Synthesis Reactivity Research Articles

Synthesis of polyvalent ion reaction of MoS2/CoS2-RGO anode materials for high-performance sodium-ion batteries and sodium-ion capacitors

Metal sulfide is the most promising anode material for sodium storage devices due to its high theoretical capacity and low cost. However, the practical application of metal sulfide is largely hindered by huge capacity fading during the sodiation/desodiation process. Here mixed bimetallic sulfides grown on reduced graphene oxide (MoS2/CoS2-RGO) are prepared via a facile hydrothermal method. MoS2/CoS2-RGO displays a unique 2D structure which provides large specific surface area for pseudocapacitive charge storage, polyvalent ion reaction for ultrahigh capacity, and a heterostructure to high Na-ion diffusion rate. The optimized MoS2/CoS2-RGO shows a considerable reversible capacity of 593.6 mA h g−1 at 100 mA g−1 over 50 cycles and a high rate capability of 215.8 mA h g−1 even at a high specific current of 5000 mA g−1. A reaction kinetics and galvanostatic intermittent titration technique analysis indicates that MoS2/CoS2-RGO possesses fast pseudocapacitive charge storage and high Na-ion diffusion rate, benefiting the kinetics balance between anode and cathode. With this special structure, SICs containing the anode deliver a high specific energy of 152.98 W h kg−1 at 562.5 W kg−1. Similarly, the SIB exhibits a good capacities of 64 mA h g−1 at the high rates of 5C over 100 cycles.

Mesoporous Single-Atom-Doped Graphene–Carbon Nanotube Hybrid: Synthesis and Tunable Electrocatalytic Activity for Oxygen Evolution and Reduction Reactions

Mesoporous heteroatom-doped carbon-based nanomaterials are very promising as catalysts for electrochemical energy conversion and storage. We have developed a one-step catalytic chemical vapor deposition method to grow a highly graphitized graphene nanoflake (GF)–carbon nanotube (CNT) hybrid material doped simultaneously with single atoms of N, Co, and Mo (N–Co–Mo–GF/CNT). This high-surface-area material has a mesoporous structure, which facilitates oxygen mass transfer within the catalyst film, and exhibits a high electrocatalytic activity and stability in oxygen reduction and evolution reactions (ORR and OER) in alkaline media. We have shown that in this metal (M)–N–C catalyst, M (Co, Mo)–C centers are the main sites responsible for OER, while, for ORR, both M and N–C centers synergistically serve as the active sites. We systematically investigated tuning of the ORR and OER activity of the porous catalyst depending on the choice of the underlying substrate. The ORR kinetic current and OER activity for N–Co–Mo–GF/CNT were significantly enhanced when the catalyst was deposited onto a Ni substrate, resulting in an advanced electrocatalytic performance compared to the best bifunctional ORR/OER catalysts reported so far. Using a developed scanning electrochemical microscopy analysis method, we demonstrated that the higher OER reactivity on Ni was attributable to the formation of underlying catalyst/Ni interfacial sites, which are accessible due to the porous, electrolyte-permeable structure of the catalyst.

Synthesis of Triazole Derivatives Via Multi Components Reaction and Studying of (Organic Characterization, Chromatographic Behavior ,Chem-Physical properties)

In this paper, the novel component were synthesized in good yield via multi reactions like (Aldole reaction , azotation–coupling reaction, condensation reaction , substitution reaction ,cyclization reaction) by using types of conditions and multi components reactions to formation imidazole ,Thiazole ,oxazole ) derivatives with bis- triazole cycles ,imidazole and thiazole The formatted triazole compounds have been characterized through spectral and chemical techniques like (1H NMR, IR ,some of them C.NMR ) ,studying of Chromatography studying and physical properties for all Compounds.

Ir/TiONx/C high-performance oxygen evolution reaction nanocomposite electrocatalysts in acidic media: synthesis, characterization and electrochemical benchmarking protocol

More efficient utilization of iridium is of immense importance for the future development of proton exchange membrane electrolyzers. In this study, we introduce a new facile and scalable synthesis of an Ir-based high-performance oxygen evolution reaction (OER) electrocatalytic nanocomposite. The composite consists of Ir nanoparticles with an average size of 3–4 nm, which are effectively anchored on a titanium oxynitride support (TiONx), which is distributed across high-surface-area Ketjen Black carbon (Ir/TiONx/C). We provide complete structural, morphological and compositional characterization (x-ray diffraction, scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy) and propose a proper benchmark protocol to measure true electrochemical performance. Compared to the state-of-the-art Ir Black electrocatalyst, Ir/TiONx/C exhibits approximately three times higher OER performance.

