jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Yongliang Zhong | Quanyou Feng | xiaoqian wang | Lei Yang | Rong Tong
Source: ChemRxiv (preprint, 2020-10-06)
Field: Materials Science — Polymers and Plastics

Photocatalyst-Independent Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides: Stereocontrol and Mechanism Photoredox ring-opening polymerization of O-carboxyanhydrides allows for the synthesis of polyesters with precisely controlled molecular weights, molecular weight distributions, and tacticities. While powerful, obviating the use of precious metal-based photocatalysts would be attractive from the perspective of simplifying the protocol and enabling unexpected reactivity. Herein, we report the Co and Zn catalysts that are activated by external light to mediate efficient ring-opening polymerization of O-carboxyanhydrides, without the use of exogenous precious metal-based photocatalysts. Our methods allow for the synthesis of isotactic polyesters with high molecular weights (>200 kDa) and narrow molecular weight distributions (Mw/Mn < 1.1). Mechanistic studies indicate that light activates the oxidative status of CoIII intermediate that is generated from the regioselective ring-opening of the O-carboxyanhydride. We also demonstrate that the use of Zn or Hf complexes together with Co can allow for stereoselective photoredox ring-opening polymerizations of multiple racemic O-carboxyanhydrides to synthesize syndiotactic and stereoblock copolymers, which vary widely in their glass transition temperatures. Polymerization ; Ring-opening polymerization ; Chemistry ; Polyester ; Ring (chemistry) ; Copolymer ; Regioselectivity ; Photocatalysis ; Polymer chemistry ; Combinatorial chemistry ; Polymer ; Photochemistry ; Catalysis ; Organic chemistry Conducting polymers and applications ; Polyoxometalates: Synthesis and Applications ; Carbon dioxide utilization in catalysis
Authors: Haider Almkhelfe
Source: Iraqi Journal of Nanotechnology (article, 2020-12-19)
Field: Materials Science — Materials Chemistry

Controlling the Tube Diameter of SWCNTs Using High Melting Point Promotors A particular control of the diameter of Single Walled-Carbon Nanotube (SWCNT) using Chemical vapor Deposition (CVD) system will enable many promising applications in different fields. Here we demonstrate the growth of SWCNT with good control of diameter (1.5 nm ± 0.7) using a high melting temperature metal (Ru) as a catalyst promotor with the main catalyst Co at 850˚C via CVD. We hypothesis that using high melting temperature metal as a promotor, like Ru can limit the mobility/change in the shape of the formed metal nanoparticles and eventually decrease the effects of Ostwald ripening (OR). FTS-GP is used as a carbon precursor. The results have been verified by high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM) and multi-excitation Raman. Chemical vapor deposition ; Materials science ; Carbon nanotube ; Raman spectroscopy ; Nanotechnology ; Catalysis ; Melting point ; Ostwald ripening ; Transmission electron microscopy ; Chemical engineering ; Nanoparticle ; Metal ; Chemistry ; Composite material ; Metallurgy ; Optics ; Organic chemistry Carbon Nanotubes in Composites ; Graphene research and applications ; Fullerene Chemistry and Applications
Authors: Lemi Türker
Source: Earthline Journal of Chemical Sciences (article, 2020-04-14)
Field: Chemistry — Organic Chemistry

