Chemical vapor deposition ; Chemical engineering ; Tungsten ; Optoelectronics ; Sapphire ; Fabrication ; Nanotechnology ; Chemistry ; Metallurgy ; Epitaxy ; Layer (electronics) ; Optics ; Laser 2D Materials and Applications ; Gas Sensing Nanomaterials and Sensors ; ZnO doping and properties
Authors: Zi‐Han Li | Yuan‐Qi Zhai | Weipeng Chen | You‐Song Ding | Yan‐Zhen Zheng
Source: ChemRxiv (preprint, 2019-08-14)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Air-Stable Hexagonal Bipyramidal Dysprosium(III) Single-Ion Magnets with Nearly Perfect D6h Local Symmetry Local eight-coordination of the Dy(III) with D6h symmetry receives much expectation for high-performance single-molecule magnets (SMMs) due to the simultaneous fulfillment of the magnetic axiality and high coordination number (a requisite for the air stability). But the experimental realization is challenging due to the required restriction of six coordination atoms in the equatorial plane of the hexagonal-bipyramid, which is usually too crowded for the central Dy(III) ion. Here we show by using the hexaaza macrocyclic Schiff base ligand and fine-tuning the axial alkoxide/phenol type ligands, a family of hexagonal-bipyramidal Dy(III) complexes, namely [DyIII(L)(Cl)2(H2O/CH3OH)]Cl 1, [DyIII(L)(C6F5O)2(H2O)](BPh4)·2, [DyIII(L)(PhO)2](BPh4) 3, [DyIII(L)(4-MeO-PhO)2](BPh4) 4, [DyIII(L)(naPhO)2](BPh4) 5 and [DyIII(L)(Ph3SiO)2](BPh4) 6 , can be isolated. Among them, complexes 3, 4 and 5 possess nearly perfect D6h local symmetry. Complex 4 shows the highest effective magnetic reversal barrier 1338 K and an open hysteresis temperature 6 K at the field sweeping rate of 1.2 mT/s, which represents a new record for D6h SMMs. Dysprosium ; Crystallography ; Chemistry ; Coordination sphere ; Pentagonal bipyramidal molecular geometry ; Bipyramid ; Trigonal bipyramidal molecular geometry ; Hexagonal crystal system ; Ion ; Crystal structure ; Inorganic chemistry Magnetism in coordination complexes ; Porphyrin and Phthalocyanine Chemistry ; Lanthanide and Transition Metal Complexes
Authors: Alyson Silva
Source: Western CEDAR (Western Washington University) (article, 2019-01-01)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Multifunctional Microgels for Nanoparticle-Based Detection Methodologies In this study, pH-responsive microgel particles, comprised of 2-vinyl pyridine (P2VP) and styrene (PS), are explored as scaffolds to assemble metallic nanoparticles (NPs) for ultrasensitive detection strategies. Microgel particles serve as size-tunable scaffolds to assemble metal (silver or gold) NPs for surface-enhanced Raman scattering (SERS) vibrational spectroscopy. The high sensitivity of SERS arises from the enormous enhancement of the Raman scattering cross sections of molecules adsorbed to roughened metal surfaces, such as metal NPs. Using a sterically stabilized latex of random copolymers of PS and P2VP (PSxP2VPy), this polymer is capable of transitioning to a microgel state through acid-base titration. This effect can be used to manipulate the interparticle spacing between adsorbed metal NPs in order to optimize SERS enhancement. The size of these metal NPs, usually gold or silver (Au NPs or Ag NPs), can also be tuned to further optimize SERS enhancement. These microgel-NP composites are characterized and their pH-responsive behavior is demonstrated to be reversible in both bulk SERS and single-particle SERS analyses. Nanoparticle ; Nanotechnology ; Computer science ; Materials science Gold and Silver Nanoparticles Synthesis and Applications ; Biosensors and Analytical Detection ; Dendrimers and Hyperbranched Polymers
Authors: Samuel Tetteh
Source: Journal of Chemistry (article, 2019-12-24)
Field: Chemistry — Organic Chemistry