The Mechanism of N-Heterocyclic Carbene Organocatalysis through a Magnifying Glass.

The term “N‐Heterocyclic carbene organocatalysis” is often invoked in organic synthesis for reactions that are catalyzed by different azolium salts in the presence of bases. Although the mechanism of these reactions is considered today evident, a closer look into the details that have been collected throughout the last century reveals that there are many open questions and even contradictions in the field. Emerging new theoretical and experimental results offer solutions to these problems, because they show that through considering alternative reaction mechanisms a more consistent picture on the catalytic process can be obtained. These novel perspectives will be able to extend the scope of the reactions that we call today N‐heterocyclic carbene organocatalysis.

Colorimetric/fluorescent dual channel sensitive coating for early detection of copper alloy corrosion

Herein, we developed a straightforward and effective method to prepare epoxy coating for the early stage corrosion-detection of copper alloy. A selective “turn-on” chemosensor derived from rhodamine B for Cu(II), 3′,6′-Bis(diethylamino)-2-[[(2-hydroxyphenyl)methylene]amino]spiro[1H-isoindole-1,9′-[9H]xanthen]-3(2H)-one (RHS), was obtained via a two-step synthesis of acylation and schiff-base reaction. Both the colorimetric and fluorescent signals of the typical 0.5 wt% sensor-doped coating was observed, which showed that the area prior to corrosion was no significant damage. The concentration of RHS could be reduced to 0.14 wt%, after the zinc-based metal–organic framework (MOF) particle, ZIF-8, applied as a nanocontainer in this coating, and the detection sensitivity was better than the coating with bare RHS. This nondestructive strategy successfully realized early-stage corrosion detection for cupronickel in epoxy coating, which could be potentially used in the corrosion detections for copper alloys.

A Directed Route to Colloidal Nanoparticle Synthesis of the Copper Selenophosphate Cu3 PSe4.

The first colloidal nanoparticle synthesis of the copper selenophosphate Cu3 PSe4 , a promising new material for photovoltaics, is reported. Because the formation of binary copper selenide impurities seemed to form more readily, two approaches were developed to install phosphorus bonds directly: 1) the synthesis of molecular P4 Se3 and subsequent reaction with a copper precursor, (P-Se)+Cu, and 2) the synthesis of copper phosphide, Cu3 P, nanoparticles and subsequent reaction with a selenium precursor, (Cu-P)+Se. The isolation and purification of Cu3 P nanoparticles and subsequent selenization yielded phase-pure Cu3 PSe4 . Solvent effects and Se precursor reactivities were elucidated and were key to understanding the final reaction conditions.

A Directed Route to Colloidal Nanoparticle Synthesis of the Copper Selenophosphate Cu3PSe4

AbstractThe first colloidal nanoparticle synthesis of the copper selenophosphate Cu3PSe4, a promising new material for photovoltaics, is reported. Because the formation of binary copper selenide impurities seemed to form more readily, two approaches were developed to install phosphorus bonds directly: 1) the synthesis of molecular P4Se3 and subsequent reaction with a copper precursor, (P‐Se)+Cu, and 2) the synthesis of copper phosphide, Cu3P, nanoparticles and subsequent reaction with a selenium precursor, (Cu‐P)+Se. The isolation and purification of Cu3P nanoparticles and subsequent selenization yielded phase‐pure Cu3PSe4. Solvent effects and Se precursor reactivities were elucidated and were key to understanding the final reaction conditions.

Preparation of Mesoporous/Microporous MnCo2O4 and Nanocubic MnCr2O4 Using a Single Step Solution Combustion Synthesis for Bifunction Oxygen Electrocatalysis

We report the synthesis of mesoporous/microporous MnCo2O4 and cubic MnCr2O4 using solution combustion synthesis for oxygen reduction and oxygen evolution reactions. XRD and TEM analysis indicate small crystallites of MnCo2O4 forming ultra-thin layer of irregular structures that lead to porous morphology. A slightly larger crystallite size was observed for MnCr2O4. The surface oxygen defect in MnCo2O4 is much higher than MnCr2O4 that enhances the active sites for the oxygen adsorption and promotes fast dissociation in presence of more exposed Mn/Co sites during the oxygen electrocatalysis. The electrochemical properties of the synthesized catalysts were analysed using CV, LSV, EIS and CA showing high limiting current density and kinetic current density, positive onset and halfwave potential and higher number of overall electron transfer in MnCo2O4 that MnCr2O4. Chronoamperometric (CA) runs for 24 h shows excellent stability of MnCo2O4 without any significant decrease in the current or potential value in ORR and OER. On basis of the activity and stability performance, MnCo2O4 shows to be a promising bifunctional electrocatalyst, with significantly improved performance than previously reported Mn and Co mixed oxides, and comparable to Pt and Ru based catalysts in terms of durability, onset potential and Tafel slope.

