Surfactant-Free Solvothermal Synthesis of 3D Flowerlike Iron Alkoxide (Fe-EG) Micro/Nanostructures: Structure, Formation Mechanism, and Fenton Oxidation of Azo Dyes

A three-dimensional (3D) flowerlike iron alkoxide (Fe-EG) micro/nanostructure has been fabricated for the first time via a facile surfactant-free solvothermal method using CH₃COONa·3H₂O as the alkali source and systematically characterized. The green-colored 3D flowerlike Fe-EG micro/nanostructure is a polymeric ferrous glycolate with the chemical formula [Fe₂(OCH₂CH₂O)₂(HOCH₂CH₂OH)₂]_<i>n</i>. Upon quasi-in situ monitoring of the morphology and composition of the samples collected at various reaction times, a coordination/ligand substitution/reduction/polymerization mechanism for Fe-EG is tentatively proposed. The Fe-EG micro/nanostructure exhibited ∼99.7% Acid Orange 7 (AO7) degradation efficiency in 40 min with H₂O₂ as the oxidant at pH₀ = 6.0. It is believed that the high dispersion of a large amount of Fe³⁺ on the surface of in situ-formed 3D flowerlike amorphous FeOOH with a large surface area and rich porous structure by the moderate interfacial hydrolysis process of Fe-EG benefits the adsorption of dye molecules and the formation of hydroxyl radicals

DFT Studies on Copper-Catalyzed Arylation of Aromatic C–H Bonds

Cu-catalyzed arylation of aromatic C–H bonds with phenyl iodide has been investigated with the aid of density functional theory calculations at the B3LYP level. Both the neutral and anionic catalytic cycles have been examined by considering the neutral (phen)­Cu–OMe and anionic [MeO–Cu–OMe]⁻ complexes, respectively, as the active species. Various heterocycle and polyfluorobenzene substrates were studied. The relationship between the overall reaction barrier and the acidity of the cleaved C–H bond was studied in both the neutral and anionic catalytic cycles. Comparing the overall reaction barriers based on the neutral and anionic catalytic cycles, we were able to understand that some substrates prefer the anionic mechanism while others prefer the neutral mechanism. We also examined how different ligands influence the overall barriers in the neutral catalytic cycles by employing <i>N</i>,<i>N</i>′-dimethylethylenediamine (DMEDA) and <i>N</i>-methylpyrrolidine-2-carboxamide as the ligands

Novel Morphology-Controlled Hierarchical Core@Shell Structural Organo-Layered Double Hydroxides Magnetic Nanovehicles for Drug Release

Novel hierarchical core@shell structured salicylate (SA) intercalated ZnAl-LDH (layered double hydroxides) magnetic nanovehicles were obtained via a special double-drop coprecipitation strategy assembling organo-ZnAl-LDH nanocrystals onto the surface of Fe₃O₄ submicrospheres (∼480 nm) from cheap aspirin and Zn- and Al-nitrates in alkaline solutions. The obtained Fe₃O₄@SA-LDH-<i>r</i> nanovehicles exhibit varied morphologies with hexagonal LDH <i>ab</i>-face horizontal, vertical, and vertical/slant/horizontal to the surfaces of Fe₃O₄ upon proper mass ratio (<i>r</i>) of Zn-salt to Fe₃O₄ from 1.93 to 7.71 in a low supersaturation system and possess moderate drug loadings and strong superparamagnetism. An <i>in vitro</i> release study reveals that under “no MF” mode (without external magnetic field) the SA release exhibits the higher accumulated release amount and smaller half-life (<i>t</i>_0.5) for Fe₃O₄@SA-LDH-3.85 (41.2%, 1.63 min) and Fe₃O₄@SA-LDH-7.71 (51.1%, 1.66 min) probably owing to their mainly vertical LDH orientations, while the dramatically reduced SA release (10.0%) and greatly elongated <i>t</i>_0.5 (25.6 min) for Fe₃O₄@SA-LDH-1.93 may be due to its relatively stronger host–guest interaction and compact horizontally oriented LDH shell stack. Under “MF on” mode, all the magnetic samples show a detectable reduced SA release owing to the particle–particle interactions among the magnetic nanovehicles. The kinetic fittings show that the release processes of all the samples involve the bulk and surface diffusion. The SA release from Fe₃O₄@SA-LDH-1.93 is mainly determined by the interparticle diffusion among the horizontally oriented LDH shell nanocrystals while those of Fe₃O₄@SA-LDH-3.85 and Fe₃O₄@SA-LDH-7.71 mainly involve the interlayer intraparticle diffusion between LDHs layers due to their largely vertical LDH shell nanocrystals

