含螢光基團之靜電紡絲纖維應用於金屬離子感測

Preparation of Electrospun Nanofibers for Fluorescence Sensing Studies on Detection of Metal Ions

林河杰(Ho-Chieh Lin)

指導教授 ： 陳靜誼

國立中正大學/工學院/化學工程學系/碩士(2014年)

摘要

靜電紡絲是一項近年來用來製備多功能性高分子奈米纖維的新穎技術，相較於微米等級的纖維或薄膜形態，靜電紡絲奈米纖維因大幅度的提高纖維的表面積/體積比 (surface-to-volume ratio)，更適合於感測元件應用。因此本研究之目的在於製備具螢光感測能力之高分子奈米纖維薄膜，並應用於金屬離子之感測。本實驗利用自由基聚合法 (Free radical polymerization) 合成不同比例的共聚高分子 poly(NIPAAm-co-NMA)，P1、P2及P3，其比例分別為NIPAAm:NMA= 10:0.7, 10:2.5及10:4.7，並藉由調控靜電紡絲參數製備成奈米纖維，其中NIPAAm為具備LCST的溫敏性材料，其溫敏性質所造成的收縮-澎潤效應，使高分子呈現疏水或親水狀態，進而使感測系統具備開/關特性；而NMA為化學交聯鏈段，經由熱交聯後，以P3奈米纖維在水中的形態穩定性最佳。而在感測分子方面，本實驗利用鈴木-宮浦耦合反應 (Suzuki-Miyaura coupling reaction) 首次合成出螢光感測分子Phen-F-Phen，此金屬離子感測分子於有機溶液中對於過渡金屬如 Cu2+、Fe3+、Cd2+、Zn2+、Ni2+、Hg2+等，均會有螢光強度降低或螢光波長位移的效應，其中對Cu2+有較佳的選擇性。由Job’s plot得知，感測分子與Cu2+ 形成錯合物的配位比為3 : 2。目前文獻大多探討感測分子在溶液或薄膜態感測能力，本實驗則將P3共聚高分子摻混不同比例的Phen-F-Phen後，經由調控不同的靜電紡絲參數可將此功能性高分子製備成分別含有1wt%, 3 wt%及5wt% Phen-F-Phen的P3-1、P3-3及P3-5電紡纖維，利用場效發射式掃描電子顯微鏡 (FE-SEM) 觀察纖維熱交聯前後纖維形態，找出最佳化之電紡參數，並將此纖維應用於金屬離子的感測。將感測Cu2+結果繪製成Stern-Volmer曲線，其中以P3-3纖維的焠滅常數 (Ksv) 55049 M-1最大，而和其薄膜型態相比，甚至高出一個數量級，說明此功能性高分子之靜電紡絲纖維具有較高的比表面積，故電紡纖維感測能力優於其薄膜形式。熱交聯後的P3-3纖維除了在水中可以保持其結構穩定外，其螢光強度亦隨著水溶液溫度增加而減弱，而在溫度低於LCST與高於LCST感測Cu2+時，纖維展現其溫度感應開關特性。綜合以上之優點，此功能性之靜電紡絲纖維在環境感測領域發展上具有相當大的潛力。

關鍵字

奈米纖維 ； 靜電紡絲 ； 金屬離子感測器 ； 鈴木-宮浦反應

並列摘要

Electrospinning (ES) has emerged as a new technique to produce various functional nanofibers because it has the advantages of low cost, tunable morphology, and high-throughput continuous production. Among its wide applications, ES nanofibers with high surface-area-to-volume ratio and sensing functionality have the potential to use in sensory devices. In this study, the random copolymers (Poly(N-isopropylacrylamide)-co- N-hydroxymethylacrylamide) Poly(NIPAAm-co-NMA)) P1, P2, P3 were synthesized by free radical polymerization (molar ratio of NIPAAm:NMA = 10:0.7, 10:2.5 and 10:4.7). PNIPAAm segments with thermo-responsive properties exhibit a hydrophilic/hydrophobic phase transition during the heating and cooling cycle, indicating its on/off characteristic for sensory devices. The chemical cross-linking moiety of PNMA segments stabilizes the morphology of ES nanofibers in aqueous solution. The metal-ion responsive fluorophore Phen-F-Phen was synthesized by Suzuki-Miyaura coupling reaction. Among the tested metal ions, the Phen-F-Phen showed fluorescence intensity change towards transition metal ions, such as Cu2+, Fe3+, Cd2+, Zn2+, Ni2+, Hg2+ etc in THF solution. Job’s plot revealed that Phen-F-Phen reacted with Cu2+ in 3 : 2 stoichiometry. Currently, most of the studies on metal-ion sensing were carried out in the solution, or thin film, but not in the case of nanofibers. In this research, the multifunctional electrospun nanofibers P3-1, P3-3, P3-5 were prepared from blends of poly(NIPAAm-co-NMA) with 1, 3, 5 wt% fluorophore Phen-F-Phen. The morphology of crosslinked ES nanofibers with/without metal-ion, responsive fluorophore was investigated by field-emission scanning electron microscope (FE-SEM). The Stern-Volmer quenching constant Ksv values for detection Cu2+ of nanofibers were estimated to be 35718 M-1 (P3-1), 55049 M-1 (P3-3) and 24230 M-1 (P3-5), respectivey. These results show P3-3 nanofibers were more sensitive than P3-1 and P3-5 nonofibers and even 10 times larger than its dip-coating film. This indicates the high surface/volume ratio of ES fibers enhance the sensitivity and response time, compared with those of drop-cast films. In addition to dimensional stability of P3-3 nanofibers in aqueous solution, these nanofibers also showed the thermo-responsive property in sensing Cu2+ as the temperature varied. These studies suggest that the prepared multifunctional ES nanofibers have potential applications in environmentally sensory devices.

並列關鍵字

nanofibers ； electrospinning ； metal ion sensor ； Suzuki–Miyaura reaction

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