Self-Assembled Simple Hexagonal AB2 Binary Nanocrystal Superlattices: SEM, GISAXS, and Defects

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• 作者：Danielle K. Smith^† ; ; Brian Goodfellow^† ; ; Detlef-M. Smilgies^‡ ; ; Brian A. Korgel^† ;
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：March 11, 2009
• 年：2009
• 卷：131
• 期：9
• 页码：3281-3290
• 全文大小：747K
• 年卷期：v.131,no.9(March 11, 2009)
• ISSN：1520-5126

文摘

Binary superlattices (BSLs) of sterically stabilized, hydrophobic, large (A; 11.5 nm diameter) Fe₂O₃ and small (B; 6.1 nm diameter) Au nanocrystals were assembled by slow evaporation of colloidal dispersions on tilted substrates. A detailed analysis of the BSL structure was carried out using transmission and scanning electron microscopy (TEM and SEM) and grazing incidence small-angle X-ray scattering (GISAXS). The BSLs were simple hexagonal (sh) AB₂ superlattices (isostructural with the compound AlB₂; space group 191, P6/mmm) of large nanocrystals occupying a simple hexagonal lattice with small nanocrystals in the interstitial spaces. SEM and GISAXS confirmed long-range order of the BSLs and GISAXS revealed that the superlattice is slightly contracted (8−12%) perpendicular to the substrate as a result of solvent drying in the deposition process. When the sh-AB₂ superlattice deposits on a (100) plane, this shrinkage occurs in the [210] direction and changes the lattice symmetry to centered orthorhombic. Additionally, nearly periodic superlattice dislocations consisting of inserted half-planes of gold nanocrystals were observed by SEM in some BSLs.