Single Transition Research Articles

Structural elucidation of Gluten/Zein nanofibers prepared by electrospinning process: Focus on the effect of zein on properties of nanofibers

In this study, gluten/zein (G/Z) blends were electrospun with acetic acid as a solvent. The effects of zein content on the morphology, structure and properties of assembled gluten nanofibers were investigated. G/Z nanofibers were found to have diameters ranging from 209 nm to 462 nm, with smooth surfaces for ratios of 100:0 and rough surfaces for ratios of 30:70. The water contact angle (WCA) > 90 showed that mixed fibers were hydrophobic. SDS-PAGE showed that both proteins were present and were evenly distributed in G/Z nanofibers. The number of high molecular weight molecules decreased and the amount of low molecular weight molecules increased as the zein to gluten ratios increased. Nanofibers with α -helix structures were confirmed by FTIR, XRD, and CD analyses. The α-helix structure increased with increasing zein to gluten ratio in nanofibers, which also increased the characteristic of crystallinity and hydrophobicity. The characteristics of a miscible blend were confirmed by the single glass transition temperature (Tg) seen in the DSC thermograms of the G/Z nanofibers. With a decrease in the amount of zein in the nanofibers, the Tg dropped from 177.7 to 162 °C indicating that the mixed fibers were more flexible compared to the pure zein fiber.

Mitochondrial dysfunction as a probable mechanism for triggering inflammatory joint diseases

The article concerns the contribution of mitochondrial dysfunction to the development of inflammatory joint diseases. Mitochondria are the main suppliers of adenosine triphosphate (ATP). Reactive oxygen species (ROS) are a by-product of this metabolic process. Mitochondria also have an effective antioxidant mechanism: there is a certain balance between the ROS formation and their inactivation. Accumulation with age of mutations (single nucleotide substitutions, e.g., transversions, transitions, and deletions) in mitochondrial DNA, may cause a disorder in selective destruction (utilization) of damaged and dysfunctional mitochondria (mitophagy) thus leading to imbalance between the ROS production and their neutralization. This process is triggered by both internal factors (ROS overproduction) and external factors, i.e., tissue damage / injury and infection. The failure of quality control mechanisms resulting from disruption of mitophagy leads to a significant increase in terminally damaged mitochondria, which become a threat to cell survival. High level of genetic mutations accumulating with age in mitochondrial genome causes an increased formation of ROS, which, in turn, are one of the leading activators of the cytosolic NLRP3 protein, the main component of inflammasome type of the same name. Increased inflammasome formation ultimately triggers caspase-1 dependent production of pro-inflammatory interleukins-1β(IL-1β) and 18 (IL-18). Inadequate removal of damaged mitochondria leads to hyperactivation of inflammatory signaling pathways and, subsequently, to chronic systemic inflammation and development of inflammatory diseases, including primary osteoarthritis (OA). To assess the level of mitochondrial dysfunction, we assessed the numbers of mitochondrial genome copies in post-mitotic muscle cells in 48 patients aged 45 to 95 years who were diagnosed with OA of the knee or hip joints. As a result of our study, we have discovered and confirmed some regularities of human mtDNA mutations corresponding to those in vertebrates, and, in particular, in mammals. Degenerate mutation spectra (without classification of mutations by mtDNA chains and the context of surrounding nucleotides) were constructed for mtDNA in general, and for each individual sample. It was demonstrated that, in one-third of muscle samples, the critical threshold of mtDNA heteroplasmy was exceeded, at which the aberrant biochemical phenotype, in terms of oxidative phosphorylation functioning, (OXPHOS) becomes dominant. Of note, the heteroplasmy rates are lower in older patients who have had significant physical activity during their lives (sports, moderate physical work, etc.). Moreover, the heteroplasmy showed an inverse correlation with high mtDNA copy number. The results obtained can be used to diagnose pathologies in elderly, and the process of healthy aging.

