The molecular dynamics of poly(2-(2-methoxyethoxy)ethyl methacrylate), PMEO2MA, hydrogels with varying water contents were studied using broadband dielectric spectroscopy. Based on the water content, ...the PMEO2MA hydrogels were divided into two groups: (i) low water content systems (SD ≤ 0.5) with molecular dynamics dominated by polymer local and segmental movements and (ii) high water content systems (SD > 0.5) with molecular dynamics prevailing in water.
In low water content systems, four molecular processes slightly affected by water were found. Two of the processes above Tg arise from segmental motions, while two processes observed below Tg relate to local motions of PMEO2MA. The water dynamics in high water content systems vary depending on the swelling degree and significantly differ from the molecular dynamics of pure water.
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•The molecular dynamics of PMEO2MA with varying water contents was studied by BDS.•Due to the water content the PMEO2MA hydrogels were divided into two groups.•At low water content the relaxation processes are dominated by polymer movements.•For PMEO2MA gels with high water content the molecular dynamics is prevailed by water.•The BDS results correspond to DSC tests and hydration model proposed based on FT-IR.
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•NGO were incorporated into Cu-MOF using a modified solvothermal approach.•NGO improved the electroconductive properties of Cu-MOF material.•Cu-MOF/NGO/SPCE showed lower LOD and ...LOQ.•Cu-MOF/NGO/SPCE was found selective for detection of 4-NP in wastewater.
Metal-organic framework-based nanocomposites have recently received much attention in electrochemical sensors. Herein, copper-metal organic framework/nitrogen-doped graphene oxide (Cu-MOF/NGO) nanocomposites were synthesized using a solvothermal approach. The materials were characterized by field emission scanning electron microscopy/energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, Brunauer–Emmett–Teller analysis, X-ray diffraction analysis, thermogravimetric analysis, and UV-visible spectroscopy. The Cu-MOF/NGO nanocomposites were applied in the modification of a screen-printed carbon electrode (SPCE) towards detection of 4-nitrophenol (4-NP) using differential pulse voltammetry. Moreover, the electrode materials were characterized using Raman spectroscopy, atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. In ferricyanide and ferrocene redox probes, the Cu-MOF/NGO/SPCE showed improved current response and charge transfer kinetics. The Cu-MOF/NGO/SPCE showed a lower limit of detection (0.035 μmol L−1) and limit of quantification (0.116 μmol L−1) within a linear range of concentration (0.5–100 μmol L−1). The developed electrode demonstrated good analytical features of selectivity, repeatability, and reproducibility. The application of the Cu-MOF/NGO/SPCE was found to be successful in the determination of 4-NP in wastewater samples, with good recovery results in the range of 103.00 to 107.33%.
MXenes are emerging 2D materials with intriguing properties such as excellent stability and high conductivity. Here, a systematic study on the Raman spectra of 2D α‐Mo2C (molybdenum carbide), a ...promising member in MXene family, is conducted. Six experimentally observed Raman modes from ultrathin α‐Mo2C crystal are first assigned with the assistance of phonon dispersion calculated from density functional theory. Angle‐resolved polarized Raman spectroscopy indicates the anisotropy of α‐Mo2C in the b–c plane. Raman spectroscopy is further used to study the unique domain structures of 2D α‐Mo2C crystals grown by chemical vapor deposition. A Raman mapping investigation suggests that most of the α‐Mo2C flakes contain multiple domains and the c‐axes of neighboring domains tend to form a 60° or 120° angle, due to the weak MoC bonds in this interstitial carbide and the low formation energy of the carbon chains along three equivalent directions. This study demonstrates that polarized Raman spectroscopy is a powerful and effective way to characterize the domain structures in α‐Mo2C, which will facilitate the further exploration of the domain‐structure‐related properties and potential applications of α‐Mo2C.
