jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Jie Jin | Yin‐Ning Zhou | Zheng‐Hong Luo
Source: AIChE Journal (article, 2023-01-14)
Field: Chemistry — Organic Chemistry

Simulation of mass transfer and kinetics during double‐network formation using a heterogeneous model Abstract A detailed heterogeneous model considering the thermodynamic incompatibility was developed to simulate polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer network (IPN) formation. The Gibbs free energy was calculated to predict the phase separation point and a two‐film theory was used to quantify the mass transfer between the PU‐rich phase and the PMMA‐rich phase. Compared with the homogeneous model, the cross‐linking density of PMMA increases rapidly during the network formation, because the monomer dispersion in two phases improves the possibility of free radical cross‐linking reaction, whereas the cross‐linking density of PU is unaffected. Simulations show that the partitioning of monomer significantly affects the PMMA network structure. The phase separation is strongly dependent on the onset of MMA polymerization. The proposed model allows visualizing of the IPN formation process and provides direction for reducing the extent of phase separation. Moreover, the structural information derived from the simulations can be further related to the properties. Monomer ; Methyl methacrylate ; Kinetics ; Phase (matter) ; Polymer ; Materials science ; Gel point ; Mass transfer ; Polymerization ; Polyurethane ; Dispersion (optics) ; Polymer chemistry ; Network formation ; Structure formation ; Gibbs free energy ; Chemical engineering ; Thermodynamics ; Chemistry ; Composite material ; Organic chemistry ; Computer science ; Physics Advanced Polymer Synthesis and Characterization ; Polymer composites and self-healing ; Polymer crystallization and properties
Authors: Ken Kato | Hiroki Takahashi | H Tamaki | Toshimichi Fujiwara | Yoh Matsuki
Source: ChemRxiv (preprint, 2023-08-31)
Field: Materials Science — Materials Chemistry

Nanodiamond-based hyperpolarization for in-situ magic-angle-spinning nuclear magnetic resonance spectroscopy of proteins Diamond-based hyperpolarization of external molecular spins has a significant impact on the modality of the nuclear magnetic resonance (NMR) spectroscopy and its sensitivity. The current nitrogen-vacancy (NV) center-based hyperpolarization and optical detection technique however faces a challenge in its implementation at high external field conditions required for the analysis of complex chemical entities such as proteins. In this work, we demonstrate that the surface electrons of nanodiamonds can be an attractive alternative with a number of practical benefits to this end. We first show at a very high external field condition (16.4 T) and low temperature (30 K) that the 13C spin polarization 200-fold higher than the conventional NMR can be achieved for the external bio-molecules within ~3 nm from the diamond surface with no laser illumination and no lattice orientation dependence. This latter property enabled us to record sensitivity-enhanced high-resolution multi-dimensional NMR data on protein sample under continuous sample spinning. We also show that the smallness of the nanodiamond (~5 nm), stability to bio-reduction and richness in surface chemistry enables a molecular-specific delivery of the diamond particle to targeted protein amyloid fibers within crowded cellular environment for a selective hyperpolarization. Overall, this work opens up new avenues to highly sensitive and targeted in-situ MAS NMR spectroscopy, relevant to biology and other fields. Hyperpolarization (physics) ; Nanodiamond ; Diamond ; Spins ; Nuclear magnetic resonance spectroscopy ; Materials science ; Magic angle spinning ; Spectroscopy ; Solid-state nuclear magnetic resonance ; Nanotechnology ; Nuclear magnetic resonance ; Chemical physics ; Chemistry ; Physics ; Condensed matter physics Diamond and Carbon-based Materials Research ; Atomic and Subatomic Physics Research ; Advanced NMR Techniques and Applications
Authors: Yu Huang | Yanqin Rong | Wenjia Zhang | Zibin Zhang | Xiaoyuan Zhang | Wenting Liang | Cheng Yang
Source: RSC Advances (article, 2023-01-01)
Field: Chemistry — Inorganic Chemistry

