Handbook of Aggregation-Induced Emission, Volume 2

73 73 Kim, S., Pudavar, H.E., Bonoiu, A. et al. (2007). Aggregation‐enhanced fluorescence in organically modified silica nanoparticles: A novel approach toward high‐signal‐output nanoprobes for two‐photon fluorescence bioimaging. Advanced Materials 19 (22): 3791–3795.

74 74 Han, W.K., Zhang, S., Qian, J.Y. et al. (2019). Redox‐responsive fluorescent nanoparticles based on diselenide‐containing aiegens for cell imaging and selective cancer therapy. Chemistry—An Asian Journal 14 (10): 1745–1753.

75 75 Lu, H.G., Zhao, X.W., Tian, W.J. et al. (2014). Pluronic F127‐folic acid encapsulated nanoparticles with aggregation‐induced emission characteristics for targeted cellular imaging. RSC Advances 4 (35): 18460–18466.

76 76 Zhang, J.X., Xu, B., Tian, W.J. et al. (2018). Tailoring the morphology of AIEgen fluorescent nanoparticles for optimal cellular uptake and imaging efficacy. Chemical Science 9 (9): 2620–2627.

77 77 Jing, J., Xue, Y.‐R., Liu, Y.‐X. et al. (2020). Co‐assembly of HPV capsid proteins and aggregation‐induced emission fluorogens for improved cell imaging. Nanoscale 12 (9): 5501–5506.

78 78 Ma, K., Liu, G.J., Yan, L.L. et al. (2019). AIEgen based poly(l‐lactic‐co‐glycolic acid) magnetic nanoparticles to localize cytokine VEGF for early cancer diagnosis and photothermal therapy. Nanomedicine 14 (9): 1191–1201.

79 79 Lu, H.G., Su, F.Y., Mei, Q. et al. (2012). Using fluorine‐containing amphiphilic random copolymers to manipulate the quantum yields of aggregation‐induced emission fluorophores in aqueous solutions and the use of these polymers for fluorescent bioimaging. Journal of Materials Chemistry 22 (19): 9890–9900.

80 80 Zhang, Y., Chen, Y.J., Li, X. et al. (2014). Folic acid‐functionalized AIE Pdots based on amphiphilic PCL‐b‐PEG for targeted cell imaging. Polymer Chemistry 5 (12): 3824–3830.

81 81 Wang, Z.L., Yan, L.L., Zhang, L. et al. (2014). Ultra bright red AIE dots for cytoplasm and nuclear imaging. Polymer Chemistry 5 (24): 7013–7020.

82 82 Zhong, W.Y., Yu, J.S., Huang, W.L. et al. (2001). Spectroscopic studies of interaction of chlorobenzylidine with DNA. Biopolymers 62 (6): 315–323.

83 83 Liu, J.N., Bu, W.B., Pan, L.M. et al. (2012). Simultaneous nuclear imaging and intranuclear drug delivery by nuclear‐targeted multifunctional upconversion nanoprobes. Biomaterials 33 (29): 7282–7290.

84 84 Gottesman, M.M., Fojo, T., and Bates, S.E. (2002). Multidrug resistance in cancer: Role of ATP‐dependent transporters. Nature Reviews Cancer 2 (1): 48–58.

85 85 Kang, B., Mackey, M.A., and El‐Sayed, M.A. (2010). Nuclear targeting of gold nanoparticles in cancer cells induces dna damage, causing cytokinesis arrest and apoptosis. Journal of the American Chemical Society 132 (5): 1517–1519.

86 86 Li, H.Y., Zhang, X.Q., Zhang, X.Y. et al. (2014). Biocompatible fluorescent polymeric nanoparticles based on AIE dye and phospholipid monomers. RSC Advances 4 (41): 21588–21592.

87 87 Ma, K., Li, X., Xu, B. et al. (2014). A sensitive and selective “turn‐on” fluorescent probe for Hg2+ based on thymine‐Hg2+‐thymine complex with an aggregation‐induced emission feature. Analytical Methods 6 (7): 2338–2342.

88 88 Ma, K., Wang, H., Li, X. et al. (2015). Turn‐on sensing for Ag+ based on AIE‐active fluorescent probe and cytosine‐rich DNA. Analytical and Bioanalytical Chemistry 407 (9): 2625–2630.

89 89 Li, X., Ma, K., Zhu, S.J. et al. (2014). Fluorescent aptasensor based on aggregation‐induced emission probe and graphene oxide. Analytical Chemistry 86 (1): 298–303.

