Elucidating the Mechanistic Origin of a Spin State-Dependent FeNx-C Catalyst toward Organic Contaminant Oxidation via Peroxymonosulfate Activation.

Atomically dispersed metals on nitrogen-doped carbon matrices have attracted extensive interest in the removal of refractory organic pollutants. However, a thorough exploration of the particular structure for each active site and specific effects of these sites still remains elusive. Herein, an Fe-pyridinic N4 structure in a single-atom catalyst (FeNx-C) was constructed using a facile pyrolysis strategy, and it exhibited superior catalytic activity in peroxymonosulfate (PMS) activation toward organic contaminant oxidation. The various Fe species and relative amounts of each Fe site in the FeNx-C catalyst were validated using X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy, which showed critical dependencies on the precursor ratio and calcination temperature. The positive correlations between relative content of high-spin state species (FeII and FeIII) and catalytic performance were found to determine the reactive species generation and electron transfer pathway in the FeNx-C/PMS system. Moreover, catalytic performance and theoretical calculation results revealed that FeII-N4 in the high-spin state (S = 2) tends to activate PMS to form sulfate and hydroxyl radicals via a one-electron transfer process, while the FeIII-N4 moiety (S = 5/2) is prone to high-valent iron species generation with lower free energy. Benefiting from finely tuned active sites, a single-atom FeNx-C catalyst achieved favorable applicability in actual wastewater treatment with efficient resistance of the common water matrix. The present work advances the mechanistic understanding of spin state-dependent persulfate activation in single-atom catalysts and provides guidance to design a superior catalyst based on spin state descriptions.

Self-Assembly of Nanosheet-Supported Fe-MOF Heterocrystals as a Reusable Catalyst for Boosting Advanced Oxidation Performance via Radical and Nonradical Pathways.

Heterojunction catalysts have drawn increasing interest for the visible light-driven Fenton reaction and bring tremendous opportunities for environmental remediation. Herein, a BiOI/MIL-53(Fe) Z-scheme heterojunction (named BMFe) was synthesized for the first time via a facile strategy. Compared with pristine BiOI and MIL-53(Fe) catalysts, the two-dimensional/three-dimensional (2D/3D) heterojunction catalyst manifested remarkable catalytic performance toward degradation of phenol, bisphenol A, methylene blue, and carbamazepine, which is attributed mainly to the interfacial integration and efficient charge separation. By virtue of coupling at the interface, as confirmed by XPS, 57Fe Mössbauer spectroscopy, and DFT calculations, the BMFe catalyst promoted the transfer of electron-hole pairs via Z-scheme and improved the chemical activation of hydrogen peroxide. The subsequent holes, free radicals, and nonradicals can effectively and continuously decompose pollutants, achieving a positive synergistic effect between photocatalysis and Fenton reactions. Simultaneously, the specially designed BiOX(X = Br, Cl)/MIL-53(Fe) and BiOI/Fe-MOFs(MIL-101, MIL-88) heterojunctions also exhibited advanced oxidative capacity for organic pollutants. Given their practical value for industrial applications, BMFe beads (1.0 ± 0.15 mm) synthesized via a blend cross-linking method can significantly advance long-term stability and recyclability. The integration of Fe-based metal-organic frameworks with bismuth oxyhalide semiconductors provides a new perspective on developing heterojunction catalysts for environmental remediation.

Determination of genotoxic potential by comparison of structurally related azo dyes using DNA repair-deficient DT40 mutant panels.

Azo dyes, including Sudan I, Orange II and Orange G, are industrial dyes that are assumed to have genotoxic potential. However, neither the type of DNA damage induced nor the structural features responsible for toxicity have been determined. We used a panel of DNA-repair-pathway-deficient mutants generated from chicken DT40 cells to evaluate the ability of these azo dyes to induce DNA damage and to identify the type of DNA damage induced. We compared the structurally related azo dyes Sudan I, Orange II and Orange G to identify the structural features responsible for genotoxicity. Compared with wild type cells, the double-strand break repair defective RAD54-/-/KU70-/- cells were significantly more sensitive to Sudan I, but not to Orange II or Orange G. The quantum-chemical calculations revealed that Sudan I, but not Orange II or Orange G, has a complete planar aromatic ring structure. These suggest that the planar feature of Sudan I is critical to the inducing of double-strand breaks. In summary, we used a DNA-repair mutant panel in combination with quantum-chemical calculations to provide a clue to the chemical structure responsible for genotoxicity.

Analyte-Size-Dependent Ionization and Quantification of Monosaccharides in Human Plasma Using Cation-Exchanged Smectite Layers.

Smectite, a synthetic inorganic polymer with a saponite structure, was subjected to matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Typical organic matrix molecules 2,4,6-trihydroxyacetophenone (THAP) and 2,5-dihydroxybenzoic acid (DHBA) were intercalated into the layer spacing of cation-exchanged smectite, and the complex was used as a new matrix for laser desorption/ionization mass spectrometry. Because of layer spacing limitations, only a small analyte that could enter the layer and bind to THAP or DHBA could be ionized. This was confirmed by examining different analyte/matrix preparation methods and by measuring saccharides with different molecular sizes. Because of the homogeneous distribution of THAP molecules in the smectite layer spacing, high reproducibility of the analyte peak intensity was achieved. By using isotope-labeled (13)C6-d-glucose as the internal standard, quantitative analysis of monosaccharides in pretreated human plasma sample was performed, and the value of 8.6 ± 0.3 µg/mg was estimated.

Non-HPLC rapid separation of metallofullerenes and empty cages with TiCl4 Lewis acid.

Rapid and efficient separation/purification of pure metallofullerenes M(x)@C(n) (M = metal; x = 1, 2; n > 70) and carbide metallofullerenes of the type M(y)C(2)@C(n-2) (y = 2, 3, 4; n - 2 > 68) has been reported. The present method utilizes rapid and almost perfect preferential formation of TiCl(4) (generally known as a Lewis acid)-metallofullerene complexes, which easily decompose to provide pure metallofullerene powders by a simple water treatment. The present method enables one to separate the metallofullerenes up to >99% purity within 10 min without using any type of high-performance liquid chromatography (HPLC). It is found that the oxidation potentials of the metallofullerenes are crucial factors for efficient purification. The current separation/purification technique may open a brand-new era for inducing further applications and commercialization of endohedral metallofullerenes.

Oxidation of element 102, nobelium, with flow electrolytic column chromatography on an atom-at-a-time scale.

We report here on the successful oxidation of element 102, nobelium (No), on an atom-at-a-time scale in 0.1 M alpha-hydroxyisobutyric acid (alpha-HIB) solution using a newly developed technique, flow electrolytic column chromatography. It is found that the most stable ion, No(2+), is oxidized to No(3+) within 3 min and that the oxidized No complex with alpha-HIB holds the trivalent state in the column above an applied potential of 1.0 V.

Fluoride complexation of element 104, rutherfordium.

Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the 18O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effects on the fluoride complexation of Rf.