A practical synthesis of (Z)-3-alkenoates

Deconjugative protonation of ($\text{E}$)-2-alkenoate with bulky alkoxy group using potassium disilazide as the base gives (Z)-3-alkenoate selectively.     

Determination of selenium(IV) and other forms of selenium dissolved in sea water by anion-exchange resin loaded with sulfonic acid derivative of bismuthiol-II and hydride generation atomic-absorption spectrometry

Summary A sulfonic acid derivative of bismuthiol-II (bisIIS) was synthesized from 4-hydrazinobenzene sulfonic acid and carbon disulfide. Selenium(IV) was adsorbed selectively and quantitatively on the anion-exchange resin loaded with bis-IIS. Selenium adsorbed on the resin was eluted by the use of penicillamine and determined by hydride generation atomic absorption spectrometry (hydride generation/AAS). Selenium(VI) and other forms of selenium, which were not adsorbed onto the resin, were collected on the resin after digestion with nitric acid followed by reduction with hydrochloric acid. Separative preconcentration of selenium(IV), selenium(VI) and other forms of selenium in 0.5 mol/l sodium chloride could be carried out successfully by the proposed procedures. However, in the case of estuarial sea water containing a large quantity of organic substances, selenium(IV) could not be separated, because organic substances interfered with the reduction of selenium(VI) to selenium(IV) by the use of hydrochloric acid. Selenium(IV) and total amount of selenium(VI) and other forms of selenium dissolved in polluted sea water samples were determined by the proposed procedures.

---

Bestimmung von Selen (IV) und anderen in Meereswasser gelösten Selenformen mit Hilfe eines mit dem Sulfonsäurederivat von Bismuthiol-II beladenen Anionenaustauschers und der Hydrid-AAS

     

Comparison of InGaN/GaN light emitting diodes grown on m ‐plane and a ‐plane bulk GaN substrates

InGaN/GaN‐based light emitting diodes (LEDs) grown on m ‐plane, a ‐plane and off‐axis between m ‐ and a ‐plane GaN bulk substrates were investigated. A smooth surface was obtained when a ‐plane substrate was applied; however, large amounts of defects were observed. Photoluminescence measurements of the LEDs with a well thickness of 2.5 nm revealed that all the LEDs showed the peak emission wavelength at 389 nm. The PL intensity of the a ‐plane LED is one order of magnitude lower than that of the m ‐plane LED. The a ‐plane LEDs showed significant lower electroluminescence output powers than m ‐plane LEDs, suggesting that excitons are trapped by the defects, which act as non‐radiative recombination centers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Formation of microcrystalline structure in a-Si:H films prepared by RF sputtering

Formation of microcrystalline structure in a-Si:H films prepared by RF sputtering has been investigated by TEM and FT-IR. The Films deposited in pure H₂ have grain-like structure and tend to crystallize with increasing the gas pressure, while the films deposited in Ar containing 10 % H₂ usually become amorphous. With increasing input power and the gas pressure, however, the latter films tend to have amorphous-microcrystalline mixed structure, and corresponding to this structural change, shift of optical absorption edge to lower energy and decreases of resistivity and activation energy of its temperature dependence are observed.