Aggregation-induced emission: materials, mechanism, and applications

Resume : Cancer has been one of the major threats to human health for a long time. With the advantages of relatively small size, lack of immunogenicity, ease of synthesis and various modifications, aptamer has been a powerful candidate to replace monoclonal antibodies for cancer imaging and therapy. Herein, a facile and simple one-step method to fabricate aptamer-targeting organic dots based on self-assembling method has been developed. As-prepared aptamer organic-dots, which integrated the advantages of AIEgens with the cell-targeting capabilities of aptamers, showed specific targeting ability, highly stability, and good biocompatibility. Based on this general method, a variety of biocompatible highly bright organic fluorescent nanoprobes with specific recognition and highly sensitivity could be facilely constructed for long-term, real-time sensing and biomedical imaging.

Resume : Arylacrylonitriles are important building block for the synthesis of biologically active molecules such as flavonoid pigments, sexual pheromones and vitamin A. It is also used as precursor for high electron affinity polymers, which can be used to manufacture light-emitting diodes(LED) with air-stable electrodes. Our group synthesized and characterized a series of substituted 3-phenyl-2-arylacrylonitriles derivatives earlier. Regarding of previous work, we select compounds with groups -N(CH3)2 -N(Ph)2, (Cz), (Py), Halogen atom (X), and CN, attached to arylacrylonitrile derivatives to study their physicochemical properties and supramolecular architectures using X-ray diffraction and DFT method. Hirshfeld surfaces and 2D finger print plots are constructed to identify the differences in intermolecular interactions and contacts between different crystal structures. The lattice energies of the crystal structures are calculated using PIXEL method and the energetics of various intermolecular interactions are quantified. A comparative study in the context of molecular conformation, lattice energy and Hirshfeld surface analysis for the title compound along with their analogs was carried out. The structure of the title compound is optimized in the gas phase using the M05-2X functional with 6-31+G(d) basis set. The harmonic vibrational frequencies are computed at the same level of theory to confirm the global minima, and to get a better understanding and quantified the energy of the intermolecular interactions that could contribute of crystal packing yielded. To calculate the energy of these interactions it was used PIXEL method. Moreover, intermolecular interactions in the crystal structure are visualized using Hirshfeld surface analysis and the relative contributions of various interactions are estimated using 2D fingerprint plots. Furthermore, existence of various intra- and intermolecular interactions is confirmed through Atoms-in-molecules (AIM) analysis study. Percino M. J., Cerón M., Soriano-Moro G., Castro M. E., Chapela V. M., Bonilla J., Reyes M., López-Sandoval R.. CrystEngComm. 2014, 21(4) 389. Percino M. J., Cerón M., Rodríguez O., Soriano-Moro G., Castro M. E., Chapela V. M., Siegler M. A., Pérez-Gutiérrez E., Molecules, 2016, 21(4), 389 Percino, J.; Cerón, M.; Venkatesan, P.; Ceballos, P.; Bañuelos, A.; Rodríguez, O.; Siegler, M. A.; Robles, F.; Chapela, V. M.; Soriano-Moro, G.; Pérez-Gutiérrez, E.; Bonilla-Cruz, J.; Thamotharan, S. Crystal Growth & Design 2017, 17 (4), 1679-1694 Venkatesan, P.; Rajakannan, V.; Venkataramanan, N. S.; Ilangovan, A.; Sundius, T.; Thamotharan, S. Journal of Molecular Structure 2016, 1119, 259-268. Venkatesan, P.; Thamotharan, S.; Ilangovan, A.; Liang, H.; Sundius, T Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2016, 153, 625-636.

Resume : Aggregation-induced emission (AIE) luminogens have received widespread and growing attention in many fields, such as optoelectronics, chemosensing and bioimaging and biomedicine, since the discovery of AIE phenomenon in 2001. In recent years, there are still many new breakthroughs in the field of AIE by the researchers from all around the world. Herein, I will share some advance in the novel applications of AIE luminogens and newly established strategies to construct AIE luminogens. AIE luminogens has been used for bioimaging for a long time, but we use a biocompatible, inexpensive delivery system based on the natural saponins, achieving ultrafast delivery of AIE NPs into cancer cells.1 This can be as a general method to deliver AIE luminogens with fast time. Besides, we take advantage of the twisted intramolecular charge-transfer (TICT) effect of AIE-active molecular rotors to explore a visual humidity sensor, which has excellent sensitivity and fast response/recovery time.2 This is a successful application of AIE luminoges by rational use of their photophysical properties. Usually, -bonds connected with aromatic rings is regarded as basically structures for constructing efficient fluorophores, however, we design three molecular with isolated phenyl rings emit visible light, which is due to the intramolecular through-space conjugation between the isolated phenyl rings and the the restriction of the intramolecular motions (RIM).3 This might open a new area which combines high molecular flexibility and high fluorescent efficiency. Another newly proposed strategy to construct AIE luminogens is introducing anion-+ interactions to block the detrimental - stacking. The nonionic analogue suffered from the aggregation-caused quenching (ACQ) effect effectively illustrate the effect of anion-+ interactions on the AIE characteristic.4 (1) Nicol, A.; Kwok, R. T. K.; Chen, C.; Zhao, W.; Chen, M.; Qu, J.; Tang, B. Z. J. Am. Chem. Soc. 2017, 139, 14792-14799. (2) Cheng, Y.; Wang, J.; Qiu, Z.; Zheng, X.; Leung, N. L. C.; Lam, J. W. Y.; Tang, B. Z. Adv. Mater. 2017, 29, 10.1002/adma.201703900. (3) Zhang, H.; Zheng, X.; Xie, N.; He, Z.; Liu, J.; Leung, N. L. C.; Niu, Y.; Huang, X.; Wong, K. S.; Kwok, R. T. K.; Sung, H. H. Y.; Williams, I. D.; Qin, A.; Lam, J. W. Y.; Tang, B. Z. J. Am. Chem. Soc. 2017, 139, 16264-16272. (4) Wang, J.; Gu, X.; Zhang, P.; Huang, X.; Zheng, X.; Chen, M.; Feng, H.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z. J. Am. Chem. Soc. 2017, 139, 16974-16979.

Resume : Prediction of mechanochromism of organic molecule is an appealing yet challenging puzzle, since no concrete design strategy has been developed so far. In this article, we demonstrate a potent strategy to gain a deep understanding of structure-property relationship to design multistimuli responsive mechanochromic material. To achieve our goal, a variety of new donor (D)-acceptor (A) luminogens exhibiting aggregation induced emission (AIE) has been prepared through C-H bond activation using ruthenium (Ru) metal catalyzed one pot synthetic strategy.

Resume : Organic dyes with Aggregation-Induced Emission Enhancement properties have attracted much attention for biological imaging, because they can combine several advantages when compared to conventional dyes: they only shine in targeted sub-cellular organelles, thus reducing background pollution; they can be easy to produce, easy to use, and easy to modify to fine-tune their photo-physical properties. Series of organic dyes based on a double hemi-salen or dibenzalazine core have been prepared and characterized. They are almost non emissive in dilute solution, but become highly fluorescent when they are in the crystalline or aggregate state. Their AIEE properties have been rationalized through the study of their crystal structures, and the emission wavelength of the dyes has been fine-tuned by modifying the substituents. To broaden the scope of application of these fluorophores, water soluble derivatives have been prepared, presenting the same photo-physical properties. Their interaction with cyclodextrins and DNA has been studied: upon formation of inclusion complex or interaction with DNA, the emission intensity is enhanced, in a way similar to when the dyes crystallize. These preliminary results illustrate the potential of these fluorophores for applications such as biological imaging and supramolecular detection of macromolecules.

Resume : The vast majority of Aggregation-Induced Emission (AIE) luminogens are blue or green emissive, while only few emit red or even NIR light. However, red/near-IR (NIR) fluorescent molecules with AIE characteristics are of great interest in a wide range of fields from optoelectronic to biological applications (i.e. solid state lightning, biosensing and bioimaging). To further enrich red-emitting AIE systems and expand the applications of AIE materials, it is meaningful to convert other conventional red/NIR-emitting dyes like polymethines, porphyrins and phthalocyanines into AIE-active materials. In this work we present the synthesis and spectral characteristics of different polymethine dyes (cyanines and squaraines) with a broad range of absorption and emission from visible to NIR region. Starting from our first experiment on a single squaraine dye aggregate, which afforded both a broad absorption spectrum and a strong and relatively narrow emission NIR (centred at 1.59 eV), with a remarkable Stokes shift, we will show a tentative structure-properties relationship useful to identify the most important molecular moieties able to enlarge the AIE characteristics both in term of large Stokes shift and quantum yield.

Resume : Photodynamic therapy (PDT), which relies on photosensitizers (PS) and light to generate reactive oxygen species to kill cancer cells or bacteria, has attracted much attention in recent years. PSs with both bright emission and efficient singlet oxygen generation have also been used for image-guided PDT. However, simultaneously achieving effective singlet oxygen generation, long wavelength absorption, and stable far-red (FR)/near-infrared (NIR) emission with low dark toxicity in a single PS remains challenging. In addition, it is well known that when traditional PSs are made into nanoparticles, they encounter quenched fluorescence and reduced singlet oxygen production. In 2014, PSs with aggregation-induced emission (AIE) were developed to address this issue. AIE PSs show much stronger fluorescence in the aggregated state than in solution, owing to the mechanism of restriction of intramolecular motions. More importantly, the AIE PSs also offer high singlet oxygen production efficiency in the aggregated state. To date, AIE PSs have been widely applied in image-guided PDT and bacterial killing. Herein, we want to report our recently design strategy for effective AIE PSs with FR/NIR emission, and their applications in image-guided PDT.

Resume : Polymerizations are difficult to monitor and visualize in real time unless using expensive on line instruments. In this work, we demonstrated a facile and efficient approach to in situ visualize polymerization. A group of tetraphenylethylene (TPE)-containing dithiocarbomates with potential aggregation-induced emission (AIE) characteristics were synthesized and used as agents for the reversible addition fragmentation transfer (RAFT) polymerization. The spatial-temporal control character of photochemistry enabled the RAFT polymerizations to be “frozen” and “unfrozen” under alternating visible light irradiation at room temperature. The emission of TPE was sensitive to the local viscosity change, which allowed the visualization of tricky or crosslinking reactions in real time. Quantitative information, such as molecular weight or extent of gel formation could be easily acquired by “naked eyes” without destroying the reaction system.

