jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Faisal Rasool | Amir Sohail
Source: OAJ Materials and Devices (article, 2022-04-09)
Field: Chemistry — Physical and Theoretical Chemistry

Spectrophysics of Coumarin-Based Chromophore In this work, we comprehensively explore the spectral and photophysical properties of a coumarin-based dye (1) in neat solvents. The modulation of stokes shifts, emission quantum yields (ФF) and excited-state lifetimes of 1by local environment (polarity, polarizability, viscosity and hydrogen bonding) signifies the formation of intramolecular charge state (ICT) from the amino group to the coumarin moiety. Collectively, in the more viscous polar solvents the rotation of the amino group is restricted, exponentially decreasing the non-radiative rate constants (knr). Keywords :#SPECTROPHYSICS #INTERMOLECULAR_CHARGE_TRANSFER #NON-RADIATIVE_RATE_CONSTANT #EXCITED-STATE_LIFETIME #LOCAL_ENVIRONMENT. Intramolecular force ; Photochemistry ; Excited state ; Chemistry ; Intermolecular force ; Moiety ; Reaction rate constant ; Chromophore ; Polarizability ; Hydrogen bond ; Relaxation (psychology) ; Molecule ; Atomic physics ; Stereochemistry ; Organic chemistry Photochemistry and Electron Transfer Studies ; Photochromic and Fluorescence Chemistry ; Free Radicals and Antioxidants
Authors: Annika Ketola | Miika Leppänen | Tuomas Turpeinen | Petri Papponen | Anna Sundberg | Kai Arstila | Elias Retulainen
Source:  (article, 2022-01-01)
Field: Materials Science — Surfaces, Coatings and Films

Wet Fibre Surface – Does it Behave Like a Gel? The physico-chemical characteristics of wet fibre surfaces and their role in fibre bonding and paper properties have been under debate and research for decades. The gel-likeness of the fibre surfaces has been addressed in many studies but has not been explicitly demonstrated. In this study, the structure of wet beaten kraft pulp fibre surface and its similarity with microfibrillated cellulose (CMF) was shown using helium ion microscopy (HIM) imaging. Beaten kraft fibres and CMF were dried using two mild drying methods to preserve the delicate fibrillated structures. The fibre surface had a strong resemblance with gel-like CMF material. The amount of external fibrillation varied along the fibre length and was often shown to extend tens of micrometers from the fibre surface. The gel-like behaviour of wet fibrillated material was demonstrated using rheological tests. The examined CMF and CNF samples with solids contents of 1.97% and 1.06%, respectively, showed gel-like behaviour. A low gelling point suggests that fibrillated fibre surfaces have the ability to transfer forces at very low consistencies, and that the ability increases as a power function of the solids content. This is assumed to play a remarkable role in increasing inter-fibre adhesion and in transmitting inter-fibre forces within consolidating webs, whether arising from external tensions or internal drying stresses. Materials science ; Surface (topology) ; Computer science ; Composite material ; Mathematics ; Geometry Surface Modification and Superhydrophobicity ; Textile materials and evaluations
Authors: Franco Cataldo
Source: Preprints.org (preprint, 2022-12-07)
Field: Materials Science — Polymers and Plastics

Thermochemistry of Sulfur-Based Vulcanization and of Devulcanized and Recycled Natural Rubber Compounds The vulcanization of rubber compounds is an exothermal process. A carbon black-filled and natural rubber-based (NR) formulation was mixed with different levels of sulfur (0.5, 1.0, 2.0, 4.0 and 6.0 phr) and studied with Differential Scanning Calorimetry (DSC) for the determination of the vulcanization enthalpy. It was found that the vulcanization enthalpy is dependent from the amount of sulfur present in the compound and the vulcanization heat released was -18.4 kJ/mol S if referred to the entire rubber compound formulation or -46.0 kJ/mol S if the heat released is referred only to the NR present in the compound. The activation energy for the vulcanization of the rubber compounds was also determined by a DSC study at 49 kJ/mol and found quite independent from the sulfur content of the compounds under study. A simplified thermochemical model is proposed to explain the main reactions occurring during the vulcanization. The model correctly predicts that the vulcanization is an exothermal process although it gives an overestimation of the vulcanization enthalpy which is larger for the EV vulcanization package and smaller for the conventional vulcanization system. If the devulcanization is conducted mechanochemically in order to break selectively the sulfur-based crosslinks, then the natural rubber compounds recovered from used tires can be re-vulcanized again and the exothermicity of such process can be measured satisfactorily with DSC analysis. This paper not only proposes a simplified mechanism of vulcanization and devulcanization but also proposes an analytical method to check the devulcanization status of the recycled rubber compound in order to distinguish truly devulcanized rubber from reclaimed rubber. Vulcanization ; Sulfur ; Natural rubber ; Enthalpy ; Differential scanning calorimetry ; Chemistry ; Materials science ; Polymer chemistry ; Thermodynamics ; Chemical engineering ; Organic chemistry ; Engineering Polymer Nanocomposites and Properties ; Thermal and Kinetic Analysis ; Polymer crystallization and properties
Authors: Daniel Rozsar | Alistair J. M. Farley | Iain McLauchlan | Darren J. Dixon
Source: ChemRxiv (preprint, 2022-12-20)
Field: Chemistry — Organic Chemistry

