合成鐵鉑-半導體(II-VI)奈米複合材料及利用陽離子交換反應形成Type-II半導體之性質鑑定

Characterization and Synthesis of FePt- semiconductor (II-VI) hybrid nanostructures and Synthesis of Type-II semiconductor by Cation Exchange Reactions

林玠嫺(chieh-hsien lin)

指導教授 ： 陳家俊

國立臺灣師範大學/理學院/化學系/碩士(2010年)

摘要

在本篇論文中我們合成CdS與CdSe奈米棍，且控制 FePt 奈米粒子選擇性的在半導體的末端生長，合成出CdS-FePt 、CdSe-FePt 半導體奈米棒末端接磁性粒子的奈米複合材料，並且具有光學和磁性性質。在光學部分我們利用光激發光螢光光譜儀（PL）可得知當CdS、CdSe接上FePt奈米粒子後，由於Schottky barrier的關係會使電子產生轉移且無法再結合，導致其放光強度降低。而在磁性部分我們利用超導量子干涉儀（SQUID）得知材料為超順磁性且其飽和磁化率有下降的趨勢。之後還可加入Au奈米粒子合成CdS-FePt-Au、CdSe-FePt-Au這種具有多成分的奈米異質結構。利用穿透式電子顯微鏡（TEM）、能量分散光譜儀（EDS）、粉末X-ray繞射儀（XRD）、紫外光可見光光譜儀（UV-Visible）鑑定其尺寸、結構、元素組成。
　　此外，我們還利用合成出的CdS-FePt奈米複合材料，在室溫下進行離子交換反應，利用hard-soft acid-base (HSAB) 原理，使其在形狀不變的情況下經由置換反應形成具有不同結構的type-II半導體奈米複合材料，而且藉由控制加入Cu+離子的濃度，使得奈米複合棍狀材料中Cd元素被置換的程度不同，之後我們再利用能量分散光譜儀（EDS）、粉末X-ray繞射儀（XRD）和紫外光可見光光譜儀（UV-Visible）去証實不同Cu/Cd比例的type-II CdS-Cu2S-FePt形成。

關鍵字

複合材料 ； 半導體

並列摘要

In this study, we successfully synthesized CdS-FePt and CdSe-FePt nanorod by the selective growth of FePt nanoparticles on the tip of semiconductor nanorod. Moreover, these hybrid nanostructures still exhibited the optical and magnetic properties. However, the quenched emission of hybrid nanostructures was observed by photoluminescence spectrometer (PL). The intensity reduction resulted from the formation of a Schottky barrier. The formation of barrier made the electron only transferred from the semiconductor nanorod to FePt particle on the tip of nanorod and then, the electron and hole did not recombination within the semiconductor nanorod. Also, the hysteresis loops showed that CdS-FePt and CdSe-FePt were superparamagnetic. Particularly, the significant drop in saturation magnetization of CdS-FePt and CdSe-FePt were due to the presence of the non-magnetic phase, such as CdS and CdSe in hybrid nanostructures. Further, CdS-FePt-Au and CdSe-FePt-Au nanorod were prepared by the reduction of Au precursor. All hybrid nanostructures were examined by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and energy dispersive spectroscopy (EDX).
According to hard-soft acid-base theory (HSAB theory), Cu+ in methanol was used to substitute for the Cd2+ in CdS-FePt nanorod. Through the cation exchange reaction (CER), the heterostructures of CdS-Cu2S-FePt and Cu2S-FePt were synthesized at room temperature. In detail, the extent of conversion during CER depended on the Cu+/Cd2+ ratio. In the other words, low amount of Cu+ produced partial conversion to CdS-Cu2S-FePt and an excess amount of Cu+ leaded to full conversion to Cu2S-FePt. Finally, The results of TEM, XRD, EDS, and Ultra-Violet and Visible Spectroscope (UV-Vis) demonstrated the formation of CdS-Cu2S-FePt and Cu2S–FePt.

參考文獻

8. Haase, M. A.; Qiu, J.; Depuydt, J. M.; Cheng, H. Applied Physics Letters 1991, 59, 1272

51. Li, X. M.; Shen, H. B.; Li, S.; Niu, J. Z.; Wang, H. Z.; Li, L. S. Journal of Materials Chemistry 2010, 20, 923-936

50. Luther, J. M.; Zheng, H. M.; Sadtler, B.; Alivisatos, A. P. Journal of the American Chemical Society 2009, 131, 16851

63. Luther, J. M.; Zheng, H. M.; Sadtler, B.; Alivisatos, A. P. Journal of the American Chemical Society 2009, 131, 16851

66. Luther, J. M.; Zheng, H. M.; Sadtler, B.; Alivisatos, A. P. Journal of the American Chemical Society 2009, 131, 16851