Tailoring carboxylatopillar[5]arene-modified magnetic graphene oxide nanocomposites for the efficient removal of cationic dyes A carboxylatopillar[5]arene-embellished (CP5) magnetic graphene oxide nanocomposite (MGO@CP5) was smoothly constructed <i>via</i> a mild layer-by-layer method. The morphology, structure, and surface characteristics of this nanocomposite was investigated by field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, zeta potential, and other techniques. Benefiting from a high capture ability for small molecules of CP5 as a supramolecular host molecule, along with a negative surface charge and large surface area of MGO@CP5, this nanocomposite exhibits an ultrafast, efficient adsorption property for representative cationic dyes: methylene blue (MB) and basic fuchsin (BF). The removal efficiency of MB and BF can reach nearly 99% within 3 min, while the maximum adsorption capacity of the two dyes reaches 240 mg g<sup>-1</sup> for MB and 132 mg g<sup>-1</sup> for BF. Furthermore, owing to excellent magnetic responsiveness from the tight loading of Fe<sub>3</sub>O<sub>4</sub> nanoparticles on graphene oxide, MGO@CP5 could be easily and magnetically separated, regenerated, and reused four times without an evident reduction in the removal efficiency (>95%). Impressively, the adsorption property of MGO@CP5 reveals a strong tolerance to pH changes and ionic strength interference, which renders it a promising adsorbent in the field of water treatment. Graphene ; Cationic polymerization ; Oxide ; Nanocomposite ; Materials science ; Chemical engineering ; Chemistry ; Polymer chemistry ; Organic chemistry ; Nanotechnology Metal-Organic Frameworks: Synthesis and Applications ; Molecular Sensors and Ion Detection ; Supramolecular Self-Assembly in Materials
Authors: Michael Wenzel | Roland Mitrić
Source: The Journal of Chemical Physics (article, 2023-12-18)
Field: Chemistry — Physical and Theoretical Chemistry

Prediction of fluorescence quantum yields using the extended thawed Gaussian approximation Spontaneous emission and internal conversion rates are calculated within harmonic approximations and compared to the results obtained within the semi-classical extended thawed Gaussian approximation (ETGA). This is the first application of the ETGA in the calculation of internal conversion and emission rates for real molecular systems, namely, formaldehyde, fluorobenzene, azulene, and a dicyano-squaraine dye. The viability of the models as black-box tools for prediction of spontaneous emission and internal conversion rates is assessed. All calculations were done using a consistent protocol in order to investigate how different methods perform without previous experimental knowledge using density functional theory (DFT) and time-dependent DFT (TD-DFT) with B3LYP, PBE0, ωB97XD, and CAM-B3LYP functionals. Contrasting the results with experimental data shows that there are further improvements required before theoretical predictions of emission and internal conversion rates can be used as reliable indicators for the photo-luminescence properties of molecules. We find that the ETGA performs rather similar to the vertical harmonical model. Including anharmonicities in the calculation of internal conversion rates has a moderate effect on the quantitative results in the studied systems. The emission rates are fairly stable with respect to computational parameters, but the internal conversion rate reveals itself to be highly dependent on the choice of the spectral line shape function, particularly the width of the Lorentzian function, associated with homogeneous broadening. Internal conversion ; Density functional theory ; Azulene ; Gaussian ; Harmonic ; Quantum ; Function (biology) ; Materials science ; Computational physics ; Molecular physics ; Chemistry ; Physics ; Computational chemistry ; Spectral line ; Quantum mechanics ; Photochemistry Photochemistry and Electron Transfer Studies ; Spectroscopy and Quantum Chemical Studies ; Free Radicals and Antioxidants
Authors: Kaicheng Zhu | Saber Naserifar | William A. Goddard | Haibin Su
Source: Physical Chemistry Chemical Physics (article, 2023-01-01)
Field: Materials Science — Materials Chemistry