90 90 Ma, L., Xu, B., Liu, L.J. et al. (2018). A label‐free fluorescent aptasensor for turn‐on monitoring ochratoxin a based on AIE‐active probe and graphene oxide. Chemical Research in Chinese Universities 34 (3): 363–368.

91 91 Zhu, Z.C., Zhou, J., Li, Z. et al. (2015). Dinuclear zinc complex for fluorescent indicator‐displacement assay of citrate. Sensors and Actuators B‐Chemical 208: 151–158.

92 92 Lu, H.G., Xu, B., Dong, Y.J. et al. (2010). Novel fluorescent pH sensors and a biological probe based on anthracene derivatives with aggregation‐induced emission characteristics. Langmuir 26 (9): 6838–6844.

93 93 Zhang, S., Ma, L., Ma, K. et al. (2018). Label‐free aptamer‐based biosensor for specific detection of chloramphenicol using AIE probe and graphene oxide. Acs Omega 3 (10): 12886–12892.

94 94 Li, X., Ma, K., Lu, H.G. et al. (2014). Highly sensitive determination of ssDNA and real‐time sensing of nuclease activity and inhibition based on the controlled self‐assembly of a 9,10‐distyrylanthracene probe. Analytical and Bioanalytical Chemistry 406 (3): 851–858.

95 95 Wang, H., Ma, K., Xu, B. et al. (2016). Tunable supramolecular interactions of aggregation‐induced emission probe and graphene oxide with biomolecules: An approach toward ultrasensitive label‐free and “turn‐on” DNA sensing. Small 12 (47): 6613–6622.

96 96 Ma, K., Wang, H., Li, H. et al. (2017). Label‐free detection for SNP using AIE probes and carbon nanotubes. Sensors and Actuators B—Chemical 253: 92–96.

97 97 Wang, Z.L., Ma, K., Xu, B. et al. (2013). A highly sensitive “turn‐on” fluorescent probe for bovine serum albumin protein detection and quantification based on AIE‐active distyrylanthracene derivative. Science China—Chemistry 56 (9): 1234–1238.

98 98 Sun, B.J., Yang, X.J., Ma, L. et al. (2013). Design and application of anthracene derivative with aggregation‐induced emission charateristics for visualization and monitoring of erythropoietin unfolding. Langmuir 29 (6): 1956–1962.

99 99 Ma, K., Wang, H., Li, H.L. et al. (2016). A label‐free aptasensor for turn‐on fluorescent detection of ATP based on AIE‐active probe and water‐soluble carbon nanotubes. Sensors and Actuators B—Chemical 230: 556–558.

Yue Zheng and Aijun Tong

Department of Chemistry, Tsinghua University, Beijing, China

A Schiff base (named after Hugo Schiff [1]) is a compound with the general structure R 2C = NR′ (R′ ≠ H). It is a subclass of imines, being either secondary ketimines or aldimines formed by the condensation of active carbonyl groups of ketones or aldehydes with primary amines, respectively [2]. In salicylaldehyde Schiff base (SSB) derivatives, including salicylaldehyde azine and salicylidene aniline, imine and ortho ‐hydroxyl groups can form stable six‐membered ring structures through intramolecular hydrogen bonding, which allows the entire molecule to rotate freely around nitrogen–nitrogen or carbon–nitrogen single bonds ( Figure 3.1). In good solvent, the free rotation of the molecule around the single bond can dissipate the energy of the excited molecule, and the molecule appears to be weakly fluorescent; in poor solvent, the aggregated molecules are emissive due to the restriction of the free single bond rotation as the excited electrons return to their ground state. Such an emission mechanism follows the restricted intramolecular rotation (RIR) process of typical AIE molecules.

Distinct from most AIEgens, SSBs are widely followed and studied because the unique molecular structure renders the AIE process often accompanied by excited‐state intramolecular proton transfer (ESIPT) procedure. ESIPT refers to a phototautomerization process by which organic molecules undergo a proton transfer via intramolecular hydrogen bonding between adjacent proton donors and acceptors in the excited state after light irradiation [3]. Such a procedure always proceeds extremely fast at a subpicosecond time scale. Because molecules with ESIPT properties always have large Stokes shifts, they can effectively avoid the self‐absorption or the internal filtering effects of fluorescence and therefore have wide applications in designing or constructing molecular probes and luminescent materials [4]. ESIPT process is easily affected by the environment (temperature, pressure, polarity, viscosity, and acidity, etc.); its application in the field of fluorescent sensors has thus attracted widespread attention.