Bifunctional Iminophosphorane-Catalyzed Enantioselective Nitroalkane Addition to Unactivated α,β-Unsaturated Esters Herein we describe the enantioselective conjugate addition of nitroalkanes to unactivated α,β-un-saturated esters, catalyzed by a bifunctional iminophosphorane (BIMP) superbase. The transformation provides the most direct access to pharmaceutically relevant enantioenriched γ-nitroesters, utilizing feedstock chemicals, via unprecedented, yet fundamental reactivity. The methodology exhibits a broad substrate scope, including alkyl, aryl and heteroaryl electrophiles substituted in the β-position, and represents the most general entry to enantioenriched γ-nitroesters. The methodology was successfully applied on a gram scale with reduced catalyst loading, and additionally catalyst recovery was carried out, furthermore, the formal synthesis of a range of drugs, and the enantioselective synthesis of (S)-rolipram were achieved. Enantioselective synthesis ; Bifunctional ; Chemistry ; Combinatorial chemistry ; Catalysis ; Substrate (aquarium) ; Superbase ; Organocatalysis ; Reactivity (psychology) ; Conjugate ; Aryl ; Organic chemistry ; Electrophile ; Alkyl Synthetic Organic Chemistry Methods ; Asymmetric Hydrogenation and Catalysis ; Chemical Synthesis and Analysis
Authors: Baptiste Amouroux | Ali Eftekhari | Clément Roux | Pierre Roblin | Mathieu Pasturel | Ute Resch‐Genger | Christian Würth | Fabienne Gauffre | Michel Sliwa | Aude Bouchet | Christophe Coudret
Source: ChemRxiv (preprint, 2022-12-21)
Field: Materials Science — Materials Chemistry

Synthesis and emission dynamics of ultrasmall (sub-3 nm) UCNPs containing a reduced number of emitters Reducing the size of rare earth, alkali metal fluoride crystals formulated as upconverting nanoparticles (UCNP) down to few nm can lead to unique luminescent devices due to a reduced number of emitters. The synthesis of such Na(Gd-Yb)F4:Tm nanocrystals is still challenging. The most critical issue is to keep detectable emission despite the high surface to volume ratio and the limited number of emitting ions. The preparation of sub-3 nm diameter emissive, ꞵ-phase UCNPs with few emitters was achieved using a gadolinium-rich composition, an in-situ mixing of the precursor (NaOH and NH4F), and a microwave high-temperature cycling sequence which allowed the precise control of the particle size and dispersity. Such particles can contain only a single activator ion (Tm3+). Coating of these core particles with a NaGdF4 inert shell was carried-out in order to moderate the surface quenching deleterious influence. The reduced number of activators offers an unprecedented platform to study the role of cross relaxation in the global luminescence. This was tackled by time resolved luminescence measurements using an original combination of standard Yb3+ sensitizer NIR-excitation and direct Tm3+ activator UV-excitation. Luminescence ; Materials science ; Activator (genetics) ; Ion ; Dispersity ; Nanoparticle ; Nanocrystal ; Gadolinium ; Nanotechnology ; Analytical Chemistry (journal) ; Fluorescence ; Phosphor ; Lanthanide ; Optoelectronics ; Chemistry ; Optics Luminescence Properties of Advanced Materials ; Inorganic Fluorides and Related Compounds ; Solid State Laser Technologies
Authors: Mengjie Wang | Lanping Dang | Wan Xu | Zhiying Ma | Liuliu Shao | Guangxia Wang | Chunli Li | Hua Wang
Source:  (preprint, 2022-04-27)
Field: Chemistry — Organic Chemistry

Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures 2,5-Di(trimethylsilanyl)dithieno[2,3- b :3′,2′- d ]thiophene ((TMS) 2 - bb - DTT ), 2,5- di(trimethylsilanyl)diseleno[2,3- b :3′,2′- d ]thiophene ((TMS) 2 - bb - DST ), and 2,5- di(trimethylsilanyl)diseleno[2,3- b :3′,2′- d ] selenophene ((TMS) 2 - bb - DSS ) were used as starting materials to synthesize three S-shaped double helicenes (i. e., DH - 1 , DH - 2 , and DH - 3 ) through monobromination, formylation, the Wittig reaction, and double oxidative photocyclization. Photocyclization was a highly regioselective process. The molecular structures of DH - 1 and DH - 2 were confirmed by X-ray single-crystal analysis. Multiple intermolecular interactions, such as C-S, C-Se, S-S, S-Se, and Se-Se, were observed in the crystal packing structures of these compounds. Spectroscopic results and our previous work showed that the combination of molecular structure change and heteroatom replacement from S to Se could precisely modulate molecular energy levels. Thiophene ; Regioselectivity ; Formylation ; Heteroatom ; Chemistry ; Double bond ; Wittig reaction ; Stereochemistry ; Crystal structure ; Crystallography ; Ring (chemistry) ; Polymer chemistry ; Organic chemistry ; Catalysis Synthesis and Properties of Aromatic Compounds ; Photochromic and Fluorescence Chemistry ; Porphyrin and Phthalocyanine Chemistry
Authors: Yu‐Fei Song | Tianyang Shen | Ya Bai | Zelin Wang | Xiaoliang Sun | Guihao Liu | Sha Bai | Jiaxin Li | Lirong Zheng
Source: Research Square (preprint, 2022-05-24)
Field: Materials Science — Materials Chemistry

Trace Amount of Water Boosting Highly Selective Coupling of Methane to Ethane via a Noble-Metal Free Ni2+-doped MgO/Al2O3 Photocatalyst Abstract Direct and selective coupling of methane into high-value added products under mild conditions is a grand challenge since the activation of the inert C-H bonds (439 kJ mol − 1 ) and the inhibition of over-oxidation are simultaneously required. Herein, we report the fabrication of a noble-metal free Ni 2+ -doped MgO/Al 2 O 3 photocatalyst (NiMgAl-x, x represents calcination temperature) through facile topotactic conversion of the corresponding NiMgAl-layered double hydroxides (denoted as NiMgAl-LDH). EXAFS spectroscopy demonstrates that for NiMgAl-x, the Ni 2+ ions are isomorphically doped into MgO cell and no NiO phase is formed. By involving trace amounts of water, photo-oxidation of methane to ethane can be accomplished by using NiMgAl-800 as catalyst in a flow reactor with a high production rate (454.30 µmol g − 1 h − 1 ) and a superior selectivity (97.8%), which was the highest yield among all the noble-metal free photocatalysts reported so far. Detailed characterizations reveal the electron-enriched surface oxygens of NiMgAl-800 generated during the topotatic process lead to the enhanced photocatalytic activity. In-situ DRIFT experiments and DFT calculations show that the introduced H 2 O molecules can modulate the Gibbs free energy of ŸCH 3 towards a coupling conductive pathway instead of production of CO 2 , resulting in an increased C 2 H 6 selectivity and inhibited CO 2 production. Noble metal ; Catalysis ; Photocatalysis ; Calcination ; Inorganic chemistry ; Selectivity ; Oxidative coupling of methane ; Metal ; Chemistry ; Materials science ; Organic chemistry Layered Double Hydroxides Synthesis and Applications ; Advanced Photocatalysis Techniques ; Magnesium Oxide Properties and Applications
Authors: Abdelhak Lachguar | Eric Deydier | Agnès Labande | Éric Manoury | Rinaldo Poli | Jean‐Claude Daran
Source: Acta Crystallographica Section E Crystallographic Communications (article, 2022-06-14)
Field: Chemistry — Organic Chemistry

