奈米粒子之精準形狀控制合成及其不同晶面所展現之性質

Synthesis of Nanocrystals with Precise Morphology Control and Their Facet-dependent Properties

黃暄益(Michael H. Huang)

《化學》 71卷2期 (2013/06) Pp. 103-110

https://doi.org/10.6623/chem.2013010

摘要

具一系列形貌演繹控制之奈米粒子的合成有相當的困難度，但成功製備出這些奈米粒子就可以更了解什麼因素控制他們的形狀，也能夠更精確地觀察其不同晶面所展現的物理與化學現象。本實驗室之前已成功發展出合成具一系列形貌演繹控制的金、氧化亞銅、氧化銀、硫化鉛、金與鈀的核殼結構、及金與氧化亞銅的核殼結構。從這些研究中發現經由氧化還原反應形成的奈米粒子，調整還原反應的速率並作部份金屬上的鹵素配位基之置換，可有效合成出具一系列形貌演變的奈米晶體。如奈米粒子是經由沉澱反應形成，則可藉由使用合適的起始物來降低反應的平衡常數以獲得具形貌控制的奈米粒子。實驗觀察到反應最初期形成的許多具分枝狀的結構先結合成較大且單晶的多面體雛形，再經過一段時間的表面重整才得到最後晶面平整的多面體。金正立方體、八面體、截角八面體、及菱形十二面體都可自組裝地形成大的超晶體。這些奈米粒子的各種表面晶面會表現出很不同的光催化、有機催化、電性、及分子吸附等現象。

關鍵字

奈米粒子 ； 核殼奈米結構 ； 晶面相關性質 ； 形狀控制合成 ； 成長機制 ； 超晶體

並列摘要

Growth of nanocrystals with systematic shape evolution can be quite synthetically challenging, but their preparation offers new understanding of factors controlling the particle shapes and enables more precise comparisons of their facet-dependent physical and chemical properties. We have successfully developed the syntheses of gold, Cu_2O, Ag_2O, PbS, Au−Pd, and Au−Cu_2O nanocrystals and core-shell heterostructures with systematic shape evolution. These studies showed that control of reduction rate and halide ligand replacement in redox reactions and slowing down the equilibrium constants in precipitation reactions by use of proper precursors can be quite effective. Metal nanocrystals were found to be produced from aggregation of the initially-formed dendritic structures to form larger crystalline cores. A period of surface reconstruction is required to yield the final particle morphology with sharp faces. Au nanocubes, octahedra, truncated octahedra and rhombic dodecahedra can self-assemble to form large supercrystals with polyhedral shapes. These nanocrystals have shown facet-dependent photocatalytic, organocatalytic, electrical and molecular adsorption properties.

並列關鍵字

Nanoparticles ； Core-shell heterostructures ； Facet-dependent properties ； Shapecontrolled synthesis ； Growth mechanism ； Supercrystals