jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Alexandru Căciuleanu | Felix Vöhringer | Ivana Fleischer
Source: ChemRxiv (preprint, 2023-03-20)
Field: Chemistry — Inorganic Chemistry

Titanium-catalysed deoxygenation of benzylic alcohols and lignin model compounds We report a catalytic system for direct deoxygenation of benzylic alcohols by using non-precious precatalyst Cp2TiCl2 and 2 MeTHF as solvent. Mechanistic studies showed that the used silane Me(EtO)2SiH acts both as H-donor and regenerating agent of the active catalytic species. This method tolerates a wide variety of functional and protecting groups and enables sequential deoxygenation-dehalogenation and deoxygenation-hydrogenation reactions. The procedure was successfully applied in the exhaustive reduction of lignin model substrates into value-added compounds. Deoxygenation ; Chemistry ; Catalysis ; Lignin ; Organic chemistry ; Halogenation ; Solvent ; Silane ; Combinatorial chemistry Asymmetric Hydrogenation and Catalysis ; Catalysis and Hydrodesulfurization Studies ; Lignin and Wood Chemistry
Authors: Jyothi Neeli | Nitchal Kiran Jaladi | Nagamani Sangula | Vijaya Lakshmi Garlapati | Srinivasa Rao Kurapati
Source: Physica Scripta (article, 2023-11-10)
Field: Materials Science — Materials Chemistry

Samarium-modified NBT ceramics: a comprehensive exploration of cumulative effects Abstract In the present report, ceramic specimens of sodium bismuth titanate [Na 0.5 (Bi 1-x Sm x ) 0.5 TiO 3 ] were prepared through solid-state reaction method with variations in the dopant concentrations specifically, x = 0.0, 0.1, 0.3, 0.5. The structural, optical, mechanical, and magnetic properties of lead-free NBT ceramics were investigated. The rhombohedral phase with space group R3c was confirmed in all prepared ceramic samples using X-ray diffraction patterns and Rietveld analysis. SEM micrographs and Energy Dispersive x-ray spectroscopy (EDAX) assess the morphology, grain size, overall structure, and stoichiometry of the developed compounds. FTIR spectroscopy was used for characterizing and identifying the functional groups. UV–vis spectroscopy revealed that band gap values decreased as dopant concentration increased, confirming the use of NBT-based perovskite as a photoactive material. PL spectra at room temperature exhibited reddish-orange emission. Colour coordinates and CCT values are in the range of 3483 K to 5912 K. At a concentration of x = 0.3, the materials displayed a high Vickers hardness of 8.20 GPa and exhibited minimal wear with low frictional coefficient values. Ferromagnetic behaviour at room temperature (RTFM) was detected in Sm-modified ceramic samples, as confirmed by the VSM study. The cumulative effect impact of the rare earth dopant cation at the Bi-site of NBT was widespread and demonstrated significant potential for use in optoelectronic devices. Materials science ; Dopant ; Rietveld refinement ; Ceramic ; Band gap ; Vickers hardness test ; Analytical Chemistry (journal) ; Bismuth ferrite ; Spectroscopy ; Fourier transform infrared spectroscopy ; Grain size ; Perovskite (structure) ; Composite material ; Chemical engineering ; Microstructure ; Doping ; Multiferroics ; Crystal structure ; Crystallography ; Ferroelectricity ; Chemistry ; Optoelectronics Ferroelectric and Piezoelectric Materials ; Perovskite Materials and Applications ; Microwave Dielectric Ceramics Synthesis
Authors: Kaiyu Cai | Dan Zhang | José M. Castro
Source: Journal of Composites Science (article, 2023-08-08)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Technical Feasibility of a Thermally Activated Nanotape for Electromagnetic Interference Applications Multiwalled carbon nanotube (MWCNT) nanopaper (NP)-reinforced in-mold coating (IMC) nanocomposites were fabricated by dip soaking without organic solvent. The thermally activated IMC resin was selected to provide electromagnetic interference shielding protection for sheet molding compound (SMC) material as well as other plastic materials due to the proven good adhesion of IMC resin to the substrate. In this work, the technical feasibility of a continuous fabrication process was evaluated for a nanopaper/IMC (NP/IMC) composite. The curing behavior of the candidate IMC resin was studied for a better understanding of the fabrication of NP/IMC nanotape as a prepreg (with 10% polymerization), as well as the final curing once the nanotape was applied to the substrate. The required limiting maximum temperature to prevent curing during infiltration was established. This allows the fabrication of multilayer nanotape or coatings by stacking several layers of tape to improve the EMI shielding protection. To be specific, the average EMI shielding effectiveness for a one-layer composite was 21 dB, while it increased to 48 dB on average for a six-layer composite. Materials science ; Fabrication ; Composite material ; Curing (chemistry) ; Electromagnetic shielding ; Composite number ; Coating ; Nanocomposite ; Electromagnetic interference ; Compression molding ; Mold ; Electronic engineering Electromagnetic wave absorption materials ; Tribology and Wear Analysis ; Material Properties and Applications
