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Highly luminescent CdSe quantum dots (QDs) with narrow spectra were synthesised by the reaction of CdCl 2 •2.5H 2 O, Se and hydrazine hydrate (N 2 H 4 •H 2 O), respectively, in water and in the presence of 3-mercaptopropionic acid as the stabiliser. The effects of the experimental conditions, including the refluxing time and the selenium to cadmium molar ratio, on the luminescent properties of the obtained QDs have been investigated. Furthermore, the obtained QDs were characterised by UV-vis absorption spectra, photoluminescence (PL) spectra, X-ray powder diffraction and transmission electron microscopy, respectively. The results showed that the proposed method led to the formation of the cubic CdSe QDs with a narrow fluorescence full-width at half-maximum (47 nm) and a high PL quantum yield (up to 16%), respectively.

ABSTRACT. L-Cysteine (Cys)-capped CdTe quantum dots (QDs) were prepared when sodium tellurite worked as a tellurium source and sodium borohydride acted as a reductant. The influences of various experimental variables, including pH values, Cd/Te and Cd/Cys molar ratios, on the photoluminescence (PL) quantum yield (QY) of the obtained CdTe QDs have been systematically investigated. Experimental results indicated that green to red emitting CdTe QDs with maximum quantum yield of 19.4% can be prepared at pH 11.5 and n(Cd ):n(Cys) = 1:0.07:2.0. X-Ray powder diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the crystal structure and shape of CdTe QDs. The results showed that the prepared CdTe QDs were of cubic zinc blend crystal structure in a sphere-like shape.

A facile method for the synthesis of highly luminescent cadmium telluride (CdTe) quantum dots (QDs) in an aqueous solution is presented. Ascorbic acid and sodium tellurite were used as the reducing agent and tellurium source, respectively, to synthesise CdTe QDs under mild conditions. In this method, the preparation of the Te precursor and the growth of CdTe QDs were achieved with a one-step synthetic route. CdTe QDs with five different emission wavelengths of 506, 517, 541, 564 and 575 nm were obtained by tuning the refluxing time. The quantum yields of these QDs were 5.4, 10.9, 37.4, 53.3 and 40.1%, respectively. The X-ray powder diffraction and transmission electron microscopy characterisation indicated that the obtained QDs had a pure cubic zinc blended structure with spherical shape. The main advantage of the present method is that both the reducing agent and tellurium precursor are stable and cheap. Furthermore, no toxic gases are released in the preparation process. It is a low cost and green method suitable for large-scale synthesis.