Resume : The need of novel efficient fluorophors for the recognition and labeling of biomolecules such as proteins enzymes and cells is one of the most challenging disciplines in modern biosupramolecular chemistry. Our group uses a phenomenon called aggregation induced emission. Molecules with this ability show fluorescence, contrary to normal fluorophores, when aggregated or in the solid state. Recently we found a novel class of facile thioethers with this remarkable characteristic. Our system can be easily modified and was used for the detection of proteins and bacteria. Furthermore we investigated the formation of fluorescent micelles using hydrogen bonding. Currently different compounds were investigated concerning their fluorescence properties. A range of emission in the visible region was found ranging from 430 to 590 nm. Interestingly delayed fluorescence was observed for specific compounds leading to the assumption, that and intersystem crossing to a triplet state occurs leading to a long lived fluorescence state, termed phosphorescence.

Resume : Metabolic glycoengineering of unnatural glycans with bioorthogonal chemical groups and subsequent click reaction with fluorescent probes have been widely used in monitoring various bioprocesses. Herein, we developed a dual-responsive metabolic precursor that could specifically generate unnatural glycans with azide groups on the membrane of targeted cancer cells with high selectivity. Moreover, a water-soluble fluorescent light-up probe with aggregation-induced emission characteristic was synthesized, which turned its fluorescence on upon click reaction with azide groups on cancer cell surface, enabling special cancer cell imaging with low background signal. Furthermore, the probe can generate 1O2 upon light irradiation, endowing its dual role as an imaging and therapeutic agent for cancer cells. Therefore, the concepts of cancer cell specific metabolic precursor cRGD-S-Ac3ManNAz and AIE light-up probe are promising in bioorthogonal labeling and cancer-specific imaging and therapy.

Resume : Organic luminescent materials with aggregation-induced emission (AIE) properties have attracted concentrated interest due to their outstanding properties in solid state. Increasing attention has been paid to single crystals based on AIE molecules for their high thermo-stability, long-range ordering and unique opto-electronic properties. Hence, it is of great importance to design new organic materials via crystal engineering strategies to optimize the molecular stacking and obtain excellent opto-electronic capabilities. Here we present a successful example of achieving high solid state fluorescence efficiency and amplified spontaneous emission (ASE) via cross-dipole stacking based on BDPVB single crystals. Moreover, a novel butterfly-like molecule BDPV2T is presented to show both high fluorescence efficiency and high charge carrier mobility in its J-aggregate single crystals. Apart from these, the protonation and the fluorescence change based on BP4VA crystals has been studied, showing that the fluorescence variety comes from the difference in the aggregation structures. The investigations based on aggregation structures and opto-electronic properties can provide novel insights into developing novel AIE materials.

Resume : The aggregation-induced emission (AIE), conceptually coined in 2001 by our group [1], refers to a unique phenomenon that a kind of luminogens are weakly or non-emissive when molecularly dissolved but induced to emit intensely upon aggregation. The research on AIE has drawn tremendous interests among the scientists worldwide and become one of the hottest research topics in chemistry and materials sciences. Currently, hundreds of low-mass AIE luminogens have been prepared. However, the research on AIE-active polymers, which inherently possess good film-forming ability and amplification effect in sensing, have paid little attention [2]. In this talk, we will first present our recent efforts on preparing AIE-active polymers by our developed alkyne-based click polymerizations [3]. The unique properties and potential applications of resultant polymers, such as photo-cross-linked and fluorescent patterns, high light refractivity, sensitive detection of explosives, will also be reported. Moreover, non-aromatic maleic anhydride-based AIE-active polymers will be presented, and their clusteroluminescence mechanism will also be briefly discussed [4]. This work was supported by the National Natural Science Foundation of China(21788102, 21525417 and 21490571). References: [1] (a) Luo, J.; Xie, Z.; Lam, J. W. Y.; Cheng, L.; Chen, H.; Qiu, C.; Kwok, H. S.; Zhan, X.; Liu, Y.; Zhu, D.; Tang, B. Z. Chem. Commun. 2001, 37, 1740. (b) Mei, J.; Leung, N. L. C.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z.Chem. Rev. 2015, 115, 11718. [2] (a) Qin, A.; Lam, J. W. Y. Tang, B. Z. Prog. Polym. Sci. 2012, 37, 182. (b) Hu, R.; Leung N. L. C.; Tang, B. Z. Chem. Sov. Rev. 2014, 43, 4494. [3] (a) Li, H.; Sun, J. Z.; Qin, A.; Tang, B. Z. Chinese J. Polym. Sci. 2012, 30, 1. (b) Yao, B.; Hu, T.; Zhang, H.; Li, J.; Sun, J. Z.; Qin, A.; Tang, B. Z. Macromolecules, 2015, 48, 7782. (c) Dong, W.; Wu, H.; Chen, M.; Shi, Y.; Sun, J. Z.; Qin, A.; Tang, B. Z. Polym. Chem. 2016, 7, 5835. [4] Zhou, X.; Luo, W.; Nie, H.; Xu, L.; Hu, R.; Zhao, Z.; Qin, A.; Tang, B. Z. J. Mater. Chem. C. 2017, 5, 4775.

Resume : In the present paper, we will discuss a class of molecules that are not phosphorescent in deaerated fluid solution and whose room temperature phosphorescence is switched on either by rigidification of the matrix or by metal complexation.[1] The hexathiobenzene chromophore is not phosphorescent in fluid solution and becomes highly phosphorescent upon crystallization or rigidification of the matrix.[2] Analogously, the terpyridine appended persulfurated chromophore is non-emissive in solution, but displays a green phosphorescence emission in the solid state due to the restriction of intermolecular motion in the solid state.[4] Upon addition of Mg2+ to an air-equilibrated THF solution of the hexaterpyridine ligand, a supramolecular polymer is formed, in which a Mg2+ ion is coordinated by two terpyridine units of two different molecules. The reduced mobility of the organic moiety in the polymeric structure is reflected by the appearance of a bright phosphorescence with band shape very similar to that of the ligand in the solid state. The light-harvesting polymeric antenna can be disassembled upon fluoride ions addition, thereby switching off luminescence and offering a new tool for fluoride ion sensing. Current studies are devoted to the use of the hexathiobenzene chromophore for oxygen sensing. [1] Coord. Chem. Rev. 2017, 346, 62; Chem. Commun. 2017, 53, 2081 [2] Dyes Pigm. 2014, 110, 113; J. Mater. Chem. C. 2013, 1, 2717–2724. [3] J. Am. Chem. Soc. 2014, 136, 6395.

Resume : Despite the promising prospect of luminescent liquid crystal, there exists contradicts in the design and synthesis of luminescent liquid crystals: traditional organic luminescent materials usually form aggregation caused quenching (ACQ) in their aggregated state, while molecular aggregation or self-organization is an intrinsic natural process to form mesophases. The combination of luminogens with aggregation induced emission (AIE)characteristics and traditional mesogens may generate high efficiency luminescent liquid crystals and regarded as the most promising method to solve contradicts between luminescence and liquid crystallinity on the standpoint of molecular design. Tetraphenylethene (TPE) is a typical propeller molecule with AIE characteristics and their derivatives by mini-dendron can form high efficiency luminescent liquid crystal phases with hexagonal columnar phase. In this report, TPE and 1,1,2,2-tetrakis(4-(phenylethynyl)phenyl)ethane were modified to form hexagonal columnar luminescent liquid crystals. Because of the mini-dendron, the resultant molecules can form luminescent liquid crystal or molecular liquids even at room temperature. The samples are completely free of ACQ and the quantum yield in liquid crystal state can be up to 49%. DSC, 1D WAXD and other methods were applied to characterize the phase structures of the resultant luminescent liquid crystals. Acknowledgement: The work reported in this paper was supported by National Natural Science Foundation of China (21674065) and Natural Science Foundation of Guangdong Province (2016A030312002). Keywords: aggregation-induced emission, liquid crystal, tetraphenylethene, hexagonal columnar phase

Resume : Our group developed a series of tellurium-based heterocycles that exhibited aggregation-induced phosphorescence at room temperature in the presence of the known quencher oxygen.[1-4] Using a combination of experimental and computational studies, we now show that the phosphorescent character in a series of structurally related bismuth (Bi) heterocycles can be understood using a set of fundamental concepts (related to enhanced spin-orbit coupling from Bi). In addition we demonstrate that emissive bismuth-containing polymers can be prepared along with the attainment of stable red-colored phosphorescence, the latter being a key advancement from the viewpoint of developing next generation bio-imaging materials. [1] G. He, W. Torres Delgado, D. J. Schatz, C. Merten, A. Mohammadpour, L. Mayr, M. J. Ferguson, A. Brown, K. Shankar, E. Rivard, Angew. Chem., Int. Ed. 2014, 53, 4587-4591. [2] G. He, B. D. Wiltshire, P. Choi, A. Savin, S. Sun, A. Mohammadpour, M. J. Ferguson, R. McDonald, S. Farsinezhad, A. Brown, K. Shankar, E. Rivard, Chem. Commun. 2015, 51, 5444-5447. [3] E. Rivard, Chem. Lett. 2015, 44, 730-736. [4] W. Torres Delgado, C. A. Braun, M. P. Boone, O. Shynkaruk, Y. Qi, R. McDonald, M. J. Ferguson, P. Data, S. K. C. Almeida, I. de Aguiar, G. L. C. de Souza, A. Brown, G. He, E. Rivard, ACS Appl. Mater. Interfaces, 2018, DOI: 10.1021/acsami.7b11628.

