Nano Archive

Gradiently alloyed ZnxCd1-xS colloidal photoluminescent quantum dots synthesized via a noninjection one-pot approach

Ouyang, Jianying and Ratcliffe, Christopher I. and Kingston, David and Wilkinson, Baptiste and Kuijper, Jasmijn and Wu, Xiaohua and Ripmeester, John A. and Yu, Kui (2008) Gradiently alloyed ZnxCd1-xS colloidal photoluminescent quantum dots synthesized via a noninjection one-pot approach. JOURNAL OF PHYSICAL CHEMISTRY C, 112 (13). pp. 4908-4919.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp710852q

Abstract

High-quality colloidal photoluminescent (PL) ZnCdS quantum dots (QDs) with gradient distribution of components, consisting of Cd-rich inner cores and Zn-rich outer shells, were synthesized via a noninjection one-pot approach. This newly developed synthetic approach uses zinc stearate (Zn(St)2), cadmium acetate dihydrate (Cd(OAc)2·2H2O), and elemental sulfur as Zn, Cd, and S source compounds, respectively. The growth of the cubic-structured QDs was carried out at 240 °C in a reaction flask consisting of the source compounds, 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 of the growing QDs, including absorption and photoemission, was monitored in detail; the evolution monitored indicates that the growth kinetics, the composition, and the distribution of the Zn and Cd in the resulting ternary 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 structural characterization 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 fabricated with relatively low Zn and S feed amount, such as 1Zn−1Cd−1S feed molar ratio. In general, our noninjection approach features great synthetic reproducibility and is easy to scale up, with a plausible alloying mechanism of the formation of a Cd-rich core in the early growth stage, followed by a gradual formation of Zn-rich outer layers with increasing zinc content toward the surface.

Item Type:Article
Subjects:Physical Science > Nano objects
Physical Science > Quantum phenomena
Material Science > Nanochemistry
ID Code:5955
Deposited By:IoN
Deposited On:06 Aug 2009 10:24
Last Modified:06 Aug 2009 10:24

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