One-pot synthesis of 1-substituted-5-alkylselanyl-1H-tetrazoles from isoselenocyanates: unexpected formation of N-alkyl-N-arylcyanamides and (Z)-Se-alkyl-N-cyano-N,N′-diarylisoselenoureas

1-Substituted-5-alkylsulfanyl-1H-tetrazoles are well known class of organic substances with various applications in medicinal chemistry or photographic industry. Their selenium analogues, 1-substituted-5-alkylselanyl-1H-tetrazoles are, however, much less explored because of the lack of suitable methods for their preparation. In this work we investigated the synthesis of 1-alkyl/aryl-5-alkylselanyl-1H-tetrazoles from synthetically available alkyl/arylisoselenocyanates. One-pot reactions of arylisoselenocyanates with sodium azide and alkylating agent led to the target 5-alkylselanyl-1-aryl-1H-tetrazoles but also to interesting side products, namely N-alkyl-N-arylcyanamides and (Z)-Se-alkyl-N-cyano-N,N′-diarylisoselenoureas. Nevertheless, when alkylisoselenocyanates were utilized as the substrates, the reactions led exclusively to the formation of 1-alkyl-5-alkylselanyl-1H-tetrazoles in good yields. This simple one-pot procedure brings new possibilities for the preparation of variously substituted selenium compounds. It also opens the way to further investigations of selenium isosteres of the widely utilized 5-thiotetrazole moiety in biomedical applications.     

The band alignment at CdS/Cu2ZnSnSe4 heterojunction interface

Band alignment at CdS/Cu₂ZnSnSe₄ heterojunction interface is studied by X‐ray photoemission spectroscopy. The Cu₂ZnSnSe₄ thin films are prepared by selenization of electrodeposited Cu‐Zn‐Sn precursors. CdS overlayers with different thickness are sequentially grown on the Cu₂ZnSnSe₄ substrate by pulsed laser deposition process. Photoemission spectra are obtained before and after each growth to study the conduction and valence band offsets at the heterojunction interface. The determined conduction band offset of 0.34 eV indicates a spike‐like ‘type I’ band alignment at CdS/Cu₂ZnSnSe₄ interface. The spike will avoid interface recombination, and it is low enough that electron could transfer from the Cu₂ZnSnSe₄ layer to the buffer layer which is suitable for solar cell's fabrication. Copyright © 2012 John Wiley & Sons, Ltd.     

Functional silver nanostructured surfaces applied in SERS and SIMS

Present article deals with functionality of silver nanostructured surfaces prepared by potentiostatic electrochemical deposition on the paraffin impregnated graphite electrode as template‐free substrates. The effect of the electrodeposition conditions on two silver surface functions: analytical signal enhancement in Surface‐enhanced Raman spectroscopy and pre‐ionization function, applied in secondary ion mass spectrometry (SIMS) is reported. Functional silver nanostructured substrate was prepared at a potential ?850 mV with a deposition duration of 20 min. Analytical signal enhancement factors of 3.2 ×10⁵ for Raman peak at 649 cm^?1, 3.0×10⁵ for peak at 810 cm^?1 and 2.7×10⁵ for peak at 1539 cm^?1 were determined for Rhodamine 6G at deposited surface. Slight pre‐ionization effect has been observed in SIMS, and 1.2×10⁵ fold signal enhancement was established for fragment of Rhodamine 6G with m/z 429 (M‐CH₃‐Cl). Electrochemical preparation of nanostructures represents a step towards surface integration directly into miniaturized systems and sensors. Copyright © 2013 John Wiley & Sons, Ltd.     

THE ROLE OF INTERFACIAL INTERACTIONS IN THE PARTICLE/BUBBLE ATTACHMENT

The Van Oss surface thermodynamic theory of polar and apolar interfacial interactions was extended to the interaction between mineral surfaces and bubbles across liquid media. The acid base (polar) interfacial interactions are supposed to be responsible for the hydration repulsion between a hydrophilic mineral and a bubble as well as for the hydrophobic attraction between a hydrophobic mineral and the bubble.     

Dispersion Mechanism of Superfine SiC Particles in the Different Condition Liquid

SiC@A1(OH)₃-Y(OH)₃ core-shell composite particles are synthesized by co-precipitation method for strengthening the antioxidation of SiC at high temperature. To reach better A1(OH)₃-Y(OH)₃ composite shell and higher coating ratio on the SiC particles surfaces, SiC particles must be adequately dispersed in the SiC suspension during the coating process. The dispersion mechanism of SiC particles is investigated by the sedimentation method. Through test and analysis, the optimum conditions of the dispersion of SiC particles in the SiC suspension are sedimentating for 10 minutes, ultrasonic dispersion for 10 minutes, the lower SiC concentration, pH = 9, the dispersant content for the 2% volume of SiC suspension and using the polyelectrolyte dispersant, respectively.     

Pu and Am sorption to the Baltic Sea bottom sediments

Sorption of Am and Pu isotopes to bottom sediments of the Baltic Sea has been studied under natural and laboratory conditions. Data obtained from sequential extraction, sorption of Am(III), Pu(IV) and Pu(V) as well as oxidation state distribution experiments have shown that Pu(V) sorption mechanism includes a very fast Pu(V) reduction (reaction rate ≤ 2.33 × 10^?3 s^?1) to Pu(IV) by humic substances and/or by Fe(II) to Pu(IV) and partly to Pu(III). Following reduction Pu isotopes were bound to various components of bottom sediments via ion exchange and surface complexation reactions and a slow incorporation into the crystalline structure of Fe minerals. Kinetics experiments showed that the sorption of Pu(V), Pu(IV) and Am(III) to bottom sediments from natural seawater was controlled by the inert layer diffusion process.     

The preparation of the 239Np tracer from 243Am and the purification of the stock solution

The present work describes preparation of ²³⁹Np tracer from ²⁴³Am stock solution and the purification of this solution from ferric cation. The method of the preparation of tracer involves stabilization of Np(IV) by ascorbic acid and ferric nitrate, separation of ²³⁹Np from ²⁴³Am by extraction chromatography and determination of recoveries of ²³⁹Np by means of gamma spectroscopy. We used the commercially available sorbents TEVA^®Resin for the ²³⁹Np preparation and DGA Resin for ²⁴³Am purification. All sorbents were purchased from Eichrom Industries, Inc. The first eluate from the column can be stored for a future preparation of the tracer and fraction with ²³⁹Np will be used to monitor radiochemical yield of ²³⁷Np.     

Some key ordered macroporous composites

This review summarizes recent progress of the ordered macroporous composites with the opals and inverse opal structure. Synthesis and performance of the composites are emphasized. Composition of the ordered composites is tunable ranging within metal, metal alloy, metal oxide, polymer, carbon and hydrogel. The ordered structure gives brilliant color effects, which is useful for sensors and photonic crystals. The interconnected macroporous structure provides easiness for mass transportation and species culturing.     

The influence of finite dimensions on the static ordering of the S*C phase in an electric field

Abstract

A ferroelectric liquid-crystalline sample of a finite length along the helical axis is studied in an external electric field applied perpendicular to the helical axis. By taking into account the linear coupling to the field, the equilibrium state is found for the case of free boundary conditions. Just below the critical field which induces the transition into the homogeneous S*_C phase the domain-like structure appears as in the case of an infinite sample. The helical period in a finite sample is not a continuous function of the field, but it increases in finite jumps. We show that the finiteness of the sample has also an influence on the dielectric response at zero field.