本研究的目的在於將具有螢光感測能力之共聚高分子製備成奈米靜電紡絲纖維，並將其應用於水相環境中銅金屬離子的感測。靜電紡絲(electrospinning)是近年來用於製備多功能性高分子奈米纖維的新穎技術，由靜電紡絲技術製備的纖維尺寸可達奈米等級，可提供相當高的比表面積(surface-to-volume ratio)，遠勝於傳統製備的微米等級纖維或薄膜型態，因而被廣泛應用於感測器上。本實驗使用自由基聚合法(free radical polymerization)合成出不同比例之共聚高分子poly(HEMA-co-NMA-co-RS)，分別為PRS3-2、PRS3-5、PRS3-8，並分別藉由靜電紡絲技術將其製備成奈米纖維。PHEMA末端含OH基，過去也常作為隱形眼鏡或水凝膠等材料，因為優秀的親水性的功能，可以與水分子形成氫鍵，增加親水性，幫助互溶，PNMA作為奈米纖維交聯片段，可更進一步進行熱交聯，使纖維型態在溶液中仍維持穩定不至於回溶，PRS為本研究所合成具有銅金屬離子感測性之螢光單體，先以酸性環境將硫化羅丹名基團之螺內醯胺(spirolactam)開環，產生硫化羅丹明基團之放射峰，達成OFF-ON的機制，再利用席夫鹼辨識基團與銅金屬離子進行螯合，由於銅金屬離子本身為順磁性，會使螢光淬滅使羅丹名基團之放射峰減弱，形成一個ON-OFF的螢光機制。
PRS高分子在溶液態和靜電奈米纖維對Cu^(2+)溶液具有高選擇性，且具備高競爭性不受其他金屬離子干擾Cu^(2+)的檢測，藉由Stern Volmer plots之定量分析結果，奈米纖維之螢光淬滅常數K_sv於[Cu^(2+)]= 0.1~10µM 區間展現高線性相關性，偵測極限低具備良好靈敏度，感測器與Cu^(2+)以化學劑量1:1結合。靜電紡絲纖維小巧可折疊方便於攜帶，不溶於溶液的特性也可避免汙染待測物，綜合上述原因證實了PRS靜電紡絲奈米纖維可作為良好螢光感測器。

This study is to prepare fluorescent sensing-capable copolymer into nanoscale electrospun fibers and apply them for the detection of copper metal ions in aqueous solutions. Electrospinning is a novel technique used in recent years to fabricate multifunctional polymer nanofibers. Fibers prepared by electrospinning can achieve nanoscale dimensions, providing a significantly high surface-to-volume ratio, surpassing traditional microscale fibers or thin films. Therefore, electrospun fibers have been widely applied in sensors. In this experiment, poly(HEMA-co-NMA-co-RS) copolymers with different ratios of fluorescent-sensing moieties (PRS3-2, PRS3-5, and PRS3-8) were synthesized using free radical polymerization. These copolymers were then electrospun into nanofibers. PNMA serves as a crosslinking segment in the nanofibers and can undergo further thermal crosslinking to maintain fiber morphology in solution without dissolution. PRS is a fluorescent monomer synthesized in this study with copper metal ion sensing capability. Initially, the spirolactam ring of the rhodamine-based unit was opened under acidic conditions, resulting in the emission peak of rhodamine. This mechanism achieves an OFF-ON response. Subsequently, the Schiff base recognition group was utilized to chelate with copper metal ions. The paramagnetic nature of copper metal ions leads to fluorescence quenching and a weakened emission peak of rhodamine, forming an ON-OFF fluorescence mechanism.

(1) Xu, Z.; Zhang, L.; Guo, R.; Xiang, T.; Wu, C.; Zheng, Z.; Yang, F. A highly sensitive and selective colorimetric and off–on fluorescent chemosensor for Cu2+ based on rhodamine B derivative. Sensors and Actuators B: Chemical 2011, 156 (2), 546-552.
(2) AbouElhamd, A. R.; Al-Sallal, K. A.; Hassan, A. Review of Core/Shell Quantum Dots Technology Integrated into Building’s Glazing. Energies 2019, 12 (6), 1058.
(3) Patil, A.; Salunke-Gawali, S. Overview of the chemosensor ligands used for selective detection of anions and metal ions (Zn2+, Cu2+, Ni2+, Co2+, Fe2+, Hg2+). Inorganica Chimica Acta 2018, 482, 99-112.
(4) Tang, J.; Ma, S.; Zhang, D.; Liu, Y.; Zhao, Y.; Ye, Y. Highly sensitive and fast responsive ratiometric fluorescent probe for Cu2+ based on a naphthalimide-rhodamine dyad and its application in living cell imaging. Sensors and Actuators B: Chemical 2016, 236, 109-115.
(5) Brown, D. R.; Kozłowski, H. Biological inorganic and bioinorganic chemistry of neurodegeneration based on prion and Alzheimer diseases. Dalton transactions 2004, 13, 1907-1917.
(6) Front Matter. In Molecular Fluorescence, 2012; p I-XXI.
