jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Po‐Chih Yang | Yueh-Han Chien | Shih-Hsuan Tseng | Chia-Chung Lin | Kaiyu Huang
Source: Polymers (article, 2019-12-06)
Field: Chemistry — Organic Chemistry

Synthesis and Self-Assembly of Multistimulus-Responsive Azobenzene-Containing Diblock Copolymer through RAFT Polymerization This paper gathered studies on multistimulus-responsive sensing and self-assembly behavior of a novel amphiphilic diblock copolymer through a two-step reverse addition-fragmentation transfer (RAFT) polymerization technique. N-Isopropylacrylamide (NIPAM) macromolecular chain transfer agent and diblock copolymer (poly(NIPAM-<i>b</i>-Azo)) were discovered to have moderate thermal decomposition temperatures of 351.8 and 370.8 °C, respectively, indicating that their thermal stability was enhanced because of the azobenzene segments incorporated into the block copolymer. The diblock copolymer was determined to exhibit a lower critical solution temperature of 34.4 °C. Poly(NIPAM-<i>b</i>-Azo) demonstrated a higher photoisomerization rate constant (<i>k</i><sub>t</sub> = 0.1295 s<sup>-1)</sup> than the Azo monomer did (<i>k</i><sub>t</sub> = 0.088 s<sup>-</sup><sup>1</sup>). When ultraviolet (UV) irradiation was applied, the intensity of fluorescence gradually increased, suggesting that UV irradiation enhanced the fluorescence of self-assembled cis-isomers of azobenzene. Morphological aggregates before and after UV irradiation are shown in scanning electron microscopy (SEM) and dynamic light scattering (DLS) analyses of the diblock copolymer. We employed photoluminescence titrations to reveal that the diblock copolymer was highly sensitive toward Ru<sup>3+</sup> and Ba<sup>2+</sup>, as was indicated by the crown ether acting as a recognition moiety between azobenzene units. Micellar aggregates were formed in the polymer aqueous solution through dissolution; their mean diameters were approximately 205.8 and 364.6 nm at temperatures of 25.0 and 40.0 °C, respectively. Our findings contribute to research on photoresponsive and chemosensory polymer material developments. Copolymer ; Raft ; Azobenzene ; Reversible addition−fragmentation chain-transfer polymerization ; Polymer chemistry ; Polymerization ; Chain transfer ; Materials science ; Self-assembly ; Polymer science ; Radical polymerization ; Nanotechnology ; Polymer ; Composite material Advanced Polymer Synthesis and Characterization ; Dendrimers and Hyperbranched Polymers ; Hydrogels: synthesis, properties, applications
Authors: Biswanath Das | Afnan Al‐Hunaiti | Brenda N. Sánchez-Eguía | Erica Zeglio | Serhiy Demeshko | Sebastian Dechert | Steffen Braunger | Matti Haukka | Timo Repo | Iván Castillo | Ebbe Nordlander
Source: Frontiers in Chemistry (article, 2019-03-01)
Field: Chemistry — Inorganic Chemistry