3(4)-Amino-4(3)-nitro-1,2,5-oxadiazole-2-oxides and their Ring-opened Isomers-A DFT Treatment Amino and nitro substituted 1,2,5-oxadiazole-2-oxide isomers and their ring-opened nitroso forms have been subjected to density functional treatment at the level of B3LYP/6-311++G(d,p). The transition states for the ring opening processes are obtained and the corresponding activation energies have been calculated. Also, 1,3- and 1,5-proton tautomerism yielding imine, oxime and aci forms are investigated. For all the structures, the stabilities, the HOMO, LUMO energies and the interfrontier molecular orbital energy gaps are obtained and the effects of substituents (NH2 and NO2) are discussed. Oxadiazole ; Nitroso ; Ring (chemistry) ; Chemistry ; Tautomer ; Nitro ; Imine ; HOMO/LUMO ; Nitroso Compounds ; Oxime ; Computational chemistry ; Molecular orbital ; Density functional theory ; Medicinal chemistry ; Stereochemistry ; Organic chemistry ; Molecule ; Catalysis Structural and Chemical Analysis of Organic and Inorganic Compounds ; Chemical Reaction Mechanisms ; Chemical Reactions and Mechanisms
Authors: Thomas Lorenz
Source: Online Publication Service of Würzburg University (Würzburg University) (article, 2020-12-18)
Field: Chemistry — Organic Chemistry

Conjugated Polymers with BN Units in the Main Chain In recent years <mi>PI</mi>-conjugated organoboron polymers and BN-doped polycyclic aromatic hydrocarbons have attracted a lot of interest due to their great potential in organic electronics. However, there are only few known examples of conjugated polymers with BN units in their main chain. Within this work silazane cleavage with silicon-boron (Si/B) exchange for the synthesis of a novel class of inorganic-organic hybrid polymers is demonstrated. These polymers consist of alternating NBN and para-phenylene units in the main chain. Photophysical studies and TD-DFT calculations for the polymer and molecular model systems were carried out, revealing a low extent of <mi>PI</mi>-conjugation across the NBN units. The new polymers can be used as macromolecular polyligands by a cross-linking reaction with a ZrIV compound. In the next chapter the synthesis and characterization of the first poly(p-phenylene iminoborane) is presented. This novel inorganic–organic hybrid polymer can be described as a BN analogue of the well-known poly(p-phenylene vinylene) (PPV) and is also accessible using the previously described Si/B exchange as synthetic strategy. Photophysical investigations and TD-DFT calculations on the polymer and corresponding model oligomers provide clear evidence for <mi>PI</mi>-conjugation across the B=N units and extension of the conjugation path with increasing chain length. Furthermore, a possible application of Si/B exchange for the synthesis of polysulfoximines was explored. Herein, diaryl sulfoximines and a p-phenylene bisborane serve as building blocks for new BN- and BO-doped alternating inorganic–organic hybrid copolymers. While the BN-linked polymers were accessible by a facile silicon/boron exchange protocol, the synthesis of polymers with B–O linkages in the main chain is achieved by salt elimination. In the last chapter the concept of Si/B exchange was investigated for the synthesis of BP-linked oligomers. Herein oligomers with sterically less demanding substituents (substituents: 2,4,6-trimethylphenyl or 2,4,6-tri-iso-propylphenyl) at the phosphorus are accessible using Si/B exchange, but the oligomer with Mes* (2,4,6-tri-tert-butylphenyl) as substituent needed a salt elimination pathway to give the desired product. Experimental data and theoretical investigations indicate, that the P-substituent has a high influence on the geometry of the phosphorus center and therefore on the possible conjugation over the BP units. Conjugated system ; Polymer ; Materials science ; Phenylene ; Copolymer ; Condensation polymer ; Polymer chemistry ; Organic electronics ; Macromolecule ; Chemistry ; Transistor Organoboron and organosilicon chemistry ; Conducting polymers and applications ; Luminescence and Fluorescent Materials
Authors: Celia Idelson | Leah Webster | Tobias Krämer | F. Mark Chadwick
Source: ChemRxiv (preprint, 2020-08-19)
Field: Chemistry — Organic Chemistry