Synthesis and crystal structure of [(<i>S<sub>p</sub> </i>)-(2-phenylferrocenyl)methyl]trimethylammonium iodide dichloromethane monosolvate As a follow-up to our research on the chemistry of disubstituted ferrocene derivatives, the synthesis and the structure of the title compound, [Fe(C<sub>5</sub>H<sub>5</sub>)(C<sub>15</sub>H<sub>19</sub>N)]I·CH<sub>2</sub>Cl<sub>2</sub>, is described. The cation mol-ecule is built up from a ferrocene disubstituted by a tri-methyl-ammonium methyl group and a phenyl ring. The asymmetric unit contains the iodide to equilibrate the charge and a disordered di-chloro-methane solvate. The disordered model results from a roughly statistical exchange (0.6/0.4) between one Cl and one H. The packing of the structure is stabilized by weak C-H⋯<i>X</i> (<i>X</i> = I, Cl), C-H⋯π(Cp) and C-Cl⋯π(phen-yl) inter-actions, building a three-dimensional network. The cation has planar chirality with <i>S<sub>p</sub></i> (Fc) absolute configuration. The structure of the title compound is compared with related disubstituted (tri-meth-ylammonio)-methyl ferrocenes. Dichloromethane ; Chemistry ; Iodide ; Crystal structure ; Methyl iodide ; Bromide ; Medicinal chemistry ; Chlorinated solvents ; Crystallography ; Organic chemistry ; Solvent Ferrocene Chemistry and Applications ; Metal complexes synthesis and properties ; Crystal structures of chemical compounds
Authors: Owen Kendall | Lesly Melendez-Correa | Jiawen Ren | Samantha Prabath Ratnayake | Billy J. Murdoch | Edwin Mayes | Joel van Embden | Daniel E. Gómez | Arrigo Calzolari | Enrico Della Gaspera
Source: ChemRxiv (preprint, 2022-11-16)
Field: Materials Science — Materials Chemistry

Photoactive p-type spinel CuGa2O4 nanocrystals Herein we report the synthesis and characterization of spinel copper gallate (CuGa2O4) nanocrystals (NCs) with an average size of 3.7 nm via a heat-up colloidal reaction. CuGa2O4 NCs have a band gap of ~2.5 eV and strong p-type character, in agreement with ab initio simulations. These novel NCs are demonstrated to be photoactive, generating a clear and reproducible photocurrent under blue light irradiation when deposited as thin films. Crucially, the ability to adjust the Cu:Ga ratio within the NCs, and its effect on the optical and electronic properties of the NCs was also demonstrated. These results position CuGa2O4 NCs as a novel material for optoelectronic applications, including hole transport and light harvesting. Photocurrent ; Nanocrystal ; Spinel ; Materials science ; Ab initio ; Band gap ; Copper ; Irradiation ; Colloid ; Characterization (materials science) ; Optoelectronics ; Photochemistry ; Nanotechnology ; Physical chemistry ; Chemistry ; Physics ; Organic chemistry Copper-based nanomaterials and applications ; ZnO doping and properties ; Dielectric properties of ceramics
Authors: Kalpa de Silva | Proity Nayeeb Akbar | R. Blümel
Source: Research Square (preprint, 2022-08-30)
Field: Chemistry — Analytical Chemistry

Space-Resolved Chemical Information from Infrared Extinction Spectra Abstract Based on the classical Lorentz model of the index of refraction, a new method is presented for the extraction of the complex index of refraction from the extinction efficiency, Qext , of homogeneous and layered dielectric spheres that simultaneously removes scattering effects and corrects measured extinction spectra for baseline shifts, tilts, curvature, and scaling. No reference spectrum is required and fit functions may be used that automatically satisfy the Kramers-Kronig relations. Thus, the method yields pure absorbance spectra for unambiguous interpretation of the chemical information of the sample. In the case of homogeneous spheres, the method also determines the radius of the sphere. In the case of layered spheres, the method determines the substances within each layer. Only a single-element detector is required. Using simulated Qext data of polymethyl-methacrylate and polystyrene homogeneous and layered spheres, we show that our reconstruction algorithm is reliable and accurately extracts pure absorbance spectra from Qext data. Reconstructing the pure absorbance spectrum from a published, experimentally measured raw absorbance spectrum shows that our method simultaneously corrects spectra for scattering effects and, given shape information, corrects raw spectra for systematic errors that result in spectral distortions such as baseline shifts, tilts, curvature, and scaling. Absorbance ; Spectral line ; Scaling ; Refractive index ; Scattering ; Extinction (optical mineralogy) ; Optics ; Curvature ; SPHERES ; Chemistry ; Computational physics ; Molar absorptivity ; Spectral shape analysis ; Physics ; Molecular physics ; Geometry ; Mathematics Spectroscopy and Chemometric Analyses ; Optical Imaging and Spectroscopy Techniques ; Spectroscopy Techniques in Biomedical and Chemical Research
Authors: G. Kostadinova | Rumen Lyapchev | Joanna Stoycheva | Lyuben Borislаvov | Alia Tadjer | Marc de Wergifosse | Julia Romanova
Source: ChemRxiv (preprint, 2022-02-16)
Field: Chemistry — Organic Chemistry