Di- and Tetrairon(III) μ-Oxido Complexes of an N3S-Donor Ligand: Catalyst Precursors for Alkene Oxidations The new di- and tetranuclear Fe(III) μ-oxido complexes [Fe<sub>4</sub>(μ-O)<sub>4</sub>(PTEBIA)<sub>4</sub>](CF<sub>3</sub>SO<sub>3</sub>)<sub>4</sub>(CH<sub>3</sub>CN)<sub>2</sub>] (<b>1a</b>), [Fe<sub>2</sub>(μ-O)Cl<sub>2</sub>(PTEBIA)<sub>2</sub>](CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub> (<b>1b</b>), and [Fe<sub>2</sub>(μ-O)(HCOO)<sub>2</sub>(PTEBIA)<sub>2</sub>](ClO<sub>4</sub>)<sub>2</sub> (MeOH) (<b>2</b>) were prepared from the sulfur-containing ligand (2-((2,4-dimethylphenyl)thio)-N,N-bis ((1-methyl-benzimidazol-2-yl)methyl)ethanamine (PTEBIA). The tetrairon complex <b>1a</b> features four μ-oxido bridges, while in dinuclear <b>1b</b>, the sulfur moiety of the ligand occupies one of the six coordination sites of each Fe(III) ion with a long Fe-S distance of 2.814(6) Å. In <b>2</b>, two Fe(III) centers are bridged by one oxido and two formate units, the latter likely formed by methanol oxidation. Complexes <b>1a</b> and <b>1b</b> show broad sulfur-to-iron charge transfer bands around 400-430 nm at room temperature, consistent with mononuclear structures featuring Fe-S interactions. In contrast, acetonitrile solutions of <b>2</b> display a sulfur-to-iron charge transfer band only at low temperature (228 K) upon addition of H<sub>2</sub>O<sub>2</sub>/CH<sub>3</sub>COOH, with an absorption maximum at 410 nm. Homogeneous oxidative catalytic activity was observed for <b>1a</b> and <b>1b</b> using H<sub>2</sub>O<sub>2</sub> as oxidant, but with low product selectivity. High valent iron-oxo intermediates could not be detected by UV-vis spectroscopy or ESI mass spectrometry. Rather, evidence suggest preferential ligand oxidation, in line with the relatively low selectivity and catalytic activity observed in the reactions. Chemistry ; Ligand (biochemistry) ; Acetonitrile ; Catalysis ; Medicinal chemistry ; Selectivity ; Moiety ; Sulfur ; Formate ; Photochemistry ; Alkene ; Inorganic chemistry ; Stereochemistry ; Organic chemistry Metal-Catalyzed Oxygenation Mechanisms ; Metal complexes synthesis and properties ; Magnetism in coordination complexes
Authors: Benjamin Nji Wandi | Vilja Siitonen | Pedro Dinis | Vladimir Vukić | Tiina A. Salminen | Mikko Metsä‐Ketelä
Source: FEBS Journal (article, 2019-12-26)
Field: Chemistry — Inorganic Chemistry

Evolution‐guided engineering of non‐heme iron enzymes involved in nogalamycin biosynthesis Microbes are competent chemists that are able to generate thousands of chemically complex natural products with potent biological activities. The key to the formation of this chemical diversity has been the rapid evolution of secondary metabolism. Many enzymes residing on these metabolic pathways have acquired atypical catalytic properties in comparison with their counterparts found in primary metabolism. The biosynthetic pathway of the anthracycline nogalamycin contains two such proteins, SnoK and SnoN, belonging to nonheme iron and 2-oxoglutarate-dependent mono-oxygenases. In spite of structural similarity, the two proteins catalyze distinct chemical reactions; SnoK is a C2-C5″ carbocyclase, whereas SnoN catalyzes stereoinversion at the adjacent C4″ position. Here, we have identified four structural regions involved in the functional differentiation and generated 30 chimeric enzymes to probe catalysis. Our analyses indicate that the carbocyclase SnoK is the ancestral form of the enzyme from which SnoN has evolved to catalyze stereoinversion at the neighboring carbon. The critical step in the appearance of epimerization activity has likely been the insertion of three residues near the C-terminus, which allow repositioning of the substrate in front of the iron center. The loss of the original carbocyclization activity has then occurred with changes in four amino acids near the iron center that prohibit alignment of the substrate for the formation of the C2-C5″ bond. Our study provides detailed insights into the evolutionary processes that have enabled Streptomyces soil bacteria to become the major source of antibiotics and antiproliferative agents. ENZYMES: EC number 1.14.11. Enzyme ; Biochemistry ; Secondary metabolism ; Chemistry ; Cofactor ; Streptomyces albus ; Biosynthesis ; Heme ; Stereochemistry ; Streptomyces ; Dioxygenase ; Polyketide ; Metabolic pathway ; Biology ; Bacteria ; Genetics Metal-Catalyzed Oxygenation Mechanisms ; Microbial Natural Products and Biosynthesis ; Enzyme Structure and Function
Authors: Roderick Jesus Jude M. Regalado | Emmanuel A. Punzalan | David P. Peñaloza
Source: Epitoanyag-Journal of Silicate Based and Composite Materials (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

