By a News Reporter-Staff News Editor at Physics Week -- New research on Nanocrystals is the subject of a report. According to news reporting out of Antwerp, Belgium, by VerticalNews editors, research stated, "We report a study of Zn2+ by Cd2+ cation exchange (CE) in colloidal ZnSe nanocrystals (NCs). Our results reveal that CE in ZnSe NCs is a thermally activated isotropic process."
Our news journalists obtained a quote from the research from the University of Antwerp, "The CE efficiency (i.e., fraction of Cd2+ ions originally in solution, Cd-sol, that is incorporated in the ZnSe NC) increases with temperature and depends also on the Cd-sol/ZnSe ratio. Interestingly, the reaction temperature can be used as a sensitive parameter to tailor both the composition and the elemental distribution profile of the product (Zn,Cd)Se NCs. At 150 degrees C ZnSe/CdSe core/shell hetero-NCs (HNCs) are obtained, while higher temperatures (200 and 220 degrees C) produce (Zn1-xCdx)Se gradient alloy NCs, with increasingly smoother gradients as the temperature increases, until homogeneous alloy NCs are obtained at T>= 240 degrees C. Remarkably, sequential heating (150 degrees C followed by 220 degrees C) leads to ZnSe/CdSe core/shell HNCs with thicker shells, rather than (Zn1-xCdx)Se gradient alloy NCs. Thermal treatment at 250 degrees C converts the ZnSe/CdSe core/shell HNCs Into (Zn1-xCdx)Se homogeneous alloy NCs, while preserving the NC shape. A mechanism for the cation exchange in ZnSe NCs is proposed, in which fast CE takes place at the NC surface, and is followed by relatively slower thermally activated solid-state cation diffusion, which is mediated by Frenkel defects."
According to the news editors, the research concluded: "The findings presented here demonstrate that cation exchange in colloidal ZnSe NCs provides a very sensitive tool to tailor the nature and localization regime of the electron and hole wave functions and the optoelectronic properties of colloidal ZnSe-CdSe NCs."
For more information on this research see: Tailoring ZnSe-CdSe Colloidal Quantum Dots via Cation Exchange: From Core/Shell to Alloy Nanocrystals. ACS Nano, 2013;7(9):7913-7930. ACS Nano can be contacted at: Amer Chemical Soc, 1155 16TH St, NW, Washington, DC 20036, USA. (American Chemical Society - www.acs.org; ACS Nano - www.pubs.acs.org/journal/ancac3)
Our news journalists report that additional information may be obtained by contacting E. Groeneveld, University of Antwerp, EMAT, B-2020 Antwerp, Belgium. Additional authors for this research include L. Witteman, M. Lefferts, X.X. Ke, S. Bals, G. Van Tendeloo and C.D. Donega.
Keywords for this news article include: Europe, Antwerp, Belgium, Quantum Dots, Nanotechnology, Quantum Physics, Emerging Technologies
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