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Mercaptoacetic acid-capped CdTe quantum dots (QDs) are potential luminescent markers for biological analysis. The photoluminescence (PL) stability of the QDs in buffer solutions determines their practicability as markers in electrophoresis. The stability of the QDs was thus investigated in electrophoresis buffers including tris-borate-ethylenediaminetetraacetic acid (TBE) and tris-acetate-ethylenediaminetetraacetic acid (TAE). The QDs were completely unstable in high-concentrated buffers (≥0.1×). In the case of low concentrations (≤0.07× for TAE, ≤0.035× for TBE), the PL intensity of the QDs in two kinds of buffers decreased with increasing buffer concentrations. A red-shifted PL peak wavelength and PL intensity fluctuation were observed after dispersing the QDs in diluted TAE buffer solutions with concentrations of ≤0.07× for long time. According to the Stern-Volmer plots of PL degradation, the factors leading to the degradation were complicated, which was attributed to the actions of the components including tris, borate or acetic acid, and ethylenediaminetetraacetic acid as well as their mutual effects. [ABSTRACT FROM AUTHOR]

The synthesis and photoluminescence (PL) properties of aqueous CdTe/ZnO core/shell quantum dots (QDs) have been investigated by using thiolglycolic acid as a capping reagent. The highlighted contribution of the present study was CdTe QDs coated with a ZnO shell by controlling the hydrolysis process of Zn(OAc). The QDs benefitted from overcoming the high lattice mismatch between CdTe and ZnO. The PL peak wavelength of the CdTe/ZnO QDs with high PL quantum yields up to 88% was located in a range between 547 and 596 nm by adjusting the size of CdTe cores and the thickness of ZnO shells. The results of X-ray diffraction analysis and transmission electron microscopy observation indicate that the dot-shaped CdTe/ZnO QDs (566 nm) with an average size of 2.2 nm in diameter belong to the cubic CdTe crystal structure. Due to the passivation of surface defects, it is found that the luminescence decay curves accord with a biexponential decay model of exciton and trap radiation behavior. The average PL lifetimes of CdTe (571 nm) and CdTe/ZnO (596 nm) QDs at room temperature are 27.3 and 35.1 ns, respectively. [ABSTRACT FROM AUTHOR]

Silver particles with various morphologies were prepared by a facile synthesis via the reduction of silver ions in an ethylene glycol solution with poly(vinyl pyrrolidone) (PVP) and trace amounts of sodium chloride. Preparative conditions such as reaction temperature (from 120 to 160 °C), time, and the concentration of starting materials were optimized for the purpose of controlling the morphology of Ag particles. Scanning electron microscopy indicated Ag particles with various morphologies such as rod, cubic, and spherical. The creation of various morphologies was ascribed to the select adsorption ability of PVP and the erosion behavior of the chloride ion. Because of the morphology dependence of the Ag particles on the preparative conditions, this strategy provided a platform for controlling the morphologies of metallic particles. [ABSTRACT FROM AUTHOR]

CdTe quantum dots (QDs) were prepared in an aqueous solution using various mercaptocarboxylic acids, such as 3-mercaptopropionic acid (MPA) and thioglycolic acid (TGA), as stabilizing agents. The experimental result indicated that these stabilizing agents played an important role for the properties of the QDs. Although both TGA and MPA-capped CdTe QDs exhibited the tunable photoluminescence (PL) from green to red color, the TGA-capped QDs revealed a higher PL quantum yield (QY) up to 60% than that of MPA-capped QDs (up to 50%) by using the optimum preparation conditions, such as a pH value of ~11.2 and a TGA/Cd molar ratio of 1.5. PL lifetime measurements indicate that the TGA-capped QDs exhibited a short average lifetime while the MPA-capped QDs revealed a long one. Furthermore, the average lifetime of the TGA-capped QDs increased with the increase of the QDs size, while a decreased lifetime for the MPA-capped QDs was obtained. This means that the PL lifetime depended strongly on the surface state of the CdTe QDs. These results should be utilized for the preparation and applications of QDs. [ABSTRACT FROM AUTHOR]