jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Federico Caporaletti | S. Capaccioli | Sofia Valenti | Mirko Mikolasek | A. I. Chumakov | G. Monaco
Source: Nature Communications (article, 2021-03-25)
Field: Materials Science — Materials Chemistry

Experimental evidence of mosaic structure in strongly supercooled molecular liquids When a liquid is cooled to produce a glass its dynamics, dominated by the structural relaxation, become very slow, and at the glass-transition temperature T<sub>g</sub> its characteristic relaxation time is about 100 s. At slightly elevated temperatures (~1.2 T<sub>g</sub>) however, a second process known as the Johari-Goldstein relaxation, β<sub>JG</sub>, decouples from the structural one and remains much faster than it down to T<sub>g</sub>. While it is known that the β<sub>JG</sub>-process is strongly coupled to the structural relaxation, its dedicated role in the glass-transition remains under debate. Here we use an experimental technique that permits us to investigate the spatial and temporal properties of the β<sub>JG</sub> relaxation, and give evidence that the molecules participating in it are highly mobile and spatially connected in a system-spanning, percolating cluster. This correlation of structural and dynamical properties provides strong experimental support for a picture, drawn from theoretical studies, of an intermittent mosaic structure in the deeply supercooled liquid phase. Supercooling ; Relaxation (psychology) ; Glass transition ; Chemical physics ; Dynamical heterogeneity ; Cluster (spacecraft) ; Materials science ; Molecular dynamics ; Thermodynamics ; Chemistry ; Physics ; Computational chemistry ; Computer science ; Polymer Material Dynamics and Properties ; Glass properties and applications ; Photochemistry and Electron Transfer Studies
Authors: Shorouk S. Mukhtar | Ashraf S. Hassan | Nesrin M. Morsy | Taghrid S. Hafez | Hamdi M. Hassaneen | Fatma M. Saleh
Source: Egyptian Journal of Chemistry (article, 2021-06-19)
Field: Chemistry — Organic Chemistry

Overview on Synthesis, Reactions, Applications, and Biological Activities of Schiff Bases Schiff bases exhibited various pharmacological and biological activities such as antibacterial, cytotoxic effects, antifungal, and antimalarial. Schiff bases were used for designing organic compounds, metal complexes, or nanoparticles. Also, Schiff bases were applied in various fields as corrosion inhibitors, catalysts, and optical properties. Therefore, this review article focused on some synthesis, reactions, applications, and biological activities of Schiff bases especially Schiff bases-heterocyclic moiety conjugates in the ten last years. Schiff base ; Combinatorial chemistry ; Chemistry ; Polymer chemistry Synthesis and Characterization of Heterocyclic Compounds ; Metal complexes synthesis and properties ; Synthesis of Tetrazole Derivatives
Authors: Nils Bäumer | Kalathil K. Kartha | Stefan Buss | Iván Maisuls | Jasnamol P. Palakkal | Cristian A. Strassert | Gustavo Fernández
Source: Chemical Science (article, 2021-01-01)
Field: Materials Science — Biomaterials

