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A facile approach for the synthesis of hyperbranched polyacrylates is developed. Tetraphenylethene-containing di- and tetra-acrylates are synthesized by esterification of bis(4-hydroxylphenyl) diphenylethene and tetrakis(4-hydroxylphenyl) ethene with acryloyl chloride and polymerized using azobisisobutyronitrile in refluxing THF, furnishing high molecular weight (M-w up to 87 100) polyacrylates with glycogen-like structures and closed-loops in nearly quantitative yields (isolation yield up to 99%). All the polymers are soluble in common organic solvents and are thermally stable with degradation temperatures up to 357 degrees C under nitrogen. Whereas the monomers and polymers are nonemissive or faintly emissive in solutions, they become strong emitters in the aggregated state, demonstrating a phenomenon of aggregation-induced or enhanced emission. The emission of the monomer and polymer spots on the TLC plates can be turned "off" and "on" continuously and reversibly by wetting and dewetting processes by vapors of organic solvents. The polymers are photosensitive and UV irradiation of their films through copper masks crosslinks the exposed parts, generating fluorescent negative photoresist patterns. The polymers possess good optical transparency and show high refractive indices (RI = 1.6825-1.5653) in a wide wavelength region (400-1700 nm) with low chromatic dispersion. The emission of the polymer nanoaggregates can be quenched efficiently by picric acid with large quenching constants up to 2.07 x 10(5) M-1, suggesting that they are sensitive fluorescent sensors for explosive detection. The fluorescent polymers become weakly emissive when hydrolyzed under appropriate conditions, implicative of their utility in controlled drug delivery.

A strategy towards efficient mechanochromic luminogens with high contrast is developed. The twisted propeller-like conformations and effective intermolecular interactions not only endow the luminogens with AIE characteristics and high efficiency in the crystalline state, but also render them to undergo conformational planarization and disruption in intermolecular interactions upon mechanical stimuli, resulting in remarkable changes in emission wavelength and efficiency.

The detection of nucleic acids, such as DNA and RNA, plays a significant role in genetic engineering, forensics, and bioinformatics. Traditional nucleic acid probes are mainly intercalators, which are potential mutagens, or groove binders that show high preference only for double-stranded DNA. We herein present two versatile fluorescent probes for nucleic acid detection and visualization. The nonemissive tetraphenylethene derivatives (TTAPE) are induced by DNA/RNA to emit, thereby showing a novel phenomenon of aggregation-induced emission (AIE). This kind of light-up property enables the quantitation and visualization of nucleic acids in aqueous solution and electrophoretic gels, respectively. The cationic TTAPE can penetrate cells with a compromised plasma membrane easily but cannot enter live cells with an intact membrane, thus making them useful for the differentiation between dead and live cells. On account of the high binding affinity to DNA, TTAPE can selectively label the chromosomes and nuclei in fixed cells, which provides a simple and fast method for the observation of cell mitosis. Owing to their AIE characteristics, the dye molecules aggregate in DNA-rich regions and exert appreciable quantum efficiency as well as superior photostability.

Tracking the dynamics of mitochondrial morphology has attracted much research interest because of its involvement in early stage apoptosis and degenerative conditions. To follow this process, highly specific and photostable fluorescent probes are in demand. Commercially available mitochondria trackers, however, suffer from poor photostability. To overcome this limitation, we have designed and synthesized a fluorescent agent, tetraphenylethene-triphenylphosphonium (TPE-TPP), for mitochondrial imaging. Inherent from the mitochondrial-targeting ability of TPP groups and the aggregation-induced emission (AIE) characteristics of the TPE core, TPE-TPP possesses high specificity to mitochondria, superior photostability, and appreciable tolerance to environmental change, allowing imaging and tracking of the mitochondrial morphological changes in a long period of time.

In this work, we report the synthesis and photophysical studies of a new luminogen, A3MN, a diaminomaleonitrile-functionalized Schiff base. A3MN is aggregation-enhanced emission (AEE)-active: the emission of A3MN is enhanced with the aggregate formation. A3MN also possesses twisted intramolecular charge transfer (TICT) properties, showing noticeable solvatofluorochromism. Interestingly, the crystals of A3MN are nonemissive; the defect areas of the crystal, however, are highly emissive, as confirmed by spectroscopic methods and confocal microscopy. By taking advantage of this defect sensitive feature, a "turn-on" type of mechanofluorochromic material is developed, the emission of which is significantly enhanced under pressure or shear force. The detection limit reaches 0.1 Newton owing to its "turn-on" nature. Such defect-induced emission also renders A3MN sensitive to various kinds of mechanical actions, including hitting, friction, sculpture, and ultrasonic vibration.