Resume : Organic fluorescence probes have attracted more and more attention in chemical sensors and bioimaging applications due to their highly sensitive and handy features. However, most of probes with π-conjugated structure suffered from aggregation-caused quenching (ACQ) effect in high-concentration solutions or in the aggregated states, which limited their application in high performance imaging. Aggregation-induced emission (AIE), an opposite photophysical phenomenon to ACQ, is attracting intense interest because of the fundamental importance and promising practical applications. As an important AIEgens, the materials based on excited state intramolecular proton transfer (ESIPT) process attract more attentions in getting high performance imaging. In our groups, a kind of asymmetrical SAA-based compounds were developed and named as “s-SAA”. Their preparing process usually exhibited facile synthetic procedures and low cost purification from commercial raw materials. Excitingly, these materials can selectively target and accumulate in cellular LDs, and locate at lysosome of cells after inserting morpholine. Additionally, their behaviors of identifying and discriminating special bacteria or fungi are developed in further, which could not only provide more valuable information for this dynamic process in visual monitoring, but also be benefit of the development of therapeutic mechanism and pharmacology.

Resume : Precisely targeted transportation of long-term tracing regent to nucleus with low toxicity is one of the most challenging concerns in revealing the cancer cell behaviours. In this work, a dual-targeted peptide-conjugated fluorescent probe was synthesized which contained multi-functional peptide delivery system and fluorescence imaging reagent. Thanks to the good water solubility of peptide, the fluorescence of TCNTP is initially quenched, however, turned on when bind to integrin avb3 and CD13. In terms of precisely targeting protocol, enduring staining effect and benignancy to living cells, the aggregation-induced emission based probe TCNTP has distinct advantages over the conventional dye. As a proof-of-concept, the targeting ability of TCNTP towards integrin avb3 and CD13 in living cells was monitored in real time in co-cultured MDA-MB-231&A375 cells and HT-1080&A375 cells. The colocalization experiments using commercial nucleus imaging dye Hoechst 33258 reveal that TCNTP can serve as a fluorescence light-up nuclear penetrating dye with the aid of functional peptide and AIEgens. Different from Hoechst 33258, the harmless physical internalization processes and indelible cellular staining property guarantee its long-term tumor cell tracing ability. The fluorescence stains of TCNTP are carried to daughter cells with low toxicity and remain visible even after the tenth culture cycle. Moreover, its precisely targeted interaction with organelles may account for the leak-free marking inside the cells. These incredible features make TCNTP a potential vehicle for drug and nucleic acid delivery thus extends the application scope of theranostics.

Resume : Different nanostructures such as spherical micelles, cylindrical micelles and vesicles are accessible by self-assembly of amphiphilic copolymers. The morphologies depend on the chemical structure of the copolymer, hydrophilic/ hydrophobic volume ratio, solvent properties, etc. Moreover, controlling the spatial configuration of amphiphilic polymer is also an interesting strategy to tune the final morphology.TPE-based derivatives show AIE which is in contrast to the ACQ observed for conventional fluorophores. Thus, the combination of polymer nanostructures with TPE provides an innovative approach to bio-imaging and drug bio-distribution. Meanwhile, (Z)- and (E)-isomers could be prepared from bi-functionalized TPE. It will be relevant to study the influence of spatial configuration in morphology and photoluminescence, as well as the effect of photo-stimulated Z/E isomerization on the stability of nanostructures. Here we report on a series of TPE-containing amphiphilic polymers with cholesterol as a hydrophobic block and PEG as the hydrophilic part. The results have revealed that (Z)- and (E)- amphiphilic polymers self-assembled into nanostructures with different morphologies and showed different AIE properties. In addition, we report that the prepared TPE-containing polymersomes could be opened and release encapsulated molecules under UV-illumination. These polymersomes could be potentially used to combine the cell imaging and drug carrier in the same system.

Resume : We have recently reported an “AIEgen” like behavior of a photosynthetic complex (PC) excreted by purple non-sulfur bacteria Rhodobacter capsulatus SB1003 [1]. AIEgens are fluorogen that exhibit aggregation induced fluorescence emission [2]. The PCs which are supposedly porphyrin derivatives show aggregation-induced emission enhancement [3], critical to variations in concentration, temperature, and static magnetic field. The present report shows that the AIEgen like behavior of the PC is drastically altered when the bacterial growth medium contains graphene. The presence of graphene, however, attenuates the temperature or static magnetic field induced aggregation switches as reported in our previous study [1]. Though graphene quenches the fluorescence intensity of the PC, the emission enhancement by PCs become more intense with increasing dose of graphene indicating a gradual increase in the quantum yield of the AIEgen. In the present study, we report the fluorescence enhancement dynamics of the PCs in presence of different types and forms of graphene, as well as the graphene defect density sensitive extent of fluorescence enhancement. We infer that graphene may alter the dynamics of aggregation pattern of the porphyrin rings present in the PC, changing the efficiency of enhanced emission [4]. The sensitivity of this differential amplification to the defect-density of the graphene flakes may be a consequence of this graphene catalyzed porphyrin aggregation. The amplified emission of this AIEgen even at low concentration may be a consequence of aggregation enhancing property of graphene. References: 1. Bose, Anirban, et al. "BistabilityIn Fluorescence From A Purple Non-Sulfur Bacteria." bioRxiv (2017): 132498. 2. Kwok, Ryan TK, et al. "Biosensing by luminogens with aggregation-induced emission characteristics." Chemical Society Reviews 44.13 (2015): 4228-4238. 3. Biel, ALAN J. "Control of bacteriochlorophyll accumulation by light in Rhodobacter capsulatus." Journal of bacteriology168.2 (1986): 655-659. 4. Xu, Yuxi, et al. "Chemically converted graphene induced molecular flattening of 5, 10, 15, 20-tetrakis (1-methyl-4-pyridinio) porphyrin and its application for optical detection of cadmium (II) ions." Journal of the American Chemical Society131.37 (2009): 13490-13497.

Resume : Saponins are a class of naturally occurring bioactive and biocompatible glycosides produced by plants. Saponins are amphiphilic composed of one or more hydrophilic sugar moieties and a lipophilic steroid group. Some saponins such as α-hederin exhibit unique cell membrane interactions. At concentrations above their critical micelle concentration, α-hederin will interact and aggregate with membrane cholesterol to form transient pores in the cell membrane. In this project, we utilized the unique cell membrane permeabilization properties of α-hederin to deliver AIEgens into both mammalian and plant cells. For mammalian cells, we used α-hederin as a micelle to encapsulate and stabilize large red emitting AIE nanoparticles of varying sizes. We were able to successfully deliver these nanoparticles into cells in under 5 min. This is around 20x faster than previously reported nanoparticle delivery systems since this delivery method is diffusion rather than endocytosis dependent. We found this method to be biocompatible, inexpensive, ultrafast and applicable to deliver a wide variety of AIEgens into mammalian cells. For plant cells, bioimaging has been a persistent challenge because the cell wall is extremely difficult for most fluorescent probes to traverse. This is a particular issue for AIEgens which has limited their application in plant cell biology. In this study, we developed several techniques to permeabilize the cell wall using saponin allowing AIEgens to enter and stain plant cells. We confirmed the entry of our AIEgen probes by performing a series of plasmolysis experiments. Arabidopsis thaliana was used to demonstrate that our AIEgens could be used to stain a variety of plant tissues including xylem, phloem and meristematic tissues. We found that this method was compatible with both wild type and mutant GFP transgenic Arabidopsis thaliana plants. The photostability and resolution of our AIEgens was higher than that of commercially used dyes like propidium iodide.

Resume : Organic solar cell (OSC) technology has attracted much attention due to its promise as low-cost conversion of solar energy. Despite recent progress, several limitations are holding back OSC development. For instance, best-efficiency OSCs are mostly based on relatively thin (100 nm) active layers. Thick-film OSCs generally exhibit lower fill factors and efficiencies compared to the best thin-film OSCs. Here we report multiple cases of high-performance thick-film (300 nm) OSCs (efficiencies up to 11.7%, fill factors up to 77%). Our simple temperature dependent aggregation control and materials design rules allowed us to develop, within a short time, over twenty polymer:fullerene combinations, all of which yielded higher efficiency than previous state of art devices (~10%). The common structural feature of the three new donor polymers, the 2-octyldodecyl (2OD) alkyl chains sitting on quaterthiophene, causes a temperature-dependent aggregation behavior that allows for the processing of the polymer solutions at moderately elevated temperature, and more importantly, controlled aggregation and strong crystallization of the polymer during the film cooling and drying process. This results in a well-controlled and near-ideal polymer:fullerene morphology (containing highly crystalline, preferentially orientated, yet small polymer domains) that is controlled by polymer aggregation during warm casting and thus insensitive to the choice of fullerenes. This approach can be applied to non-fullerene OSCs. The energy loss from the optical bandgap (Egap) to the open-circuit voltage (Voc) of a solar cell is a simple measure of its effectiveness in generating voltage. For best-efficiency (>10%) organic solar cells (OSCs), the energy loss is typically in the range of 0.85-0.9 eV, while the loss is only 0.4-0.55 eV for other more efficient solar cell systems. High energy loss is one key factor that limits the performance of OSCs. In this paper, we report efficient (9.5%) OSCs with a high Voc of 1.11 V, despite a relatively narrow opti-cal bandgap of 1.66 eV for the absorber. Importantly, the high efficiency and low energy loss were achieved without using the conventional fullerene acceptors, which have dominated OSCs for nearly two decades. The origin of the small energy loss of our non-fullerene OSCs can be attributed to two factors. First, our OSC exhibits a high electroluminescence (EL) quantum efficiency that is comparable to those of inorganic solar cells and that helps to reduce non-radiative recombination loss. Second, the absence of any sub-gap charge transfer (CT) state in our OSC significantly reduces radiative recombination loss. The most striking observation is that the Voc of the blend-based cell is identical to that of the cell based on the pure donor polymer. This indicates that the presence of the non-fullerene acceptor in the blend does not introduce any noticeable energy loss, yet it functions efficiently as an acceptor. These findings create a new avenue of progress toward next-generation OSCs that will move much beyond the limit that has been anticipated before. References: 1. Li, Z., Jiang, K., Yang, G., Lai, J.Y.L., Ma, T., Zhao, J., Ma, W.*, Yan, H.*. “Donor polymer design enables efficient non-fullerene organic solar cells” Nature Communications, (2016), 7, 13094 2. Liu J., Chen S., Qian D., Gautam B., Yang G., Zhao J., Zhang F., Ma W., Ade H., Inganäs O., Gundogdu K., Gao F., Yan, H.. “Fast charge separation in a non-fullerene organic solar cell with a small driving force”. Nature Energy, (2016), 1, 16089 3. Zhao, J., Li, Y., Yang, G., Jiang, K., Lin, H., Ade, H., Ma, W., Yan, H. ”Efficient organic solar cells processed from hydrocarbon solvents. Nature Energy, (2016), 1, 15027 4. Liu, Y., Zhao, J., Li, Z., Mu, C., Ma, W., Hu, H., Jiang, K., Lin, H., Ade, H. and Yan, H., “Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells.” Nature Communications., (2014), 5, 5293