Tuning energy landscapes and metal–metal interactions in supramolecular polymers regulated by coordination geometry Herein, we exploit coordination geometry as a new tool to regulate the non-covalent interactions, photophysical properties and energy landscape of supramolecular polymers. To this end, we have designed two self-assembled Pt(ii) complexes <b>1</b> and <b>2</b> that feature an identical aromatic surface, but differ in the coordination and molecular geometry (linear <i>vs.</i> V-shaped) as a result of judicious ligand choice (monodentate pyridine <i>vs.</i> bidentate bipyridine). Even though both complexes form cooperative supramolecular polymers in methylcyclohexane, their supramolecular and photophysical behaviour differ significantly: while the high preorganization of the bipyridine-based complex <b>1</b> enables an H-type 1D stacking with short Pt⋯Pt contacts <i>via</i> a two-step consecutive process, the existence of increased steric effects for the pyridyl-based derivative <b>2</b> hinders the formation of metal-metal contacts and induces a single aggregation process into large bundles of fibers. Ultimately, this fine control of Pt⋯Pt distances leads to tuneable luminescence-red for <b>1</b> <i>vs.</i> blue for <b>2</b>, which highlights the relevance of coordination geometry for the development of functional supramolecular materials. Supramolecular chemistry ; Luminescence ; Polymer ; Coordination geometry ; Metal ; Nanotechnology ; Materials science ; Geometry ; Supramolecular polymers ; Chemical physics ; Crystallography ; Chemistry ; Molecule ; Crystal structure ; Optoelectronics ; Organic chemistry ; Mathematics ; Composite material Supramolecular Self-Assembly in Materials ; Metal-Organic Frameworks: Synthesis and Applications ; Luminescence and Fluorescent Materials
Authors: Mikkel Baldtzer Liisberg | Zahra Shakeri Kardar | Stacy M. Copp | Cecilia Cerretani | Tom Vosch
Source: The Journal of Physical Chemistry Letters (article, 2021-01-21)
Field: Materials Science — Materials Chemistry

Single-Molecule Detection of DNA-Stabilized Silver Nanoclusters Emitting at the NIR I/II Border The near-infrared (NIR) I and II regions are known for having good light transparency of tissue and less scatter compared to the visible region of the electromagnetic spectrum. However, the number of bright fluorophores in these regions is limited. Here we present a detailed spectroscopic characterization of a DNA-stabilized silver nanocluster (DNA-AgNC) that emits at around 960 nm in solution. The DNA-AgNC converts to blue-shifted emitters over time. Embedding these DNA-AgNCs in poly(vinyl alcohol) (PVA) shows that they are bright and photostable enough to be detected at the single-molecule level. Photon antibunching experiments were performed to confirm single emitter behavior. Our findings highlight that the screening and exploration of DNA-AgNCs in the NIR II region might yield promising bright, photostable emitters that could help develop bioimaging applications with unprecedented signal-to-background ratios and single-molecule sensitivity. Nanoclusters ; Materials science ; Molecule ; Near-infrared spectroscopy ; DNA ; Optoelectronics ; Common emitter ; Nanotechnology ; Chemistry ; Optics ; Physics Nanocluster Synthesis and Applications ; Gold and Silver Nanoparticles Synthesis and Applications ; Advanced Nanomaterials in Catalysis
Authors: Andrew Leduc | R. Gray Huffman | Joshua Cantlon | Saad Khan | Nikolai Slavov
Source: bioRxiv (Cold Spring Harbor Laboratory) (preprint, 2021-04-26)
Field: Chemistry — Spectroscopy

Exploring functional protein covariation across single cells using nPOP Many biological processes, such as the cell division cycle, are reflected in protein covariation across single cells. This covariation can be quantified and interpreted by single-cell mass-spectrometry (MS) with sufficiently high throughput and accuracy. Towards this goal, we developed nPOP, a method that uses piezo acoustic dispensing to isolate individual cells in 300 picoliter volumes and performs all subsequent sample preparation steps in small droplets on a fluorocarbon-coated slide. This design enabled simultaneous sample preparation of thousands of single cells, including lysing, digesting, and labeling individual cells in volumes of 8-20 nl. Protein covariation analysis identified cell-cycle dynamics that were similar across cell types and dynamics that differed between cell types, even within sub-populations of melanoma cells defined by markers for drug-resistance priming. The melanoma cells expressing these markers accumulated in the G1 phase of the cell cycle, displayed distinct protein covariation across the cell cycle, accumulated glycogen, and had lower abundance of glycolytic enzymes. The non-primed melanoma cells exhibited gradients of protein abundance and covariation, suggesting transition states. These results were validated by different MS methods. Together, they demonstrate that protein covariation across single cells may reveal functionally concerted biological differences between closely related cell states. Cell cycle ; Biology ; Cell ; Cell type ; Single-cell analysis ; Cell biology ; Cell division ; Computational biology ; Chemistry ; Genetics Mass Spectrometry Techniques and Applications ; Advanced Proteomics Techniques and Applications ; Single-cell and spatial transcriptomics
Authors: Haifeng Zhu | Shuqing Feng | Zihui Kong | Xu Huang | Peng Lü | Jing Wang | Wai‐Yeung Wong | Zhi Zhou | Mao Xia
Source: Applied Surface Science (article, 2021-05-30)
Field: Materials Science — Materials Chemistry