A heteroatom-containing organic fluorophore 1-(4-pyridinyl)-1-phenyl-2-(9-carbazolyl)ethene (CP3E) was designed and synthesized. CP3E exhibits the effect of intramolecular charge transfer (ICT) caused by the donor-acceptor interaction between its carbazole and pyridine units. Whereas it emits faintly in solution, it becomes a strong emitter in the aggregated state, demonstrating the phenomenon of aggregation-induced emission (AIE). Its emission can be reversibly switched between blue and dark states by repeated protonation and deprotonation. Such behaviour enables it to work as a fluorescent pH sensor in both solution and the solid state and as a chemosensor for detecting acidic and basic organic vapors. Analyses by NMR spectroscopy, single-crystal X-ray diffraction and computational calculations suggest that the change in electron affinity of the pyridinyl unit and molecular conformation of CP3E upon protonation and deprotonation is responsible for such sensing processes.

The luminescent liquid crystals (LLCs) are expected to solve the conflicts between the aggregation caused quenching and the requirement of aggregation or self-organization for LCs. Herein, we developed a new strategy of applying aggregation-induced emission (AIE) phenomenon to the molecular design of LCs towards LLCs. In this report, a calamitic liquid crystal based on tolane with AIE characteristics was successfully synthesized and the chemical structure was characterized by H-1, C-13 NMR, and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) high-resolution mass spectra. The fluorescence behavior was studied by fluorescence spectroscopy and the liquid crystal phase behaviors were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM). The crystal structure was obtained by X-ray diffraction crystallography with P1 space group. Results demonstrated that the sample was AIE active and the LC phases sequence during cooling was nematic, smectic C and smectic B phase.

The aryl-substituted pyrrole derivative, 4-(2,5-diphenyl-1H-pyrrol-1-yl)benzoic acid (TPPA), was found to have a controllable fluorescence in the solid state due to its propeller-shaped molecular design and adjustable molecular packing. Melding a carboxylic acid unit with triphenylpyrrole turned the typical aggregation-induced emission (AIE) luminogen into a luminogen that only emits intensely in a certain aggregation form-i.e., when it is crystallized from dimethyl formamide (DMF). A thermal responsive solid material was developed by exploiting this property. Its fluorescence remained almost unchanged at relatively low temperature (<70 degrees C) but was greatly quenched when the temperature reached similar to 85 degrees C. Based on thermal analysis and microscopic investigations, this distinct quenching effect was attributed to the thermal volatilization of DMF. The DMF loss in the crystal lattice inevitably loosened the molecular packing, thus opening a non-radiative relaxation pathway to quench the fluorescence. The rapid response (less than 30 s), high selectivity (loss of fluorescence at >85 degrees C), good reversibility and solvent-free procedure make TPPA a thermo-responsive material for use in temperature monitoring devices.

Biotin-decorated fluorescent silica nanoparticles (FSNPs) were successfully fabricated by a sol-gel reaction of silole-functionalized siloxane followed by a sequential reaction with tetraethoxysilane, (3-aminopropyl) triethoxysilane and biotin. The FSNPs were uniformly sized, spherical in shape and monodispersed. While their silole precursor was non-emissive in solution, the suspension of the FSNPs emitted strong green light upon photoexcitation due to the aggregation-induced emission characteristics of the silole aggregates in the hybrid nanoparticles. Morphology study and cell viability, trypan blue exclusion, Annexin V-FITC/PI apoptosis and ROS generation assays showed that the FSNPs showed low toxicity to living cells. The FSNPs worked as fluorescent visualizers for selective imaging of the cytoplasm of tumor cells with over-expressed biotin receptors. The fluorescent nanoparticles were lastingly retained inside the living cells, thus enabling long-term tumor cell tracking over multiple passages and quantitative analysis of tumor cell migration.

