對於M-Fe-O(M= Mn和Co)奈米粒子的合成，如何調控M-Fe-O奈米粒子形狀和結構(結晶相)的合成策略是相當具有挑戰性。在本篇研究中，我們發展出一種新的合成方法，利用二步驟升溫或三步驟升溫的方式去調控M-Fe-O奈米粒子的形狀和結構，可以選擇性的得到氯化鈉形態(還原形態)或尖晶石形態(氧化形態)的結構，M-Fe-O奈米產物也有很高的再現性。利用二步驟升溫過程能夠控制兩種結晶相的形成，經由空氣環境下反應過程，可形成熱力學穩定的尖晶石型態奈米方塊，或是經由氮氣環境下反應過程，可形成動力學控制的氯化鈉型態奈米方塊；另一方面，利用三步驟升溫的方式，反應於空氣環境下進行，可以得到熱力學穩定的尖晶石型M-Fe-O奈米粒子，形狀為截面八面體。
本研究發展一種簡單且有效率的磁性奈米材料合成策略，反應物固定使用Fe(acac)3做為M-Fe-O奈米粒子的鐵源，搭配外來金屬M (M=Mn (Mn(ac)2和Mn(acac)2)和Co (Co(ac)2和Co (Co(acac)2))與Fe(acac)3反應，將兩種金屬前驅物分別加入到油酸(oleic acid)和三辛胺(trioctylamine)的混合溶液中進行高溫裂解反應，製備出Mn-Fe-O和Co-Fe-O三元性鐵系氧化物磁性奈米粒子。製作三元性鐵系氧化物系列的反應系統中，反應過程將決定形成產物的結構和形狀，例如溶劑、保護劑(比如是油酸、油胺等等)、金屬的來源、升溫速率和反應溫度等條件，每一項參數皆扮演了一定的角色。研究結果指出：低溫的條件下，反應產物由尖晶石結構組成(熱力學穩定的產物)，磁性奈米顆粒的形狀為截面八面體。過去研究指出，油酸分子常作為控制形狀或當作穩定劑的角色，但我們研究發現油酸分子可以做為調控M-Fe-O奈米粒子結晶相的試劑，可選擇性的得到氯化鈉形態或尖晶石形態的結構，使得磁性M-Fe-O奈米粒子的磁行為可以被調控。

Significant studies have achieved beautiful control in particle size, while the shape- and phase-control synthesis of nanoparticles remains an open challenge. In this study, we have developed a generalized methodology to selectively prepare either a NaCl-type (reduced form) or spinel-type ferrite (oxidized form) M-Fe-O (M = Mn, Co) crystallites with high reproducibility. A two-step heating process was able to control formation of two types of crystal phase, either a thermodynamic spinel-type under air or a kinetic-control of NaCl-type (rock salt structure) under Ar in cubic morphology. On the other hand, the three-step heating procedure in air obtained the spinel-type with a thermodynamic equilibrium octahedral shape exclusively. Either using metal acetates (M(ac)2), or metal acetylacetonates (M(acac)2) as the starting precursors (M = Mn, Co) can be introduced to prepare NaCl-type (reduced form) or spinel-type ferrite (oxidized form) crystallites with identical experimental parameters, including precursor concentration, reaction temperature, reaction time, and heating rate. The oleic acid molecule, reaction temperature, and heating rate employed in the synthesis were carefully examined and found acting as determined roles behind the reaction processes. Apart from the previous literature reports as shape-directed and/or stabilizing agents, the oleic acid molecule played an additional phase-tuning role.

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