Bi3+ occupancy rearrangement in K2-xAxMgGeO4 phosphor to achieve ultra-broad-band white emission based on alkali metal substitution engineering Phosphor ; Luminescence ; Alkali metal ; Excited state ; Thermal stability ; Materials science ; Emission spectrum ; Emission intensity ; Photoluminescence ; Chemistry ; Optoelectronics ; Atomic physics ; Spectral line ; Physics ; Organic chemistry Luminescence Properties of Advanced Materials ; Perovskite Materials and Applications ; Radiation Detection and Scintillator Technologies
Authors: Chunhua Fang | Yuning Tao | Jianguo Wang | Haixin You | Yan Cui | Mi Zhou
Source: Frontiers in Energy Research (article, 2021-12-01)
Field: Materials Science — Materials Chemistry

Research on Leakage Current Waveform Spectrum Characteristics of Artificial Pollution Porcelain Insulator The surface discharge development processes of polluted porcelain insulators for power transmission lines are tightly related with the development of leakage current (LC), the characteristics of LC, the insulating condition, and discharge intensity of the insulator surface have an important significance for revealing the contamination discharge state of insulators. In order to analyze the LC characteristics of porcelain insulators in the process of pollution flashover, artificial pollution flashover tests on porcelain insulators were conducted in the artificial fog cabinet, and the characteristics of LC waveforms in time-domain and frequency-domain were simultaneously measured and analyzed during the tests. The results indicated that the amplitude of LC, fundamental harmonic, the third harmonic, and fifth harmonic had a strong correlation, the maximum of LC( I m ), the rate of total harmonics ( THD ), and the phase difference of fundamental harmonic (θ) were used for the representation of the characteristics of the LC waveform. The LC has the characteristics of high amplitude, low proportion harmonic, and small phase difference between the fundamental harmonic and voltage before the flashover occurrence. The test results provide effective reference for porcelain insulators in pollution flashover forecasting. Arc flash ; Waveform ; Harmonics ; Insulator (electricity) ; Materials science ; Voltage ; Total harmonic distortion ; Acoustics ; Amplitude ; Environmental science ; Electrical engineering ; Engineering ; Optoelectronics ; Optics ; Physics High voltage insulation and dielectric phenomena ; Image Enhancement Techniques ; High-Voltage Power Transmission Systems
Authors: André J. van der Vlies | Jiayi Xu | Masoud Ghasemi | Carol M. Bator | Amanda Bell | Brett Rosoff-Verbit | Bin Liu | Enrique D. Gomez | Urara Hasegawa
Source: Biomacromolecules (article, 2021-11-11)
Field: Chemistry — Organic Chemistry