A Computational and Structural Database Study of the Metal-Carbene Bond in Groups IA, IIA, and IIIA Imidazol-2-Ylidene Complexes Imidazol-2-ylidenes are important N-heterocyclic carbenes which have become universal ligands in organometallic and coordination chemistry. Generally classified as σ -donor ligands, these compounds have been used to stabilize various metal complexes which hitherto were less stable in their catalytic processes. Herein, the number and distribution of group IA, group IIA, and group IIIA metal-imidazol-2-ylidene complexes retrieved from the Cambridge Structural Database (CSD) are assessed. The data showed that the mean M-C carbene bond length increases with increasing ionic size but is similar across each diagonal. Dominant factors such as Lewis acidity and electrostatic attractions were found to control the bonding modes of the respective ions. Generally, the metal ions show preference for tetrahedral coordination with larger cations forming complexes with higher coordination numbers. For their high number of entries (101), tetrahedrally coordinated boron complexes with various electron withdrawing and electron donating groups were studied computationally at the DFT/B3LYP level of theory. The strength of the B-C carbene bond was found to depend on steric interactions between bulky groups on the borenium atom and substituents on the N-positions of the imidazol-2-ylidene ligand. This observation was further confirmed by estimation of the binding energy, natural charge, and the electron distribution in the B-C carbene bond. Chemistry ; Carbene ; Steric effects ; Ligand (biochemistry) ; Crystallography ; Ionic bonding ; Metal ; Bond length ; Coordination number ; Computational chemistry ; Catalysis ; Ion ; Stereochemistry ; Crystal structure ; Organic chemistry N-Heterocyclic Carbenes in Organic and Inorganic Chemistry ; Catalytic Cross-Coupling Reactions ; Synthetic Organic Chemistry Methods
Authors: Yachu Du | Kyle N. Plunkett
Source: ChemRxiv (preprint, 2019-08-02)
Field: Chemistry — Organic Chemistry

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.&lt;br&gt; Chromophore ; Dimer ; Monomer ; Polycyclic aromatic hydrocarbon ; Aromaticity ; Chemistry ; Photochemistry ; Redox ; Planar ; Ring (chemistry) ; Aromatic hydrocarbon ; Hydrocarbon ; Molecule ; Organic chemistry ; Polymer ; Computer science Synthesis and Properties of Aromatic Compounds ; Photochemistry and Electron Transfer Studies
Authors: Ana Bornadiego | Jesús Dı́az | Carlos Fernández Marcos
Source: PeerJ Organic Chemistry (article, 2019-10-15)
Field: Chemistry — Organic Chemistry

Direct multicomponent synthesis of benzocoumarins A straightforward and versatile protocol for the synthesis of dibenzo[ b,d ]pyran-6-ones from readily available 3-carbonylcoumarins is reported. Our strategy is based on a reaction cascade of successive [4+1] and [4+2] cycloadditions that occur in one single operation. This work illustrates the unprecedented use of a multicomponent reaction of isocyanides for the preparation of this biologically relevant type of compounds. Notably, in this highly convergent and atom-economic process, one new single and two new double carbon-carbon bonds are formed in a simple synthetic operation. Cascade ; Pyran ; Combinatorial chemistry ; Carbon atom ; Chemistry ; Simple (philosophy) ; Computer science ; Biochemical engineering ; Organic chemistry ; Alkyl ; Engineering Multicomponent Synthesis of Heterocycles ; Oxidative Organic Chemistry Reactions ; Synthesis of Organic Compounds
Authors: Elvira Vidović | Fabio Faraguna | Ante Jukić
Source: Chemical and Biochemical Engineering Quarterly (article, 2019-01-01)
Field: Materials Science — Biomaterials

Miscibility and Properties of Low Molecular Mass Poly(L-lactide) and Poly(methyl methacrylate) Blends Modification of biobased PLLA properties by mixing with conventional PMMA via melt mixing in Brabender mixer was performed. Despite negative results of theoretical miscibility calculations by the group contribution approach of Coleman, Graf and Painter,&lt;br /&gt; homogeneous blend morphologies were prepared as recorded with scanning electron&lt;br /&gt; microscopy (SEM). All PLLA/PMMA blends displayed a single glass transition temperature. With increasing fraction of PMMA in blends, the increase in Tg from 58 °C to 93 °C was recorded by differential scanning calorimetry (DSC). Added PMMA improved&lt;br /&gt; mechanical properties, while the flexibility of PLLA/PMMA blends gradually decreased as revealed by DMA measurements. Miscibility ; Differential scanning calorimetry ; Materials science ; Glass transition ; Scanning electron microscope ; Methyl methacrylate ; Poly(methyl methacrylate) ; Polymer chemistry ; Mass fraction ; Chemical engineering ; Mixing (physics) ; Dynamic mechanical analysis ; Polymer blend ; Composite material ; Copolymer ; Polymer ; Thermodynamics biodegradable polymer synthesis and properties ; Additive Manufacturing and 3D Printing Technologies ; Microplastics and Plastic Pollution
Authors: Julius Hornung
Source: mediaTUM – the media and publications repository of the Technical University Munich (Technical University Munich) (article, 2019-01-01)
Field: Chemistry — Inorganic Chemistry