Fluorescent self-assembled organogels are interesting supramolecular soft materials with polymer-like structures and have received particular attention due to their fascinating properties and promising practical applications. However, most planar pi-conjugated gelators are highly emissive in the solution state but become weak emitters when self-assembled. Recently, a novel phenomenon of aggregation-induced emission (AIE) has drawn increasing research interest and has been the subject of numerous investigations. This intriguing finding paves a new way for creating fluorescent organogels by utilizing gelators with AIE characteristics. This review focuses on the recent advances in fluorescent organogels with gelation-enhanced emission features. Various kinds of low molecular weight gelators consisting of typical AIE luminogens, conventional planar chromophores, and photoactive molecules are introduced and the mechanisms for the emission enhancement are discussed.

Fluorescence-based techniques have found wide applications in life science. Among various luminogenic materials, fluorescent nanoparticles have attracted much attention due to their fabulous emission properties and potential applications as sensors. Here, we describe the fabrication of fluorescent silica nanoparticles (FSNPs) containing aggregation-induced emission (AIE) luminogens. By employing surfactant-free sol-gel reaction, FSNPs with uniform size and high surface charge and colloidal stability are generated. The FSNPs emit strong light upon photoexcitation, due to the AIE characteristic of the silole aggregates in the hybrid nanoparticles. The FSNPs are cytocompatible and can be utilized as fluorescent visualizer for intracellular imaging for HeLa cells. © 2013 Springer Science+Business Media New York.

Acetylenic polymers are a group of specialty materials with novel properties. In this paper, recent progress in the development of functional acetylenic polymers is summarized. These polymers are synthesized through different polymerization approaches such as Sonogashira polycoupling, decarbonylative chloroarylation polyaddition, and polycyclotrimerization. Efforts in the development of new monomers and catalyst exploration as well as reaction optimization have lead to a large quantity of linear and hyperbranched polymers with high molecular weights and good processability. The polymer functionalization is realized by incorporating functional units into the monomer structures, which endow the resulting polymers with fascinating properties such as aggregation-induced emission, optical nonlinearity, light refractivity, photosensitivity, photopatternability, redoxactivity, and magnetism.

Triphenylene-containing acetylenes with one or three methylene units as spacers and the corresponding mesogen-jacketed liquid crystalline polyacetylenes (MJLCPAs) were designed and synthesized, the mesomorphic properties and phase behaviors of the monomers and novel side-chain liquid crystalline polymers were investigated. The monomers [HC C(CH2)(m)C18H6(OC6H13)(5); m = 1, 3] are prepared by consecutive etherization, coupling, and etherization reactions, and the chemical structures were confirmed by mass spectroscopy and H-1/C-13-NMR. The phase behaviors of the monomers were investigated by differential scanning calorimetry (DSC), polarized light microscopy (PLM), and wide-angle X-ray diffraction (WAXD). The results show that both of the monomers form a hexagonal columnar liquid crystal phase at room temperature. The monomers are polymerized using [Rh(nbd)Cl](2) as catalyst and producing soluble polymers in the yields of 55% and 52%, respectively. The chemical structures and phase behaviors of the two polymers are characterized and evaluated by IR, NMR, TGA, DSC, and WAXD analyses. Both of the two polymers show enhanced thermal and chemical stability with thermal decomposition temperatures up to higher than 340 degrees C due to the protection of the "jacketed effect" of the side-chain triphenylenes wrapped around the rigid polyacetylene main-chain. The polymers adopt a columnar shaped structure and self-organized into hexagonally packed columnar phase. The relative electron density maps of the columnar structure are also reconstructed.

The emission of pyrrole-substituted benzoic acid can be repeatedly switched between the dark and bright states in the solid state by chemical fuming and heating processes, enabling it to work as a rapid sensitive fluorescent sensor for primary amine detection., Zhao, Na, HKUST. zhaona@ust.hk

Tetraphenylethene (TPE) is an archetypal luminogen that exhibits a phenomenon of aggregation-induced emission (AIE), while carbazole is a conventional chromophore which shows the opposite effect of aggregation-caused quenching (ACQ) of light emission in the condensed phase. Melding the two units at the molecular level generates a group of new luminescent materials that suffer no ACQ effect but depict high solid-state fluorescence quantum yields up to unity, demonstrative of the uniqueness of the approach to solve the ACQ problem of traditional luminophores. All the TPE-carbazole adducts are thermally and morphologically stable, showing high glass-transition temperatures (up to 179 degrees C) and thermal-degradation temperatures (up to 554 degrees C). Multilayer electroluminescence devices with configurations of ITO/NPB/emitter/TPBi/Alq(3)/LiF/Al are constructed, which exhibit sky blue light in high luminance (up to 13 650 cd m(-2)) and high current and external quantum efficiencies (up to 3.8 cd A(-1), and 1.8%, respectively). The devices of the luminogens fabricated in the absence of NPB or hole-transporting layer show even higher efficiencies up to 6.3 cd A(-1) and 2.3%, thanks to the good hole-transporting property of the carbazole unit.