Topology induced crossover between Langevin, subdiffusion, and Brownian diffusion regimes in supercooled water Despite extensive studies of supercooled water, it remains challenging to understand its peculiar dynamic anomalous properties. In this work, we integrated full atomistic simulations of supercooled water over the temperature range of room temperature to 200 K using a quantum-mechanics-based polarizable force field with the dressed dynamics method that couples fast collision events and slow reorganization dynamics of hydrogen-bond networks. Our analysis unveils the salient multiscale features in the transient relaxation dynamics of supercooled water. A classical Langevin behavior dominates at fast timescales, while long-time relaxations unveil two different activation barriers in two temperature regions: below and above 230 K. The modulation of the entropy spectrum by temperature is elucidated in terms of a three-state model underlined by the complexity of the water dynamics associated with a topological transition of a strong hydrogen-bond network. This state-dependent network topology is quantitatively characterized by power-law exponents of inverse network connectivity from 200 to 298 K. This work provides valuable guidance for further studies on the transient relaxation dynamics of supercooled water. Supercooling ; Crossover ; Brownian dynamics ; Statistical physics ; Diffusion ; Brownian motion ; Langevin dynamics ; Physics ; Langevin equation ; Condensed matter physics ; Thermodynamics ; Quantum mechanics ; Computer science Material Dynamics and Properties ; Topological and Geometric Data Analysis ; Theoretical and Computational Physics
Authors: Yizhuo Jia | P.P. Man | Xinyao Guo | Liang Deng | Yang Li
Source: Polymers (article, 2023-09-30)
Field: Materials Science — Polymers and Plastics

Effects of Overload on Thermal Decomposition Kinetics of Cross-Linked Polyethylene Copper Wires During an overload fault in an energized wire, the hot metal core modifies the structure of the insulation material. Therefore, understanding the thermal decomposition kinetics of the insulation materials of the overloaded wire is essential for fire prevention and control. This study investigates the thermal decomposition process of new and overloaded cross-linked polyethylene (XLPE) copper wires using thermogravimetry-Fourier-transform infrared spectroscopy and cone calorimetry. The thermal decomposition onset temperature and activation energy of the overloaded XLPE insulation materials were reduced by approximately 15 K and 20 kJ mol<sup>-1</sup>, respectively, and its reaction mechanism function changed from D-ZLT<sub>3</sub> to A2 (0 < α < 0.5). The FTIR shows that the major spectral components produced during the pyrolysis of the XLPE insulation material are C-H stretching, H<sub>2</sub>O, CO<sub>2</sub>, C-H scissor vibrations, and C=O and C=C stretching. Additionally, the four functional groups in the PE chains produced the spectral components in the following decreasing order of wavenumber: C-H stretching > CO<sub>2</sub> > C-H scissor vibration > C=O and C=C stretching. Polyethylene ; Materials science ; Thermogravimetry ; Thermal decomposition ; Kinetics ; Activation energy ; Fourier transform infrared spectroscopy ; Copper ; Decomposition ; Composite material ; Differential scanning calorimetry ; Pyrolysis ; Thermal analysis ; Thermal ; Chemical engineering ; Chemistry ; Physical chemistry ; Organic chemistry ; Metallurgy ; Thermodynamics ; Inorganic chemistry Polymer crystallization and properties ; Thermal and Kinetic Analysis ; Polymer Nanocomposites and Properties
Authors: Yunlong Le | Guan Yun-shan | Xiaoying Ma | Weidong Zhang
Source: Polymers (article, 2023-01-15)
Field: Materials Science — Polymers and Plastics

Preparation and Boron Removal Performance of Glycidol Modified PANI Nanorods: An Optimization Study Based on Response Surface Methodology Boron removal from aqueous solutions has attracted increasing attention, offering benefits for animal and plant health as well as profound significance for exploiting Salt Lake boron resources. In this work, we synthesized novel glycidol-functionalized and hydrophilic polyaniline (PANI) nanorod adsorbents, which were prepared to separate boron compounds from boric acid aqueous solutions. The as-prepared adsorbents were significantly different from the traditional polymers' grafting reaction because they had a higher functional yield and more active position for adsorption. The maximum adsorption capacity (0.2210 mmoL∙g<sup>-1</sup>) and optimal adsorption conditions (boric acid concentration of 1307 mg/L, pH = 9.82, time of 10 h) were obtained with single-factor experimentation and the response surface method (RSM). In addition, adsorption kinetics studies showed that the adsorption reaction belonged to the pseudo-first-order kinetic model, and diffusion was the key limiting factor; therefore, the adsorption equilibrium time is more than 10 h. Finally, the related possible adsorption mechanism was investigated based on the species and the diffusion of boron in the aqueous phase. Glycidol ; Response surface methodology ; Nanorod ; Boron ; Materials science ; Surface modification ; Chemical engineering ; Nanotechnology ; Chemistry ; Chromatography ; Catalysis ; Organic chemistry ; Engineering Conducting polymers and applications ; Advancements in Battery Materials ; Supercapacitor Materials and Fabrication
Authors: Vladislav O. Khaustov | Domenica Convertino | Janis Köster | Alexei Zakharov | Michael J. Mohn | Zewdu M. Gebeyehu | Leonardo Martini | Simona Pace | Giovanni Marini | Matteo Calandra | Ute Kaiser | Stiven Forti | Camilla Coletti
Source: ACS Applied Nano Materials (review, 2023-07-06)
Field: Materials Science — Materials Chemistry