Hume-Rothery inspired Complexes and Clusters as Molecular Models for Intermediates in Heterogeneous Catalysis A conceptual link between Hume-Rothery inspired complexes/clusters and solid-state intermetallic catalysts with special emphasis on the heterogeneous semi hydrogenation of alkynes is presented. Quantum chemical calculations on the DFT level of theory reveal that [Ni(M'R)n(UHC)4-n] (M’ = Al, Ga, Zn, R = Cp*/Me, UHC = unsaturated hydrocarbons) complexes represent potential molecular models for substrate binding on related intermetallic surfaces. Furthermore, synthetic approaches towards such compounds are presented. Intermetallic ; Catalysis ; Substrate (aquarium) ; Quantum chemical ; Heterogeneous catalysis ; Computational chemistry ; Chemistry ; Materials science ; Chemical physics ; Molecule ; Organic chemistry Asymmetric Hydrogenation and Catalysis ; Organometallic Complex Synthesis and Catalysis ; Surface Chemistry and Catalysis
Authors: Rosita Diana | Angela Tuzi | Barbara Panunzi | Antonio Carella | Ugo Caruso
Source: Acta Crystallographica Section E Crystallographic Communications (article, 2019-05-24)
Field: Chemistry — Inorganic Chemistry

Crystal structures of butyl 2-amino-5-hydroxy-4-(4-nitrophenyl)benzofuran-3-carboxylate and 2-methoxyethyl 2-amino-5-hydroxy-4-(4-nitrophenyl)benzofuran-3-carboxylate The title benzo-furan derivatives 2-amino-5-hy-droxy-4-(4-nitro-phen-yl)benzo-furan-3-carboxyl-ate (BF1), C<sub>19</sub>H<sub>18</sub>N<sub>2</sub>O<sub>6</sub>, and 2-meth-oxy-ethyl 2-amino-5-hy-droxy-4-(4-nitro-phen-yl)benzo-furan-3-carboxyl-ate (BF2), C<sub>18</sub>H<sub>16</sub>N<sub>2</sub>O<sub>7</sub>, recently attracted attention because of their promising anti-tumoral activity. BF1 crystallizes in the space group <i>P</i> . BF2 in the space group <i>P</i>21/<i>c</i>. The nitro-phenyl group is inclined to benzo-furan moiety with a dihedral angle between their mean planes of 69.2 (2)° in BF1 and 60.20 (6)° in BF2. A common feature in the mol-ecular structures of BF1 and BF2 is the intra-molecular N-H⋯O<sub>carbon-yl</sub> hydrogen bond. In the crystal of BF1, the mol-ecules are linked head-to-tail into a one-dimensional hydrogen-bonding pattern along the <i>a</i>-axis direction. In BF2, pairs of head-to-tail hydrogen-bonded chains of mol-ecules along the <i>b</i>-axis direction are linked by O-H⋯O<sub>meth-oxy</sub> hydrogen bonds. In BF1, the butyl group is disordered over two orientations with occupancies of 0.557 (13) and 0.443 (13). Carboxylate ; Hydrogen bond ; Chemistry ; Benzofuran ; Intramolecular force ; Molecule ; Stereochemistry ; Dihedral angle ; Crystallography ; Moiety ; Crystal structure ; Crystal (programming language) ; Organic chemistry Crystal structures of chemical compounds ; Synthesis and Reactivity of Heterocycles ; Metal complexes synthesis and properties
Authors: Suzanne M. Jansze
Source: Infoscience (Ecole Polytechnique Fédérale de Lausanne) (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

Molecular nanostructures based on polyfunctional clathrochelate complexes This thesis describes the design and synthesis of clathrochelate metalloligands for the construction of molecular nanostructures. The low synthetic effort, versatility and stability of the clathrochelate metalloligands makes them particularly suited to the construction of coordination structures. Chapter 2 shows it is possible to control the geometry and the composition of metallasupramolecular assemblies via the aspect ratio of their ligands. Functionalized clathrochelate complexes with variable aspect ratios were used as rod-like metalloligands. Cubic FeII8L12 cages were obtained from a metalloligand with an intermediate aspect ratio. By increasing the length or by decreasing the width of the ligand, the self-assembly process resulted in the clean formation of tetrahedral FeII4L6 cages instead of cubic cages. Chapter 3 describes a simple one-step protocol, which allows large bipyridyl functionalized double clathrochelate metalloligands with an overall bent shape to be synthesized from easily accessible and/or commercially available starting materials. The ligands were used to construct PdII2L4-type coordination cages of unprecedented size. Furthermore, evidence is provided that these cages may be stabilized by close intramolecular packing of lipophilic ligand side chains. In Chapter 4, even larger triple clathrochelate metalloligands were used to form two PdII6L8-type coordination cages. With molecular weights of more than 15 kDa and Pd···Pd distances of up to 4.2 nm, these complexes are among the largest palladium cages described to date. In the 5th chapter, the stability of five different [Pdn(N donor)m]2n+ assemblies was examined by performing disassembly experiments with pyridine and with trifluoroacetic acid. Pyridine-induced disassembly was found to be most pronounced for Pd complexes containing N-donor ligands of low basicity. At the same time, these assemblies displayed high acid resistance. The contrasting stability in the presence of acid or pyridine can be used for the pH-controlled switching between different metallosupramolecular structures. The final research section (Chapter 6) shows that the addition of a metastable-state photoacid to solutions containing metal-ligand assemblies renders the systems light responsive. Upon irradiation, proton transfer from the photoacid to the ligand is observed, resulting in disassembly of the metallasupramolecular structure. In the dark, the process is fully reversed. Light-induced switching was demonstrated for six different metal ligand assemblies containing PdII, PtII or RuII complexes and bridging polypyridyl ligands. The methodology allows the liberation of guest molecules using light as a stimulus. Nanostructure ; Polymer science ; Philosophy ; Chemistry ; Nanotechnology ; Materials science Porphyrin and Phthalocyanine Chemistry ; Inorganic Fluorides and Related Compounds ; Supramolecular Self-Assembly in Materials
Authors: Natasha Maurmann | Juliana Girón Bastidas | Bruna Borstmann Jardim Leal | Patrícia Pranke
Source: International Journal of Advances in Medical Biotechnology - IJAMB (article, 2019-03-01)
Field: Materials Science — Biomaterials