Thioether-Based Polymeric Micelles with Fine-Tuned Oxidation Sensitivities for Chemotherapeutic Drug Delivery Oxidation-sensitive drug delivery systems (DDSs) have attracted attention due to the potential to improve efficacy and safety of chemotherapeutics. These systems are designed to release the payload in response to oxidative stress conditions, which are associated with many types of cancer. Despite extensive research on the development of oxidation-sensitive DDS, the lack of selectivity toward cancer cells over healthy cells remains a challenge. Here, we report the design and characterization of polymeric micelles containing thioether groups with varying oxidation sensitivities within the micellar core, which become hydrophilic upon thioether oxidation, leading to destabilization of the micellar structure. We first used the thioether model compounds, 3-methylthiopropylamide (TPAM), thiomorpholine amide (TMAM), and 4-(methylthio)benzylamide (TPhAM) to investigate the effect of the chemical structures of the thioethers on the oxidation by hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>). TPAM shows the fastest oxidation, followed by TMAM and TPhAM, showing that the oxidation reaction of thioethers can be modulated by changing the substituent groups bound to the sulfur atom. We next prepared micelles containing these different thioether groups within the core (TP, TM, and TPh micelles). The micelles containing the thioether groups with a higher oxidation sensitivity were destabilized by H<sub>2</sub>O<sub>2</sub> at a lower concentration. Micelle destabilization was also tested in human liver cancer (HepG2) cells and human umbilical vein endothelial cells (HUVECs). The TP micelles having the highest oxidation sensitivity were destabilized in both HepG2 cells and HUVECs, while the TPh micelles, which showed the lowest reactivity toward H<sub>2</sub>O<sub>2</sub>, were stable in these cell lines. The TM micelles possessing a moderate oxidation sensitivity were destabilized in HepG2 cells but were stable in HUVECs. Furthermore, the micelles were loaded with doxorubicin (Dox) to evaluate their potential in drug delivery applications. Among the micelles, the TM micelles loaded with Dox showed the enhanced relative toxicity in HepG2 cells over HUVECs. Therefore, our approach to fine-tune the oxidation sensitivity of the micelles has potential for improving therapeutic efficacy and safety of drugs in cancer treatment. Thioether ; Micelle ; Chemistry ; Prodrug ; Hydrogen peroxide ; Combinatorial chemistry ; Organic chemistry ; Biochemistry ; Aqueous solution Free Radicals and Antioxidants ; Nanoplatforms for cancer theranostics ; Metal complexes synthesis and properties
Authors: Lin Liang | Boyang Li | Wenyao Zhang | Anyang Li | Bo Zheng | Xiao‐Juan Yang | Biao Wu
Source: Angewandte Chemie International Edition (article, 2021-01-27)
Field: Chemistry — Organic Chemistry

Fine‐Tuning the Spring‐Like Motion of an Anion‐Based Triple Helicate by Tetraalkylammonium Guests Supramolecular springs are a class of molecular devices that may provide implications to the macroscopic spring behavior from the molecular level. Helical structures are suitable molecular springs because the specific twisting of the helical strands can cause spring-like (extension-contraction) movement along the axis upon external stimuli. Herein we report an anion-based triple-helicate spring, which can undergo reversible contraction-extension motion through introduction and removal of tetraalkylammonium cations, including TMA<sup>+</sup> and analogous irregular tetrahedral cations bearing different alkyl chains, while the relative orientation of the two phosphate ions changes to facilitate guest inclusion. Notably, the degree of contraction (shortening of the helical pitch) can be fine-tuned by varying the shape and size of guest cation. However, with the larger cations (TEA<sup>+</sup> , TPA<sup>+</sup> and TBA<sup>+</sup> ), the meso-helicate configuration is obtained, which interconverts with the helicate by addition/removal of TMA<sup>+</sup> ion. Supramolecular chemistry ; Ion ; Chemistry ; Alkyl ; Contraction (grammar) ; Crystallography ; Stereochemistry ; Nanotechnology ; Materials science ; Crystal structure ; Organic chemistry Supramolecular Chemistry and Complexes ; Luminescence and Fluorescent Materials ; Molecular Sensors and Ion Detection
Authors: Vetiga Somjit | Phakawan Thinsoongnoen | Saran Waiprasoet | Taweesak Pila | Pichaya Pattanasattayavong | Satoshi Horike | Kanokwan Kongpatpanich
Source: ACS Applied Materials & Interfaces (article, 2021-06-24)
Field: Chemistry — Inorganic Chemistry

