雷射捕陷控制溶液表面結晶化之顯微光譜分析

Microspectroscopic Analysis of Optical Trapping-Controlled Crystallization at Solution Surface

蔡佳穎(Chia-Ying Tsai)

指導教授 ： 杉山輝樹

國立交通大學/理學院/應用化學系所/碩士(2019年)

摘要

此研究論文分為三個主體。第一主題為「含有L-脯氨酸的雙成分溶液以雷射捕陷控制L-苯丙胺酸的多晶化作用」。摻釹釔鋁石榴石雷射源持續聚焦在兩種氨基酸莫爾濃度為1:1的樣品液體薄層的液氣介面。在雷射照射的20~40分鐘內獲得了L-苯丙胺酸的兩種假多形體:片狀結晶以及絲狀結晶。藉由結晶成長的同時測定實時拉曼光譜，以拉曼光譜的特徵峰值判定兩者分別為無水合及一水合結晶。單一無水合片狀結晶固定在雷射焦點生成，而無水合絲狀結晶則會大量在焦點外圍生成。在此次實驗條件下並未產出L-苯丙胺酸和L-脯氨酸的共結晶。
雷射捕陷誘發L-苯丙胺酸的多形體結晶化差異與雷射強度及偏振方向有顯著相關。在直線性光的條件之下，當雷射能量增強，產生無水片狀結晶的機率增加。此結果與L-苯丙胺酸的純溶液相反，我們認為是L-脯氨酸影響了結晶化前的結構穩定性。而在圓性光實驗結果中也有特殊的多形體結晶化現象。我們認為不同方向之圓性光會影響無水合片狀結晶的生成比率。因L-苯丙胺酸為掌性化合物，其旋光性質為逆時針旋轉L-(-)-Phe，此性質使其在不同方向的圓性光有不一樣的雷射捕捉效能。最終影響在不同方向的原性光生成無水合片狀結晶的比例。而L-脯氨酸也極有可能破壞L-苯丙胺酸的聚集體結構。
以雷射捕陷誘發雙成分水溶液結晶化相比單一溶液的過程機制複雜許多，必須考慮兩成分是否交互作用以及結構用何種鍵結方式-排列的穩定性。然而這樣的實驗讓我們拓展雷射捕陷結晶化的應用且能更精準地控制多形體的生成。我們也相信這些結果提供闡述水溶液中聚集化作用動態機制的重要見解。
第二主題為「以雷射捕陷對苯丙胺酸外消旋混合溶液的光學解析」。此主題以雷射捕陷誘導L-苯丙胺酸結晶化實驗結果作為基礎的延伸探討。根據過往的實驗結果，藉由控制雷射捕陷誘導的實驗參數可獲得無水的L-苯丙胺酸片狀結晶，且此結晶為具有特定夾角的平行四邊形，然而相同溶液中以自發結晶卻有兩種不同夾角的平行四邊形。此現象表示雷射捕陷使L-苯丙胺酸在溶液的氣體/液氣體介面因分子本身兩性性質而有特定規則的排列。在此實驗中雷射聚焦在D-和L-苯丙胺酸的外消旋混合溶液的氣體/液體介面。經過15分鐘雷射照射後生成兩種不同形狀的無水結晶，多片平行四邊形堆疊和單一不規則形狀的結晶。兩種結晶的生成機率不受雷射強度影響，在1.0到1.4瓦的範圍內皆為1:1。在圓性光且高雷射強度條件下，不規則形狀結晶之生成機率提高至百分之九十。此兩種結晶的拉曼光譜與純苯丙胺酸結晶之拉曼光譜並無差異，說明此結晶可能皆為消旋混合雙晶。
第三主題為「雷射捕陷雙氟硼阿伏苯宗錯合物結晶現象之螢光分析」。此錯合物被發現在自發蒸發時有活躍的螢光變化。此現象使我們能夠以測量螢光光譜研究雷射誘導捕陷此錯合物的動力學和作用機制。當雷射照射在未飽和溶液中我們發現螢光光譜的變化且最終生成結晶。最初溶液的螢光光譜在450 nm 有一根尖峰並在480及550 nm 有兩個寬峰。當雷射照射40秒後溶液開始慢慢蒸發且螢光光譜550 nm 波段的強度增強，我們認為此時為錯合物的不定形結晶。持續照射雷射至120秒後溶液幾乎完全蒸發並留下結晶，此結晶的螢光光譜特徵峰落在490 nm。雖然不定型結晶和結晶並非固定發生在雷射焦點處，我們仍發現自發蒸發和雷射誘導結晶有相同的螢光變化。未來我們會持續調整實驗參數進行研究。