Poly(propylene glycol)‐Based Non‐Isocyanate Polyurethane Ionenes: Thermal, Morphological and Conductive Properties

AbstractThe synthesis and characterization of a series of polyurethane ionenes using a non‐isocyanate approach is disclosed. Imidazole‐capped, urethane‐containing prepolymers are prepared by first reacting carbonyl diimidazole (CDI) with several poly(propylene glycol) (PPG) diols with variable molecular weight, followed by subsequent reaction with 3‐aminopropylimidazole (API). Polymerization with 1,4‐dibromomethylbenzene followed by anion exchange resulted in the desired polyurethane ionenes bearing the [NTf2] counteranion as a series of viscous liquids. NMR and FTIR spectroscopy are used to characterize the intermediates and final ionenes, including molecular weight determination by end‐group analysis. A single glass transition temperature (Tg), as determined by differential scanning calorimetry (DSC), is observed for each ionene (−38 to −64 °C) with the Tg decreasing with increasing PPG molecular weight. Thermogravimetric analysis (TGA) indicated a two‐step decomposition for each ionene, with the first being degradation of the PPG segment, followed by the urethane/ionic segment. Microphase separation is observed from x‐ray scattering profiles with Bragg distances that increased with increasing PPG molecular weight. Ionic conductivity is found to be inversely dependent upon DSC Tg at lower temperatures (RT and below); however, at higher temperatures, conductivity appears to be more dependent upon the ability of ionic aggregates caused by phase separation to interact.

Vacuum Ultraviolet Fingerprints as a New Way of Disentangling Tropylium/Benzylium Isomers.

The two inseparable companions, tropylium (Tr+) and benzylium (Bz+), were interrogated by vacuum ultraviolet (VUV) radiation from 4.5 to 7.0 eV in an ion trap. These new fingerprints provide a new means of distinguishing these two intertwined C7H7+ isomers. In particular, the singular spectral signature of Tr+ in the VUV consists of a single strong electronic transition at ≈6 eV. To illustrate this diagnostic tool, we shed light on the structure of the C7H7+ intermediate that is ubiquitous when using commercial atmospheric pressure photoionization (APPI) sources. We have identified its structure as the 7-membered ring Tr+, which contradicts some previous beliefs.

Enhancing Charge Storage of Mo2Ti2C3 MXene by Partial Oxidation

AbstractDriving the pseudocapacitive redox intercalation in 2DMXenes with neutral electrolytes is important for safer, more sustainable, and improved electrochemical charge storage. Single transition metal MXenes, such as Ti3C2, have shown great promise for energy storage, owing to their high conductivity and redox activity. Mixed metallic MXenes, such as out‐of‐plane ordered Mo2Ti2C3, have remained underexplored in energy storage because of the absence of redox activity in most of the electrolytes. Simultaneous structural modifications and instigating intercalation pseudocapacitance in neutral electrolytes could be a viable strategy for enhancing their electrochemical properties. Herein, a facile synthesis of partially oxidized Mo2Ti2C3 MXene (PO‐Mo2Ti2C3) exhibiting improved charge storage capability is demonstrated. Optical, structural, and spectroscopic analyses indicate the formation of oxide nanostructures upon thermal oxidation of Mo2Ti2C3 . This leads to an enhanced energy storage capability with remarkably improved cyclability as well as a high Coulombic efficiency in a neutral LiCl electrolyte. This work highlights the importance of structural modifications of MXenes to enhance their charge storage and shows the promise of less explored double transition metal MXenes in energy storage.

