Formation of 1,2,4-trioxolanes via 9,10-dicyanoanthracene(DCA)-sensitized photo-oxygenation of 2,2-diaryl-3-(2,2-diarylvinyl)oxiranes

9,10-Dicyanoanthracene-sensitized photo-oxygenation of 2,2-diaryl-3-(2,2-diarylvinyl)oxiranes 3 in acetonitrile did not afford the corresponding 1,2,4-trioxepines 4, but 1,2,4-trioxolanes 7. The structural assignment of 7 was reported, and the mechanism of the formation of 7 was proposed.     

Convection-Flow-Assisted Preparation of a Strong Electron Dopant,Benzyl Viologen,for Surface-Charge Transfer Doping of Molybdenum Disulfide

Transition metal dichalcogenides (TMDCs) have received attention as atomically thin post-silicon semiconducting materials. Tuning the carrier concentrations of the TMDCs is important, but their thin structure requires a non-destructive modulation method. Recently, a surface-charge transfer doping method was developed based on contacting molecules on TMDCs, and the method succeeded in achieving a large modulation of the electronic structures. The successful dopant is a neutral benzyl viologen (BV⁰); however, the problem remains of how to effectively prepare the BV⁰ molecules. A reduction process with NaBH₄ in water has been proposed as a preparation method, but the NaBH₄ simultaneously reacts vigorously with the water. Here, a simple method is developed, in which the reaction vial is placed on a hotplate and a fragment of air-stable metal is used instead of NaBH₄ to prepare the BV⁰ dopant molecules. The prepared BV⁰ molecules show a strong doping ability in terms of achieving a degenerate situation of a TMDC, MoS₂. A key finding in this preparation method is that a convection flow in the vial effectively transports the produced BV⁰ to a collection solvent. This method is simple and safe and facilitates the tuning of the optoelectronic properties of nanomaterials by the easily-handled dopant molecules.     

Complete removal of paint from metal surface by ablation with a TEA CO2 laser

For high-speed metal surface cleaning, we applied TEA CO₂ laser pulses to ablate painted materials on metal surfaces and examined the efficiency of removal under different surface and irradiation conditions. Surfaces treated with a line-focused laser beam were analyzed with an energy dispersive X-ray analyzer and inspected with optical microscopic observation. Although paints were selectively ablated from the metal surface, the cleaning efficiency was found to depend on surface conditions of substrates. An application of a small amount of dimethyl formamide was effective for completely removing of resin without scorching the surface.     

Pd(O) promoted transformation of N-tosyl-2-(1,3-butadienyl)-aziridine into N-tosyl-2-vinyl-3-pyrroline

1,3-Butadienylaziridines activated by N-tosyl group smoothly rearrange to vinylpyrrolidine derivatives in the presence of a catalytic amount of Pd(PPh₃)₄. Transformation of dienylazetidines into vinylpiperidine derivatives is also described.     

An estimation of the distribution functions of doped Tb and Nd in glasses by fluorescence measurements

The distribution functions of doped Tb³⁺ and Nd³⁺ in silicate, germanate, borate and phosphate glasses, in which cross-relaxation among active ions plays an important role, have been estimated by fluorescence measurements. In order to analyze both the steady state and the transient fluorescence characteristics, a non-linear model for the resonant energy transfer has recently been developed. The experimental fluorescence intensity and decay curves, measured as a function of acceptor concentration, suggested a modified distribution function, which included the effect of the segregation of donors and acceptors. The number of segregated Tb³⁺ ions at the second nearest neighbor position around a Tb³⁺ ion was estimated to be 0.1–3.4, depending on the host glass.     

Analysis of Adsorbed Urea and Alkylthiourea on Alumina Surface by Inelastic Electron Tunneling Spectroscopy

Inelastic electron tunneling spectroscopy is used in the analysis of chemisorbed species of urea and alkylthiourea on the alumina surface using an Al-Al₂O₃-Pb tunnel junction. Tunneling spectra of urea, thiourea, N,N′-dimethylthiourea (DMTU), and tetramethylthiourea (TMTU) were taken and analyzed for designated band positions and intensities by comparing with the corresponding IR spectrum. These molecules seem to exhibit similar adsorption behavior onto alumina surface. Thiourea and urea interact with the surface through the nitrogen lone pairs and orient perpendicularly on the Lewis acid site of the alumina surface. DMTU and TMTU are still adsorbed through the nitrogen atoms, but the molecular plane has a somewhat inclined orientation to the alumina surface.     

Mercury L3 and sulfur K-edge studies of Hg-bound thiacrowns and back-extracting agents used in mercury remediation

Effective methods for the removal of mercury from water are in demand due to the high levels of mercury released from industrial and natural processes. Polymer pendant thiacrown compounds used for the sequestration of Hg(II) from aqueous solutions passed through columns have shown great promise as effective tools for remediation. The mercury can potentially be removed from the columns by extraction with diethyldithiocarbamate (dtc) and diphenylthiocarbazone, aka dithizone (dtz). In this study, Hg L3 and sulfur K-edge X-ray absorption spectroscopy are used to contrast the structure of the mercury thiacrown complex Hg[17]aneS5 with the structure of mercury bound to two potential back-extracting agents, Hg(dtc)₂ and Hg(dtz)₂. In Hg(dtc)₂, it was found that Hg(II) was bound to four sulfur atoms, with two Hg-S bond lengths of 2.66 Å and two Hg-S at 2.49 Å. In Hg(dtz)₂, Hg(II) was bound to two sulfur atoms with Hg-S bond distances of 2.38 Å and two nitrogen atoms with Hg-N at 2.54 Å. This contrasts with Hg[17]aneS5 with three Hg-S bonds at 2.40 Å. Mercury L3 and S K-edge results show that electron density shifts from sulfur in dtc and dtz, to mercury in Hg(dtc)₂ and Hg(dtz)₂.The increase in the number of bonds, and the more stable geometry and electron distribution in the back-extraction complexes confirms that these compounds are more stable than the mercury thiacrown complex, and thus suitable for regeneration of the pendant-arm [17]aneS₅ for further remediation processes.