Bio-Nanotechnology Center, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyoja-dong, Nam-gu, Pohang, Kyungbuk 790-784, Korea.
J Am Chem Soc. 2012 May 9;134(18):7576-9. doi: 10.1021/ja212205q. Epub 2012 May 1.
Photochemical etching of CdSe nanoplatelets was studied to establish a relationship between the nanocrystal surface and the photochemical activity of an exciton. Nanoplatelets were synthesized in a mixture of octylamine and oleylamine for the wurtzite (W) lattice or in octadecene containing oleic acid for the zinc-blende (ZB) lattice. For photochemical etching, nanoplatelets were dispersed in chloroform containing oleylamine and tributylphosphine in the absence or presence of oleic acid and then irradiated with light at the band-edge absorption maxima. Etching phenomena were characterized using UV-vis absorption spectroscopy and transmission electron microscopy. The absorption spectra of both W and ZB CdSe nanoplatelets showed that the exciton was confined in one dimension along the thickness. However, the two nanoplatelets presented different etching kinetics and erosion patterns. The rate of etching for W CdSe nanoplatelets was much faster than that for ZB nanoplatelets. Small holes were uniformly perforated on the planar surface of W nanoplatelets, whereas the corners and edges of ZB nanoplatelets were massively eroded without a significant perforation on the planar surface. This suggests that the amine-passivated surface of trivalent cadmium atoms on CdSe nanoplatelets is photochemically active, but the carboxylate-passivated surface of divalent cadmium atoms is not. Hence, the ligand, which induces the growth of W or ZB CdSe nanoplatelets, mediates the surface-dependent photochemical etching. This result implies that an electron-hole pair can be extracted from the planar surface of amine-passivated W nanoplatelets but from the corners and edges of carboxylate-passivated ZB nanoplatelets.
CdSe 纳米片的光化学刻蚀研究旨在建立纳米晶表面与激子光化学活性之间的关系。纳米片在辛胺和油胺的混合物中合成，用于六方晶格（W）或在十八烯中含有油酸，用于闪锌矿晶格（ZB）。对于光化学刻蚀，纳米片在含有油胺和三丁基膦的氯仿中分散，在不存在或存在油酸的情况下，然后用光照射到带边吸收最大值。使用紫外可见吸收光谱和透射电子显微镜对刻蚀现象进行了表征。W 和 ZB CdSe 纳米片的吸收光谱表明激子在厚度方向上被限制在一维。然而，这两种纳米片呈现出不同的刻蚀动力学和侵蚀模式。W CdSe 纳米片的刻蚀速率比 ZB 纳米片快得多。W 纳米片的平面上均匀地穿孔，而 ZB 纳米片的角和边缘则大量侵蚀，平面上没有明显的穿孔。这表明 CdSe 纳米片上三价镉原子的胺钝化表面具有光化学活性，但二价镉原子的羧酸盐钝化表面没有。因此，诱导 W 或 ZB CdSe 纳米片生长的配体介导了表面依赖性的光化学刻蚀。这一结果表明，电子-空穴对可以从胺钝化的 W 纳米片的平面上提取，但可以从羧酸盐钝化的 ZB 纳米片的角和边缘上提取。