Diverse phase transitions in Kuramoto model with adaptive mean-field coupling breaking the rotational symmetry

We consider the paradigmatic Kuramoto oscillators coupled via an adaptive mean-field variable that breaks the rotational symmetry. The evolution equation for the mean-field variable is governed by the linear ordinary differential equation corresponding to a low-pass filter with a time-scale parameter, which attenuates the mean-field signal by filtering its high frequency components. We find distinct phase transitions among the incoherent state, standing wave state and synchronized stationary state in both forward and reverse traces in the entire range of the time-scale parameter. In particular, one can observe two distinct continuous transitions, a continuous transition followed by a discontinuous transition, or a single discontinuous transition among the distinct dynamical states in the forward trace depending on the range of the time-scale parameter, which determines the degree of attenuation. Further, one can also observe two distinct continuous transitions or a single discontinuous desynchronization transition in the reverse trace depending on the time-scale parameter. We derive the evolution equations for the macroscopic order parameters governing the dynamics of the discrete set of coupled phase oscillators. We also deduce the analytical conditions for the stability of the Hopf, pitchfork and saddle–node bifurcations, and find them to be in consistent with the dynamical transitions observed using the simulation.

Possible intermediate quantum spin liquid phase in α-RuCl3 under high magnetic fields up to 100 T

Pursuing the exotic quantum spin liquid (QSL) state in the Kitaev material α-RuCl3 has intrigued great research interest recently. A fascinating question is on the possible existence of a field-induced QSL phase in this compound. Here we perform high-field magnetization measurements of α-RuCl3 up to 102 T employing the non-destructive and destructive pulsed magnets. Under the out-of-plane field along the c* axis (i.e., perpendicular to the honeycomb plane), two quantum phase transitions are uncovered at respectively 35 T and about 83 T, between which lies an intermediate phase as the predicted QSL. This is in sharp contrast to the case with in-plane fields, where a single transition is found at around 7 T and the intermediate QSL phase is absent instead. By measuring the magnetization data with fields tilted from the c* axis up to 90° (i.e., in-plane direction), we obtain the field-angle phase diagram that contains the zigzag, paramagnetic, and QSL phases. Based on the K-J-Γ-{{{Gamma }}}^{{prime} } model for α-RuCl3 with a large Kitaev term we perform density matrix renormalization group simulations and reproduce the quantum phase diagram in excellent agreement with experiments.

Metal-metal bonds in Zintl clusters: Synthesis, structure and bonding in [Fe2Sn4Bi8]3– and [Cr2Sb12]3–

We report here the synthesis and characterization of two new members of the M2E12 family of endohedral Zintl clusters, [Fe2Sn4Bi8]3– and [Cr2Sb12]3–, both of which contain open-shell metal dimers encapsulated inside a triple-decker cluster of main-group atoms. The 75-electron [Fe2Sn4Bi8]3– cluster has a D4h-symmetric structure, while [Cr2Sb12]3–, despite having the same 75-electron count, is strongly distorted to a geometry that resembles a CrSb8 crown capped by a CrSb4 unit. The structural differences between the two are driven by the increasing availability of 3d electron density in the earlier transition metal, which leads, ultimately, to different electronic configurations in the two clusters. The trends precisely mirror those observed in the ME10 and ME12 families containing a single transition metal ion.

Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD 235088 b (TOI-1430 b) with CARMENES

HD 235088 (TOI-1430) is a young star known to host a sub-Neptune-sized planet candidate. We validated the planetary nature of HD 235088 b with multiband photometry, refined its planetary parameters, and obtained a new age estimate of the host star, placing it at 600–800 Myr. Previous spectroscopic observations of a single transit detected an excess absorption of He I coincident in time with the planet candidate transit. Here, we confirm the presence of He I in the atmosphere of HD 235088 b with one transit observed with CARMENES. We also detected hints of variability in the strength of the helium signal, with an absorption of −0.91 ± 0.11%, which is slightly deeper (2σ) than the previous measurement. Furthermore, we simulated the He I signal with a spherically symmetric 1D hydrodynamic model, finding that the upper atmosphere of HD 235088 b escapes hydrodynamically with a significant mass loss rate of (1.5−5) × 1010 g s−1 in a relatively cold outflow, with T = 3125 ±375 K, in the photon-limited escape regime. HD 235088 b (Rp = 2.045 ± 0.075 R⊕) is the smallest planet found to date with a solid atmospheric detection – not just of He I but any other atom or molecule. This positions it a benchmark planet for further analyses of evolving young sub-Neptune atmospheres.

TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K Dwarf

We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600 (V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of 6.80 ± 0.31 R ⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R ⊕ and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets. Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems with multiple giant exoplanets.

Density functional theory study of NO adsorption on the transition metal M (M=Cu, Fe and Mn) modified TiO2 surface

To study the effect of different kinds of transition metals and their proportions on NO adsorption on TiO2 surface, the density functional theory (DFT) method was used to calculate the energetic, geometric structure and electronic structure of the adsorption of NO on transition metal M (M = Cu, Fe and Mn)-anatase TiO2 (101) surface. The above transition metals were adsorbed on anatase TiO2 (101) surface in three different adsorption ratios, which are single transition metal adsorption model, mixed 2:2 and 1:3 ratio models. On the basis of the study, 13 models were established to study the effects of transition metals and adsorption ratio on NO oxidation to determine the optimal adsorption model. It has been found from the energetic calculations that mixed adsorption model is more stable for the adsorption of NO. The results of electronic structure and charge distribution analysis showed that a large quantity of active electron clusters are distributed around Mn and Fe atoms, which are attached to a large area of N atoms in NO, indicating that Mn and Fe can provide more electrons for catalytic reaction and facilitate electron exchange between catalyst and NO. Among all the adsorption models, the 3Fe+1Mn–TiO2 and 3Mn+1Fe–TiO2 models are superior, i.e., they can exchange more electrons with NO before the catalytic reaction, which is conducive to the subsequent catalytic reaction.

Advanced Analytical Electron Microscopy Techniques for Probing Individual PGM-Free Catalyst Sites

Hydrogen fuel cells currently utilize expensive platinum group metal nanoparticles as catalysts [1]. To reduce the cost of catalyst materials, large efforts to develop viable platinum group metal-free (PGM-free) catalyst materials, which often consist of single transition metal atoms embedded in nitrogen-doped graphitic carbon structures, are being undertaken [2]. Given the atomic-scale nature of the metal sites in these materials, their performance and stability are highly dependent on the local coordination environment and consequently electronic structure of the sites [3]. A detailed understanding of the local elemental composition and lattice structure of individual sites, and how these properties vary between sites, is therefore needed to further develop improved PGM-free catalyst materials. While many bulk techniques are available that can provide average properties of these sites, such as Mössbauer and X-ray absorption spectroscopies, techniques with high spatial resolution are needed to measure the properties of individual sites. As a result, scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDS) has proven an invaluable tool for characterization of these materials due to its ability to probe structural and electronic properties at the atomic scale [4]. However, combined with the instability of many metal sites under the electron probe, the quantity and type of information accessible by conventional STEM instrumentation and acquisition methods is limited. To better understand the local coordination environment and electronic structure of individual sites, as well as how these properties vary site to site, new techniques and hardware are therefore needed.Here, we demonstrate advancements in STEM-EELS and -EDS that allow the quality and quantity of spectroscopic information obtained from individual sites to be significantly improved over conventional method. First, we demonstrate direct real-space mapping of metal sites by using a direct electron detector in the EELS spectrometer. This increases the data acquisition rate and signal-to-noise ratio sufficiently to map metal atom positions at the atomic scale. In addition, we show how automated metal atom position identification and subsequent probe positioning allow the rate at which metal sites are probed to be increased by another order of magnitude while simultaneously increasing the quantity of data obtained from each site. Using EELS and EDS signals acquired in parallel, this automated acquisition method enables a wide range of metal site elements to be identified, as well as the local coordination environment around the sites to be determined. Combined with electronic structure measurements of the metal atoms themselves, this technique provides significantly more information about individual sites than conventional methods. The techniques presented here are therefore poised to significantly improve our understanding of the local coordination environment and electronic structure of individual PGM-free metal sites, as well how these properties vary site to site, accelerating development of these low-cost hydrogen fuel cell catalyst materials [5].