Chiral donor\u2013acceptor azetines as powerful reactants for synthesis of amino acid derivatives

Coupling reactions of amines and alcohols are of central importance for applications in chemistry and biology. These transformations typically involve the use of a reagent, activated as an electrophile, onto which nucleophile coupling results in the formation of a carbon-nitrogen or a carbon–oxygen bond. Several promising reagents and procedures have been developed to achieve these bond forming processes in high yields with excellent stereocontrol, but few offer direct coupling without the intervention of a catalyst. Herein, we report the synthesis of chiral donor–acceptor azetines by highly enantioselective [3 + 1]-cycloaddition of enoldiazoacetates with aza-ylides and their selective coupling with nitrogen and oxygen nucleophiles via 3-azetidinones to form amino acid derivatives, including those of peptides and natural products. The overall process is general for a broad spectrum of nucleophiles, has a high degree of electronic and steric selectivity, and retains the enantiopurity of the original azetine.

Tuning Molecular Vibrational Energy Flow within an Aromatic Scaffold via Anharmonic Coupling.

From guiding chemical reactivity in synthesis or protein folding to the design of energy diodes, intramolecular vibrational energy redistribution harnesses the power to influence the underlying fundamental principles of chemistry. To evaluate the ability to steer these processes, the mechanism and time scales of intramolecular vibrational energy redistribution through aromatic molecular scaffolds have been assessed by utilizing two-dimensional infrared (2D IR) spectroscopy. 2D IR cross peaks reveal energy relaxation through an aromatic scaffold from the azido- to the cyano-vibrational reporters in para-azidobenzonitrile (PAB) and para-(azidomethyl)benzonitrile (PAMB) prior to energy relaxation into the solvent. The rates of energy transfer are modulated by Fermi resonances, which are apparent by the coupling cross peaks identified within the 2D IR spectrum. Theoretical vibrational mode analysis allowed the determination of the origins of the energy flow, the transfer pathway, and a direct comparison of the associated transfer rates, which were in good agreement with the experimental results. Large variations in energy-transfer rates, approximately 1.9 ps for PAB and 23 ps for PAMB, illustrate the importance of strong anharmonic coupling, i.e., Fermi resonance, on the transfer pathways. In particular, vibrational energy rectification is altered by Fermi resonances of the cyano- and azido-modes allowing control of the propensity for energy flow.

Expression of Bioinformatically Candidate miRNAs including, miR-576-5p, miR-501-3p and miR-3143, Targeting PI3K Pathway in Triple-Negative Breast Cancer.

Background: Triple-negative breast cancer (TNBC) is an invasive and lethal form of breast cancer. PI3K pathway, which often activated in TNBC patients, can be a target of miRNAs. The purpose of this study was bioinformatic prediction of miRNAs targeting the key genes of this pathway and evaluation of the expression of them and their targets in TNBC. Materials and Methods: We predicted miRNAs targeting PIK3CA and AKT1 genes using bioinformatics tools. Extraction of total RNA, synthesis of cDNA and quantitative real-time polymerase chain reaction were performed from 18 TNBC samples and normal adjacent tissues and cell lines. Results: Our results demonstrated that miR-576-5p, miR-501-3p and miR-3143 were predicted to target PIK3CA, AKT1 and both of these mRNAs, respectively and were down-regulated while their target mRNAs were up-regulated in clinical samples and cell lines. The analysis of the receiver operating characteristic curve was done for the evaluation of the diagnostic value of predicted miRNAs in TNBC patients. Conclusion: The findings of our study demonstrated the reverse correlation between miRNAs and their target genes and therefore the possibility of these miRNAs to be proposed as new candidates for TNBC targeted therapies.

