Infrared Emitting and Photoconducting Colloidal Silver Chalcogenide Nanocrystal Quantum Dots from a Silylamide-Promoted Synthesis

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• 作者：Maksym Yarema ; Stefan Pichler ; Mykhailo Sytnyk ; Robert Seyrkammer ; Rainer T. Lechner ; Gerhard Fritz-Popovski ; Dorota Jarzab ; Krisztina Szendrei ; Roland Resel ; Oleksandra Korovyanko ; Maria Antonietta Loi ; Oskar Paris ; Günter Hesser ; Wolfgang Heiss
• 刊名：ACS Nano
• 出版年：2011
• 出版时间：May 24, 2011
• 年：2011
• 卷：5
• 期：5
• 页码：3758-3765
• 全文大小：953K
• 年卷期：0
• ISSN：1936-086X

文摘

Here, we present a hot injection synthesis of colloidal Ag chalcogenide nanocrystals (Ag₂Se, Ag₂Te, and Ag₂S) that resulted in exceptionally small nanocrystal sizes in the range between 2 and 4 nm. Ag chalcogenide nanocrystals exhibit band gap energies within the near-infrared spectral region, making these materials promising as environmentally benign alternatives to established infrared active nanocrystals containing toxic metals such as Hg, Cd, and Pb. We present Ag₂Se nanocrystals in detail, giving size-tunable luminescence with quantum yields above 1.7%. The luminescence, with a decay time on the order of 130 ns, was shown to improve due to the growth of a monolayer thick ZnSe shell. Photoconductivity with a quantum efficiency of 27% was achieved by blending the Ag₂Se nanocrystals with a soluble fullerene derivative. The co-injection of lithium silylamide was found to be crucial to the synthesis of Ag chalcogenide nanocrystals, which drastically increased their nucleation rate even at relatively low growth temperatures. Because the same observation was made for the nucleation of Cd chalcogenide nanocrystals, we conclude that the addition of lithium silylamide might generally promote wet-chemical synthesis of metal chalcogenide nanocrystals, including in as-yet unexplored materials.