Fabrication of Long-Range Ordered Nanocrystal Assembly and Supercrystals on Substrates Using Gold Nanocubes, Octahedra and Rhombic Dodecahedra as Building Blocks

用奈米金立方體、八面體及菱形十二面體在基板上製備大範圍且有序的奈米晶體排列和超級晶體

林曄生(Yeh-Sheng Lin)

指導教授 ： 黃暄益

國立清華大學/理學院/化學系/碩士(2010年)

摘要

We have successfully fabricated long-range (~2.5 mm) ordered gold nanocube (~40 nm) and octahedra (~40 nm) assembled structures on the substrates at room temperature in moist condition. Gold nanocube (~40 nm) and rhombic dodecahedral nanocrystals (~40 nm) at high CTAC and particle concentrations can form respectively cubic or octahedral supercrystals on a wafer at 90 ºC in an environment with high humdity. Rhombic dodecahedral (~40 nm) and octahedral (~40 nm) nanocrystals at high CTAC and particle concentrations can assemble into platelike and rhombic dodecahedral supercrystal at room temperature under this humid condition. It may not form supercrystals using larger nanocubes (~75 nm), octahedral (~65 nm) and rhombic dodecahedral (~55 nm) nanocrystals. The key conditions for fabricating supercrystals are size–dependent, high surfactant and particle concentrations, and a sufficient long time for nanocrystal assembly.
We have found two types of gold nanocube assembly. At room temperature, each cube in the second layer sits right in the center of four cubes underneath, while nanocubes contact each other by face-to-face fashion at high temperature. There are three types of octahedral gold nanocrystal assembled structures. One packing structure is through faces contacting the substrate. Another assembled structure is with their edges contacting the underlying substrate. The third assembled structure is unstable in which the octahedra contact each other exactly face to face and five octahedra organize into a unit. No strong force exists between layer 1 and layer 2.
Rhombic dodecahedra (~40 nm) and ordered nanocube (~40 nm) assembly may form “hot spots” and have been shown to exhibit good SERS enhancement, while disordered nanocube and fused octahedral (~40 nm) structures do not. UV－vis spectra of gold nanocube assembly show absorption bands in the near-infrared region .

關鍵字

排列 ； 奈米 ； 超級晶體

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