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化学进展 2011, Vol. 23 Issue (4): 623-636 前一篇   后一篇

• 特约稿 •

聚集诱导发光机理研究

张双1, 秦安军1, 孙景志1*, 唐本忠1,2*   

  1. 1. 浙江大学高分子科学与工程学系 高分子合成与功能构造教育部重点实验室 杭州 310027;
    2. 香港科技大学化学系 香港
  • 收稿日期:2010-09-01 修回日期:2010-11-01 出版日期:2011-04-24 发布日期:2011-02-25
  • 通讯作者: e-mail:sunjz@zju.edu.cn;tangbenz@ust.hk E-mail:sunjz@zju.edu.cn;tangbenz@ust.hk
  • 基金资助:

    国家自然科学基金项目(No.20974028,50873086,21074113,Z406018)资助

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Mechanism Study of Aggregation-Induced Emission

Zhang Shuang1, Qin Anjun1, Sun Jingzhi1*, Tang Benzhong1,2*   

  1. 1. Key Laboratory of Macromolecular Synthesis and Functionalization, Ministry of Education, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China;
    2. Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Hong Kong, China
  • Received:2010-09-01 Revised:2010-11-01 Online:2011-04-24 Published:2011-02-25

与传统荧光生色团聚集后导致荧光猝灭相反,有一类化合物在单分子状态下荧光微弱甚至观察不到荧光,而在聚集状态下荧光显著增强,这就是聚集诱导发光(AIE)现象。AIE现象独特的优越性使得众多研究组开发出越来越多的新AIE体系,其机理也被广泛而深入地研究。本文总结了目前为止已经提出的AIE机理,包括分子内旋转受限、分子内共平面、抑制光物理过程或光化学反应、非紧密堆积、形成J-聚集体以及形成特殊激基缔合物等;着重评述了目前研究最为全面、适用范围最广的分子内旋转受限机理。同时介绍了一些基于这些机理设计的新AIE体系。

关键词： 聚集诱导发光, 机理, 分子内旋转受限, 新AIE体系

Aggregation of classical fluorophores always quenches their light emission, which is notoriously known as aggregation-caused quenching (ACQ). The ACQ effect prevents many fluorophores from finding aggregation-state applications. In contrast, a group of fluorophores is weakly luminescent or even nonluminescent in isolated state but highly emissive in aggregate state. Aggregation-induced emission (AIE) was coined for this novel phenomenon. Because of their unique advantages, more and more new AIE systems with emission colors covering the entire visible spectral region were developed by numerous research groups. Their applications as solid-state emitters and chemo/bio-sensors were explored widely and deeply. Deciphering the working principle of the AIE phenomenon is of great value in terms of helping gain new photophysical insights and guide further efforts in the development of new AIE materials with high luminescence efficiencies. However, whilst the mature theories to explain the ACQ effect had been written into textbooks, the “abnormal” AIE phenomenon still poses a challenge to our current understanding of solid-state luminescence. In this review article, we summarize the accessible mechanisms for the AIE phenomenon, such as restricted intramolecular rotation (RIR), intramolecular coplanarization, inhibition of intramolecular photochemical or photophysical process, relatively loose molecular packing, J-aggregate formation, and special excimer formation. Particularly, we emphasize on the description of RIR mechanism, which is the most universal and best studied one among the proposed mechanisms. In addition, some new AIE systems based on these mechanisms are introduced briefly.

Key words: aggregation-induced emission, mechanism, restricted intramolecular rotation, new AIE systems

中图分类号: 