Asymmetric Bis-PNP Pincer Complexes of Zirconium and Hafnium - a Measure of Hemilability Asymmetrically-bound pyrrollide-based bis-PNP pincer complexes of zirconium and hafniumhave been formed. The [κ2-PNPPh][κ3-PNPPh]MCl2 species are in direct contrast to previouszirconium PNP pincer complexes. The pincer ligands are fluxional in their binding and theenergy barrier for exchange has been approximated using VT-NMR spectroscopy and theresult validated by DFT calculations. Pincer movement ; Hafnium ; Zirconium ; Chemistry ; Crystallography ; Inorganic chemistry ; Catalysis ; Organic chemistry Organometallic Complex Synthesis and Catalysis ; Metal complexes synthesis and properties ; Magnetism in coordination complexes
Authors: Riccardo Marin | Daniel Jaque | Antonio Benayas
Source: Zenodo (CERN European Organization for Nuclear Research) (article, 2020-12-23)
Field: Materials Science — Materials Chemistry

Switching to the brighter lane: pathways to boost the absorption of lanthanide-doped nanoparticles Lanthanide-doped nanoparticles (LNPs) are spreadily colonizing several fields, such as biological (multimodal) imaging, photodynamic therapy, volumetric encoding displays, and photovoltaics. Yet, the electronic transitions of lanthanide ions obey the Laporte rule, which dramatically cripples their light absorption capabilities. As a result, the brightness of these species is severely curbed. This intrinsically poor absorption capabilities is the fundamental obstacle for untapping the full potential of LNPs in several the fields. Among others, the three most promising physicochemical approaches challenge arisen during the last two decades to face the challenge of increasing LNP absorption are plasmonic enhancement, organic-dye sensitization, and coupling with semiconductors. The fundamental basis, remarkable highliths, and comparative achievements of each of these pathways for absorption betterment are critically discussed in this minireview, also incuding a detailed discussion of the exciting perspectives ahead. Lanthanide ; Doping ; Nanoparticle ; Absorption (acoustics) ; Materials science ; Chemistry ; Nanotechnology ; Optoelectronics ; Ion ; Composite material ; Organic chemistry Advanced Nanomaterials in Catalysis ; Catalytic Processes in Materials Science ; Quantum Dots Synthesis And Properties
Authors: Péter Kisszékelyi | S. Nagy | Zsuzsanna Fehér | Péter Huszthy | József Kupai
Source: Magyar kémiai folyóirat, Kémiai közlemények (article, 2020-01-01)
Field: Chemistry — Organic Chemistry

Membránszűréssel visszaforgatható homogén organokatalizátorok előállítása és alkalmazása Humanities ; Art Inorganic and Organometallic Chemistry
Authors: Eric J. Moore
Source: UR Research (University of Rochester) (article, 2020-01-01)
Field: Chemistry — Organic Chemistry

Design of artificial and thermostable myoglobin-basedbiocatalysts for carbene transfer reactions Thesis (Ph. D.)--University of Rochester. Department of Chemistry, 2020. Myoglobin ; Chemistry ; Carbene ; Cofactor ; Heme ; Metalloprotein ; Cyclopropanation ; Stereochemistry ; Combinatorial chemistry ; Catalysis ; Organic chemistry ; Enzyme Cyclopropane Reaction Mechanisms ; Catalytic Cross-Coupling Reactions
Authors: Laura Abad Galán | Nadège Hamon | Christophe Nguyen | Enikő Molnár | János Kiss | Jonathan Mendy | Kamel Hadj‐Kaddour | Mélanie Onofre | György Trencsényi | Cyrille Monnereau | Maryline Beyler | Gyula Tircsó | Magali Gary‐Bobo | Olivier Maury | Raphaël Tripier
Source: ChemRxiv (preprint, 2020-11-17)
Field: Materials Science — Materials Chemistry

