Department of Chemical and Biomolecular Engineering, Specialized Graduate School of Hydrogen and Fuel Cell, Yonsei University, Seoul 120-749, Republic of Korea.
Phys Chem Chem Phys. 2009 Nov 14;11(42):9759-65. doi: 10.1039/b912962f. Epub 2009 Aug 24.
Controlling the shape and composition of metal nanocrystals can be beneficial for tuning the optical or catalytic properties in a variety of applications. In this study, surface-specific overgrowth of platinum was found on shaped gold nanocrystals of cubes, octahedra and spheres. Platinum overgrowth was observed on the planar faces of gold cubes, while the overgrowth occurred at the vertices of gold octahedra, indicating that platinum was selectively reduced on the Au (100) surface for each gold nanocrystal shape. The platinum nuclei covered the entire surface for gold spheres, which don't have well-defined surfaces. As the Pt/Au ratio increased, a full platinum shell was formed. Solution-based UV-Vis absorption spectra of the composite nanocrystals showed that the absorption peak was red-shifted with increasing platinum coverage. The optical response of a single composite nanocrystal was measured by dark field microscope, which also demonstrated a red shift in the scattering spectrum with increasing platinum coverage. The extent of a red shift depended on the shape and composition of the composite nanocrystals.
控制金属纳米晶体的形状和组成可以有益于调整各种应用中的光学或催化性能。在这项研究中，我们发现了形状为立方体、八面体和球体的金纳米晶体表面上的铂的特定的外延生长。铂的外延生长出现在金立方体的平面上，而外延生长发生在金八面体的顶点上，这表明铂在每个金纳米晶体形状的 Au(100)表面上被选择性地还原。对于没有明确表面的金球体，铂核覆盖了整个表面。随着 Pt/Au 比值的增加，形成了完整的铂壳。复合纳米晶体的基于溶液的紫外可见吸收光谱显示，随着铂覆盖率的增加，吸收峰发生红移。通过暗场显微镜测量了单个复合纳米晶体的光学响应，也证明了随着铂覆盖率的增加，散射光谱发生红移。红移的程度取决于复合纳米晶体的形状和组成。