Singlet fission tinkertoys based on N-heterocyclic carbenes: а study with the spin-flip simplified time-dependent density functional theory method Singlet fission is a photophysical process in organic matter, in which one absorbed photon is converted in two triplet excitons. Discovered over 50 years ago, today singlet fission attracts scientific interest because it opens new horizons for the development of highly efficient organic-based solar cells beyond the Shockley–Queisser limit. However, a relatively small amount of singlet fission chromophores is available and, with respect to molecular design, little is known about the relationship between compounds’ structure and singlet fission propensity. Here, we report the molecular design of new singlet fission materials based on dimers of N-heterocyclic carbenes (NHC) and their ‘locked’ analogues. The study applies the recently introduced spin-flip simplified time-dependent density functional theory (SF-sTD-DFT) approach, which allows the modelling of sizeable molecules with diradical character like most of the successful singlet fission chromophores. To motivate the choice of method for the study NHC-based chromophores, the SF-sTD-DFT results are benchmarked against high level calculations using the equation-of-motion spin-flip coupled-cluster method with single and double substitutions. Armed with a reliable computational strategy, we have explored in detail the singlet fission propensity variation of the compounds due to the following structural factors: topology, type of substituents, cis-trans conformation, extension of the conjugation and modulation of the heterocyclic aromaticity, as well as the length of the latch in the ‘locked’ analogues. The results reveal new strategies for the design of singlet fission materials and contribute to the deeper understanding of the excited state tunability at the molecular level. Singlet fission ; Chromophore ; Diradical ; Singlet state ; Density functional theory ; Chemistry ; Chemical physics ; Coupled cluster ; Excited state ; Fission ; Molecule ; Computational chemistry ; Photochemistry ; Atomic physics ; Physics ; Nuclear physics ; Neutron ; Organic chemistry N-Heterocyclic Carbenes in Organic and Inorganic Chemistry ; Organic Light-Emitting Diodes Research ; Ammonia Synthesis and Nitrogen Reduction
Authors: Owen Kendall | Lesly Melendez-Correa | Jiawen Ren | Samantha Prabath Ratnayake | Billy J. Murdoch | Edwin Mayes | Joel van Embden | Daniel E. Gómez | Arrigo Calzolari | Enrico Della Gaspera
Source: ChemRxiv (preprint, 2022-11-16)
Field: Materials Science — Materials Chemistry

Colloidal synthesis of photoactive p-type spinel copper gallate nanocrystals Herein we report the synthesis and characterization of spinel copper gallate (CuGa2O4) nanocrystals (NCs) with an average size of 3.7 nm via a heat-up colloidal reaction. CuGa2O4 NCs have a band gap of ~2.5 eV and a strong p-type character, in agreement with ab initio simulations. These NCs are demonstrated to be photoactive, generating a reproducible photocurrent under blue light irradiation when deposited as a thin film. The ability to adjust the Cu:Ga ratio within the NCs, and its effect on the optical and electronic properties of the NCs was also demonstrated. Nanocrystal ; Photocurrent ; Copper ; Materials science ; Colloid ; Spinel ; Gallate ; Band gap ; Ab initio ; Photochemistry ; Chemical engineering ; Nanotechnology ; Chemistry ; Optoelectronics ; Physical chemistry ; Nuclear chemistry ; Organic chemistry ; Metallurgy Copper-based nanomaterials and applications ; ZnO doping and properties ; Quantum Dots Synthesis And Properties
Authors: Ahmad Shoujaa
Source: Biomedical Journal of Scientific & Technical Research (article, 2022-04-04)
Field: Chemistry — Organic Chemistry

Recent Methods in Cancer Treatment and Diagnosis Conventional cancer treatments and diagnosis, such as surgery, radiotherapy, chemotherapy, biopsy, and X-rays have been used for decades to detect cancer and to treat the patients who suffer from the malady symptoms, however the conventional cancer treatment is harmful to healthy cells, and the conventional cancer detection is not sufficiently sensitive, because it is possible only after substantial growth of cancerous cells. Novel strategies for the treatment and detection of cancer, such as Nanotechnology may greatly enhance the cure opportunities for patients and improve the quality of their life by minimizing the toxic effects of anticancer drugs. In the Nanotechnology methods, such as Sodium Chloride Nanoparticles (SCNPs), Liposomes, Magnetic Nanoparticle (MNPs), Quantum Dots (QDs), and Gold Nanoparticles (AuNPs), the nanoparticles can be designed and formulated to create therapeutic agents that targeting the cancerous cells. In this review, the details of these possi-ble detection, diagnosis and treatment methods of nanotechnology are discussed carefully. Pharmacy ; Medicine ; Family medicine ; Cancer treatment ; Traditional medicine ; Library science ; Internal medicine ; Cancer Synthesis and biological activity ; Computational Drug Discovery Methods ; Cancer Research and Treatments