One-pot preparation of PS/silica hydrophobic coating by solution-casting using D-limonene as dispersing medium Different polystyrene (PS) coatings were prepared and optimized by dissolving PS in D-limonene and subsequent dispersion of varying amounts of different chemically modified silica nanoparticles. Among the materials prepared, a PS coating filled with silica nanoparticles organo-modified with long alkyl carbon chains results in high hydrophobicity (120.8 as compared to bare PS coating -67.0) and excellent film-formation. Coating ; Limonene ; Casting ; Dispersant ; Chemical engineering ; Materials science ; Hydrophobic silica ; Chemistry ; Composite material ; Dispersion (optics) ; Chromatography Silicone and Siloxane Chemistry
Authors: Romain Breitwieser | Adrien Garnier | Thomas Auvray | Anh‐Tu Ngo | Benoı̂t Baptiste | Nicolas Menguy | Anna Proust | Christophe Petit | Florence Volatron | Caroline Salzemann
Source: Frontiers in Chemistry (article, 2019-11-29)
Field: Materials Science — Materials Chemistry

Protective Effect of Polyoxometalates in {Mo132}/Maghemite Binary Superlattices Under Annealing The binary assembly DDA-{Mo<sub>132</sub>}/OA-γ-Fe<sub>2</sub>O<sub>3</sub> (DDA = didodecyldimethylammonium, {Mo<sub>132</sub>} = [Mo<sub>132</sub>O<sub>372</sub>(CH<sub>3</sub>COO)<sub>30</sub>(H<sub>2</sub>O)<sub>72</sub>]<sup>42-</sup>, OA = oleic acid) constitutes one of the two examples in the literature of binary superlattices made of a mixing of nanocrystals and oxo-clusters. In a precedent work, we reported in details the preparation of such magnetic binary systems and studied the effect of the nature of the polyoxometalates (POMs) on the magnetic properties. In the present paper, we study the stability of this model binary assembly under heating at various temperatures. Indeed, especially if magnetic and/or transport properties are targeted, an annealing can be essential to change the phase of the nanocrystals in a more magnetic one and/or to desorb the organic capping of the nano-objects that can constitute an obstacle to the electronic communication between the nano-objects. We gave evidence that the maghemite organization in the binary assembly is maintained until 370°C under vacuum thanks to the presence of the POMs. This latter evolve in the phase MoO<sub>3</sub>, but still permits to avoid the aggregation of the nanocrystals as well as preserve their periodical arrangement. On the contrary, an assembly made of pure γ-Fe<sub>2</sub>O<sub>3</sub> nanocrystals displays a clear aggregation of the nano-objects from 370°C, as attested by transmission and scanning electronic microscopies and confirmed by magnetic measurements. The stability of the magnetic nanocrystals in such POMs/nanocrystals assemblies opens the way to (i) the elaboration of new binary assemblies from POMs and numerous kinds of nanocrystals with a good control on the magnetic properties and to (ii) the investigation of new physical properties as exchange coupling, or magneto-transport in such systems. Nanocrystal ; Maghemite ; Superlattice ; Materials science ; Annealing (glass) ; Nanotechnology ; Binary number ; Chemical engineering ; Chemical physics ; Nanoparticle ; Chemistry ; Metallurgy ; Optoelectronics Polyoxometalates: Synthesis and Applications ; Nanocluster Synthesis and Applications ; Advanced Nanomaterials in Catalysis
Authors: Tim Verhagen | Barbara Pacáková | Martin Kalbáč | Jana Vejpravová
Source: Nanomaterials (article, 2019-03-04)
Field: Materials Science — Materials Chemistry

