Gradiently Alloyed ZnxCd1-xS Colloidal Photoluminescent Quantum Dots Synthesized via a Noninjection One-Pot Approach
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- 作者：Jianying Ouyang ; Christopher I. Ratcliffe ; David Kingston ; Baptiste Wilkinson ; Jasmijn Kuijper ; Xiaohua Wu ; John A. Ripmeester ; Kui Yu
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：April 3, 2008
- 年：2008
- 卷：112
- 期：13
- 页码：4908 - 4919
- 全文大小：1043K
- 年卷期：v.112,no.13(April 3, 2008)
- ISSN：1932-7455
文摘
High-quality colloidal photoluminescent (PL) ZnCdS quantum dots (QDs) with gradient distribution ofcomponents, consisting of Cd-rich inner cores and Zn-rich outer shells, were synthesized via a noninjectionone-pot approach. This newly developed synthetic approach uses zinc stearate (Zn(St)2), cadmium acetatedihydrate (Cd(OAc)2·2H2O), and elemental sulfur as Zn, Cd, and S source compounds, respectively. Thegrowth of the cubic-structured QDs was carried out at 240 
C in a reaction flask consisting of the sourcecompounds, together with stearic acid (SA), 2,2'-dithiobisbenzothiazole (MBTS), and 1-octadecene (ODE);all of these chemicals were loaded at room temperature. The temporal evolution of the optical properties ofthe growing QDs, including absorption and photoemission, was monitored in detail; the evolution monitoredindicates that the growth kinetics, the composition, and the distribution of the Zn and Cd in the resultingternary ZnxCd1-xS QDs are sensitive to feed Zn-Cd-S molar ratios. Detailed investigation on the feed Zn-Cd-S molar ratio affecting the QD growth and optical property was performed, together with detailed structuralcharacterization by solid-state NMR including cross polarization (CP) and dipolar dephased cross polarization(DDCP); also, the resulting QDs were characterized by XPS, TEM, and XRD. Accordingly, the synthesis-structure-property relationship was explored systematically. Tuning the feed Zn-Cd-S stoichiometry, high-quality ZnxCd1-xS QDs exhibiting sharp excitonic absorptions, narrow PL emissions with full width at half-maximum (fwhm) on the order of 19-21 nm, and high PL quantum yield (QY, up to 23%), could be fabricatedwith relatively low Zn and S feed amount, such as 1Zn-1Cd-1S feed molar ratio. In general, our noninjectionapproach features great synthetic reproducibility and is easy to scale up, with a plausible alloying mechanismof the formation of a Cd-rich core in the early growth stage, followed by a gradual formation of Zn-rich outerlayers with increasing zinc content toward the surface.
C in a reaction flask consisting of the sourcecompounds, together with stearic acid (SA), 2,2'-dithiobisbenzothiazole (MBTS), and 1-octadecene (ODE);all of these chemicals were loaded at room temperature. The temporal evolution of the optical properties ofthe growing QDs, including absorption and photoemission, was monitored in detail; the evolution monitoredindicates that the growth kinetics, the composition, and the distribution of the Zn and Cd in the resultingternary ZnxCd1-xS QDs are sensitive to feed Zn-Cd-S molar ratios. Detailed investigation on the feed Zn-Cd-S molar ratio affecting the QD growth and optical property was performed, together with detailed structuralcharacterization by solid-state NMR including cross polarization (CP) and dipolar dephased cross polarization(DDCP); also, the resulting QDs were characterized by XPS, TEM, and XRD. Accordingly, the synthesis-structure-property relationship was explored systematically. Tuning the feed Zn-Cd-S stoichiometry, high-quality ZnxCd1-xS QDs exhibiting sharp excitonic absorptions, narrow PL emissions with full width at half-maximum (fwhm) on the order of 19-21 nm, and high PL quantum yield (QY, up to 23%), could be fabricatedwith relatively low Zn and S feed amount, such as 1Zn-1Cd-1S feed molar ratio. In general, our noninjectionapproach features great synthetic reproducibility and is easy to scale up, with a plausible alloying mechanismof the formation of a Cd-rich core in the early growth stage, followed by a gradual formation of Zn-rich outerlayers with increasing zinc content toward the surface.