Xing Xiaowei,Wang Dongming,Chen Zhi,Zheng Bodan,Li Baohong,Wu Dudu
Colloidal mercaptoacetic acid capped ZnTe quantum dots (QDs) are prepared to target iron ions as a fluorescence sensor. The results show that the obtained QDs present excellent selectivity for the detection of Fe 3+ and display a good linearity from 2.0 × 10 − 6 to 1.0 × 10 − 4 mol L − 1 . The optimum fluorescence intensity for detecting Fe 3+ is found in a buffer (pH 7.0) at 25 °C. The detection limitation of Fe 3+ ions is 4.89 × 10 − 6 mol L − 1 under optimized conditions. The quenching rate constant K q (1.24 × 10 13 L mol − 1 s − 1 ) is calculated and confirmed to describe a static quenching procedure. Moreover, the obtained probes are used to detect Fe 3+ ions in lake water samples, showing perspectives of environmental determination for future research.
Colloidal semiconductor magic-size clusters (MSCs) remain poorly understood with regard to their formation and transformation. We show that ZnTe MSC-324 (with an optical absorption peak at 324 nm) and MSC-398 evolve in reactions of Zn and Te precursors, while CdTe MSC-371 and MSC-481 develop in reactions of Cd and Te precursors. We propose that MSCs evolve from their precursor compounds (PCs). Chemical self-assembly results in the formation of ZnTe PC-324 and CdTe PC-371, which, respectively, transform to ZnTe PC-398 and CdTe PC-481 via monomer addition. When the ZnTe MSCs are mixed with Cd(OAc)2/OLA (cadmium acetate in oleylamine), the CdTe MSCs also evolve. We further hypothesize that cation exchange occurs on the ZnTe PCs, resulting in CdTe PCs that transform to their counterpart CdTe MSCs. Moreover, ZnTe PC/MSC-324 and CdTe PC/MSC-371 have similar Zn/Cd-to-Te stoichiometries, as do ZnTe PC/MSC-398 and CdTe PC/MSC-481. Accordingly, the Te precursor quantitatively dictates the coassembly of Zn or Cd and Te precursors as well as the monomer addition. The present findings advance the understanding of the initial PC formation, PC-to-PC transformation, PC-to-MSC isomerization, and PC-to-monomer fragmentation.
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.
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