New fluorescent polymeric nanocomposites synthesized by antimony dodecyl-mercaptide thermolysis in polymer

In this work, the formation of semiconductive Sb2S3 nanoparticles inside amorphous polystyrene has been achieved by thermal degradation of the corresponding antimony dodecyl-mercaptide, Sb(SC12H25)3. The thermolysis of the dodecyl-mercaptide precursor was studied as both pure phase and mercaptide solution in polystyrene. The thermal decom- position of the antimony mercaptide precursor at 350°C, under vacuum, showed the formation of a mixture of antimony trisulfide (stibnite, Sb2S3) and zero-valent antimony (Sb) phase. X-ray Powder Diffraction (XRD) and Rietveld analysis carried out on the obtained nanostructured powder confirmed the presence of Sb and Sb2S3 phases in 10.4 wt% and 89.6 wt% amount, respectively. The same pyrolysis reaction was carried out in the polymer and the resulting nanocompos- ite material was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-VIS spec- troscopy, and fluorescence spectroscopy. The nanocomposite structural characterization indicated the presence of well-dispersed nanoclusters of antimony and stibnite (15-30 nm in size) inside the amorphous polymeric phase. Optical measurements on the obtained nanocomposite films showed a strong emission at 432 nm upon excitation at 371 nm, prob- ably related to the presence of Sb2S3 nanoclusters

Dielectric function of nanocrystalline silicon with few nanometers (<3 nm) grain size

The dielectric function of nanocrystalline silicon (nc-Si) with crystallite size in the range of 1 to 3 nm has been determined by spectroscopic ellipsometry in the range of 1.5 to 5.5 eV. ATauc–Lorentz parameterization is used to model the nc-Si optical properties. The nc-Si dielectric function can be used to analyze nondestructively nc-Si thin films where nanocrystallites cannot be detected by x-ray diffraction and Raman spectroscopy

Methane and n-butane oxidation with CO2 under radiofrequency plasmas of moderate pressures

The oxidation of methane and n-butane with CO2 has been studied in 35 MHz electrical discharges, operated at variable gas flow rates (6-30 (STP) min-1), power densities (2-8 cal cm-3 s -1) and constant pressure of 20 torr. Evidence is presented that the primary step of the process is the rupture of a C-H bond and that the main route for the conversion of both methane and n-butane into CO is via the intermediate C2-hydrocarbons (C2H2, C 2H4, C2H6).L'oxydation du méthane et du n-butane avec CO2 a été étudiée dans des décharges électriques de 35 MHz sous une pression de 20 torr en variant, vitesses de flux (6-301 (TPS) min.-1), et puissance spécifiques (2-8 cal cm-3 s-1). Les résultats présentés mettent en évidence la première étape du processus, qui est la rupture d'une liaison C-H, puis une seconde, l'oxydation des hydrocarbures intermédiaires en C2 (C2H2 , C2H4, C2H6) qui est la voie principale pour convertir méthane et n-butane en CO

Palladium-assisted multicomponent synthesis of 2-aryl-4 aminoquinolines and 2-aryl- 4-amino[1,8]naphthyridines

A palladium-mediated multicomponent domino reaction leading to 2-aryl-4-amino-quinolines and 2-aryl-4-amino[1,8]naphthyridines is reported. The scope of the reaction was examined using carbon monoxide, two 2-ethynyl-arylamines, four aryl iodides, and 10 primary amines as substrates. The selection of the appropriate catalytic system was achieved testing several palladium/phosphine systems and overrides previously reported drawbacks associated with the use of primary amines in related reactions. Moreover several features concerning the role of both palladium [(0) and (II)] and phosphines are reported

Correlation between serum and fecal concentrations of reproductive steroids throughout gestation in goats

Non-invasive techniques such as the measurement of fecal steroids are now widely used to monitor reproductive hormones in captive and free-ranging wild-life. These methods offer great advantages and deserve to be used in domestic animals. The aim of the present study was to determine the endocrine profile of dairy goats throughout pregnancy by the quantification of fecal progestins and estrogens and assess its con-elation with serum concentrations. Blood and fecal samples were collected weekly from I I adult, multiparous goats, from mating through pregnancy and 2 weeks post-partum. The extraction of estradiol and progesterone fecal metabolites was performed by dilution in ethanol. The radioimmunoassay (RIA) in solid phase was used to quantify serum 17 beta-estradiol (estradiol) and progesterone, as well as their fecal metabolites. The mean concentrations of both fecal and serum estradiol started to increase between weeks 7 and 11, reached peak values near parturition and then decreased sharply (range: 19.8 +/- 5.8 ng/g of feces to 608.6 +/- 472.4 ng/g of feces and 0.007 +/- 0.005 ng/ml to 0.066 +/- 0.024 ng/ml). An increase in both fecal and blood progestagens occurred in the second week, mean concentrations remained greater until week 20, and then decreased in the last week of gestation and 2 weeks post-partum (range: 108.8 +/- 43.6 ng/g of feces to 3119.5 +/- 2076.9 ng/g of feces and 0. 12 +/- 0.04 ng/ml to 13.10 +/- 4.29 ng/ml). The changes in blood and fecal hormone concentrations were analyzed and compared throughout gestation for each single goat, for each breed and for the whole group. Results indicated that matched values of serum and fecal hormone concentrations were correlated (r = 0.79; p < 0.001 for progesterone and r = 0.84;p < 0.001 for estradiol mean concentrations in the whole group). Regression analysis showed that logarithmic model allows significant prediction of serum from fecal concentrations with an R-2 = 0.729 (y = 0.013 1n x - 0.021) for estradiol and R-2 = 0.788 (y = 3.835 1n x - 18.543) for progesterone. Neither fecal nor serum concentrations were affected by the breed but a significant effect of the number of fetuses on progestin concentrations was found. Therefore, the profiles of progesterone and estradiol fecal metabolites reflect the serum concentrations of the same hormones in pregnant goats. (C) 2006 Elsevier B.V. All rights reserved