By employing a new synthetic strategy, a series of oligomers and a polymer composed of different number of tetraphenylethene and triphenylamine units was designed and synthesised. The optical physics properties and electroluminescence behaviours were studied comparatively. All the molecules demonstrate an aggregation-induced emission (AIE) phenomenon and bear very high quantum yields in the solid state. The emission wavelengths and quantum efficiencies alternate with the change of the molecular configurations and achieve their maximum at the largest oligomer. The thermal stabilities also become higher along with the increase in the molecular weight. The molecules have suitable HOMO levels that match the work function of the indium tin oxide (ITO) anode. They can act as both light-emitting and hole-transporting materials in OLEDs. Thus the present strategy combines the intrinsic emissive nature of AIE materials and the good hole-transport capability of aromatic amines, thereby achieving a win-win for both optical and electrical properties. Glowing recommendation: A series of oligomers and a polymer composed of different numbers and configuration of tetraphenylethene and triphenylamine units have been synthesised. Their optical and electroluminescence behaviours were studied systematically. All the molecules demonstrate aggregation-induced emission (see figure) and have very high quantum yields in the solid state. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Melding a benzothiazolium unit with tetraphenylethene generates a new hemicyanine luminogen with aggregation-induced emission characteristics; the luminogen exhibits crystochromism and its solid-state emission can be repeatedly tuned from yellow or orange to red by grinding-fuming or grinding-heating processes due to the transformation from the crystalline to the amorphous state and vice versa.

The 1,3-dipolar cycloaddition of azides and active internal alkynes has been well studied, but is rarely utilized as a tool for polymer preparation. In this work, an efficient polymerization route is developed. Polycycloaddition of diazide (4) and bis(benzoylethynyl)-benzenes and -butane (3) at elevated temperature has produced the first examples of soluble 1,4,5-trisubstituted polytriazoles PI with satisfactory molecular weights (Mw up to 16 400) in excellent yields (up to 98.6%). All the obtained polymers are thermally stable, losing merely 5% of their weights at temperatures higher than 367 degrees C. They exhibit higher refractive indices than some commercial plastics and can be crosslinked upon UV irradiation to generate a 3D photopattern with high resolution. The metal-free feature of such a methodology offers a facile tool to prepare functional materials free from the contamination of metal species.

Luminescent materials with efficient solid-state emissions are important for the advancement of optoelectronics. Recently, a new class of propeller-like luminogenic molecules with aggregation-induced emission (AIE) characteristics has drawn increasing research interest. Among them, tetraphenylethene (TPE) is an archetypal luminogen with a simple molecule structure but shows a splendid AIE effect. Utilizing TPE as a building block, an effective strategy to create efficient solid-state emitters is developed. In this feature article, we review mainly our recent work on the construction of luminogenic materials from TPE and present their applications in organic light-emitting diodes. The applicability of the synthetic strategy and the utility of the resulting materials are demonstrated. © The Royal Society of Chemistry 2012.

Fluorescence enhancement by graphene oxide (GO) is reported, a surprising result as graphene and GO are widely considered as highly efficient fluorescence quenchers. Enhancement of aggregation-induced emission of silole fluorophores (in DES in the figure) in hydrophobic nanoparticles is demonstrated under certain concentration conditions, notably low GO concentration. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A series of tetraphenylethene-containing BODIPYs with emissions from visible to near-IR and large Stokes shifts up to 142 nm have been designed and synthesized. They show solvatochromic fluorescence and can be utilized as fluorescent visualizers for intracellular imaging.

