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Selenourea
About: Selenourea is a research topic. Over the lifetime, 353 publications have been published within this topic receiving 4054 citations.
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TL;DR: A tunable library of N,N,N'-trisubstituted selenourea precursors and their reaction with lead oleate at 60-150 °C to form carboxylate-terminated PbSe nanocrystals in quantitative yields is reported.
Abstract: We report a tunable library of N,N,N′-trisubstituted selenourea precursors and their reaction with lead oleate at 60–150 °C to form carboxylate-terminated PbSe nanocrystals in quantitative yields. Single exponential conversion kinetics can be tailored over 4 orders of magnitude by adjusting the selenourea structure. The wide range of conversion reactivity allows the extent of nucleation ([nanocrystal] = 4.6–56.7 μM) and the size following complete precursor conversion (d = 1.7–6.6 nm) to be controlled. Narrow size distributions (σ = 0.5–2%) are obtained whose spectral line widths are dominated (73–83%) by the intrinsic single particle spectral broadening, as observed using spectral hole burning measurements. The intrinsic broadening decreases with increasing size (fwhm = 320–65 meV, d = 1.6–4.4 nm) that derives from exciton fine structure and exciton–phonon coupling rather than broadening caused by the size distribution.
87 citations
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TL;DR: The inhibition by selenium required the preincubation of the metal with sulfhydryl compounds such as dithiothreitol (DTT), indicating that the formation of selenotrisulfide or some other adduct(s) is essential for the inhibition.
74 citations
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TL;DR: In this article, a vesicle mediated high performance liquid chromatographic (HPLC)-microwave digestion (MW)-hydride generation (HG) system coupled on-line with AAS and inductively coupled plasma mass spectrometry (ICP-MS) was assessed for selenium species separation and detection.
Abstract: A vesicle mediated high performance liquid chromatographic (HPLC)–microwave digestion (MW)–hydride generation (HG) system coupled on-line with atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) has been assessed for selenium species separation and detection. Selenocystine, selenomethionine, selenoethionine, selenourea, SeIV and SeVI are separated by vesicle mediated chromatography prior to on-line selenocompounds microwave digestion with a KBrO3–HBr mixture to generate SeIV continuously, which is finally transformed into SeH2, in a continuous manner with a merging flow of sodium tetrahydroborate(III). Analytical characteristics of this coupling are compared with those obtained coupling HPLC–ICP-MS via conventional nebulisation. Detection limits (DLs) obtained for selenocystine, selenomethionine, selenoethionine, selenite and selenate in spiked human urine, when ICP-MS was used as detector, ranged between 1.0 and 5.3 µg l–1 (51–267 pg), while precision ranged between±3.4 and±8.4%. This continuous system, vesicle mediated HPLC–MW–HG–atomic detection, allows the separation and detection of selenocystine, selenourea, selenomethionine, selenoethionine, selenite and selenate in human urine. The analytical versatility of such coupling (with ICP-MS as the atomic detector) allows basal selenium speciation in urine. Three different normally occurring selenium species in human urine, simply diluted (1+1), have been found. The relative sophistication of the vesicle mediated–HPLC–MW–HG–ICP-MS interface, versus HPLC–ICP-MS via conventional nebulisation, can be justified because of its considerably higher sensitivity for most of the selenocompounds assayed, lower matrix interferences and the possibility of simultaneous interference free 77Se and 78Se monitoring.
68 citations
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TL;DR: In this article, the normal coordinate analysis of 13 in-plane vibrations of these molecules, including the in plane vibrations of urea-18O assigned by Laulicht [1] has been made using Wilson's GF matrix method and the Urey Bradley force field.
68 citations
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TL;DR: In this article, a two-phase approach at a toluene-water interface was used to synthesize colloidal CdSe and CdS quantum dots at low temperatures (60-90 degrees C).
Abstract: Colloidal CdSe and CdS quantum dots were synthesized at low temperatures (60-90 degrees C) by a two-phase approach at a toluene-water interface. Oil-soluble cadmium myristate (Cd-MA) was used as cadmium source, and water-soluble Na2S, thiourea, NaHSe, Na2SeSO3, and selenourea were used as sulfur and selenium sources, respectively. When a cadmium precursor in toluene and a selenium precursor in water were mixed, CdSe nanocrystals were achieved at a toluene-water interface in the range of 1.2-3.2 nm in diameter. Moreover, we also synthesized highly luminescent CdSe/CdS core-shell quantum dots by a two-phase approach using poorly reactive thiourea as sulfur source in an autoclave at 140 degrees C or under normal pressure at 90 degrees C. Colloidal solutions of CdSe/CdS core-shell nanocrystals exhibit a photoluminescence quantum yield (PL QY) up to 42% relative to coumarin 6 at room temperature.
67 citations