DFT Studies on Copper-Catalyzed Hydrocarboxylation of Alkynes Using CO₂ and Hydrosilanes

In this paper, DFT calculations have been carried out to study the reaction mechanism of copper-catalyzed hydrocarboxylation of alkynes using CO₂ and hydrosilanes. In addition to hydrocarboxylation of alkynes, possible competitive reactions such as hydrosilylation of alkynes, hydrosilylation of CO₂, and silacarboxylation of alkynes have also been investigated and compared. Through these DFT calculations, we are able to understand the reason only hydrocarboxylation of alkynes has been observed experimentally

Why Is There a Barrier in the Coupling of Two Radicals in the Water Oxidation Reaction?

Two radicals can form a bond without an energetic barrier. However, the radical coupling mechanism in ruthenium-catalyzed water oxidation has been found to be associated with substantial activation energies. Here we have investigated the coupling reaction of [RuO­(bda)­L₂]⁺ catalysts with different axial L ligands. The interaction between the two oxo radical moieties at the Ru­(V) state was found to have a favorable interaction in the transition state in comparison to the prereactive complex. To further understand the existence of the activation energy, the activation energy has been decomposed into distortion energy and interaction energy. No correlation between the experimental rates and the calculated coupling barriers of different axial L was found, showing that more aspects such as solvation, supramolecular properties, and solvent dynamics likely play important roles in the equilibrium between the free Ru^VO monomer and the [Ru^VO···ORu^V] dimer. On the basis of our findings, we give general guidelines for the design of catalysts that operate by the radical coupling mechanism

DFT Studies on Gold-Catalyzed Cycloisomerization of 1,5-Enynes

Gold-catalyzed cycloisomerization of 1,5-enynes has been investigated with the aid of density functional theory calculations at the B3LYP level of theory. We have examined how substituents influence the reaction paths in the cycloisomerization of 1,5-enynes catalyzed by both AuCl and [AuL]⁺ (L = phosphine)

Analyzing the pathways enriched in genes associated with nicotine dependence in the context of human protein–protein interaction network

<p>Nicotine dependence is the primary addictive stage of cigarette smoking. Although a lot of studies have been performed to explore the molecular mechanism underlying nicotine dependence, our understanding on this disorder is still far from complete. Over the past decades, an increasing number of candidate genes involved in nicotine dependence have been identified by different technical approaches, including the genetic association analysis. In this study, we performed a comprehensive collection of candidate genes reported to be genetically associated with nicotine dependence. Then, the biochemical pathways enriched in these genes were identified by considering the gene’s propensity to be related to nicotine dependence. One of the most widely used pathway enrichment analysis approach, over-representation analysis, ignores the function non-equivalence of genes in candidate gene set and may have low discriminative power in identifying some dysfunctional pathways. To overcome such drawbacks, we constructed a comprehensive human protein–protein interaction network, and then assigned a function weighting score to each candidate gene based on their network topological features. Evaluation indicated the function weighting score scheme was consistent with available evidence. Finally, the function weighting scores of the candidate genes were incorporated into pathway analysis to identify the dysfunctional pathways involved in nicotine dependence, and the interactions between pathways was detected by pathway crosstalk analysis. Compared to conventional over-representation-based pathway analysis tool, the modified method exhibited improved discriminative power and detected some novel pathways potentially underlying nicotine dependence. In summary, we conducted a comprehensive collection of genes associated with nicotine dependence and then detected the biochemical pathways enriched in these genes using a modified pathway enrichment analysis approach with function weighting score of candidate genes integrated. Our results may provide insight into the molecular mechanism underlying nicotine dependence.</p

The Ru-tpc Water Oxidation Catalyst and Beyond: Water Nucleophilic Attack Pathway versus Radical Coupling Pathway