Processable UiO-66 Metal–Organic Framework Fluid Gel and Electrical Conductivity of Its Nanofilm with Sub-100 nm Thickness Zr-based UiO-66 metal–organic framework (MOF) is one of the most studied MOFs with a wide range of potential applications. While UiO-66 is typically synthesized as a microcrystalline solid, we employ a particle downsizing strategy to synthesize UiO-66 as fluid gel with unique rheological properties, which allows the solution-based processing as sub-100 nm films and enhances the electrical conductivity of its pristine structure. Film thicknesses ranging from 40 to 150 nm could be achieved by controlling the spin-coating parameters. The generality of the method is also demonstrated for other Zr-based MOFs including MOF-801 and MOF-808. The impact of particle size and film thickness at the nanoscale on electrical properties of UiO-66 is shown to realize new features that are distinct from those of the bulk powder phase. An electrical insulator UiO-66 shows a significant increase in the electrical conductivity (10–5 S cm–1 compared to 10–7 S cm–1 in the bulk powder phase) when the 10 nm particles are distributed on the substrate with a thickness less than 100 nm. The findings establish a new route for processing of MOF materials as thin films with fine-tuned thickness and offer a new perspective for transport properties of Zr-based MOFs without structural modification. Materials science ; Electrical resistivity and conductivity ; Nanoscopic scale ; Metal-organic framework ; Microcrystalline ; Chemical engineering ; Phase (matter) ; Conductivity ; Insulator (electricity) ; Nanoparticle ; Nanotechnology ; Particle size ; Composite material ; Crystallography Metal-Organic Frameworks: Synthesis and Applications ; Magnetism in coordination complexes ; Covalent Organic Framework Applications
Authors: Mena N. Gadalla | Andrew S. Greenspon | Rodrick Kuate Defo | Xingyu Zhang | Evelyn L. Hu
Source: Proceedings of the National Academy of Sciences (article, 2021-03-17)
Field: Materials Science — Materials Chemistry

Enhanced cavity coupling to silicon vacancies in 4H silicon carbide using laser irradiation and thermal annealing The negatively charged silicon monovacancy [Formula: see text] in 4H silicon carbide (SiC) is a spin-active point defect that has the potential to act as a qubit in solid-state quantum information applications. Photonic crystal cavities (PCCs) can augment the optical emission of the [Formula: see text], yet fine-tuning the defect-cavity interaction remains challenging. We report on two postfabrication processes that result in enhancement of the [Formula: see text] optical emission from our PCCs, an indication of improved coupling between the cavity and ensemble of silicon vacancies. Below-bandgap irradiation at 785-nm and 532-nm wavelengths carried out at times ranging from a few minutes to several hours results in stable enhancement of emission, believed to result from changing the relative ratio of [Formula: see text] ("dark state") to [Formula: see text] ("bright state"). The much faster change effected by 532-nm irradiation may result from cooperative charge-state conversion due to proximal defects. Thermal annealing at 100 °C, carried out over 20 min, also results in emission enhancements and may be explained by the relatively low-activation energy diffusion of carbon interstitials [Formula: see text], subsequently recombining with other defects to create additional [Formula: see text]s. These PCC-enabled experiments reveal insights into defect modifications and interactions within a controlled, designated volume and indicate pathways to improved defect-cavity interactions. Silicon carbide ; Annealing (glass) ; Irradiation ; Materials science ; Silicon ; Laser ; Optoelectronics ; Thermal ; Metallurgy ; Optics ; Nuclear physics Diamond and Carbon-based Materials Research ; Semiconductor materials and devices ; Thin-Film Transistor Technologies
Authors: Jakub Bińczak | Krzysztof Dziuba | Anna Chrobok
Source: Materials (review, 2021-05-27)
Field: Materials Science — Biomaterials