Resume : Recently, AIEgens with various cores and functional groups have been widely developed. However, most of them including the double bonds (C=C, C=N, N=N, etc) showed highly chemical reactivity and low photostability.1 Therefore, it would be favorable to develop new AIEgens with the well-defined structures and stable aromatic cores.2 Quinoline and its derivatives are useful in diverse applications, such as quinine for the treatment of malaria. The luminogens with the quinoline moiety could be potentially explored as both the probes and the biomedicines. Recently, we designed and synthesized a series of triphenylquinoline (TPQ) based luminogens via one-pot multicomponent reaction. All the luminogens are highly emissive in solid states and their AIE characters could be converted by the subtly structural modification . The solid-state quantum yield could further promote to 50 % by incorporating the donor group on one end of the molecule. The intramolecular donor-acceptor interaction allows us to fine tune quantum yields, the emissive colors as well as the molecular packing. We believe TPQ-based AIEgens provides a new platform for the construction of novel organic solid luminogens from both fundamental and practical viewpoints. References: 1. Mei, J.; Leung, N. L. C.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z., 2015, 115, 11718-11940. 2. Jiang, M.; Gu, X.; Kwok, R. T. K.; Li, Y.; Sung, H. H. Y.; Zheng, X.; Zhang, Y.; Lam, J. W. Y.; Williams, I. D.; Huang, X.; Wong, K. S.; Tang, B. Z., DOI: 10.1002/adfm.201704589

Resume : The general mechanism RIM (restriction of intramolecular motion) of AIE originally refers to the enhanced restriction of the molecular motion from a single molecule to its aggregated state. However, RIM can be also realized by making the compound’s structure more rigid through structural modification. According to the RIM mechanism, we expect that a more rigid structure should fluoresce in solution and thus result in non-AIE property. Follow this original speculation and our struggling perseverance to figure out the deep mechanism of AIE, here we combine computational method and ultrafast time-resolved spectroscopy to study a series of TPE derivatives with increased structural rigidity and different AIE properties.

Resume : For the past few years we have been developing structurally simple, easy to make, modular, and tunable hydrazone-based functional materials (e.g., switches, sensors and fluorophores).1 This presentation will deal with our recent advances with these systems, with an emphasis on hydrazone-based fluorescent molecular rotors (viscometers),2,3 and switchable solid-state emitters. Representative references: 1. I. Aprahamian Chem. Commun. 2017, 53, 6674–6684 2. H. Qian, M. E. Cousins, E. H. Horak, A. Wakefield, M. D. Liptak, I. Aprahamian Nature Chem. 2017, 9, 83–87 3. Y. Yang, X. Su, C. Carroll, I. Aprahamian Chem. Sci. 2012, 3, 610–613.

Resume : This study uses a specially designed aggregation-induced emission fluorogen (AIEgen) to in vivo track the dynamics of Hg2+ and MeHg+ in a common species of freshwater zooplankton Daphnia carinata (D. carinata) by two methods, direct Hg2+ absorption and ingestion of Hg2+ contaminated food. The response of D. carinata to Hg2+ and MeHg+ via environment absorption differed distinctly from the response through food intake of Hg2+ contaminated algae Euglena gracilis. Meanwhile, the response of D. carinata to Hg2+ and MeHg+, especially through the food intake are completely different. The D. carinata suffered much higher mortality through direct Hg2+ and MeHg+ absorption than through food intake with significantly different mortality mechanisms. Fluorescent image analysis showed that the major recipient organs of Hg2+ in D. carinata were the compound eyes and carapace, but not the brain or heart. However, MeHg+ preferred to accumulate in the compound as well the intestine and shell gland. In the first time, the AIEgen provides an easy way to understand the toxicological pathway of the small aquatic organism leading to death under toxic substances.

Resume : Stimuli-responsive functional supramolecular machines and polymers are attracting broad attention.[1] Multicolor photoluminescence, including especially white-light emission, were achieved based on a siingle host-guest supramolecular systems.[2] Room temperature phosphorescence induced by cyclodextrin (CD-RTP) and cucurbituril (CB-RTP) is provided with the advantages of good selectivity, long life, large Stokes shifts and consequently application in the area of molecular recognition. Another supramolecular polymeric hydrogel based on the host-guest recognition between α-CD and α-BrNp polymer is constructed, which can self-heal within only about one minute in natural atmosphere. Moreover, this Stimuli-responsive functional supramolecular machines and polymers are attracting broad attention.[1] Multicolor photoluminescence, including especially white-light emission, were achieved based on a siingle host-guest supramolecular systems.[2] Room temperature phosphorescence induced by cyclodextrin (CD-RTP) and cucurbituril (CB-RTP) is provided with the advantages of good selectivity, long life, large Stokes shifts and consequently application in the area of molecular recognition. Another supramolecular polymeric hydrogel based on the host-guest recognition between α-CD and α-BrNp polymer is constructed, which can self-heal within only about one minute in natural atmosphere. Moreover, this supramolecular polymer system can be excited to engender CD-RTP signals.[3] A pH-switchable molecular shuttle encoded by RTP emission change was also constructed by complexation of CB[7] and 6-bromoisoquinoline derivative. A RTP encoding [2]rotaxane shuttle[4] and photo-responsive supramolecular polymers with morphology adjustment were also developed.[5-6] Amorphous, efficient, room-temperature phosphorescent metal-free polymers were facilely prepared and their applications as encryption ink explored as well.[7] A seriouos of amorphous metal-free room-temperature phosphorescent small cyclodextrin derivative molecules were prepared and there multicolor photoluminescence realized via a host-guest and dual-emission strategy.[8] The construction of these supramolecular shuttles and polymer and their RTP function investigation would be of significant importance for the development of switchable smart materials.[9] References [1]. X. Ma, H. Tian. Acc. Chem. Res.47, (2014), 1971. [2]. Q.-W. Zhang, X. Ma, H. Tian et al. J. Am. Chem. Soc., 138, (2016), 13541. [3]. H. Chen, X. Ma, H. Tian et al. Angew. Chem. Int. Ed, 53, (2014), 14149. [4]. X. Ma et al. Chem. Sci. 7, (2016), 4582. [5]. T. Li, X. Ma, H. Tian et al. Adv. Opt. Mater., 4, (2016), 840-847. [6] R. Sun, X. Ma, H. Tian, Q. Li et al. J. Am. Chem. Soc., 135, (2013), 5990-5993. [7] H. Chen, X. Ma, H. Tian et al. Adv. Opt. Mater., 4, (2016), 1397. [8] D. Li, F. Lu, J. Wang, W. Hu, X.-M. Cao, X. Ma and H. Tian. J. Am. Chem. Soc., (2018), DOI: 10.1021/jacs.7b12800. [9] X. Yao, X. Ma et al.Adv. Opt. Mater., 4, (2016), 1322.

Resume : Thermally activated delayed fluorescence (TADF) has been proposed as a new strategy to achieve a high external quantum efficiency in organic light-emitting diodes (OLEDs). Luminescent organic molecules with a small energy gap (ΔEst) between the lowest excited singlet and triplet states enable nonradiative triplet excitions to convert to emissive singlet excitons, leading to an increase in the fluorescence intensity. In order to realize a small ΔEst, it is necessary to separate the highest molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the molecule. By combining electron-donating and electron-withdrawing units, the HOMO and LUMO distributions can be separated in a molecule. Carborane is a class of boron-clusters, and possesses a strong electron-withdrawing property originating from its three-center two-electron bonds. In this study, we designed and synthesized new carborane-based luminescent molecules. Owing to the strong electron-withdrawing property of the carborane units, these molecules have a small ΔEst and exhibited efficient TADF emissions as well as high photoluminescence quantum yields in their aggregated states. We fabricated OLEDs using these molecules as TADF emitters, which showed high external quantum efficiencies.

Resume : The photophysical process of organic optoelectronic materials has always been the cornerstone of organic electronics, in which the properties and the controllability of excited states are the key factors tuning the performance of materials. Recently, several triplet-related photophysical processes have led to many revolutionary developments to the research area, providing numbers of organic optoelectronic functional materials such as TADF, TTA, and SF. Meanwhile, aggregation-induced emission (AIE), as an intriguing photophysical phenomenon that a series of non-emissive molecules in solutions are induced to emit strongly in the aggregate or solid state coined by Prof Ben Zhong Tang in 2001, provides a new stage for the exploration of practically useful luminescent materials for optical, electronic, energy and biomedical applications. As an efficient triplet promoter, nitrobenzene can transfer singlet states to non-luminescent triplet states through rapid intersystem crossing process. On the other hand, nitrobenzene ring can also provide abundant intermolecular interactions including the weak hydrogen bonds. In this talk, we will firstly investigate the role of nitrobenzene in the construction of novel triplet-involved AIE systems and the development of highly sensitive stimulus response materials.

Resume : This work provides a novel strategy for the construction and characterization of novel luminescent architectures with high efficiency fluorescence and optical activity through self-assembling of aggregation-induced emission (AIE) polymers. By introducing chiral amino acid pendent into AIE scaffolds, we have prepared chiral polytriazole with the backbone of tetraphenylethene (TPE) and amino acid attachment by Cu(I)-catalyzed click polymerization. The chiral polymer products emit weak fluorescence in their good solvent, but show intensive luminescence as nano aggregation suspensions upon addition of water, demonstrating a typical AIE property. By tuning the water content of the poor solvent, the polymer can self-assemble into various nanostructures such as vesicles, “pear-necklace” to helical nanofibers and microfibers. Their self-assembly and morphology transition processes can be observed by fluorescence microscopy, which provides a higher-contrast visualized images that directly correlate the assemblies with their fluorescence. Moreover, this series of polymers also have efficient solid-state emission, excellent optical transparency and good film-forming ability also exhibits aggregation-induced circular dichroism (AICD) and aggregation-induced circularly polarized luminescence (AICPL), demonstrating the great potential for fabricating novel functional materials which have versatile optical and electronic properties with promising applications in optoelectronic devices.