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[1] Jenekhe S A, Osaheni J A. Science, 1994,265: 765-768
[2] Friend R H, Gymer R W, Holmes A B, Burroughes J H, Marks R N, Taliani C, Bradley D D C, Dos Santos D A, Brédas J L, Lgdlund M, Salaneck W R. Nature, 1999, 397: 121-128
[3] Chen C T. Chem. Mater., 2004,16: 4389-4400
[4] Tang C W, VanSlyke S A, Chen C H. J. Appl. Phys., 1989,65: 3610-3616
[5] Thomas K R J, Lin J T, Tao Y T, Chuen C H. Adv. Mater., 2002,14: 822-826
[6] He F, Xu H, Yang B, Duan Y, Tian L L, Huang K K, Ma Y G, Liu S Y, Feng S H, Shen J C. Adv. Mater., 2005, 17: 2710-2714
[7] Figueira-Duarte T M, Del Rosso P C, Trattnig R, Sax S, List E J W, Müllen K. Adv. Mater., 2010, 22: 990-993
[8] Luo J D, Xie Z L, Lam J W Y, Cheng L, Chen H Y, Qiu C F, Kwok H S, Zhan X W, Liu Y Q, Zhu D B, Tang B Z. Chem. Commun., 2001, 1740-1741
[9] Hong Y N, Lam J W Y, Tang B Z. Chem. Commun., 2009, 4332-4353
[10] Liu J Z, Lam J W Y, Tang B Z. J. Inorg. Organomet. Polym., 2009, 19: 249-285
[11] Wang M, Zhang G X, Zhang D Q, Zhu D B, Tang B Z. J. Mater. Chem., 2010, 20: 1858-1867
[12] 钱立军(Qian L J),支俊格(Zhi J G),佟斌(Tong B),杨帆(Yang F),赵玮(Zhao W),董宇平(Dong Y P). 化学进展(Progress in Chemistry), 2008, 20(5):673-678
[13] 钱妍(Qian Y),解令海(Xie L H),王双清(Wang S Q),杨国强(Yang G Q). 南京邮电大学学报(自然科学版)(Journal of Nanjing University of Posts and Telecommunications (Natural Science)), 2008, 28(1):1-8
[14] 闫继明(Yan J M),秦安军(Qin A J),孙景志(Sun J Z),唐本忠(Tang B Z). 科学通报(Chinese Science Bulletin), 2010, 55(13):1206-1213
[15] Zhao Y S, Fu H B, Peng A D, Ma Y, Xiao D B, Yao J N. Adv. Mater., 2008, 20: 2859-2876
[16] Shimizu M, Hiyama T. Chem. Asian J., 2010, 5: 1516-1531
[17] Chen J W, Law C C W, Lam J W Y, Dong Y P, Lo S M F, Williams I D, Zhu D B, Tang B Z. Chem. Mater., 2003, 15: 1535-1546
[18] Wong K S, Wang H, Lanzani G. Chem. Phys. Lett., 1998, 288: 59-64
[19] Barr J W, Bell T W, Catalano V J, Cline J I, Phillips D J, Procupez R. J. Phys. Chem. A, 2005, 109: 11650-11654
[20] Fan X, Sun J L, Wang F Z, Chu Z Z, Wang P, Dong Y Q, Hu R R, Tang B Z, Zou D C. Chem. Commun., 2008, 2989-2991
[21] Ren Y, Lam J W Y, Dong Y Q, Tang B Z, Wong K S. J. Phys. Chem. B, 2005, 109: 1135-1140
[22] Ren Y, Dong Y Q, Lam J W Y, Tang B Z, Wong K S. Chem. Phys. Lett., 2005, 402: 468-473
[23] Li Z, Dong Y Q, Mi B X, Tang Y H, Huвler M, Tong H, Dong Y P, Lam J W Y, Ren Y, Sung H H Y, Wong K S, Gao P, Williams I D, Kwok H S, Tang B Z. J. Phys. Chem. B, 2005, 109: 10061-10066
[24] Zhang X J, Jenekhe S A. Macromolecules, 2000, 33: 2069-2082
[25] Lin T, He Q G, Bai F L, Dai L M. Thin Solid Films, 2000, 363: 122-125
[26] Natrajan L S, Blake A J, Wilson C, Weinstein J A, Arnold P L. Dalton Trans., 2004, 3748-3755