Heterocontact-Triggered 1H to 1T′ Phase Transition in CVD-Grown Monolayer MoTe<sub>2</sub>: Implications for Low Contact Resistance Electronic Devices Single-layer molybdenum ditelluride (MoTe<sub>2</sub>) has attracted attention due to the smaller energy difference between the semiconducting (1H) and semimetallic (1T') phases with respect to other two-dimensional transition metal dichalcogenides (TMDs). Understanding the phenomenon of polymorphism between these structural phases is of great fundamental and practical importance. In this paper, we report a 1H to 1T' phase transition occurring during the chemical vapor deposition (CVD) synthesis of single-layer MoTe<sub>2</sub> at 730 °C. The transformation originates at the heterocontact between monoclinic and hexagonal crystals and progresses to either yield a partial or complete 1H to 1T' phase transition. Microscopic and spectroscopic analyses of the MoTe<sub>2</sub> crystals reveal the presence of Te vacancies and mirror twin boundaries (MTB) domains in the hexagonal phase. The experimental observations and theoretical simulations indicate that the combination of heterocontact formation and Te vacancies are relevant triggering mechanisms in the observed transformation. By advancing in the understanding and controlling of the direct synthesis of lateral 1T'/1H heterostructures, this work contributes to the development of MoTe<sub>2</sub>-based electronic and optoelectronic devices with low contact resistance. Chemical vapor deposition ; Monoclinic crystal system ; Heterojunction ; Materials science ; Monolayer ; Transition metal ; Phase transition ; Condensed matter physics ; Phase (matter) ; Crystallography ; Chemical physics ; Hexagonal crystal system ; Nanotechnology ; Chemistry ; Optoelectronics ; Crystal structure ; Catalysis ; Physics 2D Materials and Applications ; Quantum Dots Synthesis And Properties ; Graphene research and applications
Authors: Aryana Rodgers | Matthew Sawaged | Dmitry Ostrovsky | Liliya Vugmeyster
Source: The Journal of Physical Chemistry B (article, 2023-03-23)
Field: Chemistry — Spectroscopy

Effect of Cross-Seeding of Wild-Type Amyloid-β<sub>1–40</sub> Peptides with Post-translationally Modified Fibrils on Internal Dynamics of the Fibrils Using Deuterium Solid-State NMR Post-translationally modified (PTM) amyloid-β (Aβ) species can play an important role in modulating Alzheimer's disease pathology. These relatively less populated modifications can cross-seed the wild-type Aβ peptides to produce fibrils that retain many structural and functional features of the original PTM variants. We focus on studies of internal flexibility in the cross-seeded Aβ<sub>1-40</sub> fibrils originating from seeding with two PTM variants with modifications in the disordered N-terminal domain: Δ<i>E</i>3 truncation and S8-phosphorylation. We employ an array of <sup>2</sup>H solid-state NMR techniques, including line shape analysis over a broad temperature range, longitudinal relaxation, and quadrupolar CPMG, to assess the dynamics of the cross-seeded fibrils. The focus is placed on selected side-chain sites in the disordered N-terminal domain (G9 and V12) and hydrophobic core methyl and aromatic groups (L17, L34, M35, V36, and F19). We find that many of the essential features of the dynamics present in the original PTM seeds persist in the cross-seeded fibrils, and several of the characteristic features are even enhanced. This is particularly true for the activation energies of the rotameric motions and large-scale rearrangements of the N-terminal domain. Thus, our results on the dynamics complement prior structural and cell toxicity studies, suggesting that many PTM Aβ species can aggressively cross-seed the wild-type peptide in a manner that propagates the PTM's signature. Fibril ; Chemistry ; Solid-state nuclear magnetic resonance ; Molecular dynamics ; Peptide ; Biophysics ; Amyloid (mycology) ; Crystallography ; Relaxation (psychology) ; Biochemistry ; Nuclear magnetic resonance ; Biology ; Physics ; Computational chemistry ; Neuroscience Advanced NMR Techniques and Applications ; Alzheimer's disease research and treatments ; Advanced Neuroimaging Techniques and Applications
Authors: Fuqiang Yang | Jianzhou Zhang | Yue Zhang
Source: Materials (article, 2023-08-24)
Field: Materials Science — Metals and Alloys