Resume : In this presentation, the synthesis and application of fluoroquinolone-based amidine structures will be described. The amidines were synthesized in good yields under mild conditions using a newly developed cycloaddition approach from electrophilic azides and enamines. The propeller-shaped molecules displayed intriguing physical properties, and were evaluated for their aggregation-induced emission enhancement effects. The fluoroquinolone scaffold resulted in antibacterial activities, and the compounds readily assembled into stable nanoaggregates upon precipitation in water. The nanoaggregates displayed increased luminescence and could be used to both kill and image bacteria. This represents a strategy in the design and development of pure theranostic nanodrugs for combating drug-resistant bacterial infections. The amidine structures also elicited interesting solvatochromic properties, and their emission showed responsiveness to viscosity, polarity and hydrogen-bonding interactions. In particular, these molecules elicited high responses towards guest molecules with hydrogen bond donating ability, a feature that enabled the development of probes to quantify trace amount of analytes in aprotic solvents.

Resume : Nowadays, aggregation-induced emission (AIE) has been a hot research topic. Massive endeavors of scientists were devoted to study the structure-property relationship of low-mass molecules.1 However, the work on AIE-active polymers has been rarely reported.2 Recently, we has established a Ru(II)-catalyzed click polymerization (RuAACP), and 1,4- and 1,5-regioregular polytriazoles (1,4- and 1,5-PTAs) could be produced by simple control of ligands. In this work, using this effective polymerization, we successfully obtained tetraphenylethene (TPE)-containing 1,4- and 1,5-PTAs with similar molecular weights and small variation in the linking manner. It was found that 1,4-PTA exhibited a longer conjugation and redder luminescence compared to its 1,5-PTA counterparts. Thanks to the typical AIE luminogen of TPE moiety, both of 1,4- and 1,5-PTAs showed AIE characteristics. However, they had very different performances when they were used as fluorescent chemosensors to detect Pd2+. 1,5-PTA showed very high sensitivity (Kq up to 587785 L/mol) and selectivity. In contrast, 1,4-PTA doesn’t work. We surmised that the difference coordination ability between 1,5-triazole ring and 1,4-triazole ring with Pd2+ is primary reason.

Resume : Monitoring of biological processes and diagnosis of diseases are important for the physiological functions of living organisms and related to the health. Fluorescent techniques play a great role in recognizing the mechanism of life and pathogenesis of diseases, guiding therapeutic effect in theranostics. The conventional organic fluorophores unavoidably face a problem of aggregation-caused quenching (ACQ), where their fluorescence is quenched at high concentrations due to the formation of strong π-π stacking, leading to quick photo-bleaching for bioimaging. Luminogens with aggregation-induced emission characteristic (AIEgens) could serve as superior agents for biological process monitoring and disease theranostics with the advantages of high brightness, large Stokes shift and excellent photostability compared to commercial dyes. Herein, we synthesized a series of AIEgens as aldose reductase inhibitors to treat Diabetes mellitus. The AIEgens not only could target mitochondrion and aldose reductase for imaging and therapy but also possess the performance of two-photon excitation (from 700 nm to 1000 nm). Two-photon imaging has the merits of a higher 3D resolution, lesser photobleaching, a reduced autofluorescence and deeper penetration in tissue. The AIEgens with the imaging and therapy abilities are beneficial to understanding the mechanism of diseases and directing the drug design for the human health.

Resume : Stereochemistry involves the study of spatial configurations of one molecule and their characteristic properties. This research area has been widely explored due to their potential applications such as asymmetric catalysis, stereoselective synthesis, drug discovery and so on. (Z)- and (E)-isomers of carbon-carbon double bonds represent one class of the most indispensable configurations in stereochemistry. Numerous (Z)- and (E)-derivatives have been exploited to learn their distinct biological roles and pharmic properties in life and material sciences.the development of novel stereoisomers with very different properties is not only helpful to understand biological processes but also expected to create new functional materials. In this study, we employed oligoethylene glycol monomethyl ether (OEG) as polar unit to synthesize amphiphiles of TPE. Pure stereoisomers of OEG-functionalized tetraphenylethene ((Z)-TPEOEG and (E)-TPEOEG) were easily separated by high-performance liquid chromatography (HPLC) and their geometric structures were validated by 2D COSY and NOESY spectroscopies. Both (Z)- and (E)-isomers inherit AIE features of TPE. (Z)-TPEOEG self-assemblies into vesicles while its (E)-counterpart forms micelles in water. Furthermore, the (Z)-isomer exhibits a lower critical solution temperature (LCST) of 39.0 C, but no such behavior was observed for (E)-TPEOEG even at high temperature of 52.0 C. These macroscopic differences are undoubtedly resulted from configuration differences in (Z)- and (E)-TPEOEG. Our findings add families of (Z)- and (E)-derivatives and will guide further construction of AIE materials based on TPE stereoisomers.

Resume : Developing of simple, robust and reliable nucleic acids detection strategy holds tremendous promise for cancers or pathogens’ diagnostic. Here, a versatile “seesaw” strategy was proposed for dual mode detection of nucleic acids with naked eye. In this design, aggregation-induced emission (AIE) based fluorometric assay and gold nanoparticles based colorimetric assay were combined to construct an aqueous “seesaw”, whose balance was determined by the quantity of target nucleic acid. After intergating with hybridization chain reaction (HCR) technique, we achieved a reliable detection of DNA and microRNA from two signal channels with detection limit of 100 fM and 10 nM, respectively. The proposed seesaw strategy that integrates fluorometric and colorimetric assay holds great potentials for nucleic acids point-of-care testing.

Resume : Photosensitizers (PSs) are materials that are capable of generating reactive oxygen species (ROS) that causing oxidative damage to target cells or tissues. So far, the structure-property relationship of PSs is not fully established. In this work, we demonstrate a facile method for improving the ROS generation of the materials. The common small molecular aggregation-induced emission (AIE) dyes with donor-acceptor structure displaying low ROS generation can be changed into highly efficient PSs by making them into conjugated polymers. The resulting polymers can induce efficiency cancer cell death both in vitro and in vivo under light irradiation. Meanwhile, the brightness of the AIE polymers made it act as fluorescence probe for accurate diagnosis of tumor in vivo. Our approach provided a facile and efficiency theranostic combined photodynamic therapy and fluorescence imaging with AIE characteristics.

Resume : Luminogens with aggregation-induced emission (AIE) characteristics have attracted much attention because of their broad applications in optoelectronics, bioprobes and environmental monitoring. Amongst them, red/near-infrared AIE luminogens are especially desired in the field of biological applications, but most of them are far from satisfactory. Herein, a series of novel red/near-infrared fluorophores based on an electron-withdrawing benzo[1,2-b:4,5-b']dithiophene 1,1,5,5-tetraoxide (BDTO) core are synthesized and characterized and their crystallographic, spectroscopic, electrochemical properties are investigated. These BDTO-based fluorophores possess both AIE and hybridized local and charge-transfer (HLCT) characteristics, and show greatly red-shifted emission wavelength, enhanced emission efficiency, enlarged two-photon absorption cross section and increased reactive oxygen species (ROS) generation efficiency in comparison with the dyes based on benzo[1,2-b:4,5-b']dithiophene (BDT). The nanoparticles (NPs) with strong red/near-infrared emission are fabricated using BDTO-based fluorophores, and their biological applications are systematically investigated. The results reveal that the NPs show good performance in targeted photodynamic ablation of cancer cells and in vivo two-photon fluorescence imaging of blood vessels in mouse brain

Resume : Organoboron complexes are among the most important fluorescent dyes. Especially, boron dipyrromethene (BODIPY) dyes have gained prominence. BODIPY dyes can be tuned the fluorescence wavelength from blue to near infrared by modifying the substituent groups or annulation of an aromatic ring in solution. However, most BODIPY dyes lose their excellent fluorescence properties in the solid-state. BODIPY dyes generally exhibit limited fluorescence in the solid-state due to their high planarity, which easily leads to π–π interactions between neighboring fluorophores, and their small Stokes shift (5–20 nm, in most cases) which causes serious self-quenching at high concentration. Therefore, considerable effort has been devoted to the development of novel fluorescent boron complexes. Recently, we reported boron complexation using ligands based on quinone, pyrimidine, pyrazine, benzothiazole, pyridomethene and squarylium. Some synthesized boron complexes exhibited aggregation-induced emission properties. In this conference, we will report the aggregation-induced emission properties of boron complexes.

Resume : RNA interference (RNAi) is emerging as one of the most powerful technologies for sequence-specific suppression of genes and presents a great potential in biomedical applications ranging from gene analysis to diseases therapeutics. Considering the drawbacks of current siRNA delivery vehicles in biocompatibility and efficacy, the development of high efficient siRNA delivery nanocarrier associated with self-monitoring functionality is of great significance. Herein, by taking advantage of aggregation-induced emission luminogens (AIEgens), a new generation of inorganic/organic core@shell nanocarrier that allowed efficient delivery and real-time monitoring of siRNA in living cells had been developed. The phenoxy and amine groups in the nanocarriers behaved as a proton-absorber and promoted the release of siRNA from endosome. The AIE properties provided a unique fluorescence imaging modality for long-term tracking and intracellular localization of siRNA during transfection. Comparing to the commercial siRNA transfection reagents, the present system displayed a pretty higher efficiency and reproducibility in terms of intracellular transfection and target down regulation with a much lower cytotoxicity.

Resume : A novel AIE-acitive TPA-CN-TPE polyamide was successfully synthesized and introduced as electret layer in the organic phototransistor-type memory device. The strong green PL emitted from TPA-CN-TPE under UV illumination could increase the memory window of the device ranging from 20 to 42 V caused by photo-induced charges from pentacene layer. The high photoresponsivity and photosensitivity of the resulted devices manifest great potential for multinary data storage and photodetector within single device. With the significant photo-induced charge trapping in the TPA-CN-TPE electret layer, the device reveals a high DR up to 14 bits. Therefore, this facile concept offers the efficient fabrication of highly UV-responsive phototransistors for UV sensors and nonvolatile memory devices on data storage application.

