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Traditional Si solar cells have a narrow active absorption cross section among the short wavelength range (200-400 nm). The down-shifting process can efficiently improve the spectral response of Si solar cells by converting shorter wavelengths (i.e., ultraviolet, UV) to longer wavelengths (i.e., the visible range). Here, ZnSe quantum dots (QDs), prepared by an aqueous solution method and employed as a luminescent down-shifting layer, were spin coated onto the upper surface of manufactured Si solar cells. Measurements under standard test conditions (AM1.5,100 mW/[cm.sup.2]) show that the efficiency of the ZnSe QDs-Si hybrid solar cell is increased from 11.48% to 12%. The improvement of the ZnSe QDs-Si hybrid solar cell is ascribed to the efficient down-shifting process of ZnSe QDs, which enhances spectra response in the UV region for Si solar cells. The mechanism of this optical coupling and efficiency enhancement is investigated in detail. These results support the case that low-cost ZnSe QDs can be employed as efficient downshifting material on large-area solar cells. PACS Nos.: 81.07Ta, 77.84Bw, 88.40hj. Les cellules solaires Si traditionnelles ont une section efficace d'absorption faible dans le domaine des ondes courtes (200-400 nm). Un mecanisme de decalage vers le bas (downshifting) peut ameliorer l'efficacite des cellules solaires Si en convertissant les courtes longueurs d'onde (ultraviolet, UV) vers les longueurs d'onde du visible. Nous employons ici des points quantiques (QD) de ZnSe, prepares en solution aqueuse, comme couche de convertisseur vers le bas et les appliquons par enduction centrifuge sur la surface de la cellule solaire Si manufacturee. Des mesures faites sous des conditions standardisees (AM1.5,100 mW/[cm.sup.2]) montrent que l'efficacite de la cellule solaire hybride ZnSe QD-Si voit son efficacite passer de 11.48% a 12%. Nous attribuons l'amelioration du cas hybride ZnSe QD-Si a une conversion efficace par les QD de ZnSe, qui augmente la reponse spectrale de la cellule Si dans l'UV. Nous etudions ici en detail le mecanisme de ce couplage optique et l'amelioration qu'il apporte. Ces resultats supportent l'utilisation des QD ZnSe peu chers comme convertisseurs efficaces pour les cellules solaires. [Traduit par Redaction], 1. Introduction The superior photoelectric characteristics of semiconductor quantum dots (QDs) offer attractive advantages for high efficiency solar cells. To increase the efficiency of solar cells, three luminescence procedures including [...]

A novel strategy for the enhancement of electrochemiluminescence (ECL) was developed by combining CdSe nanocrystals (NCs), carbon nanotube--chitosan (CNT--CHIT), and 3-aminopropyl-triethoxysilane (APS). A label-free ECL immunosensor for the sensitive detection of human IgG (HIgG) was fabricated. The colloidal solution containing CdSe NCs/CNT--CHIT composite was first covered on the Au electrode surface to form a robust film, which showed high ECL intensity and good biocompatibility. After APS as a cross-linker was covalently conjugated to the CdSe NCs/CNT--CHIT film, the ECL intensity was greatly enhanced. And, an intensity about 20-fold higher than that of the CdSe NCs/CNT--CHIT film was observed. After antibody was bound to the functionalized film via glutaric dialdehyde (GLD), the modified electrode could be used as an ECL immunosensor for the detection of HIgG. The specific immunoreaction between HIgG and antibody resulted in the decrease in ECL intensity. The ECL intensity decreased linearly with HIgG concentration in the range of 0.02-200 ng [mL.sup.-1], and the detection limit was 0.001 ng [mL.sup.-1]. The immunosensor has the advantages of high sensitivity, speed, specificity, and stability and could become a promising technique for protein detection.

An analysis of the tail feathers of 104 osprey nestlings (Pandion haliaetus L.) from Lake Asnen, southern Sweden, was undertaken for total mercury and selenium content. Results indicate that the bioaccumulated quantity of selenium that is thought to be protective for the organisms against the toxic effects of mercury is somewhat insufficient to bind all body mercury.

3H-1, 2-benzothiaselenol-3-one (BTSe) converts nucleoside H-phosphonate and nucleoside H-phosphonothioate diesters into the corresponding phosphoroselenoate and phosphorothioselenoate diesters. BTSe is soluble in organic solvents and exhibits enhanced rate of selenium transfer. The BTSe conversion is stereospecific and retains the configuration at the phosphorus center and is also useful in the conversion of phosphite triesters into the corresponding phosphoroselenoates.

Mitomycins A (MMA) and C (MMC) are prepared and 13C- and D-labeled at C-6 foruse in pharmacokinetic studies. The process involves displacing the exo-methylene of 6-demethyl-7,7-(ethylenedioxy)-6-methylenemitosane with phenylselenenamides. The product then undergoes 13C- and D-labeling with isotopic methyl iodide and potassium carbonate, followed by reductive deselenenylation. Conversion to (C-6-CH3-13C)MMC and (C-6-CH3-2H3)MMC is achieved with methanolic ammonia while the corresponding MMAs from the same intermediate are obtained by reaction with methanolic potassium carbonate.

Protection of the C-2 position of 2, 3-dideoxyribosyl acetate with an alpha-phenylselenenyl group allows the stereoselective synthesis of 2',3'-dideoxy- and 2',3'-didehydro-2', 3'-dideoxynucleosides in favor of the beta-isomers. The selenenyl group is easily removed by treatment with tributyltin hydride or triethylborane to give the 2',3'-dideoxynucleoside or with hydrogen peroxide in catalytic pyridine to yield the didehydro form. The technique is applicable to a wide range of pyrimidine and purine dideoxynucleosides with potential use as anti-HIV agents.

A symmetrical chiral C2 organoselenium reagent can mediate asymmetrical ring closures. This enables the synthesis of substituted heterocycle derivatives that are enatiometrically enriched. The study was done with trans-6,6-dimethyl -4-hepten-1-ol, and the facial selectivity of symmetrical organoselenium reagent is assesed.

Byline: Pawan K. Khanna, Jin-Ook Baeg, S.M. Lee Single-step green synthesis of zinc blende ZnSe quantum dots (QDs) is performed using sodium selenide and zinc stearate. The present method is non-toxic and is considered reasonably green route where stearate ions released during the reaction act as surfactant. The size quantisation effect is revealed by blue shifted absorption bands with a band-gap energy of ~2.9 eV with respect to bulk ZnSe band-gap of 2.7 eV. Photoluminescence measurement with FWHM

The combination of clay catalysis and microwave (MW) thermolysis provides a cleaner and higher yielding Claisen rearrangement of allylic cyclic alkenols over the conventional(Johnson) methodology. When the alkenols are reacted with triethyl orthoacetateunder MW in the presence of montmorillonite, the rearranged esters are formed in 66-100% yields without any of the derived acetate byproducts. Subsequent unmasking of the carboxylate functions, selenolactonization and hydrogen proxide workup give the desired cis bicyclic unsaturated lactones in up to 90% yields.

Natural products provide an excellent starting point for the development of libraries of related molecules, which can be screened for biological activity, but the creation of combinatorial libraries can pose [...]