Authors: Jorn de Jong | Maxime A. Siegler | Sander J. Wezenberg
Source: Angewandte Chemie (article, 2023-12-08)
Field: Chemistry — Organic Chemistry

A Photoswitchable Macrocycle Controls Anion‐Templated Pseudorotaxane Formation and Axle Relocalization Abstract Important biological processes, such as signaling and transport, are regulated by dynamic binding events. The development of artificial supramolecular systems in which binding between different components is controlled could help emulate such processes. Herein, we describe stiff‐stilbene‐containing macrocycles that can be switched between ( Z )‐ and ( E )‐isomers by light, as demonstrated by UV/Vis and 1 H NMR spectroscopy. The ( Z )‐isomers can be effectively threaded by pyridinium halide axles to give pseudorotaxane complexes, as confirmed by 1 H NMR titration studies and single‐crystal X‐ray crystallography. The overall stability of these complexes can be tuned by varying the templating counteranion. However, upon light‐induced isomerization to the ( E )‐isomer, the threading capability is drastically reduced. The axle component, in addition, can form a heterodimeric complex with a secondary isophthalamide host. Therefore, when all components are combined, light irradiation triggers axle exchange between the macrocycle and this secondary host, which has been monitored by 1 H NMR spectroscopy and simulated computationally. Chemistry ; Supramolecular chemistry ; Isomerization ; Nuclear magnetic resonance spectroscopy ; Pyridinium ; Spectroscopy ; Crystallography ; Rotaxane ; Molecular machine ; Stereochemistry ; Photochemistry ; Crystal structure ; Nanotechnology ; Materials science ; Organic chemistry ; Catalysis Supramolecular Chemistry and Complexes ; Molecular Sensors and Ion Detection ; Porphyrin and Phthalocyanine Chemistry
Authors: Pratip Chakraborty | Rafael C. Couto | Nanna Holmgaard List
Source: ChemRxiv (preprint, 2023-04-18)
Field: Chemistry — Organic Chemistry

Deciphering methylation effects on S2(pp*) internal conversion in the simplest linear alpha,beta-unsaturated carbonyl Chemical substituents can influence photodynamics by altering the location of critical points and topography of the potential energy surface (electronic effect) and by selectively altering the inertia of specific nuclear modes (inertial effects). Using non-adiabatic dynamics simulations, we investigate the impact of methylation on S2(pp*) internal conversion in acrolein – the simplest linear alpha,beta-unsaturated carbonyl. Consistent with time constants reported in a previous time-resolved photoelectron spectroscopy study, S2/S1-deactivation occurs on an ultrafast timescale (~50 fs). However, our simulations do not corroborate the sequential decay model used to fit the experiment. Instead, upon reaching the S1 state, the wavepacket bifurcates: a portion undergoes ballistic S1/S0-deactivation (~80 fs) mediated by fast bond-length alternation motion, while the remaining decays on the ps-timescale in a more statistical regime. Our analysis reveals that methyl substitution, generally assumed to mainly exert inertial influence, also manifests in important electronic effects due to its weak electron-donating ability. While methylation at the beta C-atom gives rise to effects principally of inertial nature, such as retarding the twisting motion of the terminal -CHCH3 group and increasing its coupling with pyramidalization, methylation at the alpha or carbonyl C-atom modifies the potential energy surfaces in a way that also contributes to alterating the late S1-decay behavior. Specifically, our results suggest that the factor-of-two slowing of the ps-component upon alpha-methylation is a consequence of a tighter surface and reduced amplitude along the central pyramidalization, effectively restricting the access to the S1/S0-intersection seam. Our work offers new insight into the S2(pp*) internal conversion mechanisms in acrolein and its methylated derivatives and highlights site-selective methylation as a tuning knob to manipulate photochemical reactions. Chemistry ; Potential energy surface ; Methylation ; Chemical physics ; Amplitude ; Atom (system on chip) ; Internal conversion ; Physics ; Atomic physics ; Photochemistry ; Electron ; Quantum mechanics ; Molecule Radical Photochemical Reactions ; Advanced Chemical Physics Studies ; Atmospheric chemistry and aerosols