Recent Developments in Lactone Monomers and Polymer Synthesis and Application Lactones are a group of compounds that have been known for several decades. The commercial importance of lactones results from the possibility of manufacturing of a broad scope of derivatives and polymers with a wide spectrum of applications. In this work the synthesis and characterization of simple lactones are described, which due to the easy methods of the synthesis are of high importance for the industry. The chemical as well as biochemical methods are included with special attention paid to the methods that avoid metal catalysts, initiators or toxic solvents, allowing the use of the final products for the medical applications, e.g., for controlled drug-release systems, resorbable surgical threads, implants, tissue scaffolds or for the production of drugs. Lactone-based derivatives, such as polymers, copolymers, composites or three-dimensional structures are also presented. The work is focused on the methods for the synthesis of lactones and lactones derivates, as well as on the special properties and application of the studied compounds. Lactone ; Polymer ; Materials science ; Catalysis ; Monomer ; Combinatorial chemistry ; Broad spectrum ; Organic chemistry ; Copolymer ; Nanotechnology ; Chemistry biodegradable polymer synthesis and properties ; Advanced Polymer Synthesis and Characterization ; Silicone and Siloxane Chemistry
Authors: Nadir Jori | Luciano Barluzzi | Iskander Douair | Laurent Maron | Farzaneh Fadaei‐Tirani | Ivica Živković | Marinella Mazzanti
Source: Journal of the American Chemical Society (article, 2021-07-16)
Field: Chemistry — Inorganic Chemistry

Stepwise Reduction of Dinitrogen by a Uranium–Potassium Complex Yielding a U(VI)/U(IV) Tetranitride Cluster Multimetallic cooperativity is believed to play a key role in the cleavage of dinitrogen to nitrides (N<sup>3-</sup>), but the mechanism remains ambiguous due to the lack of isolated intermediates. Herein, we report the reduction of the complex [K<sub>2</sub>{[U<sup>V</sup>(OSi(O<sup>t</sup>Bu)<sub>3</sub>)<sub>3</sub>]<sub>2</sub>(μ-O)(μ-η<sup>2</sup>:η<sup>2</sup>-N<sub>2</sub>)}], <b>B</b>, with KC<sub>8</sub>, yielding the tetranuclear tetranitride cluster [K<sub>6</sub>{(OSi(O<sup>t</sup>Bu)<sub>3</sub>)<sub>2</sub>U<sup>IV</sup>}<sub>3</sub>{(OSi(O<sup>t</sup>Bu)<sub>3</sub>)<sub>2</sub>U<sup>VI</sup>}(μ<sub>4</sub>-N)<sub>3</sub>(μ<sub>3</sub>-N)(μ<sub>3</sub>-O)<sub>2</sub>], <b>1</b>, a novel example of N<sub>2</sub> cleavage to nitride by a diuranium complex. The structure of complex <b>1</b> is remarkable, as it contains a unique uranium center bound by four nitrides and provides the second example of a <i>trans</i>-N═U<sup>VI</sup>═N core analogue of UO<sub>2</sub><sup>2+</sup>. Experimental and computational studies indicate that the formation of the U(IV)/U(VI) tetrauranium cluster occurs via successive one-electron transfers from potassium to the bound N<sub>2</sub><sup>4-</sup> ligand in complex <b>B</b>, resulting in N<sub>2</sub> cleavage and the formation of the putative diuranium(V) bis-nitride [K<sub>4</sub>{[U<sup>V</sup>(OSi(O<sup>t</sup>Bu)<sub>3</sub>)<sub>3</sub>]<sub>2</sub>(μ-O)(μ-N)<sub>2</sub>}], <b>X</b>. Additionally, cooperative potassium binding to the U-bound N<sub>2</sub><sup>4-</sup> ligand facilitates dinitrogen cleavage during electron transfer. The nucleophilic nitrides in both complexes are easily functionalized by protons to yield ammonia in 93-97% yield and with excess <sup>13</sup>CO to yield K<sup>13</sup>CN and KN<sup>13</sup>CO. The structures of two tetranuclear U(IV)/U(V) bis- and mononitride clusters isolated from the reaction with CO demonstrate that the nitride moieties are replaced by oxides without disrupting the tetranuclear structure, but ultimately leading to valence redistribution. Chemistry ; Cleavage (geology) ; Nitride ; Ligand (biochemistry) ; Nucleophile ; Yield (engineering) ; Potassium ; Cluster (spacecraft) ; Uranium ; Pyrrole ; Medicinal chemistry ; Crystallography ; Stereochemistry ; Catalysis ; Organic chemistry ; Receptor Inorganic Chemistry and Materials ; Radioactive element chemistry and processing ; Organometallic Complex Synthesis and Catalysis