Design of Polyazamacrocyclic Gd3+ Theranostic Agent Combining MRI and Two-Photon PDT New “all-in-one” theranostic systems, combining a magnetic resonance imaging (MRI) contrast agent with a biphotonic photodynamic therapy (2P-PDT) photosensitiser generating cytotoxic singlet oxygen, were envisaged and synthesised. They are based on azamacrocycles, regiospecifically functionalised by two-photon PDT π-conjugated dibromobenzene-picolinate photosensitisers and acetate, able to complex gadolinium(III) and allow an MRI signal. Our approach was to use two different macrocyclic platforms, tacn and pyclen, for modulating simultaneously the structures, properties and solubility of the complexes. Photophysical properties of the ligands and their gadolinium(III) complexes were fully investigated. The Gd3+-pyclen derivative showed the best water solubility and the greatest value of singlet oxygen generation of the series with φΔ = 0.53 enabling in vitro studies. The biological PDT activity under mono and biphotonic excitation was evaluated in human breast cancer cells (MCF-7). While a very low dark toxicity was observed, an almost total cell death was induced after only 3 successive irradiations of 1.57 sec. Finally, its relaxivity was measured in a DMSO/H2O solvents mixture with r1p = 11.21 and r2p = 24.60 mM-1s -1 at 3.0 T and T1- and T2-weighted phantom MR images were obtained highlighting a first generation of “all-in-one” PDT/MRI theranostic agents. Singlet oxygen ; Photodynamic therapy ; Gadolinium ; Chemistry ; Magnetic resonance imaging ; Two-photon excitation microscopy ; Conjugated system ; Nuclear magnetic resonance ; Photochemistry ; Materials science ; Fluorescence ; Oxygen ; Organic chemistry ; Polymer ; Medicine ; Optics ; Radiology Lanthanide and Transition Metal Complexes ; Photodynamic Therapy Research Studies ; Nanoplatforms for cancer theranostics
Authors: Titus Masese | Yoshinobu Miyazaki | Josef Rizell | Godwill Mbiti Kanyolo | Terüo Takahashi | Miyu Ito | Hiroshi Senoh | Tomohiro Saito
Source: ChemRxiv (preprint, 2020-11-16)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Unveiling Structural Disorders in Honeycomb Layered Oxide: Na2Ni2TeO6 Honeycomb layered oxides have garnered tremendous research interest in a wide swath of disciplines owing to not only the myriad physicochemical properties they exhibit, but also due to their rich crystal structural versatility. Herein, a comprehensive crystallographic study of a sodium-based Na2Ni2TeO6 honeycomb layered oxide has been performed using atomic-resolution transmission electron microscopy, elucidating a plethora of atomic arrangement (stacking) disorders in the pristine material. Stacking disorders in the arrangement honeycomb metal slab layers (stacking faults) occur predominantly perpendicular to the slabs with long-range coherence length and enlisting dislocations in some domains. Moreover, the periodic arrangement of the distribution of alkali atoms is altered by the occurrence of stacking faults. The multitude of disorders innate in Na2Ni2TeO6 envisage broad implications in the material functionalities of related honeycomb layered oxide materials and will bolster renewed interest in their material science. Stacking ; Materials science ; Honeycomb ; Oxide ; Nanotechnology ; Crystallography ; Chemistry ; Composite material ; Metallurgy Multiferroics and related materials ; Layered Double Hydroxides Synthesis and Applications ; Advanced Condensed Matter Physics
Authors: Matthieu Fortin‐Deschênes
Source: PolyPublie (École Polytechnique de Montréal) (article, 2020-07-01)
Field: Materials Science — Materials Chemistry