Authors: Sahar Shekarabi | Mohammad Amin Zare Pour | Hui Su | Wenjun Zhang | Chi He | Oleksandr Romanyuk | Agnieszka Paszuk | Shanshan Hu | Thomas Hannappel
Source: arXiv (Cornell University) (preprint, 2023-10-23)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Photoemission study and band alignment of GaN passivation layers on GaInP heterointerface III-V semiconductor-based photoelectrochemical (PEC) devices show the highest solar-to-electricity or solar-to-fuel conversion efficiencies. GaInP is a relevant top photoabsorber layer or a charge-selective contact in PEC for integrated and direct solar fuel production, due to its tunable lattice constant, electronic band structure, and favorable optical properties. To enhance the stability of its surface against chemical corrosion which leads to decomposition, we deposit a GaN protection and passivation layer. The n-doped GaInP(100) epitaxial layers were grown by metalorganic chemical vapor deposition on top of GaAs(100) substrate. Subsequently, thin 1-20 nm GaN films were grown on top of the oxidized GaInP surfaces by atomic layer deposition. We studied the band alignment of these multi-junction heterostructures by X-ray and ultraviolet photoelectron spectroscopy. Due to the limited emission depth of photoelectrons, we determined the band alignment by a series of separate measurements in which we either modified the GaInP(100) surface termination or the film thickness of the grown GaN on GaInP(100) buffer layers. On n-GaInP(100) surfaces prepared with the well-known phosphorus-rich (2x2)/c(4x2) reconstruction we found up-ward surface band bending (BB) of 0.34 eV, and Fermi level pinning due to the present surface states. Upon oxidation, the surface states are partially passivated resulting in a reduction of BB to 0.12 eV and a valence band offset (VBO) between GaInP and oxide bands of 2.0 eV. Between the GaInP(100) buffer layer and the GaN passivation layer, we identified a VBO of 1.8 eV. The corresponding conduction band offset of -0.2 eV is found to be rather small. Therefore, we evaluate the application of the GaN passivation layer as a promising technological step not only to reduce surface states but also to increase the stability of the surfaces of photoelectrochemical devices. Passivation ; Heterojunction ; Materials science ; Optoelectronics ; X-ray photoelectron spectroscopy ; Band bending ; Epitaxy ; Chemical vapor deposition ; Layer (electronics) ; Surface states ; Band offset ; Band gap ; Nanotechnology ; Valence band ; Chemical engineering Ga2O3 and related materials ; solar cell performance optimization ; Photocathodes and Microchannel Plates
Authors: Yi‐Hsin Lin | Victor Reshetnyak | Kai-Han Chang | Yan Li
Source: Journal of Optical Microsystems (article, 2023-12-14)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Special Section Guest Editorial: Micro-optical Systems Based on Liquid Crystals Section (typography) ; Special section ; Materials science ; Liquid crystal ; Optics ; Nanotechnology ; Optoelectronics ; Computer science ; Engineering physics ; Physics ; Operating system Liquid Crystal Research Advancements
Authors: D. Radić | Petra Grozić | Barbara Keran | A. M. Kadigrobov
Source: Research Square (preprint, 2023-05-15)
Field: Materials Science — Materials Chemistry

Charge Stripes in the Graphene-based Materials Abstract We present an analytical model of the charge density wave instability in graphene sheets within the intercalated graphite CaC6 compound. The instability yields the experimentally observed uniaxial charge stripes of periodically modulated electron density, coupled to the softest phonon mode of the superlattice consisting of the Ca atoms intercalated between graphene planes. The Fermi surface of the chemically doped graphene undergoes the novel type of instability driven by the mechanism that gains the condensation energy of the stripe state by the topological reconstruction of the Fermi surface. This mechanism appears to be entirely different from the one based on the Fermi surface nesting, which has been considered a paradigm in the present literature concerning the onset of charge density waves. Graphene ; Condensed matter physics ; Superlattice ; Instability ; Charge density wave ; Fermi surface ; Charge density ; Electron ; Materials science ; Graphite ; Fermi energy ; Charge (physics) ; Fermi level ; Doping ; Phonon ; Physics ; Nanotechnology ; Superconductivity ; Quantum mechanics Graphene research and applications ; Carbon Nanotubes in Composites ; Fullerene Chemistry and Applications