Expression of Bioinformatically Candidate miRNAs including, miR-576-5p, miR-501-3p and miR-3143, Targeting PI3K Pathway in Triple-Negative Breast Cancer

Background: Triple-negative breast cancer (TNBC) is an invasive and lethal form of breast cancer. PI3K pathway, which often activated in TNBC patients, can be a target of miRNAs. The purpose of this study was bioinformatic prediction of miRNAs targeting the key genes of this pathway and evaluation of the expression of them and their targets in TNBC. Materials and Methods: We predicted miRNAs targeting PIK3CA and AKT1 genes using bioinformatics tools. Extraction of total RNA, synthesis of cDNA and quantitative real-time polymerase chain reaction were performed from 18 TNBC samples and normal adjacent tissues and cell lines. Results: Our results demonstrated that miR-576-5p, miR-501-3p and miR-3143 were predicted to target PIK3CA, AKT1 and both of these mRNAs, respectively and were down-regulated while their target mRNAs were up-regulated in clinical samples and cell lines. The analysis of the receiver operating characteristic curve was done for the evaluation of the diagnostic value of predicted miRNAs in TNBC patients. Conclusion: The findings of our study demonstrated the reverse correlation between miRNAs and their target genes and therefore the possibility of these miRNAs to be proposed as new candidates for TNBC targeted therapies. [GMJ.2019;8:e1646]

Supramolecular Iron Complex Formed Between Nitrogen Riched Phenanthroline Derivative and Iron With Improved Oxygen Reduction Activity in Alkaline Electrolyte.

In this work, the synthesis and evaluation of a new type non-noble metal oxygen reduction reaction (ORR) catalyst is reported. The catalyst is a complex containing iron ions and multiple N active sites, which displayed excellent oxygen reduction activity in alkaline medium. 2-(2-(4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)pyridin-2-yl)pyridin-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (PIPhen) was synthesized and used as a ligand to form a rich nitrogen iron coordination complex (Fe-PIPhen), and the complex was then loaded onto the carbon powder to form the target catalyst of Fe-PIPhen/C. The physical characterization of the catalyst was conducted by using Scanning Electron Microscopy (SEM), nitrogen adsorption-desorption and X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller analysis etc. Electrochemical characterizations were realized by taking cyclic voltammetry (CV), linear sweep voltammetry (LSV) and rotating ring disk electrode (RRDE). The results show that Fe-PIPhen/C possesses the good performance; it exhibits a high electrocatalytic activity, which is mainly via a four electron ORR pathway, with a low hydrogen peroxide yield of 2.58%. And, the average electron transfer number of 3.93 was obtained in alkaline electrolyte. In summary, Fe-PIPhen/C will likely become a promising alternative to Pt catalyst in fuel cell.

Electrospun iron and nitrogen co-containing porous carbon nanofibers as high-efficiency electrocatalysts for oxygen reduction reaction

One-dimensional carbon nanofibers hold great promise to be potential candidates as high-efficiency electrocatalysts for oxygen reduction reaction (ORR). However, the catalysts in powder form always aggregate when preparing catalyst layer, which significantly hinders the extensive application. Herein, we report the facile synthesis of iron and nitrogen co-containing porous carbon nanofibers derived from PAN nanofibers existing as a flexible film via the electrospinning method, which could avoid aggregation when fabricating catalyst layer of fuel cells. The Fe–N/N–C NFs exhibit onset potential of 0.95 V and the half-wave potential of 0.78 V in 0.1 M KOH solution, suggesting superior electro-catalytic activity for ORR. Meantime, for Fe–N/N–C NFs catalyst, it shows a nearly four electron transferring process and the current density only decreases by 14.2% after 40,000 s. This easy and facile method provides a new idea for synthesis of oxygen reduction reaction with high-activity and good-stability.

Laser-Assisted Doping and Architecture Engineering of Fe3 O4 Nanoparticles for Highly Enhanced Oxygen Evolution Reaction.

The design and synthesis of cost-effective and highperformance oxygen evolution reaction (OER) electrocatalysts for water splitting based on earth-abundant elements is urgent but challenging. A synergistic doping and architecture engineering strategy by nanosecond laser ablation is used to generate a unique kind of highly disordered Ni-doped Fe3 O4 nanoparticle clusters. Ni dopant and increased oxygen vacancies are simultaneously incorporated into Fe3 O4 frameworks and thereby modulate the electronic configuration for an optimal binding affinity towards OER intermediates. Nanoparticles with average size of around 5 nm assemble randomly during laser ablation and construct a fluffy and porous architecture, which not only optimizes the number of exposed active sites but also accelerates mass transfer. Consequently, Ni-doped Fe3 O4 clusters are revealed as a superior OER catalyst with a small overpotential of 272 mV at 10 mA cm-2 and a small Tafel slope of 39.4 mV dec-1 , surpassing almost all spinel Fe-based OER catalysts. This work provides a new strategy to fabricate advanced cation-doped metal oxide nanostructures for related energy applications.