Resume : Lipid droplets (LDs) are highly associated with obesity, diabetes, inflammatory disorders and cancer. Therefore, direct and selective LDs visualization and monitoring in biological samples is particularly important. Reliable two-photon dye at ultra-low concentration for specific LDs imaging in live cells and live tissues has rarely been reported. Here, we synthesized a new family of AIEgens, namely NAPCNs for specific two-photon LDs staining. Their photophysical properties were investigated by one- and two-photon fluorescence spectroscopy, DFT calculations and single-crystal X-ray diffraction. The NAPCNs exhibited large Stokes shift (>110 nm), high solid fluorescence quantum yield of up to 30%, good two-photon absorption cross section (45–100 GM at 860 nm), high biocompatibility and good photostability. They could specifically stain the LDs at ultra-low concentration (50 nM) in 15 min. In vitro and ex vivo two-photon imaging of LDs in live cells and live mice liver tissues were successfully demonstrated. In addition, selective visualization of LDs in live mice liver tissues could be achieved at the depth of about 70 μm. The NAPCNs showed higher hydrophobicity than the commercial LDs dyes, which were responsible for their high specificity to target the LDs. These excellent photophysical and two-photon imaging properties render the present molecules as promising candidates for investigating LDs-associated physiological and pathological processes in biological samples.

Resume : In past three decades, organic light-emitting devices (OLED) have made great progresses in material preparation, process optimization and relevant theoretical researches, where the aromatic conjugated material plays an important role. As a representative, anthracene and its heterocyclic derivatives (such as phenothiazine, acridine and so on) have a pretty good performance in device efficiency owing to their high quantum yield and good transfer capacity, which origin from their relative planar and rigid chemical structure. While, recent studies have shown that the distribution of molecular dipoles exhibited a significant effect on their performance. Taking anthracene as an example, its dipole has two orientation (long and short axis effect) in the two-dimensional space, leading to the increase of energy gap between T1 and T2, their RISC process is tuned in high energy level and their exciton utilization ratio would be affected. Here, we choose the acridone (a class of anthracene heterocyclic derivatives) group as core, and construct multidirectional dipole distribution by introducing the donor (TPA or Cz) and accepter (Cyano group). After employing CT and RIR mechanism, one-armed and two-armed products are prepared, whose dipole orientations locate two and three form in 2D space respectively. A series of spectral characterization and device results display that one-armed products give good performance and controllable regulatory properties. By locking the RIR process in different pattern, its importance is reflected in improving the efficiency of the solid state and improving the utilization of the exciton.

Resume : Cerium (Ce) shows a great potential application in biocatalysis, drug release and biomedical science.1 As a result of its enormous usage, there is a growing demand to study the environmental, medical and biological effects of cerium. To date, the photometric detection for Ce ion is still rarely reported. Recently, luminogens with aggregation-induced emission (AIE) properties have attracted great interests. It is practically non-emissive or faintly emissive in the solution state, but becomes highly emissive as aggregates in poor solvents. Due to this unique effect, a wide range of AIEgens have been developed and utilized in detecting metal cations.2 In our research, we synthesized a tetraphenylbutadiene (TPBD) derivative with two carboxyl groups as substituents (TPBD-COOH), which remarkably exhibited the AIE property. TPBD-COOH as a novel fluorescent probe was designed for the detection of Ce3+. It shows a real-time and time-stable detection of Ce3+ with a detection limit of 2.27 μmol/L. The interaction mechanism was deducted by DLS analysis, XRD analysis, NMR and FT-IR measurements, suggesting that the Ce3+ probably binds the carboxyl group on TPBD-COOH. Moreover, Ce4+ could also be distinguished and detected in the presence of 1,2-propanediol as a reducing agent. 1. T. Pirmohamed, J. M. Dowding, S. Singh, B. Wasserman, E. Heckert, A. S. Karakoti, J. E. S. King, S. Seal, W. T. Self, Chem. Commun. 2010, 46, 2736-2738. 2. J. Mei, N. L. C. Leung, R. T. K. Kwok, J. W. Y. Lam, B. Z. Tang, 2015, 115, 11718-11940.

Resume : Aggregation-​induced emission (AIE) materials have recently been intensively explored for bioimaging applications owing to their outstanding optical feature compared with conventional organic materials. Near-infrared fluorescence has superior features in vivo, such as deep penetration, weak auto-fluorescence, minimal photo-bleaching. Thus, far red/near-infrared aggregation induced emission luminogens are in high demand. Here, we report a high efficient Far red/Near-infrared fluorescent compounds with aggregation-induced emission (AIE) properties. A new near-infrared aggregation-induced emission luminogen, namely NZA2TPE, with high brightness, good biocompatibility and excellent photostability was synthesized for bioimaging. NZA2TPE exhibits a high photoluminescence quantum yield of 78.7 % in hexane (650 nm) and 21.5% in the solid state (685 nm). It has been fabricated into nanoparticles for bioimaging. Different methods have been used to encapsulate the dye molecules to generate stabilized nanoparticles. The size of the nanoparticles can be controlled in the range from 20 nm to 150 nm. The emission maximum falls at 685 nm to 693 nm. DSPE-PEG-folate (DSPE-PEG-FA) based NZA2TPE NPs have been prepared through a simple one-pot self-assembly route, which shows high brightness and low cytotoxicity. More importantly, it exhibited specific targeting for cancer cells. Such fluorescent nanoparticles are expected to be potential for an array of biological applications.

Resume : Pure organic room-temperature phosphorescence (RTP) materials have attracted much attention recently with its growing reports in aggregation-induced emission field. The development of organic RTP compounds remain to be a challenging work due to the instability of triplet excited states at room temperature, which has long been limited to cryogenic and inert conditions. Herein, a series of dibenzofuran derivatives was designed and synthesized through facile Friedel-Crafts acylation reaction. The compounds generally contain one or two carbonyl groups on the dibenzofuran core with an unsymmetric or symmetric structures, and halogen atoms are also introduced in the structures, which is designed to promote the intersystem crossing from S1 state to T1 state. These dibenzofuran derivatives are non-emissive or weakly emissive in their solution or amorphous state. Their crystals, however, generally exhibit dual emission of fluorescence and room-temperature phosphorescence, demonstrating typical crystallization-induced emission phenomenon. Photophysical study suggests that their phosphorescence lifetime can be up to 69 ms and their phosphorescence quantum yield can be up to 4.3%. One of the dibenzofuran derivatives without any halogen atom emits white light under UV irradiation. The prompt and delayed photoluminescence spectra suggest the coexistence of a fluorescence emission at 437 nm, and a phosphorescence emission at ~575 nm, suggesting that it's a single molecular fluorescence/phosphorescence hybrid white light emitter.

Resume : Imaging-guided therapy is a promising strategy in biomedical research. In contrast to the existing bioimaging dyes with aggregation-caused quenching effect, luminogens with aggregation-induced emission characteristics (AIEgens) are better candidates for such application. AIEgens show no emission in the solution state but they are induced to emit intensely by aggregate formation. This feature is exact opposite of ACQ and is beneficial to biomedical application. Deep tissue penetration and high spatial resolution become the ultimate goals for IGT. In this regard, the combination of two-photon excitation and NIR emissive dyes help achieve low autofluorescence, low scattering, deep tissue penetration and high spatial resolution. However, NIR AIEgens that can be excited by two-photon are limited and their synthetic routes are quite complicated. In this work, three NIR-emissive AIEgens were facilely synthesized. All the compounds were characterized by 1H NMR, 13C NMR and HRMS spectroscopies. They show absorption maximum at 520560 nm and emit at 680720 nm. Their specificity to target the lipid droplets is demonstrated in cancer cell line. Two-photon imaging of lipid droplets using these dyes are carried out to achieve deep tissue imaging.

Resume : Purely organic materials with aggregation-induced delayed fluorescence (AIDF) exhibit tremendous potential in fabricating high-performance nondoped organic light-emitting diodes (OLEDs) with low efficiency roll-off. Herein, we have developed a new series of AIDF materials with unsymmetrical D-A-D′ structures, where benzoyl serves an electron acceptor, and 10H-phenoxazine and fluorene derivatives as electron donors. These AIDF emitters can be readily synthesized so that they are applicable for the large-scale commercial applications. Interestingly, they exhibit weak emissions without delayed fluorescence in THF solutions but strong emissions with obvious delayed components upon aggregate formation or in neat films, exhibiting the typical AIDF characteristics. Through combining the photophysical measurements and theoretical calculations, this phenomenon can be ascribed to the suppression of internal conversion channels of the first singlet excited state in the aggregate state, which is induced by restriction of intramolecular motion. Due to the unique AIDF properties, their nondoped OLEDs achieved excellent EL performance of up to 14.3%, 41.7 cd A-1 and 45.0 lm W-1 with extremely negligible efficiency roll off at 1000 cd m-2.

Resume : Fluorophores, whose emission can be activated and switchable by light irradiation, are of paramount importance for single-molecule localization microscopy and are promising for constructing super-resolved images in nanometer scale.[1,2] Herein, we report a new fluorescent turn-on photoactivatable fluorophore, abbreviated as o-TPE-ON+. This luminogen undergoes an unconventional photocyclodehydrogenation reaction in the presence of light irradiation, turning it from a weak fluorophore to a strong emitter (c-TPE-ON+) with high quantum yield, long excitation wavelength of above 500 nm and fluorescence insensitive to pH or environmental change. o-TPE-ON+ not only is highly cell permeable and biocompatible but also can spontaneously undergo blinking in the absence of any additives. The feasibility of applying o-TPE-ON+ to super-resolution imaging of mitochondrion is demonstrated in both fixed and live cells under physiological conditions, which enables the investigation of the dynamics of mitochondria in nanometer scale. It is anticipated that the strategy described here will open up new avenues to develop more photoactivatable small organic fluorophores for super-resolution imaging under physiological condition with organelle specifity.

Resume : A conjugated polymer showing aggregation-induced emission (AIE) characteristic was prepared, and displays relatively high selectivity towards viable cells over apoptotic and dead cells as well as microbes. This polymeric probe show tremendous advantages over low-mass organic probes, such as better biocompatibility, higher selectivity and stronger tracing ability. We figure out that the negatively charged side-chain of the polymer and the endocytosis process play crucial roles in this discrimination behavior. As far as we know, this is the first example that using AIE polymer to identify viable mammalian cells with high specificity. This work is expected to serve as a powerful tool for precise cancer therapy.