Real-Time and Atomic-Level Studies of the Growth, Phase Transformations and Stability of Two-Dimensional Pnictogens Casagrande their great transmission electron microscopy work.Merci aussi Richard Martel et Patrick Desjardins pour avoir dvelopp le systme ultra-haut vide dans lequel j'ai effectu la majorit de mes travaux.Merci Pierre Lvesque pour m'avoir transmis ses normes connaissances sur la microscopie lectronique faible nergie.Merci aussi Alain Rochefort, qui m'a gnreusement donn son aide et ses conseils propos des mthodes de calcul de structure lectronique.Merci Jol Bouchard pour son support technique au systme ultra-haut vide.Merci aussi Christophe Clment pour Physics ; Humanities ; Chemistry ; Art Graphene research and applications ; 2D Materials and Applications ; Zeolite Catalysis and Synthesis
Authors: Mauro Perfetti | Andréa Caneschi | Taisiya S. Sukhikh | Kira E. Vostrikova
Source: ChemRxiv (preprint, 2020-08-14)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Lanthanide Complexes with a Tripodal Nitroxyl Radical Showing Strong Magnetic Coupling A series of isomorphous mononuclear complexes of Ln(III) ions comprising one stable tripoidal oxazolidine nitroxyl radical were obtained in acetonitrile media starting from nitrates. The compounds, [LnRad(NO3)3] (Ln = Gd, Tb, Dy, Tm, Y; Rad = 4,4-dimethyl-2,2-bis(pyridin-2-yl)-1,3-oxazolidine-3-oxyl), have molecular structure. Their coordination polyhedron, LnO7N2, can be described as a tricapped trigonal prism with symmetry close to D3h. The value of 23 cm-1 for the antiferromagnetic coupling Gd-Rad established from the DC magnetic and EPR data is a record strength for the complexes of 4f-elements with nitroxyl radicals. The terbium derivative displays frequency-dependent out-of-phase signals in zero field indicating single-molecule magnetic behavior with an effective barrier of 57 cm-1. Chemistry ; Nitroxyl ; Oxazolidine ; Crystallography ; Acetonitrile ; Terbium ; Electron paramagnetic resonance ; Derivative (finance) ; Molecule ; Ion ; Antiferromagnetism ; Nuclear magnetic resonance ; Stereochemistry ; Photochemistry ; Condensed matter physics ; Organic chemistry Magnetism in coordination complexes ; Lanthanide and Transition Metal Complexes ; Electron Spin Resonance Studies
Authors: Y. Shimizu
Source: Chemical and Pharmaceutical Bulletin (review, 2020-04-30)
Field: Chemistry — Organic Chemistry

Development of Copper-Catalyzed Chemoselective Reactions Chemoselective reactions can contribute to streamlining synthesis of pharmaceuticals, agrochemicals, and other functional molecules by avoiding use of protecting groups. In this review, copper catalysts were demonstrated useful for developing two types of chemoselective reactions: C-C bond-forming reactions at an anomeric carbon of unprotected aldoses and difunctionalization reaction of C-C multiple bonds. The "soft" nucleophilic copper species exhibit orthogonal reactivity toward "hard" polar functional groups and preferentially react with "soft" functional groups. The catalysis also controls stereoselectivity and/or regioselectivity to provide value-added products from readily available feedstock compounds. Regioselectivity ; Chemistry ; Nucleophile ; Catalysis ; Reactivity (psychology) ; Copper ; Chemoselectivity ; Combinatorial chemistry ; Organic chemistry ; Stereoselectivity ; Functional group Catalytic C–H Functionalization Methods ; Cyclopropane Reaction Mechanisms ; Asymmetric Hydrogenation and Catalysis
Authors: Gwladys Nizou | Chiara Favaretto | Francesca Borgna | Pascal V. Grundler | Nathalie Saffon‐Merceron | Carlos Platas‐Iglesias | Olivier Fougère | Olivier Rousseaux | Nicholas P. van der Meulen | Cristina Müller | Maryline Beyler | Raphaël Tripier
Source: ChemRxiv (preprint, 2020-06-29)
Field: Materials Science — Materials Chemistry