Controlled Hydrothermal Synthesis of K<sub>2</sub>Ti<sub>6</sub>O<sub>13</sub> Nanowires and their Photo-Electronic Response

A hydrothermal method using tetrabutyl titanate and KOH as reactants for synthesis of K2Ti6O13 nanowires was developed, obtaining nanowires with a uniform diameter around 10nm. It is shown that the hydrothermal temperature and the KOH concentration have little influence in tuning the growth of K2Ti6O13 nanowires. By changing the time for hydrothermal reaction, the length of K2Ti6O13 nanowires can be controlled from several dozen of nanometers to several hundreds of nanometers. The as-prepared K2Ti6O13 nanowires exhibit a wide and strong absorption band in the ultraviolet range (around 200~300 nm), and stable photocurrent of 0.5μA/cm2, which might suggest potential applications in solar cell and water splitting.

Amphiphilic fluorescent copolymers via one-pot synthesis of RAFT polymerization and multicomponent Biginelli reaction and their cells imaging applications

Abstract

Isovolumetric synthesis of chromium carbide for selective laser reaction sintering (SLRS)

A novel synthesis approach for the in-situ formation of isovolumetric non-oxide ceramics was demonstrated for application with selective laser sintering additive manufacturing (SLS-AM) methods. By optimizing the ratio of a metal/metal-oxide precursors system, the conversion of a 86/14 molar Cr/Cr2O3 composite precursor film to Cr3C2 by gas-solid reaction with CH4 was investigated as a model reaction synthesis process. The composite precursor mixture was ball-milled to nano/micro-sizes to enhance gas-phase mass transport for conversion. The feedstock was deposited as a 250 μm thick film representative of a single SLS layer using a high-volume low-pressure spray deposition method. The effects of H2 and trace amounts of oxidizing gas impurities on the reaction thermodynamics of the conversion process and microstructural evolution were investigated. The gas-solid reactions were carried out at 950 °C with an isothermal dwell time of 0.1 h under atmospheres of Ar/H2/CH4 and Ar/CH4. The results suggest that expeditious and thorough conversion of the precursor to Cr3C2 was achieved (greater ≥90 wt% in Ar/CH4 and ≥95 wt% in Ar/H2/CH4). Phase characterization of sample cross-sections using SEM image contrast methods were used to assess apparent volumetric occupancy of the as-deposited Cr/Cr2O3 precursor film and the Cr3C2 product ceramic. Results indicate approximate fill fractions of 81.3% (SD = 1.78) and 78.9% (SD = 1.52) respectively, suggesting near isovolumetric conversion. Ultimately, the results in this model system demonstrate isovolumetric reaction syntheses techniques broadly applicable for in-situ non-oxide ceramic production via selective laser sintering-AM.

Ab initio study of diffusion of hydrogen, silver and lithium in PbS and Ag2S

Lead and silver sulfides are materials with diverse technological applications, such as photovoltaic dispositives, electrodes and catalysts. More recent applications in the formation of quantum dots and catalysts synthesis for hydrogen evolution reactions involves these sulfides and some similar compounds. It is well known that defects, and consequently the diffusion process, can change some properties and performances of such materials. Herein, a study of defect formation and ionic diffusion process were performed in PbS and Ag2S lattice structure. The activation energies for diffusion of Ag+, Li+, and H+ in PbS and Ag2S lattices were calculated at the DFT level and diffusion coefficients were estimated within the Arrhenius approximation. Pb-doped Ag2S exhibited a very small activation energy and an anomalous high diffusion coefficient for Ag+ diffusion, which is in good agreement with experimental data. Less evident is the fact that Li+ present lower diffusion coefficients than Ag+. For H+ diffusion in PbS lattice, the process is completely different. The hydrogen moves over the lattice from a sulfur site to the other, apparently cleaving and forming H-S bonds. The present work can provide more understanding of the features of defect formation and solid state ionic diffusion mechanism in sulfides from an atomic perspective. Hopefully, this results can help experimentalists in the development of more efficient materials for some important technological applications.