磁性奈米微粒與其複材之合成與特性鑑定

Abstract

摘要 本研究以奈米鈷與其合金為主題，分為三部分進行探討。第一部分利用Co2(CO)8為前驅物，在280℃熱裂解，製備粒徑約為10 nm的鈷奈米粒子，並探討不同界面活性劑對奈米粒子形成的影響。在低溫和室溫下，鈷奈米粒子分別呈現超順磁性與弱鐵磁性。 第二部分為利用鈷奈米粒子和硒化鎘量子點，合成具有核殼型鈷＠硒化鎘的磁/螢光雙功能奈米粒子，其奈米粒子平均尺寸約為12 nm (核尺寸約10 nm，殼厚約1 nm)，合成反應時間和反應溫度都會改變此核殼型奈米粒子的螢光放射波長。本論文進而探討一步合成與二步合成的製程對此雙功能性奈米粒子之影響；其中硒化鎘的螢光放射則利用螢光光譜和紫外－可見光光譜加以鑑定。 第三部分則利用有機金屬前趨物化學合成以製備釤鈷(Sm2Co17)磁性奈米粒子，所合成的釤鈷奈米粒子表面包覆油酸和油胺分子且其外徑平均約為7.35 nm。在常溫下，釤鈷奈米粒子為超順磁性；在低溫下仍呈現鐵磁性，本研究亦利用穿透式電子顯微鏡、選區電子繞射、元素分析能譜對上述奈米粒子進行粒徑和結構的解析，而超導量子干涉儀則被用以進行磁化率與磁滯曲線之量測。

Abstract This thesis mainly deals with the synthesis and characterizations of magnetic nanoparticles (NPs) and their alloys and composites. First of all, the surfactant-capped Co NPs with 10 nm in diameter was prepared by using Co2(CO)8 as a precursor, followed by thermal decomposition at 280℃. The influence of various surfactants on the formation of Co NPs has also investigated. The Co NPs were found to be superparamagnetic, but they show weak ferromagnetism at a small applied magnetic field. Secondly, we have attempted to couple CdSe quantum dots (QDs) to magnetic Co NPs to form a bifunctional magnetic/luminescence nanocomposite of Co@CdSe. The average diameter of Core-shell Co@CdSe NPs is about 12 nm ( the core diameter is about 10 nm and the shell thickness is 1nm ). The reaction time and temperature used in the preparation on were found to change the emission wavelength. We have also discussed the influence of one-pot and two-pot chemical syntheses on the formation of Co NPs. The luminescence and spectroscopy of Co@CdSe were characterized by using photoluminescence (PL) and UV-Visible spectroscopy and the major results are presented. Thirdly, we report the investigation results of an organometallic synthetic route for preparing superparamagnetic Sm2Co17 NPs. The oleic acid and oleylamine capped-Sm2Co17 NPs were found to have average size 7.35 nm. At room temperature, the Sm2Co17 NPs were observed superparamagnetic, but weak ferromagnetism at low temperature. Transmission electron microscopy (TEM), electron diffraction (ED), and energy disperse spectrometry (EDS) have been used to characterize the size distribution, identify the phases, and determine the compositions of the NPs. Temperature-and field-dependent magnetization measurements were performed by using a superconducting quantum interference device (SQUID) magnetometer to confirm the superparamagnetism and investigate magnetic hysteresis.