摘要
Two dimensional(2D)nanocrystal functional superlattices with a well controlled structure are of significant importance in photonic,plasmonic and optoelectronic applications and have been well studied,but it remains challenging to understand the formation mechanism and development pathway of the superlattice.In this study,we employed in-situ liquid cell transmission electron microscopy to study the formation of 2D superlattice and its local phase transition from hexagonal-to-square nanocrystal ordering.When colloidal nanocrystals flowed in the solution,long-range ordered hexagonal superlattice could be formed either through shrinking and rearrangement of nanocrystal aggregates or via nanocrystal attachment.As the nanocrystals’shape transformed from truncated octahedral to cube,the local superlattice rearranged to square geometry.Moreover,our observations and quantitative analyses reveal that the phase transition from hexagonal to square mainly originates from the strong van der Waals interactions between the vertical(100)facets.The tracking of 2D cube superlattice formation in real-time could provide unique insights on the governing force of superlattice assembling and stabilization.
具有精确控制结构的二维(2D)纳米晶超晶格在光子、等离子体和光电子应用中具有重要意义,并已被广泛研究,但在理解超晶格的形成机理和发展途径方面仍然存在挑战.本文采用液体池透射电镜技术原位观察了铂二维超晶格的形成和六配位到四配位的局部相转化过程.胶体纳米晶在溶液中流动时,通过纳米晶的收缩和重排或者纳米晶的附着形成长程有序的六配位超晶格.当纳米晶的形貌由截角八面体转变为立方体时,六配位超晶格重新排列为四配位立方超晶格.此外,我们的观察和定量分析结果表明,从六配位到四配位的相变主要是由垂直{100}面之间的强范德华相互作用引起的.实时追踪2D立方体超晶格的形成可以为超晶格组装和稳定机制提供独特的见解.
作者
Junyu Zhang
Shi-Gang Sun
Hong-Gang Liao
张俊玉;孙世刚;廖洪钢(State Key Lab of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University)
基金
financially supported by the National Key Research and Development Program of China (2017YFA0206500)
the National Natural Science Foundation of China (21673198, 21373008 and 21621091)