關鍵字

雷射捕陷 ； 結晶化 ； 顯微光譜

並列摘要

There are included three topics in this thesis. The first is “Optical trapping-controlled polymorphism in two-component solution”. A Nd3+:YVO4 continuous wave laser was used as a trapping light source and was always focused at an air/solution interface of the solution thin-film with a 1:1 molar ratio of two amino acids. Optical trapping for 20-40 min produced two kinds of L-phenylalanine crystals with different morphologies; whisker and plate, which were characterized by in-situ Raman spectra to be monohydrate and anhydrous form, respectively. Each crystal was generated from a different position: The single anhydrous crystal was always generated at the laser focus, while the monohydrate crystals were precipitated at the outside of the focal point. Co-crystallization consisting of L-phenylalanine and L-proline has been never observed. Manipulating laser power and polarization controlled its polymorphism. Upon linearly-polarized laser irradiation, the formation probability of the anhydrous crystal was decreased as the laser power was increased. This was opposite to the results of optical trapping-induced crystallization of L-phenylalanine without L-proline. Unique polymorphism was also observed upon the circular-polarized laser irradiation. The formation probability of the anhydrous crystal depended on the handedness of the circularly polarized light. It is known that L-Phe crystal rotates plane-polarized light in the counterclockwise (-), and thus, this result is due to the different trapping efficiency for L-phenylalanine clusters depending on the handedness of the circularly polarized light. We also consider that the destruction of L-phenylalanine clusters by adding L-proline plays a significant role in controlling polymorphism. Thus, the dynamics and mechanism of optical trapping-induced crystallization in two-component solution is much more complicated than those in one-component solution. However, optical trapping-induced crystallization in two-component solutions enables us to extend the applicability of this method and to control polymorphism more precisely. We also believe that these findings give us a new critical insight into the elucidation of molecular aggregation dynamics and mechanism in solution.
The second topic is “Optical resolution in a racemic solution of phenylalanine by optical trapping”. This topic is considered to be based on our previous results on optical trapping-induced crystallization of L-Phenylalanine. Upon optical trapping-induced crystallization of L-phenylalanine, the single anhydrous plate-like crystal can be obtained by optimizing experimental conditions. The crystal was a parallelogram, and interestingly, the tilt direction of the parallelogram was always fixed, in spite that the crystals with two kinds of tilt directions were precipitated by spontaneous nucleation. These results indicate a specific molecular ordering of L-phenylalanine fixed at the air/solution interface due to the amphiphilicity of the molecules. In this topic, the trapping laser was focused at the air/solution interface of the racemic solution of D- and L-phenylalanine. 15 min-laser irradiation produced the anhydrous crystals with two different morphologies; multiple parallelogram crystals stacking together and a single crystal with disordered shape, not a parallelogram. The formation probability of each crystal were 1:1, independent of laser powers ranging from 1.0 to 1.4 W. While, upon circular polarized laser irradiation, the formation probability of disordered shape crystal was increased up to 90 percent at higher laser power. Raman measurement of these crystals showed the same spectra as that of a pure phenylalanine crystal, possibly meaning that the generated crystal was its racemic mixture.
The third topic is “Fluorescence analysis on the crystallization behavior of difluoroboron avobenzone complex by optical trapping”. Difluoroboron avobenzone complexes were reported to show the dynamic change in fluorescence during spontaneous evaporation. This result enables us to investigate the dynamics and mechanism of optical trapping-induced crystallization by fluorescence measurement. When the trapping laser was introduced into the unsaturated solution, we observed the dynamic change in the fluorescence and crystallization eventually. The fluorescence emission for the initial solution showed one sharp peak at 450 nm with shoulders at 480 and 550 nm. During 40-sec laser irradiation, the solvent was continuously evaporated, when the fluorescence intensity at 550 nm, which was ascribed to be its amorphous state, was increased. Further laser irradiation for 80 seconds, the solution droplet was almost dried up, and the crystal with a fluorescence emission wavelength of around 490 nm was formed. However, these amorphous aggregates and crystals were not always generated from the laser focus. Also, we always observed the same fluorescence behavior in spontaneous evaporation and laser induced crystallization, so that we will optimize experimental conditions in near future.

並列關鍵字

optical trapping ； crystallization ； microspectrospcopy

參考文獻

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