The Raman spectra of 2D α‐Mo2C (molybdenum carbide) crystal is systematically studied. Six experimentally observed Raman modes of 2D α‐Mo2C are assigned for the first time. Angleresolved polarized Raman spectroscopy indicates the in‐plane anisotropy of α‐Mo2C. Raman mapping reveals the unique domain structures of α‐Mo2C flakes grown by chemical vapor deposition.
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•Synthesis of microcapsules (5−20 μm) containing isophorone diisocyanate using tris (p-isocyanatophenyl) thiophosphate as a shell forming agent.•Microcapsules show high encapsulation ...efficiency and high thermal and chemical resistance.•Microcapsules show high compatibility with epoxy coating formulations.•Electrochemical studies confirmed important healing ability of the microcapsules- containing coating.
This work aims at investigating the self-healing ability of epoxy coatings, modified with microcapsules containing highly reactive isocyanate in their core. Highly efficient, thermally and chemically stable isophorone diisocyanate microcapsules were prepared via emulsification followed by interfacial polymerization at the surface of oil droplets of the oil-in-water (O/W) emulsion. The microcapsules were incorporated into an epoxy coating to protect carbon steel from corrosion. Scanning Electron Microscopy (SEM) was used to assess the microcapsules̕ and coating morphology. The physico-chemical characterization of the microcapsules was studied by Fourier Transformed Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate the protective performance of coated steel samples and results confirmed that the barrier properties of modified coatings increased over time. The self-healing ability was studied via Localized Impedance Spectroscopy (LEIS), Scanning Vibrating Electrode Technique (SVET) and Scanning Ion-Selective Electrode Techniques (SIET) on coated steel samples containing artificial defects. This comprehensive study confirmed the ability of the capsules to heal damaged areas in the coating and to mitigate corrosion thanks to the formation of a protective polymeric barrier layer.
We present a photometric and spectroscopic analysis of the eclipsing binary KIC 10486425. Synthesis of the light curve and radial velocity measurements indicates that this binary is a circular, ...synchronized, detached system. The masses and radii of the two components are determined as , M2 = 1.11 M , and , respectively. The cooler secondary star is more evolved, while the primary is still on the zero-age main sequence, suggesting that KIC 10486425 could be an Algol system. After removal of the binarity effects from the observed Kepler data, multiple frequency analysis is applied to the outside-eclipse light residuals, revealing that the primary component of KIC 10486425 is a γ Dor type pulsating star with a dominant period of 0.758 days. A total of 160 pulsation frequencies with significant confidence are extracted in the g-mode region, from which a period-spacing pattern is identified which clearly shows a downward slope. Synthesis of the period-spacing pattern leads to a mode identification of (l = 2, m = 2) for the pulsations with an asymptotic period spacing of Δ l = 2 = 1803.5 s. The near-core rotation rate is derived as , about 15% slower than the orbital frequency of this synchronized binary, suggesting that the core and the envelope rotate differentially.
T1 and T2 relaxation times combined with 31P spectroscopy have been proven efficient for muscular disease characterization as well as for pre‐ and post‐muscle stimulation measurements. Even though ...31P spectroscopy can already be performed during muscle exercise, no method for T1 and T2 measurement enables this possibility. In this project, a complete setup and protocol for multi‐parametrical MRI of the rat gastrocnemius before, during and after muscle stimulation at 4.7 and 7 T is presented. The setup is fully MRI compatible and is composed of a cradle, an electro‐stimulator and an electronic card in order to synchronize MRI sequences with muscle stimulation. A 2D triggered radial‐encoded Look‐Locker sequence was developed, and enabled T1 measurements in less than 2 min on stimulated muscle. Also, a multi‐slice multi‐echo sequence was adapted and synchronized for T2 measurements as well as 31P spectroscopy acquisitions in less than 4 min in both cases on stimulated muscle. Methods were validated on young rats using different stimulation paradigms. Then they were applied on older rats to compare quantification results, using the different stimulation paradigms, and allowed observation of metabolic changes related to aging with good reproducibility. The robustness of the whole setup shows wide application opportunities.
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