High-efficient OER/ORR bifunctional electrocatalysts based on hexagonal boron nitride enabled by co-doping of transition metal and carbon

The construction of highly active earth-abundant electrocatalysts, which hold bifunctional oxygen reduction and evolution reactions simultaneously, is of great importance for inexpensive and high-performance electrochemical energy devices, yet still challenging. Here, we demonstrate that the inert hexagonal boron nitride (h-BN) can accommodate single atomic 3d transition metal (TM) sites by co-doping of carbon atoms as high-performance bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The TM atoms including Fe, Co, and Ni have been anchored with either four or two substituting carbon atoms forming TM–C4–BN and TM–C2N2–BN structures, in which the latter exhibits higher structural stability and stronger adsorption in response to the oxygen-containing intermediates such as OH*, O*, and OOH* in the reaction pathways. The optimal OER/ORR bifunctional catalyst is determined to be Co–C2N2–BN, showing ηOER of 0.42 V and ηORR of 0.26 V. Especially, its excellent ORR catalytic activity can be compared to that of well-known Pt(111) surface. It exhibits high thermodynamic stability and most favorable binding strength toward OER/ORR intermediates. The density functional theory calculations of the charge transfer and redistribution reveal the origin of the excellent catalytic activity in Co–C2N2–BN. This work provides a promising and feasible solution in searching for high-performance non-precious bifunctional oxygen electrocatalysts.

Characterization and fine mapping of a yellow leaf gene regulating chlorophyll biosynthesis and chloroplast development in cotton (Gossypium arboreum)

Chlorophyll biosynthesis and chloroplast development are essential for photosynthesis and plant growth. Gossypium arboreum, a valuable source of genetic variation for cotton improvement, remains poorly studied for the mechanisms regulating chlorophyll biosynthesis and chloroplast development. Here we created a G. arboreum etiolated leaf and stuntedness (els) mutant that displayed a distinct yellow color of leaves, bracts and stems throughout the whole growth, where chlorophyll accumulation in leaves was reduced and chloroplast development was delayed. The GaCHLH gene, which encodes the H subunit of magnesium chelatase (Mg-chelatase), was screened by MutMap and KASP analysis. Compared to GaCHLH, the gene Gachlh of the mutant had a single nucleotide transition (G to A) at 1549 bp, which causes the substitution of a glycine (G) by a serine (S) at the 517th amino acid, resulting in an abnormal secondary structure of the Gachlh protein. GaCHLH-silenced SXY1 and ZM24 plants exhibited a lower GaCHLH expression level, a lower chlorophyll content, and the yellow-leaf phenotype. Gachlh expression affected the expression of key genes in the tetrapyrrole pathway. GaCHLH and Gachlh were located in the chloroplasts and that alteration of the mutation site did not affect the final target position. The BiFC assay result indicated that Gachlh could not bind to GaCHLD properly, which prevented the assembly of Mg-chelatase and thus led to the failure of chlorophyll synthesis. In this study, the Gachlh gene of G. arboreum els was finely localized and identified for the first time, providing new insights into the chlorophyll biosynthesis pathway in cotton.