[27] Yu G, Yin S W, Liu Y Q, Chen J S, Xu X J, Sun X B, Ma D G, Zhan X W, Peng Q, Shuai Z G, Tang B Z, Zhu D B, Fang W H, Luo Y. J. Am. Chem. Soc., 2005, 127: 6335-6346
[28] Yin S W, Peng Q, Shuai Z G, Fang W H, Wang Y H, Luo Y. Phys. Rev. B, 2006, 73: art. no. 205409
[29] Peng Q, Yi Y P, Shuai Z G, Shao J S. J. Am. Chem. Soc., 2007, 129: 9333-9337
[30] Deng C M, Niu Y L, Peng Q, Shuai Z G. Acta Phys. Chim. Sin., 2010, 26(4): 1051-1058
[31] Tracy H J, Mullin J L, Klooster W T, Martin J A, Haug J, Wallace S, Rudloe I, Watts K. Inorg. Chem., 2005, 44: 2003-2011
[32] Mullin J L, Tracy H J, Ford J R, Keenan S R, Fridman F. J. Inorg. Organomet. Polym. Mater., 2007, 17(1): 201-213
[33] Lai C T, Hong J L. J. Phys. Chem. B, 2010, 114: 10302-10310
[34] Fukazawa A, Ichihashi Y, Yamaguchi S. New J. Chem., 2010, 34: 1537-1540
[35] Shiraishi K, Kashiwabara T, Sanji T, Tanaka M. New J. Chem., 2009, 33: 1680-1684
[36] Chen J W, Xu B, Ouyang X Y, Tang B Z, Cao Y. J. Phys. Chem. A, 2004, 108: 7522-7526
[37] Tong H, Dong Y Q, HuBler M, Lam J W Y, Sung H H Y, Williams I D, Sun J Z, Tang B Z. Chem. Commun., 2006, 1133-1135
[38] Tong H, Dong Y Q, Hong Y N, Huвler M, Lam J W Y, Sung H H Y, Yu X M, Sun J X, Williams I D, Kwok H S, Tang B Z. J. Phys. Chem. C, 2007, 111: 2287-2294
[39] Dong Y Q, Lam J W Y, Qin A J, Liu J Z, Li Z, Tang B Z, Sun J X, Kwok H S. Appl. Phys. Lett., 2007, 91: art. no. 011111
[40] Tong H, Hong Y N, Dong Y Q, Huвler M, Li Z, Lam J W Y, Dong Y P, Sung H H Y, Williams I D, Tang B Z. J. Phys. Chem. B, 2007, 111: 11817-11823
[41] Zhao Z J, Chen S M, Shen X Y, Mahtab F, Yu Y, Lu P, Lam J W Y, Kwok H S, Tang B Z. Chem. Commun., 2010, 46: 686-688
[42] Dong Y Q, Lam J W Y, Qin A J, Sun J X, Liu J Z, Li Z, Sun J Z, Sung H H Y, Williams I D, Kwok H S, Tang B Z. Chem. Commun., 2007, 3255-3257
[43] Tong H, Huвler M, Dong Y Q, Li Z, Mi B X, Kwok H S, Tang B Z. J. Chin. Chem. Soc., 2006, 53: 243-246
[44] Tong H, Hong Y N, Dong Y Q, Ren Y, Huвler M, Lam J W Y, Wong K S, Tang B Z. J. Phys. Chem. B, 2007, 111: 2000-2007
[45] Qin A J, Lam J W Y, Mahtab F, Jim C K W, Tang L, Sun J Z, Sung H H Y, Williams I D, Tang B Z. Appl. Phys. Lett., 2009, 94: art. no. 253308
[46] Zeng Q, Li Z, Dong Y Q, Di C A, Qin A J, Hong Y N, Ji L, Zhu Z C, Jim C K W, Yu G, Li Q Q, Li Z A, Liu Y Q, Qin J G, Tang B Z. Chem. Commun., 2007, 70-72
[47] Zhao Z J, Chen S M, Lam J W Y, Lu P, Zhong Y C, Wong K S, Kwok H S, Tang B Z. Chem. Commun., 2010, 2221-2223
[48] Yuan W Z, Lu P, Chen S M, Lam J W Y, Wang Z M, Liu Y, Kwok H S, Ma Y G, Tang B Z. Adv. Mater., 2010, 22: 2159-2163
[49] Tang W X, Xiang Y, Tong A J. J. Org. Chem., 2009, 74: 2163-2166
[50] Li S Y, He L M, Xiong F, Li Y, Yang G Q. J. Phys. Chem. B, 2004, 108: 10887-10892
