電子束金奈米粒子操縱術及利用穿透式電子顯微鏡臨場觀測化學反應

Electron Beam Manipulation of Gold Nanoparticles and In-situ Observation of Chemical Reaction with TEM

陳郁婷(Yu-Ting Chen)

指導教授 ： 游萃蓉

國立清華大學/工學院/材料科學工程學系/碩士(2014年)

摘要

本論文主要分為兩個部分。
第一部分是研究利用穿透式電子顯微鏡 (Transmission Electron Microscopy, TEM) 的電子束在四氯金酸 (HAuCl4) 水溶液中合成各種不同大小的金奈米粒子並操控之，以了解電子束操控金奈米粒子的作用原理。實驗結果顯示，電子束操控金奈米粒子的作用力是一個電子束對金奈米粒子距離的函數，且最主要的驅動力是Dielectrophoresis所造成的作用力。電子束吸引金奈米粒子的現象是由於觀測窗口 (observation window，為兩厚度約130 nm的平行氮化矽薄膜且相距5 μm (gap) ) 上的電荷累積，而在金奈米粒子中引發一電偶極。此電偶極感受到觀測窗口內的正電場，並向電場較強的電子束照射位置移動，因此可觀察到電子束吸引金粒子的現象。另一方面，金粒子受到電子束排斥的現象，在某些試片中亦被觀察到。推論這可能是由於電子束照射時讓某些金粒子帶正電，因此在觀測窗口內正電場的影響下向遠離電子束的方向移動。
本研究嘗試去了解利用電子束操縱粒子這個新興奈米科技的原理，期望未來藉由了解此技術的機制，加上電子束的高解析、易操控、臨場或即時觀測的能力，可將其應用到各個不同的奈米粒子操縱技術領域。
本論文第二部分，是研究並嘗試證實利用K-kit來觀測液態與固態間奈米級化學反應的可行性，而選擇銀粒子與四氯金酸水溶液間的置換反應作為目標觀察反應。實驗結果觀察到類似文獻上所提及的金銀置換反應所產生的粒子形貌變化。
除了粒子形貌變化的臨場觀測，本研究也成功地利用X光能量散佈分析儀，對K-kit這種特殊試片載體內的液態試片進行成分分析。實驗結果指出，若將單邊K-kit磨薄到100 μm以下，則可用來偵測激發X光的訊號。因此若可以配合反應時的粒子形貌改變，則反應時不同粒子形貌的成分分佈也可以被記錄。

關鍵字

電子束粒子操縱術 ； 穿透式電子顯微鏡

並列摘要

There are two parts in this thesis.
For the first part, the electron beam (E-beam) of a transmission electron microscopy (TEM) was utilized for in-situ synthesizing and manipulating Au nanoparticles with various sizes in HAuCl4 aqueous solution. From experimental observations, the driving force for E-beam manipulation was found to be a function of particle-to-beam distance, mostly contributed by the force of dielectrophoresis. It was observed that the E-beam can attract the Au nanoparticles in the HAuCl4 solution. This contributes to the dipole generated in the Au nanoparticle, induced by the non-uniform positive potential built inside the observation window. On the other hand, this positive potential would induce the repulsion force between the positively charged observation window and the positively charged Au nanoparticles. Therefore, a repulsion behaviour of the Au particle and E-beam was also observed.
In this study, the mechanism of the manipulation of particles by electron beam was investigated. By understanding the working mechanism, it is expected this emerging nanotechnology could be applied to the applications of particle manipulation with high spatial accuracy and its in-situ real-time observation.
For the second part of this thesis is to demonstrate the feasibility of observing the chemical reaction between solid and liquid at the nanometer scale by utilizing the K-kit. The galvanic replacement reaction between Ag nanoparticles and HAuCl4 aqueous solution was selected as the target reaction for observation. A morphology change of nanoparticles similar to previous reports was observed.
In addition to in-situ monitoring the morphology changes of particles, it is demonstrated that energy-dispersive X-ray spectroscopy (EDX) could be used to analyze the liquid sample in K-kit. From the experimental results, if the film-supporting structure (Si) thickness of one side of K-kit was reduced to 100 μm, then the characteristic X-ray of the liquid sample sealed in K-kit could be detected. Therefore, if the EDX results could be compared with the in-situ observation of morphology change of nanoparticle, then the component distribution of different reaction states could be acquired.

並列關鍵字

electron beam manipulation ； transmission electron microscopy

參考文獻

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