Resume : Aggregation-induced emission (AIE) materials has proved to be efficient fluorescent dyes as photosensitizers in photodynamic therapy, owing to their strong aggregated state emission, high photostability, and high ROS production yield. Herein, a series of electron-deficient 7H-naphtho[1,8-gh]quinolin-7-one derivatives with diphenylamino group and tetraphenylethene moiety were designed and synthesized with efficient aggregated state emission. The strong electron donor and electron acceptor structures endow these compounds red or near-infrared emission with the emission maxima up to 658 nm. Among them, 3-(diphenylamino)-7H-naphtho[1,8-gh]quinolin-7-one with emission maximum at 635 nm enjoys the highest emission quantum efficiency of 22.8% at solid state, which is also the smallest compound in terms of volumn size and molecular weight. This compound can be enternalized in HeLa cell in lysosome and possess high photostability, which also shows good photo-induced reactive oxygen species (ROS) production efficiency. Under the irradiation of visible white light with a light intensity of 1.67 mW·cm-2 for 20 min, cell viability decreased dramatically with the treatment of the dye and significant photo-induced cytotoxicity was observed with the IC50 value to be 6.2×10-7 M. Moreover, deep tissue penetration down to 280 μm depth is realized through two-photo imaging of mouse brain vessels with the AIE compounds under the excitation of 1040 nm laser.

Resume : Nanoparticles composed of amphiphilic copolymers are widely used in bioimaging and drug delivery areas. Among them, polymersomes have attracted special attention due to their vesicular cell- and virus-mimicking structures. Recently, luminogens with aggregation-induced emission (AIE) characteristics have emerged as a new class of fluorescent materials for organelles imaging and drug delivery monitoring. The combination of AIE luminogens (AIEgens) with polymer nanostructures, especially polymersomes, will provide innovative approaches to cell/tissue imaging and to in vivo study of drug distribution. Polypeptoids have a N-substituted pseudo-peptide structure, and have been rediscovered with interesting properties and great potential in biomedical field. By applying the ring-opening polymerization of N-thiocaboxyanhydride (NTA), polypeptoids could be conveniently prepared with controlled manners. In our study, novel amphiphilic block copolypeptoids based on polysarcosine and poly(allyl glycine) are synthesized with AIEgens attached on side chains through click chemistry. Polymer nanoparticles with AIE properties are prepared and their stimuli-responsivity are analyzed in detail.

Resume : Aggregation-induced emission (AIE) is a kind of photophysical phenomenon associated with chromophore aggregation. The concept of AIE was coined by Prof. Benzhong Tang and coworkers in 2001. In a typical AIE process, non-emissive luminogens are induced to emit by the aggregate formation. The AIE luminogens (AIEgens) are practically non-emissive when they are molecularly dissolved in a solvent as the free intramolecular rotations of molecules serve as a relaxation channel for the excited states to deactivate. However, in the aggregated state, such rotational motions are restricted due to the physical constraint. This blocks the non-radiative pathway and thus the molecules become highly fluorescent. By utilizing the state-dependent emission property, high photostability, and facile functionalization of AIEgens, many innovative AIE bioprobes have been developed as AIEgen conjugates and ultra-bright AIE nanoparticles in biomedicine for long-term theranostics. On the other hand, polymers have shown promising applications as nanocarriers of therapeutic drugs/proteins, and imaging/contrast agents due to their unique core–shell nanostructures. The aqueous self-assembly of amphiphilic polymers often afford micelles, rod, vesicles, and some unknown nanostructures. The hydrophobic moieties of the assembles can solubilize hydrophobic drugs and serve as a repository. Furthermore, the presence of hydrophilic parts in polymer such as poly(ethylene oxide) can effectively protect hydrophobic cargoes against the external milieu, minimizing non-specific protein adsorption during blood circulation and capture by the reticuloendothelial system (RES). Since the size of polymer nanocarriers is typically above the threshold for kidney filtration, polymeric delivery systems demonstrate prolonged circulation duration following intravenous injection and possess passive targeting capabilities to tumor tissues via the enhanced permeability and retention (EPR) effect. Among many parameters of polymers, polymer topology has shown potentially significant impact on the in vitro/in vivo trafficking and fate of nanocarriers and the formulated drugs. Typically, previous work has demonstrated that branched polymers exhibit remarkably extended blood circulation based on magnetic resonance imaging (MRI). However, further exploration in biomedicine concerning the polymer topology, distinct topology-regulated self-assembly, blood circulation, biodistribution, pharmacokinetics and the theranostic capability is immature. Herein, it is extremely meaningful to study AIE-featured polymer delivery systems with optimized topology for long-term theranostics in biomedicine, which takes advantage of the high photostability and long-term monitoring potency of AIEgens as well as the smart fabrication of drug-tethered polymers with flexible topology.

Resume : Near-infrared (NIR)-absorbing organic small molecules hold great promise as the phototheranostic agents for clinical translation by virtue of their intrinsic advantages such as well-defined chemical structure, high purity, and good reproducibility. However, most of the currently available ones face the challenges in varying degrees in terms of photothermal instability, and photobleaching/reactive oxygen nitrogen species (RONS) inresistance, which indeed impair their practical applications in precise diagnosis and treatment of diseases. Herein, we developed highly stable and biocompatible organic nanoparticles (ONPs) for effective phototheranostic application by design and synthesis of an organic small molecule (namely TPA-T-TQ) with intensive absorption in the NIR window. The TPA-T-TQ ONPs with no noticeable in vivo toxicity possess better capacities in photothermal conversion and photoacoustic imaging (PAI), as well as show far higher stabilities including thermal/photothermal stabilities, and photobleaching/RONS resistances, when compared with the clinically popularly used indocyanine green. Thanks to the combined merits, the ONPs can serve as an efficient probe for in vivo PAI in a high-contrast manner, which also significantly causes the stoppage of tumor growth in living mice through PAI-guided photothermal therapy. This study thus provides an insight into the development of advanced NIR-absorbing small molecules for practical phototheranostic applications.

Resume : The distribution and movement of organelles in living cells are closely related with their biological functions. Photoactivatable fluorescent probes with a high spatiotemporal imaging ability are ideal tools for organelle study. However, conventional photo-caged pro-fluorogens suffer from drawbacks of aggregation-caused quenching (ACQ) and low photoactivation efficiency. We have developed a series of photoactivatable pro-fluorogens, which can selectively accumulate in organelles and further undergo photooxidative dehydrogenation reaction to afford the aggregation-induced emission fluorogens (AIEgens). The photoactivatable AIE pro-fluorogens for organelle-specific imaging has significant advantages in terms of simple preparation, excellent photoactivation efficiency, and high spatiotemporal resolution.

Resume : Luminogens with thermally activated delayed fluorescence (TADF) can harvest singlet and triplet excitons to afford high electroluminescence (EL) efficiencies for OLEDs. However, most doped OLEDs of TADF emitters encounter a knotty problem of swift efficiency roll-off as luminance increases. In this work, we developed a series of novel luminogens with aggregation-induced delayed fluorescence (AIDF), which can easily settle the above challenge and realize nearly nil efficiency roll-off. They are composed by a carbonyl core and various electron-donating groups. Their structures and properties are investigated by crystallography, theoretical calculation, steady and transient spectroscopies, etc. They possess eximious emission with prominent delay fluorescence component in neat films, and can facilely solve the concentration or aggregation-caused emission quenching and/or exciton annihilation problem of those current TADF emitters. The nondoped OLEDs based on the neat films of these AIDF luminogens exhibit lowered turn-on voltages and increased luminance with respect to the doped OLEDs. Thanks to the excellent exciton utility, the nondoped devices furnish remarkable electroluminescence efficiencies of up to 72.9 cd A‒1, 81.8 lm W‒1 and 22.6%, and negligible efficiency roll-off. To the best of our knowledge, the present nondoped devices are the most efficient and stable devices reported so far.

Resume : Nanoparticles can be made resposive to stimuli, such as the adsorption of proteins etc. In case such stimulus causes aggregation there is an effect on the particle, for example on plasmonic, fluorescence, or magnetic properties. This concept might be used in the future for in vivo sensing. References: M. Carril, D. Padro, P. del Pino, C. Carrillo-Carrion, M. Gallego, W. J. Parak, "In situ detection of the protein corona in complex environments", Nature Communications 8, 1542 (2017). W. G. Kreyling, A. M. Abdelmonem, Z. Ali, F. Alves, M. Geiser, N. Haberl, R. Hartmann, S. Hirn, K. Kantner, D. Jimenez de Aberasturi, G. Khadem-Saba, J.-M. Montenegro, J. Rejman, T. Rojo, I. Ruiz de Larramendi, R. Ufartes, A. Wenk, W. J. Parak, "In vivo integrity of polymer-coated gold nanoparticles", Nature Nanotechnology 10, 619–623 (2015).

Resume : Organic/Polymeric materials possessing aggregation-induced emission (AIE) property have attracted ever broad interests from both academic and industrial circles. One of the main-streams for AIE-relating researches is to find novel AIE-active materials with expected properties. Pyridinyl is a functional group commonlly used in modifying the structure and property of organic functional materials. Here, we report our recent investigation on the versatile properties of pyridinyl-functionalized tetraphenylethene (TPE). Due to the conjugation of pyridinyl groups with the AIE-active flurogen of TPE, the derivatives demonstrate, the following properties: (i) Intrinsic AIE behaviour since the presence of TPE unit. (ii) Acid responsive fluorescence emission as pyridinyl is an organic base or proton acceptor. (iii) Strong solvatochromism due to the electron-withdrawing nature of the pyridinyl group. (iv) Evident mechanochromism due to the enlarged and flexible structure of the pyridinyl-functionalized TPE. (v) Self-assembling behaviour because pyridinyl is a receptor for hydrogen-bond formation. (vi) Generation of cationic species upon the formation of pyridinium salt. (vii) Formation of luminescent metal-organic frameworks owing to the coordination capacity of the pyridinyl groups.