Synergistic effect of nickel and calcium dual-atomic sites to facilitate electrochemical CO2 reduction to methanol: Combining high activity and selectivity

Atomically dispersed transition metal sites embedded into nitrogen-doped graphene provide promising potential for the electrochemical CO2 reduction to CO, but the catalytic efficiency for further hydrogenation to methanol is seriously restricted. Herein, combining the advantage of single transition metal, alkaline-earth metal, and multiple active sites, we designed nickel and calcium dual-atomic site catalysts (Ni-Ca DACs) supported on N-doped graphene to enable CO2 hydrogenation. First-principles calculations reveal that the electron-rich Ni atom serves as the carbon adsorption site, and the adjacent Ca atom with electron-deficient properties acts as the oxygen adsorption site, which largely stabilizes many CHxOy species through the O-Ca bond, especially the *OCHO, thus facilitating CO2 reduction. More importantly, a synergistic adsorption process on Ni-Ca sites promote the formation of *CHO species that is considered as the key intermediate for generation of multi-electron products. Different from the single Ni or Ca catalysts that produce mainly CO or HCOOH, the Ni-Ca DACs can selectively catalyze CO2 reduction to CH3OH, with a low limiting potential of −0.52 V, while suppressing the hydrogen evolution reaction. The outstanding catalytic activity originates from the tuned polarized charge and d-band center of active sites by synergistic interaction of adjacent Ni and Ca atoms.

Biochemical Characterization of the Copper Nitrite Reductase from Neisseria gonorrhoeae.

The copper-containing nitrite reductase from Neisseria gonorrhoeae has been shown to play a critical role in the infection mechanism of this microorganism by producing NO and abolishing epithelial exfoliation. This enzyme is a trimer with a type 1 copper center per subunit and a type 2 copper center in the subunits interface, with the latter being the catalytic site. The two centers were characterized for the first time by EPR and CD spectroscopy, showing that the type 1 copper center has a high rhombicity due to its lower symmetry and more tetragonal structure, while the type 2 copper center has the usual properties, but with a smaller hyperfine coupling constant (A// = 10.5 mT). The thermostability of the enzyme was analyzed by differential scanning calorimetry, which shows a single endothermic transition in the thermogram, with a maximum at 94 °C, while the CD spectra in the visible region indicate the presence of the type 1 copper center up to 80 °C. The reoxidation of the N. gonorrhoeae copper-containing nitrite reductase in the presence of nitrite were analyzed by visible spectroscopy and showed a pH dependence, being higher at pH 5.5-6.0. The high thermostability of this enzyme may be important to maintaining a high activity in the extracellular space and to making it less susceptible to denaturation and proteolysis, contributing to the proliferation of N. gonorrhoeae.

Properties of PLA-co-PBSu Copolymers Rapidly Synthesized by Reactive Processing

This work describes the synthesis of poly(lactic acid) by the ring-opening polymerization of L-lactide in the presence of oligo(butylene succinate) with two different molecular weights (Mn = 6100 and 16300 g/mol) as a macroinitiator during reactive processing. The macroinitiators were added in concentrations 1 wt%, 2.5 wt%, 5 wt%, 10 wt% and 15 wt% in respect to the L-lactide mass in the premix. The properties of the received copolymers were extensively studied with spectroscopic techniques, GPC, DSC, XRD, TGA as well as nanoindentation. Blocky copolymers were received with number average molecular weights ranging from 30 to 100 kg/mol, which decreased with increasing the PBSu content in the feed. The introduction of the flexible PBSu chains decreased the single glass transition detected, while DSC and XRD gave indications that both components crystallized in the copolymers with PBSu premix content > 5 wt%. Thermal stability was maintained and depended on the composition and molecular weight. Nanoindentation showed that despite the decreasing trend of hardness and elastic modulus with increasing PBSu content, the PLA-PBSu 2.5% copolymers had simultaneously higher elasticity modulus and strength compared to the other compositions, possibly because of a complementary effect of their high molecular weight and crystallinity. These copolymers were promising for production with continuous reactive extrusion, a novel, fast and economically viable method to commercially produce PLA-based polymers.

Simultaneous Enhancement of Flame Resistance and Antimicrobial Activity in Epoxy Nanocomposites Containing Phosphorus and Silver-Based Additives.