(7) Fereja, T.; Hymete, A.; Thirumurugan, G. A Recent Review on Chemiluminescence Reaction, Principle and Application on Pharmaceutical Analysis. ISRN Spectroscopy 2013, 1-12.
(8) Characteristics of Fluorescence Emission. Molecular Fluorescence, 2001; p 34-71.
(9) Akash, M. S. H.; Rehman, K. Introduction to Pharmaceutical Analysis. Essentials of Pharmaceutical Analysis, 2020; p 1-18.
(10) Thipperudrappa, J.; Biradar, D. S.; Hanagodimath, S. M. Simultaneous presence of static and dynamic component in the fluorescence quenching of Bis-MSB by CCl4 and aniline. Journal of Luminescence 2007, 124 (1), 45-50.
(11) Quenching of Fluorescence. In Principles of Fluorescence Spectroscopy, Springer US, 2006; p 277-330.
(12) Eftink, M. R. Fluorescence Quenching Reactions.Biophysical and Biochemical Aspects of Fluorescence Spectroscopy, Springer US, 1991; p1-41.
(13) Mao, L.; Liu, Y.; Yang, S.; Li, Y.; Zhang, X.; Wei, Y. Recent advances and progress of fluorescent bio-/chemosensors based on aggregation-induced emission molecules. Dyes and Pigments 2019, 162, 611-623.
(14) Dongare, P. R.; Gore, A. H. Recent Advances in Colorimetric and Fluorescent Chemosensors for Ionic Species: Design, Principle and Optical Signalling Mechanism. ChemistrySelect 2021, 6 (23), 5657-5669.
(15) Liu, M.; Yu, X.; Li, M.; Liao, N.; Bi, A.; Jiang, Y.; Liu, S.; Gong, Z.; Zeng, W. Fluorescent probes for the detection of magnesium ions (Mg(2+)): from design to application. RSC Adv 2018, 8 (23), 12573-12587.
(16) Jung, H. S.; Verwilst, P.; Kim, W.; Kim, J. Fluorescent and colorimetric sensors for the detection of humidity or water content. Chemical Society reviews 2016, 45.
(17) Akkaya, E. U.; Huston, M. E.; Czarnik, A. W. Chelation-enhanced fluorescence of anthrylazamacrocycle conjugate probes in aqueous solution. Journal of the American Chemical Society 1990, 112 (9), 3590-3593.
(18) Tian, L.; Zhang, W.; Yang, B.; Lu, P.; Lu, D.; Ma, Y.; Shen, J. Zinc(II)Induced Color-Tunable Fluorescence Emission in the ??-Conjugated Polymers Composed of the Bipyridine Unit: A Way to Get White-Light Emission. Physical Chemistry B 2005, 109, 6944-6947.
(19) Valeur, B.; Leray, I. Design principles of fluorescent molecular sensors for cation recognition. Coordination Chemistry Reviews 2000, 205 (1), 3-40.
(20) Kowser, Z.; Rayhan, U.; Akther, T.; Redshaw, C.; Yamato, T. A brief review on novel pyrene based fluorometric and colorimetric chemosensors for the detection of Cu 2+. Materials Chemistry Frontiers 2021, 5.
(21) Luo, J.; Xie, Z.; Lam, J. W.; Cheng, L.; Chen, H.; Qiu, C.; Kwok, H. S.; Zhan, X.; Liu, Y.; Zhu, D.; et al. Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole. Chem Commun (Camb) 2001, (18), 1740-1741.
(22) Mei, J.; Hong, Y.; Lam, J. W. Y.; Qin, A.; Tang, Y.; Tang, B. Z. Aggregation-Induced Emission: The Whole Is More Brilliant than the Parts. Advanced Materials 2014, 26
(23) Wang, Q.-M.; Gao, W.; Li, Y.; Yang, T.-T.; Ju, Y.; Tang, X.-H. Highly sensitive and selective fluorescent “turn-on” probe for determination of aluminum ion in aqueous solution. Spectroscopy Letters 2016, 49 (2), 80-84.
(24) Azarias, C.; Budzák, Š.; Laurent, A. D.; Ulrich, G.; Jacquemin, D. Tuning ESIPT fluorophores into dual emitters. Chemical Science 2016, 7 (6), 3763-3774.
(25) Park, S.-H.; Kwon, N.; Lee, J.-H.; Yoon, J.; Shin, I. Synthetic ratiometric fluorescent probes for detection of ions. Chemical Society Reviews 2020, 49 (1), 143-179.
(26) Sasaki, S.; Drummen, G. P. C.; Konishi, G.-i. Recent advances in twisted intramolecular charge transfer (TICT) fluorescence and related phenomena in materials chemistry. Journal of Materials Chemistry C 2016, 4 (14), 2731-2743.
(27) Hochreiter, B.; Garcia, A.; Schmid, J. Fluorescent Proteins as Genetically Encoded FRET Biosensors in Life Sciences. Sensors 2015, 15, 26281-26314.
(28) Broussard, J. A.; Green, K. J. Research Techniques Made Simple: Methodology and Applications of Förster Resonance Energy Transfer (FRET) Microscopy. Journal of Investigative Dermatology 2017, 185-191.