[51] Qian Y, Li S Y, Zhang G Q, Wang Q, Wang S Q, Xu H J, Li C Z, Li Y, Yang G Q. J. Phys. Chem. B, 2007, 111: 5861-5868
[52] Yu H, Qi L M. Langmuir, 2009, 25(12): 6781-6786
[53] Yan W B, Wan X J, Chen Y S. J. Mol. Struct., 2010, 968: 85-88
[54] Itami K, Ohashi Y, Yoshida J I. J. Org. Chem., 2005, 70: 2778-2792
[55] Wang Z X, Shao H X, Ye J C, Tang L, Lu P. J. Phys. Chem. B, 2005, 109: 19627-19633
[56] Kim S, Zheng Q D, He G S, Bharali D J, Pudavar H E, Baev A, Prasad P N. Adv. Funct. Mater., 2006, 16: 2317-2323
[57] Ning Z J, Chen C, Zhang Q, Yan Y L, Qian S X, Cao Y, Tian H. Adv. Funct. Mater., 2007, 17: 3799-3807
[58] Qian G, Dai B, Yu D B, Zhan J, Zhang Z Q, Ma D G, Wang Z Y. Chem. Mater., 2008,20: 6208-6216
[59] Dong S C, Li Z, Qin J G. J. Phys. Chem. B, 2009, 113: 434-441
[60] Zhao C H, Sakuda E, Wakamiya A, Yamaguchi S. Chem. Eur. J., 2009, 15: 10603-10612
[61] Kokado K, Chujo Y. Macromolecule, 2009, 42: 1418-1420
[62] Chen P, Lu R, Xue P C, Xu T H, Chen G J, Zhao Y Y. Langmuir, 2009, 25(15): 8395-8399
[63] He J T, Xu B, Chen P F, Xia H J, Li K P, Ye L, Tian W J. J. Phys. Chem. C, 2009, 113: 9892-9899
[64] Shimizu M, Tatsumi H, Mochida K, Shimono K, Hiyama T. Chem. Asian J., 2009, 4: 1289-1297
[65] Qian L J, Tong B, Shen J B, Shi J B, Zhi J G, Dong Y Q, Yang F, Dong Y P, Lam J W Y, Liu Y, Tang B Z. J. Phys. Chem. B, 2009,113: 9098-9103
[66] Asefa A, Singh A K. J. Luminesc., 2010, 130: 24-28
[67] Yang Z Y, Chi Z G, Xu B J, Li H Y, Zhang X Q, Li X F, Liu S W, Zhang Y, Xu J R. J. Mater. Chem., 2010, 20: 7352-7359
[68] Zhang P, Wang H T, Liu H M, Li M. Langmuir, 2010,26(12): 10183-10190
[69] Vyas V S, Rathore R. Chem. Commun., 2010, 1065-1067
[70] Park C N, Hong J I. Tetra. Lett., 2010, 51: 1960-1962
[71] An B K, Kwon S K, Jung S D, Park S Y. J. Am. Chem. Soc., 2002, 124: 14410-14415
[72] Trotter J. Acta Cryst., 1961, 14: 1135-1140
[73] Hargreaves A, Rizvi S H. Acta Cryst., 1962, 15: 365-373
[74] Ambrosch-Draxl C, Majewski J A, Vogl P, Leising G. Phys. Rev. B, 1995, 51: 9668-9676
[75] Baker K N, Fratini A V, Resch T, Knachel H C, Adams W W, Socci E P, Farmer B L. Polymer, 1993, 34: 1571-1587
[76] Tian B, Zerbi G, Müllen K. J. Chem. Phys., 1991, 95(5): 3198-3207
[77] Woo H S, Lhost O, Graham S C, Bradley D D C, Friend R H, Quattrocchi C, Brédas J L, Schenk R, Müllen K. Synth. Met., 1993, 59: 13-28
[78] An B K, Lee D S, Lee J S, Park Y S, Song H S, Park S Y. J. Am. Chem. Soc., 2004, 126: 10232-10233
[79] An B K, Gihm S H, Chung J W, Park C R, Kwon S K, Park S Y. J. Am. Chem. Soc., 2009, 131: 3950-3957
[80] Kim T H, Choi M S, Sohn B H, Park S Y, Lyoo W S, Lee T S. Chem. Commun., 2004, 2364-2366
