We introduce a facile way to synthesize high-quality CdSe quantum dots (QDs) in a high-boiling two-phase liquid/liquid system. The cadmium myristic acid salt (Cd-MA) dispersed in the dimethylbenzene and selenourea dissolved in the ethylene glycol (EG) reacted at the two-phase interface for the nucleation and growth of nanocrystals. The n -trioctylphosphine oxide (TOPO) was used as capping agent of the CdSe QDs. In this route, the selenourea used as the precursor was dissolved in viscous ethylene glycol (EG), which facilitated the control of the nanocrystal growth by virtue of the slow decomposition and diffusion of selenourea in EG. The size, shape, crystalline structure and optical properties of CdSe QDs were investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV⿿vis spectrometer and photoluminescence spectroscopy. This route could be exploited to synthesize nanocrystals with a large scale and could broaden to synthesis of metal or other semiconductor nanocrystals.
A simple, rapid, and accurate method for determination of selenocystine (SeCys 2 ), methyl selenocysteine (MeSeCys), selenourea (SeUr), selenite (Se(IV)), selenotmethionine (SeMet), and selenate (Se(VI)) in grain crops was developed, based on the coupling of ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC) and ultraviolet irradiation hydride generation atomic fluorescence spectrometry (UV-HG-AFS). The conditions of IP-RP-HPLC-UV-HG -AFS were studied. The conditions of the pretreatment sample, such as types and dosage of proteinases, were investigated. The detection limits (LODs) for six Se species were between 0.77 and 1.77 μg·L −1 . Then, the proposed method has been successfully used to analyze selenium (Se) species in Se-enriched rice paddy ( Oryza sativa L. ), soybean ( Glycine max (Linn.) Merr. ), and sweet potato ( Ipomoea batatas (L.) Lam. ) with foliar application of sodium selenite solution. SeMet was the major Se spices in Se-enriched grain crops, ranged from 77–90% of the total Se contents. The capabilities of Se enrichment were relatively larger differences in three-grain corps as follows: soybean > rice paddy > sweet potato.
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