Introducing Well-Defined Nanowrinkles in CVD Grown Graphene The control of graphene's topography at the nanoscale level opens up the possibility to greatly improve the surface functionalization, change the doping level or create nanoscale reservoirs. However, the ability to control the modification of the topography of graphene on a wafer scale is still rather challenging. Here we present an approach to create well-defined nanowrinkles on a wafer scale using nitrocellulose as the polymer to transfer chemical vapor deposition grown graphene from the copper foil to a substrate. During the transfer process, the complex tertiary nitrocellulose structure is imprinted into the graphene area layer. When the graphene layer is put onto a substrate this will result in a well-defined nanowrinkle pattern, which can be subsequently further processed. Using atomic force and Raman microscopy, we characterized the generated nanowrinkles in graphene. Graphene ; Materials science ; Nanotechnology ; Chemical vapor deposition ; Nitrocellulose ; Wafer ; Nanoscopic scale ; Graphene nanoribbons ; Substrate (aquarium) ; Graphene oxide paper ; Raman spectroscopy ; Layer (electronics) ; FOIL method ; Surface modification ; Chemical engineering ; Composite material ; Chemistry ; Membrane ; Optics Graphene research and applications ; Diamond and Carbon-based Materials Research ; Graphene and Nanomaterials Applications
Authors: Juan D. Villada | Juliana Loaiza | Manuel N. Chaur
Source: Revista de la Academia Colombiana de Ciencias Exactas Físicas y Naturales (article, 2019-07-08)
Field: Materials Science — Materials Chemistry

Electronic and electrochemical properties of a grid-like structure of Zn(II) Una nueva bis(hidrazona), altamente soluble en solventes orgánicos comunes, se sintetizó y caracterizó mediante diversas técnicas espectroscópicas. El compuesto se utilizó como ligando ditópico en la construcción de estructuras supramoleculares de tipo rejilla (rejillas supramoleculares o complejos metálicos de tipo rejilla) utilizando Zn2+ como catión metálico. El complejo supramolecular se confirmó mediante resonancia magnética nuclear RMN-1H y bidimensional. El arreglo de tipo rejilla se determinó mediante las señales de RMN-1H del anillo fenilo del ligando orgánico que cambia su velocidad de rotación y, por ende, su ambiente químico al coordinarse en dicho arreglo. Por último, se realizaron estudios de UV-Vis y voltamperometría cíclica y de onda cuadrada, con el fin de determinar las propiedades optoelectrónicas y electroquímicas de estos compuestos. Tanto la bis(hidrazona) como el complejo de tipo rejilla aquí presentados, exhiben varios potenciales de oxidación-reducción, los cuales se estudiaron en detalle mediante las técnicas mencionadas y cuyo estudio sirve de base para el desarrollo futuro de estructuras supramoleculares que puedan utilizarse como interruptores moleculares electroquímicos. © 2019. Acad. Colomb. Cienc. Ex. Fis. Nat. Physics ; Humanities ; Chemistry ; Materials science ; Art Porphyrin and Phthalocyanine Chemistry ; Conducting polymers and applications ; Electrochemical Analysis and Applications
Authors: Kazimierz Gąsiorowski | Tomasz Gębarowski | Helena Moreira | Anna Kulma | Michał Szatkowski | Jan Szopa
Source: Advances in Clinical and Experimental Medicine (article, 2019-01-17)
Field: Materials Science — Biomaterials

Impact of fabrics from transgenic flax on cultures of skin cells The W92 and M48 fabrics should be further studied as candidates for elaboration of new types of bandages, able to improve skin wound healing. Sulforhodamine B ; Cell culture ; Reactive oxygen species ; Cell migration ; Wound healing ; Nike ; Human skin ; Cell biology ; Cell ; Cell growth ; Intracellular ; Chemistry ; Molecular biology ; Biochemistry ; Biology ; Cytotoxicity ; Immunology ; In vitro Silk-based biomaterials and applications ; Wound Healing and Treatments ; Electrospun Nanofibers in Biomedical Applications
Authors: Cesare Freda | Giacinto Cornacchia | Antonio Donatelli | Mauro Corrado | Maria Martino | Anna De Girolamo Del Mauro | S. Galvagno
Source: Cerâmica (article, 2019-01-01)
Field: Materials Science — Ceramics and Composites