3D electrospinning used in medical materials Electrospinning (ES) is an interesting and efficient technique for biomedical use. This is a method used for the fabrication of polymer fibers used in tissue engineering (TE). The electrospun nano- and microfibers biomaterial, called scaffolds, are also used for regenerative medicine. The aim of the present mini-review is to present methods used to fabricate 3D fibers by electrospinning and their applications in TE. Also, discussed here are issues regarding the electrospinning limitations and research challenges. Electrospinning ; Microfiber ; Materials science ; Biomaterial ; Nanotechnology ; Fabrication ; Tissue engineering ; Regenerative medicine ; Polymer ; Biomedical engineering ; Composite material ; Engineering ; Chemistry ; Medicine Electrospun Nanofibers in Biomedical Applications ; Tissue Engineering and Regenerative Medicine ; Silk-based biomaterials and applications
Authors: Amir Joorab Doozha | Kristin M. Poduska
Source: Analytical Methods (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

Graphite oxidation chemistry is relevant for designing cleaning strategies for radiocarbon dating samples We demonstrate that mixtures of graphite and lab-oxidized graphenic carbon materials can be separated into three individual components (graphite, graphene/graphite oxide and oxidative debris) by a series of aqueous treatments. Graphite ; Graphene ; Radiocarbon dating ; Carbon fibers ; Aqueous solution ; Oxide ; Graphite oxide ; Chemistry ; Nanotechnology ; Chemical engineering ; Environmental chemistry ; Materials science ; Organic chemistry ; Geology ; Composite material ; Paleontology ; Composite number ; Engineering Graphene research and applications ; Graphite, nuclear technology, radiation studies ; Ion-surface interactions and analysis
Authors: C. Antonio Hernández | Edith Osorio‐de‐la‐Rosa | Raúl Urteaga | R.R. Koropecki | José Alberto Alvarado | H. Juárez
Source: Journal of nano research (article, 2019-02-27)
Field: Materials Science — Materials Chemistry

Optical Losses in Hybrid Microcavity Based in Porous Semiconductors and its Application as Optic Chemical Sensor In this study the experimental and theoretical optical analysis of a hybrid microcavity (HM) based in porous silicon (PS) and nanoporous anodic alumina (NAA) are presented. The microcavity was centered in the visible region at 760 nm. Distributed Bragg reflector (DBR) was obtained using galvanostatic anodizing method and while NAA by the two-step anodization technique. From SEM micrographs the HM different regions are observed. HM optical characterization in the visible region was done, considering two different light sources, point and non-point respectively. These results reveal a decrease in the quality factor (Q) from 350 to 190 when the source is exchanged; this behavior has been mainly attributed to the light scattering at NAA. Furthermore, it was possible to study Q change, through transmittance simulation using the transfer matrix and Landau-Lifshitz-Looyenga theoretical methods. When a point light source is used, there are no optical losses making possible to sense 1% of analyte resulting in a 0.29 nm redshift of the resonant peak. According with these results we propose to apply the HM as chemical optic sensor. Materials science ; Nanoporous ; Transfer-matrix method (optics) ; Anodizing ; Transmittance ; Optoelectronics ; Semiconductor ; Distributed Bragg reflector ; Visible spectrum ; Optics ; Light scattering ; Scattering ; Wavelength ; Nanotechnology ; Composite material ; Aluminium Anodic Oxide Films and Nanostructures ; Silicon Nanostructures and Photoluminescence ; Nanowire Synthesis and Applications