Aqueous synthesis of high-fluorescence ZnTe quantum dots

High fluorescence ZnTe quantum dots (QDs) were prepared by one-step aqueous method in faintly acid solution. The detailed microstructure and morphology of the prepared ZnTe QDs has been characterized by X-ray powder diffraction and high resolution transmission electron microscopy, respectively. The average size of as-prepared ZnTe QDs is about 5 nm, which is hexagonal wurtzite structure. The PL spectra consists of a strong peak around 550 nm originating from surface state emission and a weak peak around 470 nm via band edge emission. Meanwhile, ZnTe/ZnSe QDs were prepared by passivating ZnSe shell on surface of ZnTe core, which effectively prevent the Tellurium ion oxidation to reduce the zinc carrier trap and the emission peak at about 470 nm has been strengthened. ZnTe/ZnSe QDs show a higher quantum yield (21.90 %) than ZnTe QDs (10.19 %). Moreover, ZnTe/ZnSe QDs exhibit excellent stability against time.