The design and manufacture of innovative multifunctional materials possessing superior characteristics, quality and standards, rigorously required for future development of existing or emerging advanced technologies, is of great importance. These materials should have a very low degree of influence (or none) on the environmental and human health. Adjusting the properties of epoxy resins with organophosphorus compounds and silver-containing additives is key to the simultaneous improvement of the flame-resistant and antimicrobial properties of advanced epoxy-based materials. These environmentally friendly epoxy resin nanocomposites were manufactured using two additives, a reactive phosphorus-containing bisphenol derived from vanillin, namely, (4-(((4-hidroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)-2-methoxyphenyl) phenylphosphonate (BPH), designed as both cross-linking agent and a flame-retardant additive for epoxy resin; and additional silver-loaded zeolite L nanoparticles (Ze-Ag NPs) used as a doping additive to impart antimicrobial activity. The effect of BPH and Ze-Ag NPs content on the structural, morphological, thermal, flame resistance and antimicrobial characteristics of thermosetting epoxy nanocomposites was investigated. The structure and morphology of epoxy nanocomposites were investigated via FTIR spectroscopy and scanning electron microscopy (SEM). In general, the nanocomposites had a glassy and homogeneous morphology. The samples showed a single glass transition temperature in the range of 166-194 °C and an initiation decomposition temperature in the range of 332-399 °C. The introduction of Ze-Ag NPs in a concentration of 7-15 wt% provided antimicrobial activity to epoxy thermosets.

Theoretical insights into the mechanism of nitrogen-to-ammonia electroreduction on TM/g-C9N10

The discovery of metals as catalytic centers for nitrogen reduction reactions (NRR) has stimulated great enthusiasm for single-atom catalysts (SACs). However, the poor activity and low selectivity of NRR are far away from the industrial requirement. Herein, density functional theory (DFT) calculations are performed to design the new SACs and explore the electronic property and NRR performance. The single transition metal (TM = Sc to Zn) atom supported on a novel graphitic carbon nitride (g-C9N10), i.e. TM/g-C9N10 SACs are firstly proposed. It is found that most TM atoms can strongly bind with g-C9N10 through a TM-3 N configuration. Six TM/g-C9N10 (TM= V, Cr, Mn, Fe, Ni and Cu) SACs with end-on configurations are initially screened out by a series of property calculation. Finally, Mn/g-C9N10 is supposed to be the most promising candidate for NRR, due to a low overpotential of 0.125 V through the distal pathway and high NRR selectivity. Multiple-level descriptors (ΔG*N2, bond length, CDD, COHP and PDOS) shed light on the origin of NRR activity from the viewpoint of energy and electronic properties. The transition state energy barrier ensures the experimental feasibility in real conditions. Our findings are expected to broaden the understanding of SACs for N2 fixation and contribute to the design of novel substrates with effectively improved performance.

Separation of overlapping phases for Se88Te10Ag2 glass

Results of crystallization kinetics for Se88Te10Ag2 glass using differential scanning calorimetry under non-isothermal condition are described and discussed. The glass has a single glass transition and two crystalline phases that overlap. The Gaussian fit model was used to separate the overlapping crystalline phases. By applying the Matusita et al. approach to analyses the data, it was possible to determine the activation energy (Ec) and Avrami exponent (n) for the two phases. The average Ec values for the first and the second phases are 126.16 and 113.99 kJ mol−1, respectively. It was shown that the activation energy strongly depended on the heating rate. Using the Kissinger–Akahira–Sunose method, the variable activation energies with crystalline fraction are calculated. This variation demonstrates how the transition from the amorphous to the crystalline phase is a complicated process requiring several nucleation and growth mechanisms. It was discussed if the Johnson–Mehl–Avrami model to describe the crystallization for the composition under investigation. The results show SB(M, N) that model is more appropriate to represent the crystallization process for the examined composition. While the results agree with JMA models at low heating rates. Through the use of scanning electron microscopy and X-ray diffraction, the crystalline phases for the two stages were identified.