A novel thermal plasma-based technology for submicronic silicon carbide production at pilot scale Abstract Submicronic powder of silicon carbide was synthesized in a pilot novel radiofrequency plasma torch reactor. The precursors were pyrolysis char and silica powders both with micrometric size. The mass rate of the precursor powder varied in the range 600-2500 g/h. The maximum test time was approximately 3 h. With the goal to increase the process yield, several technical measures were implemented. Silicon carbide yield was above 70 wt% when the plasma flame was confined by a tube that prolonged the residence time of the reactants at the useful temperature for the advancement of reaction. The silicon carbide was characterized by XRD, SEM, and DLS. Both α and β-crystalline phases were detected. Silicon carbide ; Materials science ; Pyrolysis ; Char ; Chemical engineering ; Silicon ; Yield (engineering) ; Plasma ; Tube furnace ; Thermal spraying ; Metallurgy ; Nanotechnology ; Coating Advanced ceramic materials synthesis ; Silicon Carbide Semiconductor Technologies ; Diamond and Carbon-based Materials Research
Authors: Andrew Tan | Pengpeng Zhang
Source: Physical Chemistry Chemical Physics (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

Interfacial charge transfer enhancement<i>via</i>formation of binary molecular assemblies on electronically corrugated boron nitride Using scanning tunneling microscopy/spectroscopy (STM/STS) in conjunction with finite element simulation, we investigate the interfacial behaviors in single-component zinc phthalocyanine (ZnPc) and hexadecafluorinated zinc phthalocyanine (F16ZnPc) molecular overlayers as well as their 1 : 1 mixed-phase superstructures on h-BN/Cu(111). We show that the formation of the binary molecular superstructure drastically increases the charge transfer between F16ZnPc molecules and the substrate, which is attributed to the greater electrostatic stability of the binary assembly compared to that of the pure phase. This study highlights the significant complication in the design of donor-acceptor molecular thin films as the presence of the substrate, even a weakly interacting one, such as h-BN/metal, can still perturb the intermolecular charge transfer and thereby the physical behaviors of the hybrid system via interfacial processes. Scanning tunneling microscope ; Materials science ; Chemical physics ; Superstructure ; Boron nitride ; Substrate (aquarium) ; Phase (matter) ; Acceptor ; Intermolecular force ; Molecule ; Boron ; Phthalocyanine ; Chemistry ; Nanotechnology ; Organic chemistry ; Condensed matter physics ; Thermodynamics Graphene research and applications ; Quantum and electron transport phenomena ; Molecular Junctions and Nanostructures
Authors: Brenna C. Keegan | Daniel Ocampo | Jason Shearer
Source: Inorganics (article, 2019-07-16)
Field: Chemistry — Inorganic Chemistry