Resume : Photochromic compounds display a reversible molecular structure transformation, which result in significant absorption spectra change upon the stimulation of ultraviolet (UV) and visible light. The special optical property makes them have high potential application in optical data storage, chemical sensors, optical switches, ophthalmic lenses, security documents[1]. The fluorescent photochromic organic material is one of themost active areas. However, the fluorescence emission of most organic fluorescent molecules is quenched when it is in high concentrations or aggregated state, which is known as aggregationcaused quenching (ACQ) and commonly observed in the conventional organic dyes. Evidently, ACQ is a harmful photophysical effect in terms of light emission and practical applications，Excitedly, Tang's group discovered a new type of organic fluorescent molecules showing the aggregation-induced emission (AIE) properties in 2001, which is different from the conventional ACQ phenomenon[2]. This interesting phenomenon provides a new way to design organic fluorescent materials with more effective emission in aggregated state. Here in，we designed and synthesized a series of new fluorescent photochromic materials with aggregation induced emission[3-6].They exhibited good AIE properties, non-emissive in the solution but good fluorescent emission in the aggregate or solid state. Meanwhile, their fluorescence intensities almost exhibit good photochromic properties when upon irradiation with UV light and visible light. They showed potential application for external stimuli-responsive materials, such as photoswitch, bioprobe and so on.

Resume : Aggregation-induced emission (AIE) can be rationalized via the restriction of intramolecular rotation in the involved molecules and/or excimer formation. The enhanced luminescence recently observed for aggregates of fluorenone derivatives are a clear example of this phenomenon. In order to have deeper insights on these mechanism and on their interplay we have applied use a recently developed excited-state electrostatic embedding [2] to study AIE in 2,7 diphenylfluorenone crystals. Our results suggest that the observed enhanced emission can be easily rationalized by considering a single-molecule process, in which the field induced by the crystalline environment at the excited state enhances the relative brightness of otherwise poorly emissive states, resulting in both enhanced fluorescence and a substantial bathochromic shift in comparison with emission in dilute solution [3]. References [1]Yuan, M.-S.; Wang, D.-E.; Xue, P.; Wang, W.; Wang, J.-C.; Tu, Q.; Liu, Z.; Liu, Y.; Zhang, Y.; Wang, J. Fluorenone Organic Crystals: Two-Color Luminescence Switching and Reversible Phase Transformations between Π−π Stacking-Directed Packing and Hydrogen Bond-Directed Packing. Chem. Mater. 2014, 26, 2467−2477. [2]Wilbraham, L.; Adamo, C.; Labat, F.; Ciofini, I. Electrostatic Embedding To Model the Impact of Environment on Photophysical Properties of Molecular Crystals: A Self-Consistent Charge Adjustment Procedure. J. Chem. Theory Comput. 2016, 12, 3316−3324. [3] Presti,D.; Wilbraham, L, Targa, C.; Labat, F.; Pedone, A.; Menziani, M.C.; Ciofini, I.; Adamo, C. Understanding Aggregation-Induced Emission in Molecular Crystals: Insights from Theory J. Phys. Chem. C 2017, 121, 5747−5752

Resume : A series of dinuclear Ir( III )complexes have been synthesized and shown to exhibit both aggregation induced emission (AIE) and piezochromic luminescence (PCL) behaviour. We employed highly flexible Schiff base ligands to construct an AIE-active molecule with strong intermolecular interactions between the aryl rings in the aggregated or crystal state. The multifunctional dinuclear Ir(III) complexes are applied in second-level anti-counterfeit trademark, data encryption device and reversible monitoring device for volatile organic compounds.

Resume : Tetraphenylethene (TPE)-based functional metallosupramolecular through coordination-driven self-assembly have proven to be novel scaffolds to construct various fluorescent materials with aggregation-induced emission (AIE) properties. For example, from TPE-based ligands, a series of metal-organic frameworks (MOFs) with AIE properties have been successfully prepared. Afterwards, Stang group successfully constructed a library of TPE-based discrete organoplatinum(II) metallosupramolecular structures with rich optical properties.Recently, based on our previous research on well-defined functional metallacycles, we have expanded our related investigation towards the construction of TPE-based functional materials. Firstly, we successfully prepared a new family of tris-TPE metallacycle via coordination-driven self-assembly, which could aggregate into the ordered linear nanostructures upon threading the heparin through the metallacycles driven by multiple electrostatic interaction, thus allowing for the detection of heparin at the clinical dosage level. In addition, with the aim to build novel water-soluble TPE-based functional metallosupramolecular materials, we have developed a facile approach for synthesis of fluorescent supra-amphiphilic star polymers possessing well-defined metallacycles as the core via post-assembly polymerization. The obtained amphiphilic fluorescent star polymers presented high dispersibility in water and good biocompatibility, thus allowing for bioimaging applications.

Resume : Fluorescent molecules are sensitive to their steric environments, such as local viscosities, aggregations, binding to macromolecules and encapsulations to cavities. These fluorescent molecular systems have recently been emerged as versatile imaging/detection materials. Fluorescent molecular rotors and aggregation-induced emission luminogens (AIEgens) are representative types of steric-environment sensitive fluorophores, as they exhibit sizable changes in fluorescence intensity, lifetime, and spectral shape in response to subtle steric restrictions. Commonly used fluorophores undergo straightforward emission from an excited state, while fluorescent molecular rotors and AIEgens are designed to involve much more complicated relaxation paths. Their surrounding steric environments affect the excited-state equilibrium and/or internal conversion rate. Several AIEgens possess strong donor-acceptor structures to utilize their excited-state equilibrium, often called the “twisted intramolecular charge transfer” (TICT) state. In sterically restricted environments, interconversion between a weakly fluorescent TICT state and highly fluorescent states (e.g. locally excited (LE) or “coplanar” ICT states) is hampered, resulting enhanced fluorescence intensity and deformed spectral shape. On the other hand, inhibition of internal conversion, by restricting intramolecular motions (RIM), is the principal design strategy of AIEgens. Fast internal conversion can be induced by vibration in solution, but is suppressed in solid states. Since isomerizable double bonds and multiple aryl-aryl bonds often dominate such vibrations, these structures have been adopted in many AIEgens. In spite of recent advances in the area, it is still challenging to develop fluorophores from simple aromatic hydrocarbons that are sensitive to steric environments. Simple aromatic hydrocarbons, do not undergo any excited-state reaction within lower singlet manifolds, and introduction of either donor or acceptor on these hydrocarbons do not improve this problem. Therefore, development of novel strategies that modifies the potential energy surfaces (PESs) of the aromatic hydrocarbons to undergo excited-state reactions becomes critical. In this presentation, we report the steric-environment sensitivity of fluorescence of 9,10-bis(N,N-dialkylamino)anthracenes (BDAAs) in experimentally and theoretically. A new design strategy to tune simple aromatic hydrocarbons as efficient aggregation-induced emission (AIE) luminogens and molecular rotors is proposed. For a variety of BDAAs, prominent Stokes shifts and efficient solid-state fluorescence were observed. Calculations on BDAA-methyl suggested that in the ground state (S0) conformations, the pyramidal amine groups are highly twisted, so that their lone-pair orbitals cannot conjugate with the anthracene π orbitals. Fluorescence takes place from the S1 minima, in which one or both amine groups are planarized. The stability of the S1 excited state minima as well as destabilization of the S0 state is the origin of large Stokes shift. Experimental measurement of the non-adiabatic transition rate suggests that para disubstitution by dialkylamino (or strongly electron-donating) groups is a key for fast internal conversion. Minimum energy conical intersection (MECI) between S1 and S0 states was found to have a Dewar-benzene like structure. Although this can be reached efficiently in liquid phase for fast internal conversion, a large amplitude motion is required to reach this MECI, which is prohibited in the solid state and caused efficient AIE. This strategy is used to find experimentally that naphthalene analogues are also efficient AIE luminogens. The flexibility of alkyl chains on amino groups is also found to be important for allowed charge-transfer transition. Thus, three points (1. highly twisted N,N-dialkylamines, 2. substitution at the para positions 3. with flexible alkyl groups) were proposed for activation of small aromatic hydrocarbons. We also present some application of the AIEgens.

Resume : π-Bonds connected with aromatic rings were generally believed as the standard structures for constructing highly efficient fluorophores. Materials without these typical structures, however exhibited only low fluorescence quantum yields and emitted in the ultraviolet spectral region. In this work, three molecules, namely bis(2,4,5-trimethylphenyl)methane, 1,1,2,2-tetrakis(2,4,5-trimethylphenyl)ethane and 1,1,2,2-tetraphenylethane, with non-conjugated structures and isolated phenyl rings were synthesized and their photophysical properties were systematically investigated. Interestingly, the emission spectra of these three molecules could be well extended to 600 nm with high solid-state quantum yields of up to 70%. Experimental and theoretical analyses proved that intramolecular through-space conjugation between the “isolated” phenyl rings played an important role for this abnormal phenomenon.

Resume : Crime scene investigators (CSI) never stop being in need of novel forensic methods and technologies to help them detect and collect more useful information in crime scene, including but not limited to latent bloodstain, fingerprint, etc. Since the late 1970s, advancements in the technology of luminescence detection have greatly aided the hunt for many types of forensic evidence. Currently, aggregation-induced emission luminogens (AIEgens) have been widely applied in biological imaging, medical diagnosis and therapy, and optoelectronic materials, but rarely appear in forensic science. Bloodstains are traditionally detected and enhanced by a chemiluminescent reagent, luminol, but the observation window, namely emitting time, is comparatively short, often on the order of a few seconds. Thus, we propose to use Tetraphenylethene maleimide (TPE-MI), an AIEgen that can specifically react with thiol group in human serum albumin from blood and become yellow-emissive under ultraviolet light, to detect and enhance bloodstain in both visible and invisible type. The method is rapid and sensitive which can provide CSI with long-lasting emissive and high-resolution bloodstain visualization. As another example apart from bloodstain detection, fingerprints also play irreplaceable role in crime scene to identify criminal suspects. Here, we combine cyanoacrylate fuming with a series of AIEgens to design a novel fluorescent fingerprint development method. Even third-level minutiae (sweat pore and ridge edges) information can be clearly collected from a latent fingerprint. Besides these work, there remains large potential for AIEgens in forensic applications.