Modeling Corrosion Product Film Formation and Hydrogen Diffusion at the Crack Tip of Austenitic Stainless Steel Corrosion product films (CPFs) have significant effects on hydrogen permeation and the corrosion process at the crack tip. This paper established a two-dimensional calculation model to simulate the formation of CPFs at the crack tip and its effects on the crack tip stress status and hydrogen diffusion. The CPFs were simplified as a single-layer structure composed of Fe<sub>2</sub>O<sub>3</sub>, the effective CPFs boundary was modeled by the diffusion of oxygen, and the CPF-induced stress was modeled by hygroscopic expansion. The simulation was conducted with two stages; the first stage was to simulate the formation of CPFs formation and its effects on the crack tip stress status, while the second stage focused on the hydrogen diffusion with and without CPF formation under different external tensile loads. The results indicate that the highest compressive stress induced by the formation of CPFs is located at 50~60° of the crack contour and dramatically weakens the crack tip tensile stress at low-stress status. The CPFs can inhibit the hydrogen permeation into the crack tip, and the hydrostatic pressure effects on the redistribution of the permeated hydrogen are significant under larger external load conditions. Materials science ; Corrosion ; Hydrogen ; Stress corrosion cracking ; Ultimate tensile strength ; Crack closure ; Hydrostatic stress ; Composite material ; Stress (linguistics) ; Diffusion ; Metallurgy ; Structural engineering ; Fracture mechanics ; Finite element method ; Chemistry ; Thermodynamics Hydrogen embrittlement and corrosion behaviors in metals ; Corrosion Behavior and Inhibition ; Non-Destructive Testing Techniques
Authors: Michael Dölz | Berk Tekkaya | Sebastian Münstermann
Source: steel research international (article, 2023-09-09)
Field: Materials Science — Metals and Alloys

Numerical Investigation of the Influence of Nonmetallic Inclusions on the Local Hydrogen Concentration under Consideration of Residual Stress Fields Hydrogen as an energy carrier is politically supported and essential for the planned energy turnaround, but requires infrastructure for transport and storage of hydrogen on a large scale, which in turn requires the development of steels resistant to hydrogen‐induced damage. Since the experimental characterization of local hydrogen concentration is nearly impossible, but microstructure level effects are significant for damage initiation, it becomes essential to further develop accompanying numerical evaluation methods. These have to be able to quantitatively describe the effect of nonmetallic inclusions on the local hydrogen concentration as the detrimental effect of nonmetallic inclusions governs the resistance against hydrogen‐induced cracking. To capture this influence, the modeling approaches available in the literature are extended and made usable for tetrahedral elements. Validation is performed using numerical studies with specimens of different stress states. Submodels are exposed to a virtual cooling and then to a hydrogen loading. Based on the resulting residual stress fields, the local hydrogen concentrations around nonmetallic inclusions with different chemical compositions and geometry are investigated and evaluated. Herein, it can be shown that especially the hydrostatic stress has a large influence on the development of the local hydrogen concentration and that the influence is particularly strong for Al 2 O 3 ‐inclusions. Hydrogen ; Materials science ; Cracking ; Hydrostatic stress ; Residual stress ; Microstructure ; Hydrogen embrittlement ; Stress (linguistics) ; Hydrostatic equilibrium ; Metallurgy ; Composite material ; Structural engineering ; Finite element method ; Chemistry ; Corrosion ; Engineering ; Physics Hydrogen embrittlement and corrosion behaviors in metals ; Fatigue and fracture mechanics ; Nuclear Materials and Properties