[81] Bhongale C J, Chang C W, Lee C S, Diau E W G, Hsu C S. J. Phys. Chem. B, 2005, 109: 13472-13482
[82] Sun Y Y, Liao J H, Fang J M, Chou P T, Shen C H, Hsu C W, Chen L C. Org. Lett., 2006, 8(17): 3713-3716
[83] Xie Z Q, Yang B, Liu L L, Li M, Lin D, Ma Y G, Cheng G, Liu S Y. J. Phys. Org. Chem., 2005, 18: 962-973
[84] Xie Z Q, Yang B, Xie W J, Liu L L, Shen F Z, Wang H, Yang X Y, Wang Z M, Li Y P, Hanif M, Yang G D, Ye L, Ma Y G. J. Phys. Chem. B, 2006, 110: 20993-21000
[85] Xie Z Q, Yang B, Cheng G, Liu L L, He F, Shen F Z, Ma Y G, Liu S Y. Chem. Mater., 2005, 17: 1287-1289
[86] Yang B, Xie Z Q, Zhang H Y, Xu H, Hanif M, Gu X, He F, Yu J S, Ma Y G, Liu X D, Feng J K. Chem. Phys., 2008, 345: 23-31
[87] 杨兵(Yang B),马於光(Ma Y G),沈家骢(Shen J C). 高等学校化学学报(Chemical Journal of Chinese University), 2008, 29(12):2643-2658
[88] Ryu S Y, Kim S, Seo J, Kim Y W, Kwon O H, Jang D J, Park S Y. Chem. Commun., 2004, 71-72
[89] Jayanty S, Radhakrishnan T P. Chem. Eur. J., 2004, 10: 791-797
[90] Hu R R, Lager E, Aguilar-Aguilar A, Liu J Z, Lam J W Y, Sung H H Y, Williams I D, Zhong Y C, Wong K S, Pea-Cabrere E, Tang B Z. J. Phys. Chem. C, 2009, 113: 15845-15853
[91] Gao B R, Wang H Y, Hao Y W, Fu L M, Fang H H, Jiang Y, Wang L, Chen Q D, Xia H, Pan L Y, Ma Y G, Sun H B. J. Phys. Chem. B, 2010, 114: 128-134
[92] Yuan C X, Tao X T, Ren Y, Li Y, Yang J X, Yu W T, Wang L, Jiang M H. J. Phys. Chem. C, 2007, 111: 12811-12816
[93] Dong J, Solntsev K M, Tolbert L M. J. Am. Chem. Soc., 2009, 131: 662-670
[94] Lamère J-F, Saffon N, Dos Santos I, Fery-Forgues S. Langmuir, 2010, 26(12): 10210-10217
[95] Rabinowitch E, Epstein L F. J. Am. Chem. Soc., 1941, 63: 67-78
[96] Kasha M, Rawls H R, El-Bayoumi M A. Pure Appl. Chem, 1965, 11: 371-392
[97] Zhang H Q, Wang S M, Li Y Q, Zhang B, Du C X, Wan X J, Chen Y S. Tetrahedron, 2009, 65: 4455-4463
[98] Liu Y, Tao X T, Wang F Z, Shi J H, Sun J L, Yu W T, Ren Y, Zou D C, Jiang M H. J. Phys. Chem. C, 2007, 111: 6544-6549
[99] Liu Y, Tao X T, Wang F Z, Dang X N, Zou D C, Ren Y, Jiang M H. J. Phys. Chem. C, 2008, 112: 3975-3981
[100] Deans R, Kim J S, Machacek M R, Swager T M. J. Am. Chem. Soc., 2000, 122: 8565-8566
[101] Qin A J, Jim C K W, Tang Y H, Lam J W Y, Liu J Z, Mahtab F, Gao P, Tang B Z. J. Phys. Chem. B, 2008, 112: 9281-9288
[102] Zhao Q, Li L, Li F Y, Yu M X, Liu Z P, Yi T, Huang C H. Chem. Commun., 2008, 685-687
[103] Dong Y Q, Lam J W Y, Qin A J, Li Z, Sun J Z, Sung H H Y, Williams I D, Tang B Z. Chem. Commun., 2007, 40-42
[104] Yuan W Z, Shen X Y, Zhao H, Lam J W Y, Tang L, Lu P, Wang C L, Liu Y, Wang Z M, Zheng Q, Sun J Z, Ma Y G, Tang B Z. J. Phys. Chem. C, 2010, 114: 6090-6099
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聚集诱导发光机理研究