Authors: Zh.S. Zhilgildinov | V.M. Lisitsyn | Zh.T. Karipbayev | A.T. Tulegenova | G.K. Alpyssova | D.A. Mussakhanov | A.M. Zhunusbekov
Source: Eurasian Physical Technical Journal (article, 2023-07-10)
Field: Materials Science — Materials Chemistry

ENHANCING PHOTOMETRIC PERFORMANCE OF YAG:Ce CERAMICS: INVESTIGATING THE ROLE OF ANNEALING IN RADIATION-ASSISTED SYNTHESIS Ceramic samples of cerium-doped yttrium aluminum garnet (YAG:Ce) were successfully synthesized utilizing a high-powered electron flux field with a considerable energy level of 1.4 MeV and a power density of 23 kW/cm2. The ceramics were formed in a remarkable time span of just one second from a specifically prepared mix of yttrium, aluminum, and cerium oxides. The process of radiation-assisted synthesis of ceramics within radiation flux fields fundamentally deviates from the methodologies commonly employed today. Analyzed diffraction patterns closely align with those documented for YAG:Ce crystals, both in peak position and proportion. Furthermore, every sample consistently demonstrated a space group symmetry of Ia-3d. The luminescence and excitation spectra of ceramics synthesized in this study closely resemble those of YAG:Ce ceramics produced by other methods and YAG:Ce - based phosphors. The luminescence bands exhibit high efficiency, and the intensity ratios of the UV bands vary among the studied phosphors. The ceramics' radiation-to-luminescence conversion efficiency was found to be impressive, achieving scores of 0.57 and 0.48 in the industrial phosphors SDL 4000 and YAG-02, respectively. It was also observed that an increase in quantum efficiency of the samples could be achieved via high-temperature annealing. High conversion efficiency underscores the potential of the outlined luminescent ceramics synthesis method. Materials science ; Luminescence ; Phosphor ; Yttrium ; Ceramic ; Cerium ; Annealing (glass) ; Quantum efficiency ; Radiation ; Yttrium aluminium garnet ; Optoelectronics ; Doping ; Analytical Chemistry (journal) ; Optics ; Metallurgy ; Chemistry Luminescence Properties of Advanced Materials ; Radiation Detection and Scintillator Technologies ; Terahertz technology and applications
Authors: Karla Santacruz‐Gómez | Víctor Hugo López Durazo | Samaria Jhoana Gutiérrez Félix | Andrés Gutiérrez Velázquez | Aracely Ángulo-Molina
Source: EPISTEMUS (article, 2023-08-22)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Optimizing Surface-Enhanced Raman Spectroscopy Substrates with Gold Nanospheres, Nanorods and Nanostars Surface-Enhanced Raman Spectroscopy is a powerful technique that boosts the distinctive fingerprint signals of molecules, making them more accessible for analysis. It utilizes metallic nanoparticles, acting as amplifiers, to greatly enhance the signals emitted by the molecules. This study aimed to explore the SERS potential of gold nanoparticles (AuNPs) with different geometries using a non-resonant molecule, 4-MBA. Nanospheres (14±2 nm), nanorods (11±2 nm x 50±7 nm) and nanostars (38±4 nm) were synthesized via the HAuCl4 reduction method. All three AuNP geometries exhibited a remarkable enhancement of the Raman signal of 4-MBA by a magnitude of 104. Notably, only gold nanorods and nanostars displayed localized surface plasmon within the biological window, making them highly suitable for biological sample analysis. Meanwhile, the application of gold nanospheres should be limited to chemical SERS detection. These findings confirm the potential use of these nanostructures as SERS substrates for studying molecules with low molar... Nanorod ; Raman spectroscopy ; Surface-enhanced Raman spectroscopy ; Materials science ; Colloidal gold ; Nanotechnology ; Plasmon ; Molecule ; Nanoparticle ; Nanostructure ; Surface plasmon resonance ; Surface plasmon ; Spectroscopy ; Raman scattering ; Chemistry ; Optoelectronics ; Optics Gold and Silver Nanoparticles Synthesis and Applications ; Advanced biosensing and bioanalysis techniques ; Nanocluster Synthesis and Applications
Authors: Yingying Guo
Source: Materials (article, 2023-10-25)
Field: Materials Science — Materials Chemistry