(29) Abebe, F.; Perkins, P.; Shaw, R.; Tadesse, S. A rhodamine-based fluorescent sensor for selective detection of Cu2+ in aqueous media: Synthesis and spectroscopic properties. Journal of Molecular Structure 2020, 1205, 127594.
(30) Guan, X.; Lin, W.; Huang, W. Development of a new rhodamine-based FRET platform and its application as a Cu2+ probe. Organic & Biomolecular Chemistry 2014, 12 (23), 3944-3949.
(31) Schiff, H. Mittheilungen aus dem Universitätslaboratorium in Pisa: Eine neue Reihe organischer Basen. Justus Liebigs Annalen der Chemie 1864, 131 (1), 118-119.
(32) Senthil Kumar, K.; Bayeh, Y.; Gebretsadik, T.; Elemo, F.; Gebrezgiabher, M.; Thomas, M.; Ruben, M. Spin-crossover in iron(ii)-Schiff base complexes. Dalton Transactions 2019, 48 (41), 15321-15337.
(33) Tsai, C.-Y.; Huang, B.-H.; Hsiao, M.-W.; Lin, C.-C.; Ko, B.-T. Structurally Diverse Copper Complexes Bearing NNO-Tridentate Schiff-Base Derivatives as Efficient Catalysts for Copolymerization of Carbon Dioxide and Cyclohexene Oxide. Inorganic Chemistry 2014, 5109-5116.
(34) Zhou, Y.; Kim, H. N.; Yoon, J. A selective ‘Off–On’ fluorescent sensor for Zn2+ based on hydrazone–pyrene derivative and its application for imaging of intracellular Zn2+. Bioorganic & Medicinal Chemistry Letters 2010, 20 (1), 125-128.
(35) Chuang, W.-J.; Chiu, W.-Y. Thermo-responsive nanofibers prepared from poly(N-isopropylacrylamide-co-N-methylol acrylamide). Polymer 2012, 53 (14), 2829-2838.
(36) Chen, Y.; Miller, P. G.; Ding, X.; Stowell, C. E. T.; Kelly, K. M.; Wang, Y. Chelation Crosslinking of Biodegradable Elastomers. Advanced Materials 2020, 32 (43), 2003761.
(37) Pekel, N.; Yoshii, F.; Kume, T.; Güven, O. Radiation crosslinking of biodegradable hydroxypropylmethylcellulose. Carbohydrate Polymers 2004, 55 (2), 139-147.
(38) Song, Q.; Cao, S.; Pritchard, R. H.; Ghalei, B.; Al-Muhtaseb, S. A.; Terentjev, E. M.; Cheetham, A. K.; Sivaniah, E. Controlled thermal oxidative crosslinking of polymers of intrinsic microporosity towards tunable molecular sieve membranes. Nature Communications 2014, 5 (1), 4813.
(39) Islam, M. S.; Ang, B. C.; Andriyana, A.; Afifi, A. M. A review on fabrication of nanofibers via electrospinning and their applications. SN Applied Sciences 2019, 1.
(40) Casper, C. L.; Stephens, J. S.; Tassi, N. G.; Chase, D. B.; Rabolt, J. F. Controlling Surface Morphology of Electrospun Polystyrene Fibers:  Effect of Humidity and Molecular Weight in the Electrospinning Process. Macromolecules 2004, 37 (2), 573-578.
(41) Megelski, S.; Stephens, J. S.; Chase, D. B.; Rabolt, J. F. Micro- and Nanostructured Surface Morphology on Electrospun Polymer Fibers. Macromolecules 2002, 35, 8456-8466.
(42) Xiang, Y.; Tong, A.; Jin, P.; Ju, Y. New fluorescent rhodamine hydrazone chemosensor for Cu(II) with high selectivity and sensitivity. Org Lett 2006, 8 (13), 2863-2866.
(43) Zheng, H.; Qian, Z.-H.; Xu, L.; Yuan, F.-F.; Lan, L.-D.; Xu, J.-G. Switching the Recognition Preference of Rhodamine B Spirolactam by Replacing One Atom:  Design of Rhodamine B Thiohydrazide for Recognition of Hg(II) in Aqueous Solution. Organic Letters 2006, 8 (5), 859-861.
(44) Chen, B.-Y.; Kuo, C.-C.; Cho, C.-J.; Liang, F.-C.; Jeng, R.-J. Novel fluorescent chemosensory filter membranes composed of electrospun nanofibers with ultra-selective and reversible pH and Hg2+ sensing characteristics. Dyes and Pigments 2017, 143, 129-142.
(45) Ge, Y.; Zheng, X.; Ji, R.; Shen, S.; Cao, X. A new pyrido[1,2-a]benzimidazole-rhodamine FRET system as an efficient ratiometric fluorescent probe for Cu2+ in living cells. Analytica Chimica Acta 2017, 965, 103-110.
(46) Wen, D.; Deng, X.; Xu, G.; Wu, H.; Yu, Y. A novel FRET fluorescent probe based on BODIPY- rhodamine system for Hg2+ imaging in living cells. Journal of Molecular Structure 2021, 1236.