Many Ru water oxidation catalysts have been documented in the literature. However, only a few can catalyze the O–O bond formation via the radical coupling pathway, while most go through the water nucleophilic attack pathway. Understanding the electronic effect on the reaction pathway is of importance in design of active water oxidation catalysts. The Ru-bda (bda = 2,2′-bipyridine-6,6′-dicarboxylate) catalyst is one example that catalyzes the O–O bond formation via the radical coupling pathway. Herein, we manipulate the equatorial backbone ligand, change the doubly charged bda^2– ligand to a singly charged tpc^– (2,2′:6′,2″-terpyridine-6-carboxylate) ligand, and study the structure–activity relationship. Surprisingly, kinetics measurements revealed that the resulting Ru-tpc catalyst catalyzes water oxidation via the water nucleophilic attack pathway, which is different from the Ru-bda catalyst. The O–O bond formation Gibbs free energy of activation (Δ<i>G</i>^⧧) at <i>T</i> = 298.15 K was 20.2 ± 1.7 kcal mol^–1. The electronic structures of a series of Ru^VO species were studied by density function theory calculations, revealing that the spin density of O_RuO of Ru^VO is largely dependent on the surrounding ligands. Seven coordination configuration significantly enhances the radical character of Ru^VO

Multi-Level Architecture Optimization of MOF-Templated Co-Based Nanoparticles Embedded in Hollow N‑Doped Carbon Polyhedra for Efficient OER and ORR

Emerging clean energy technologies such as regenerative fuel cells and rechargeable metal–air batteries have attracted increasing global interest because of their high efficiency and environmental benignity, but the lack of highly active bifunctional electrocatalysts at low cost for both oxygen reduction and evolution reactions (ORR and OER) greatly hinders their commercial applications. Here, we report the multilevel architecture optimization of Co-based nanoparticles (NPs) embedded in hollow N-doped carbon polyhedra for boosting the ORR and OER, which are fabricated by a two-step pyrolysis–oxidation strategy with a Co-based MOF (ZIF-67) as precursor. The key for this strategy lies in the precise and effective control of the oxidation processes of Co NPs, which enables the synthesis of a series of Co–Co₃O₄-based nanoarchitectures that are embedded in hollow nitrogen-doped carbon polyhedra (HNCP), including core–shell Co/Co₃O₄, yolk@shell Co@Co₃O₄, and hollow Co₃O₄ NPs. Benefiting from its abundant oxygen vacancies and tetrahedral Co²⁺ and the potential synergies of CoO_<i>x</i> species and nitrogen-doped carbon as well as the efficient mass transfer of hollow and yolk–shell structures, the optimal yolk@shell Co₃O₄/HNCP-40 exhibits high activity for the OER with a low overpotential of 333 mV at 10 mA cm^–2 and a small Tafel slope of 69 mV dec^–1, which is better than those of commercial IrO₂ (its overpotential and Tafel slope are 409 mV at 10 mA cm^–2 and 104 mV dec^–1, respectively). Meanwhile, the catalyst also exhibits comparable ORR catalytic activity with a half-wave potential of 0.834 V but better stability and methanol tolerance relative to commercial Pt/C (20 wt %), making it a potential bifunctional electrocatalyst for both the OER and ORR. This MOF-templated strategy for multilevel nanostructures provides insights into the development of highly efficient and low-cost bifunctional electrocatalysts for the OER/ORR

The Ru-tpc Water Oxidation Catalyst and Beyond: Water Nucleophilic Attack Pathway versus Radical Coupling Pathway

Many Ru water oxidation catalysts have been documented in the literature. However, only a few can catalyze the O–O bond formation via the radical coupling pathway, while most go through the water nucleophilic attack pathway. Understanding the electronic effect on the reaction pathway is of importance in design of active water oxidation catalysts. The Ru-bda (bda = 2,2′-bipyridine-6,6′-dicarboxylate) catalyst is one example that catalyzes the O–O bond formation via the radical coupling pathway. Herein, we manipulate the equatorial backbone ligand, change the doubly charged bda^2– ligand to a singly charged tpc^– (2,2′:6′,2″-terpyridine-6-carboxylate) ligand, and study the structure–activity relationship. Surprisingly, kinetics measurements revealed that the resulting Ru-tpc catalyst catalyzes water oxidation via the water nucleophilic attack pathway, which is different from the Ru-bda catalyst. The O–O bond formation Gibbs free energy of activation (Δ<i>G</i>^⧧) at <i>T</i> = 298.15 K was 20.2 ± 1.7 kcal mol^–1. The electronic structures of a series of Ru^VO species were studied by density function theory calculations, revealing that the spin density of O_RuO of Ru^VO is largely dependent on the surrounding ligands. Seven coordination configuration significantly enhances the radical character of Ru^VO