Effect of Film Thickness on the Self-Assembly of CBABC Symmetric Pentablock Terpolymer Melts under 1D Confinement: A Dissipative Particle Dynamic Study The study investigates the impact of film thickness on the phase behavior of pentablock terpolymers, denoted as <i>C</i><sub>3</sub><i>B</i><sub>3</sub><i>A</i><sub>6</sub><i>B</i><sub>3</sub><i>C</i><sub>3</sub>, when subjected to wall confinement by utilizing the dissipative particle dynamics method. Phase diagrams were constructed to elucidate how factors such as block-block interaction strength, film thickness, and wall properties affect the self-assembly structures. In cases where the wall exhibits no preference for any of the blocks, lamellae phases with orientations perpendicular to the wall are observed. The order-disorder transition (ODT) temperature is found to be influenced by the interaction between the polymer and the wall in thin confinement scenarios. When the wall displays a preference for specific blocks, the orientation of lamellae structures undergoes variations. Lamellae tend to align parallel to the wall when the wall favors A or C blocks, and they orient perpendicularly when B blocks are favored. Furthermore, the mechanical properties of the lamellae structures are related to the conformations of the polymer chains. Structures where chains predominantly adopt a loop conformation exhibit enhanced elastic properties. The ratio of looping to bridging conformations can be adjusted by altering the film thickness and wall selectivity. Dissipative particle dynamics ; Dissipative system ; Materials science ; Copolymer ; Particle (ecology) ; Composite material ; Thermodynamics ; Physics ; Polymer ; Geology Block Copolymer Self-Assembly ; Advanced Polymer Synthesis and Characterization ; Polymer Surface Interaction Studies
Authors: Maëva Almeida | D. Dudzinski | Catherine AMIEL | Jean-Michel GUIGNER | Sylvain PREVOST | Clémence LE COEUR | Fabrice Cousin
Source: Preprints.org (preprint, 2023-04-25)
Field: Chemistry — Organic Chemistry

Aqueous Binary Mixtures of Stearic Acid and Its Hydroxylated Counterpart 12-Hydroxystearic Acid: Cascade of Morphological Transitions at Room Temperature We describe the behavior of mixtures of stearic acid (SA) and its hydroxylated counterpart 12-hydroxystearic acid (12-HSA) in aqueous mixtures at room temperature, as function of the 12-HSA/(fatty acid) mole ratio R. The morphologies of the self-assembled aggregates are obtained by a multi-structural approach that combines confocal and cryo-TEM microscopies with Small-Angle Neutron Scattering (SANS) and Wide-Angle X-Rays Scattering (WAXS) measurements, coupled with rheology measurements. Fatty acids are solubilized by an excess of ethanolamine counterions, so that their heads are negatively charged. The behavior is driven by the competition between mixing entropy and enthalpic effects. A clear trend towards partitioning between the two types of fatty acids is observed, presumably driven by the favorable formation of a H-bond network between hydroxyl OH function on the 12th carbon.&#x0D; For all R, the self-assembled structures are locally lamellar, with bilayers composed of crystallized and strongly interdigitated fatty acids. At high R, multi-lamellar tubes are formed, similarly as for pure aqueous solutions of 12-HSA. The doping by a low amount of SA molecules only slightly modify the dimensions of the tubes (radius and length), and slightly decreases the bilayers rigidity. The solutions have a gel-like behavior originating from entanglements between tubes and show a yield stress. At intermediate R, a partial local partitioning occurs between the two types of fatty acids. The tubes coexist in solution with helical ribbons. The two structures possibly merge to form very long snaky objects with straight and curved parts. The rigidity of the bilayers and the rheological behavior of the solutions are very similar to those of the high R case. At low R, local partitioning also occurs, and the architecture of the self-assemblies associates the two morphologies of the pure fatty acids systems, respectively 2-D planar bilayers for SA and the tubes describe above for the 12-HSA molecules: they are facetted objects with planar domains enriched in SA molecules, capped with curved domains enriched in 12-HSA molecules. The rigidity of the bilayers is strongly increased, as well their storage modulus, compared to systems with larger R. The solutions remain however viscous fluids in this regime of low R. Aqueous solution ; Stearic acid ; Lamellar structure ; Chemistry ; Small-angle X-ray scattering ; Crystallography ; Neutron scattering ; Scattering ; Chemical engineering ; Organic chemistry Surfactants and Colloidal Systems ; Lipid Membrane Structure and Behavior ; Advanced Polymer Synthesis and Characterization