雷射誘發水及四氫呋喃混合溶液中有機螢光分子結晶化

Abstract

以四烷基矽乙炔基當作取代基的芘衍生物(TXPys)像是TMPy, TEPy, 以及TIPy 各自擁有特殊的末端烷基。當它們的單體(monomer)聚集形成聚集體(aggregated structure)時，會造成不同的光譜結果像是吸收以及螢光的不同。當這些芘衍生物(TXPys)以單體存在時，展現了幾乎一樣的光物理性質，像是吸收、螢光等等，但當這些芘衍生物產生聚集之後，明顯地不同聚集螢光效應(aggregation induced emission, AIE)產生。 在這份研究當中，我們檢驗了單體(monomer)以及聚集體(aggregated structure)的吸收、螢光光譜，以及利用螢光時間解析測量單體及聚集體的螢光生命週期。此外，我們明顯地觀察到芘衍生物在水及四氫呋喃的混合溶液中聚集的情形，並將在混合溶液得到的光學性質與在單純THF溶液當中進行比較。 除了基本的光物理性質探討之外，我們利用雷射捕捉技術在四氫呋喃(THF)以及水混合四氫呋喃溶液(water/THF)中發現，在只有四氫呋喃(THF)溶液中，沒有任何現象產生，但是再水混合四氫呋喃溶液(water/THF)中，不管是TMPy,TEPy,還是TIPy皆有高濃度液滴的產生。所有的芘衍生物(TXPys) 都會藉由雷射捕捉產生高濃度的液滴，但只有在TMPy 當中有產生結晶化的情形發生，此現象可能是因為末端烷基的立體障礙性所影響。藉由共軛焦螢光顯微鏡系統量測結果發現，這些芘衍生物的液滴是介於結晶以及單體之間的螢光放光波長。利用雷射捕捉技術在兩相系統中產生有機染料分子之結晶化是一項相當新穎的嘗試，不只這三個芘衍生物(TXPys)，其他有機分子也有可能藉由這兩相系統產生結晶化，這項發現可以促進雷射捕捉在有機分子結晶化的應用。

Tetraalkylsilyethynilene substituted pyrene derivatives (TXPys), TMPy, TEPy, and TIPy, which possess different terminal alkyl groups show interesting spectroscopic behavior upon aggregation. TXPys show almost identical absorption and emission spectra irrespective to their structural difference when these compounds exist as monomer, meanwhile aggregates of these compounds show clear difference in emission characteristics. We have studied spectroscopic characteristics of TXPy monomers and aggregates by using absorption, fluorescence and time-resolved fluorescence spectroscopies. We observed and clarified aggregation behavior of TXPys in water/THF mixture binary solution at different water fraction in addition to monomer spectroscopic characteristics in neat THF solution. In the laser trapping of TXPys, neat THF and water/THF binary solution were applied. In water/THF binary solution of TMPys at low water fraction (fw), we could induce liquid droplet formation by liquid-liquid phase separation for all TXPys. Crystallization was successfully induced only for TMPy from the formed liquid droplet. Meanwhile, we could not induce crystallization and liquid droplet formation in neat THF solution of TXPys irrespective to the molecule, the concentration, and the laser power. Fluorescence microspectroscopy of the generated liquid droplet indicates that the concentration of TXPys in the liquid droplet is elevated by laser trapping-induced droplet formation. In the water/THF binary solution without TXPys, Raman microspctroscopy of generated liquid droplet suggests that fw of the droplet is highly elevated (~90 %). We have demonstrated the laser trapping-induced crystallization of dye molecule in binary solution system which shows laser-induced liquid-liquid phase separation. We consider observed water-rich droplet formation is specific laser-induced local and temporal phase separation phenomenon only can be realized by laser trapping.