利用雙物鏡顯微系統三維分析雷射捕陷誘導之 聚苯乙烯奈米粒子聚集體

Three-dimensional analysis of laser trapping-induced assembly of polystyrene nanoparticles studied by dual objective lens microscope

卡密濤(Abdullah Kamit)

指導教授 ： 增原宏

國立交通大學/理學院/應用化學系所/碩士(2020年)

摘要

我們利用高度聚焦的連續波雷射於溶液/玻璃介面展示了聚苯乙烯奈米粒子的雷射補陷，並藉由雙物鏡顯微系統直接證實了該粒子聚集體的三維結構。首先，我們透過二維影像來解析500奈米聚苯乙烯粒子的中央堆疊結構並彙整其補陷與聚集行為，我們發現使用線性偏振的雷射時，四方系的堆疊結構會產生四條從聚集體擴展，但並非從源自於正中央的線狀排列粒子，稱之為”角”，而使用圓性偏振雷射時，六方系的堆疊結構便產生六個角。接著，在捕捉750奈米與1000奈米的粒子時，此情況下的堆疊結構並未展現對雷射偏振的依存性，有趣的是，我們觀察到三個角從750奈米的粒子之聚集體中形成。透過對聚苯乙烯粒子聚集體各別的三維影像解析，我們得出體心立方、六方堆積與面心立方的結構分別會造成四角、六角與三角的聚集體。我們將聚集體有三維規則排列的事實納入理論計算的時域有限差分模擬，其結果也指出補陷雷射光會隨著三維結構向外傳遞，相當吻合我們假設的機制。若考量到光是如何在雷射補陷誘導之膠體粒子聚集體中傳遞，我們將能夠透過調整一些光學上的條件如雷射光束大小、偏振、波長以及粒子大小，來製造許多種類的光學晶體。

關鍵字

雷射捕陷 ； 膠體 ； 光傳播 ； 雙物鏡顯微 ； 聚苯乙烯奈米粒子

並列摘要

We demonstrate the laser trapping of polystyrene nanoparticles with a tightly focused continuous-wave (CW) laser beam at the solution/glass interface. By utilizing a dual objective lens microscope, we directly clarify the three-dimensional structure of the prepared particle assembly. We firstly summarize the trapping and assembly behavior of polystyrene 500 nm particles where the central packing structure of the first layer was revealed by two dimensional imaging. Tetragonal structures were observed, producing four linearly aligned particles extending from the assembly, which we term as as “horns”, when a linearly polarized laser is used. Additionally, the alignment of the horns does not originate from the central particle. When a circularly polarized light is irradiated, hexagonal structures showing six horns were observed. Secondly, we trap 750 nm and 1000 nm particles where the packing structure show no polarization dependence. Interestingly, we observed three horns forming from an assembly of polystyrene 750 nm particles. Through the three-dimenionsal imaging of the respective polystyrene assemblies, we conclude that body-centered cubic (BCC)-like, hexagonal close-packed (HCP) and face-centered cubic (FCC) structures are responsible for the four, six and three-horn assemblies, respectively. Taking the three-dimensional structures into account, we performed Finite-Difference Time-Domain (FDTD) simulations, which strongly supported our mechanism of light propagation through the respective three-dimensional structures. Considering how the light propagates in a laser trapping-induced colloidal assembly, various photonic crystals can be fabricated by tuning parameters such as the laser beam size, polarization, wavelength and the particle size.

並列關鍵字

laser trapping ； colloid ； light propagation ； dual objective microscope ； polystyrene nanoparticle

參考文獻

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