pH Dependent Reversible Formation of a Binuclear Ni2 Metal-Center within a Peptide Scaffold A disulfide-bridged peptide containing two Ni<sup>2+</sup> binding sites based on the nickel superoxide dismutase protein, {Ni<sub>2</sub>(SOD<sup>mds</sup>)}, has been prepared. At physiological pH (7.4) it was found that the metal sites are mononuclear with a square planar NOS<sub>2</sub> coordination environment with the two sulfur-based ligands derived from cysteinate residues, the nitrogen ligand derived from the amide backbone and a water ligand. Furthermore, S K-edge X-ray absorption spectroscopy indicated that the two cysteinate sulfur atoms ligated to nickel are each protonated. Elevation of the pH to 9.6 results in the deprotonation of the cysteinate sulfur atoms, and yields a binuclear, cysteinate bridged Ni<sub>2</sub><sup>2+</sup> center with each nickel contained in a distorted square planar geometry. At both pH = 7.4 and 9.6 the nickel sites are moderately air sensitive, yielding intractable oxidation products. However, at pH = 9.6 {Ni<sub>2</sub>(SOD<sup>mds</sup>)} reacts with O<sub>2</sub> at an ~3.5-fold faster rate than at pH = 7.4. Electronic structure calculations indicate the reduced reactivity at pH = 7.4 is a result of a reduction in S(3p) character and deactivation of the nucleophilic frontier molecular orbitals upon cysteinate sulfur protonation. Chemistry ; Deprotonation ; Protonation ; Nickel ; Ligand (biochemistry) ; Metal ; Sulfur ; Amide ; Crystallography ; Inorganic chemistry ; Stereochemistry ; Organic chemistry Metal-Catalyzed Oxygenation Mechanisms ; CO2 Reduction Techniques and Catalysts ; Carbon dioxide utilization in catalysis
Authors: Md. Saiful Islam | Ainul Anam | Ainul Anam Shahjamal Khan | Muhammad Abu Bakar | A Sobolev | L Mannina | N Proietti | S Carradori | M Daglia | A Giusti | R Antiochia | D Capitani | X Tang | N Mager | B Vanhorenbeke | S Hermans | J Raskin | J Wahid | Q Ahsan | C Zugravu | E Pogurschi | D Patrascu | I Petronela-Diana | C Nicolae
Source: Carpathian Journal of Food Science and Technology (article, 2019-09-29)
Field: Chemistry — Analytical Chemistry

A SIMPLE SYSTEM TO DETECT AND MEASURE FORMALIN IN FRUIT BYUSING CONDUCTIVITY, PH AND CAPACITANCE MEASUREMENT Economically motivated adulteration (EMA) of food is becoming common in some developing countries. Formalin is a harmful organic chemical substance which is often used by businessmen to keep their fruits etc. look fresh for longer times. It consists of two substances: formaldehyde and water. Formalin is used for long time preservation for various types of foods and other things from putrefaction. It affects human life as well as environmental ecology. At present, EMA by Formalin is becoming severe in countries like Bangladesh. Formalin detection is a challenging task. Most of the techniques to detect formalin are based on chemical sensors. The paper aims at detecting formalin in fruits by electrical properties such as conductivity and capacitance together with cheap pH sensor. The fruits are immersed in distilled water and conductivity, capacitance and pH of the water are measured. The result is very promising with an average error of 7.18%. For higher concentration the average error is 5.02%. Although the proposed method does not give result instantaneously, but it could lead to a method of detecting formalin mainly based on electrical properties in future. Measure (data warehouse) ; Capacitance ; Simple (philosophy) ; Conductivity ; Biological system ; Materials science ; Analytical Chemistry (journal) ; Computer science ; Process engineering ; Chromatography ; Chemistry ; Data mining ; Engineering ; Biology ; Electrode Spectroscopy and Chemometric Analyses ; Water Quality Monitoring and Analysis
Authors: Shuhei Sumino | Takahide Fukuyama | Mika Sasano | Ilhyong Ryu | Antoine Jacquet | Frédéric Robert | Yannick Landais
Source: Beilstein Journal of Organic Chemistry (article, 2019-07-31)
Field: Chemistry — Organic Chemistry

Vicinal difunctionalization of alkenes by four-component radical cascade reaction of xanthogenates, alkenes, CO, and sulfonyl oxime ethers Four-component coupling reactions between xanthogenates, alkenes, CO, and sulfonyl oxime ethers were studied. In the presence of hexabutylditin, working as a propagating radical reagent, the chain reaction proceeds, as expected, taking into account reagents polarities, affording the corresponding functionalized α-keto oximes. Although yields are modest, this rare one-pot four-component process is easy to carry out and the resulting compounds, bearing multiple functionalities, have the potential for further elaboration. Chemistry ; Sulfonyl ; Reagent ; Oxime ; Vicinal ; Component (thermodynamics) ; Organic chemistry ; Combinatorial chemistry ; Medicinal chemistry ; Alkyl Sulfur-Based Synthesis Techniques ; Catalytic C–H Functionalization Methods ; Radical Photochemical Reactions