Expanding the Scope of Pyclen-Picolinate Lanthanide Chelates to Po-Tential Theranostic Applications A family of three picolinate pyclen based ligands, previously investigated for the complexation of Y3+ and some lanthanide ions (Gd3+, Eu3+), was studied with 161Tb and 177Lu in view of potential radiotherapeutic applications. The set of six Tb3+ and Lu3+ complexes was synthesized and fully characterized. The coordination properties in the solid state and in solution were thoroughly studied. Potentiometric titrations, corroborated by DFT calculations, showed the very high stability constants of the Tb3+ and Lu3+ complexes, which are associated to remarkable kinetic inertness. A complete radiolabeling study performed with both 161Tb and 177Lu radionuclides, including experiments with regard to the stability with and without scavengers and kinetic inertness using challenging agents, proved that the ligands could reasonably compete with the DOTA analogue. To conclude, the potential of using the same ligand for both radiotherapy and optical imaging was highlighted for the first time. Lanthanide ; Chemistry ; Potentiometric titration ; Titration ; Chelation ; DOTA ; Ligand (biochemistry) ; Solid-state ; Coordination complex ; Combinatorial chemistry ; Rare earth ; Ion ; Physical chemistry ; Nuclear chemistry ; Inorganic chemistry ; Radiochemistry ; Metal ; Organic chemistry ; Mineralogy Lanthanide and Transition Metal Complexes ; Radiopharmaceutical Chemistry and Applications ; Radioactive element chemistry and processing
Source: Kinetic Mechanical Engineering (article, 2020-06-16)
Field: Materials Science — General Materials Science

Anti-corrosion Performance of Engineering Mechanical Coatings Dependent on Nanotechnology Corrosion is a common phenomenon.Both natural environment and industrial media may cause corrosion of metals.It is reported that every 90 seconds around the world, 1 ton of steel corrosion into rust, pipeline corrosion not only causes the transmission medium run, leakage phenomenon, bring huge waste, but also endanger health.Corrosion is not only an economic problem, but also a safety problem.The explosion caused by corrosion and the collapse of steel structures will bring accidents to people, endanger people's property and health safety.Corrosion not only affects the working accuracy of national defense facilities and equipment, but even causes the failure of key precision components, which seriously threatens national security.In this paper, the structure and properties of NM and the research status of nanomaterial complexes are introduced.It is pointed out that it is possible to improve the properties of composite coatings by adding different dimensional NP in epoxy powder coatings.It is suggested that powder coating instead of solvent coating will be a developing trend in metal AC application in the future.Through the experimental study, it was found that the main performance indexes of the nano composite epoxy powder coating prepared by the synergistic action of nano particle modification, ball milling mixing and melting mixing extrusion were improved in different degrees compared with the ordinary pure epoxy powder coating. Corrosion ; Nanotechnology ; Materials science ; Engineering ; Metallurgy Material Properties and Applications ; Metal and Thin Film Mechanics ; Surface Treatment and Coatings
Authors: Ali Zahid | Umer Zahid | Aamir Hasan | Muhammad Khuldoon
Source: Preprints.org (preprint, 2020-07-13)
Field: Materials Science — Materials Chemistry

Growth and Characterization of Polycrystalline Silicon Thin Films for Photocatalytic Splitting of Water in Oxide-Si Tandem Cells With the decline in fossil fuels, hydrogen-based alternatives provide a reliable and clean source for sustainable energy generation. In these endeavors, photochemical splitting for hydrogen production through tandem cells has been the source of much theoretical and experimental research in science. Much focus has been placed on interfacial band gap engineering as one of the most promising routes in the generation of hydrogen.This present work explores sputtering of n-silicon to form the active electrode in a n-Si | n-TiO2 tandem cell and investigates the effect of variations in sputtering and post sputtering treatment parameters (rapid thermal annealing and long cycle annealing) for successful deposition of crystalline Silicon. The samples were successfully characterized via Raman Spectroscopy, X-ray Diffraction and Optical Transmission Spectroscopy to ascertain prevalent crystalline order and optical band gap, under different sputtering and post-sputtering conditions. Relevant conclusions were drawn to ascertain the best possible deposition parameters of n-Si for photocatalytic water splitting. Sputtering ; Silicon ; Materials science ; Water splitting ; Tandem ; Hydrogen production ; Raman spectroscopy ; Photocatalysis ; Chemical engineering ; Annealing (glass) ; Hydrogen ; Optoelectronics ; Nanotechnology ; Thin film ; Chemistry ; Optics ; Metallurgy ; Composite material ; Catalysis Silicon Nanostructures and Photoluminescence ; Ga2O3 and related materials ; Nanowire Synthesis and Applications