Synthesis and Growth Mechanism of Lead Sulfide Quantum Platelets in Lamellar Mesophase Templates

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• 作者：Paul J. Morrison ; Richard A. Loomis ; William E. Buhro
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：September 9, 2014
• 年：2014
• 卷：26
• 期：17
• 页码：5012-5019
• 全文大小：529K
• ISSN：1520-5002

文摘

Thin (1 nm) PbS quantum platelets are prepared from lead acetate and thiourea in n-octylamine solvent at and near room temperature. Mechanistic studies establish that the quantum platelets are formed within lamellar amine-bilayer mesophase templates. UV鈥搗isible extinction spectra contain discrete features assigned to the n = 1 and n = 2 quantum-well transitions in the quantum platelets. The observed shifting of the spectral features to lower energies during growth of the quantum platelets is ascribed to increasing multi-quantum-well coupling between adjacent quantum platelets in the template stacks. Re-examination of a previously published higher-temperature synthesis of PbS nanosheets provides strong evidence for an analogous oleate-bilayer templated pathway. The lamellar mesophases investigated here undergo elastic expansion in the high-vacuum environment of the TEM, which appears to be a general phenomenon. Thus, lamellar spacings measured by TEM are larger than the actual spacings at ambient pressure.