In this work, we address a mechanistic issue on AIE process and correct a long-held misconception on stilbene photoluminescence. E-Z isomerisation has been generally recognized as the cause of emission quenching in stilbene solutions. A natural question arisen from this common belief is whether suppression of E-Z isomerisation by aggregate formation in a stilbenic fluorogen system is responsible for its AIE phenomenon. Monitoring of the structural change of a stilbene derivative named 1,2-diphenyl-1,2-di(p-tolyl)ethene by NMR during UV irradiation reveals that the E-Z isomerisation is not involved in its AIE process under the normal photoluminescence spectral measurement conditions. © 2012 The Royal Society of Chemistry.

A 3-silolene derivative, 2,2,5,5-tetrakis(dimethylsilyl)-1,1-dimethyl-3,4-diphenyl-3-silolene (TDMSHS), is first synthesized and characterized by X-ray diffraction crystallography and spectroscopic methods. Hydrosilylation polymerization of TDMSHS with 1,1-dimethyl-2,5-bis(4-ethynylphenyl)-3,4-diphenylsilole in the presence of Karstedt's catalyst generates a stereoregular silole-containing hyperbranched poly(silylenevinylene) (hb-SPSV) with a high molecular weight ($\textbackslash{}overline{M}_{\textbackslash{}rm w}$ = 146 000, $\textbackslash{}overline{M}_{\textbackslash{}rm w}$/$\textbackslash{}overline{M}_{\textbackslash{}rm n}$ = 1.5) in high yield (approximate to 95%). hb-SPSV exhibits excellent thermal stability and strong fluorescence, and the emission of its aggregates in aqueous mixture can be quenched efficiently by picric acid with large quenching constants KSV up to 414400 M-1.

Amyloid fibrillation of proteins is associated with a great variety of pathologic conditions. Development of new molecules that can monitor amyloidosis kinetics and inhibit fibril formation is of great diagnostic and therapeutic value. In this work, we have developed a biocompatible molecule that functions as an ex situ monitor and an in situ inhibitor for protein fibrillation, using insulin as a model protein. 1,2-Bis[4-(3-sulfonatopropoxyl)phenyl]-1,2- diphenylethene salt (BSPOTPE) is nonemissive when it is dissolved with native insulin in an incubation buffer but starts to fluoresce when it is mixed with preformed insulin fibril, enabling ex situ monitoring of amyloidogenesis kinetics and high-contrast fluorescence imaging of protein fibrils. Premixing BSPOTPE with insulin, on the other hand, inhibits the nucleation process and impedes the protofibril formation. Increasing the dose of BSPOTPE boosts its inhibitory potency. Theoretical modeling using molecular dynamics simulations and docking reveals that BSPOTPE is prone to binding to partially unfolded insulin through hydrophobic interaction of the phenyl rings of BSPOTPE with the exposed hydrophobic residues of insulin. Such binding is assumed to have stabilized the partially unfolded insulin and obstructed the formation of the critical oligomeric species in the protein fibrillogenesis process. © 2011 American Chemical Society.

Rational combination of aggregation-induced emission active luminogens and mesogens generates high solid-state efficiency luminescent liquid crystals, thus resolving the problem of aggregation-caused quenching normally occurs in the fabrication of luminescent mesomorphic films. © 2012 The Royal Society of Chemistry.

In organic light-emitting devices, materials with efficient electron-transporting properties, are essential. In this report, oxadiazole-containing tetraphenylethene TPE-Oxa is synthesized and its optical physics and electronic properties are investigated. The dye is almost nonluminescent when molecularly dissolved in solutions, but becomes highly emissive when aggregated in poor solvents or fabricated as thin films in the solid state. A quantum yield of unity has been achieved in its solid thin film. Inherited from the oxadiazole component, the dye molecule enjoys low-lying electronic band energies. Benefiting from the good electron-transporting and hole-blocking properties of the dye, the two-layer OLED devices using TPE-Oxa as both light-emitting and electron-transporting materials show superior performance, i.e., lower turn-on voltage, higher brightness and efficiencies, to the devices of typical configuration with a dedicated electron-transporting layer. © 2012 The Royal Society of Chemistry.

The self-assemblying behaviors of L-alanine methyl ester-containing polyphenylacetylene (PPA-Ala, in Chart 1) were investigated upon the evaporation of its solvent on mica and on air/water interfaces. The introduction of chiral amino acid attachments to the polyphenylacetylene backbone induced a helical conformation of the backbone, which was stabilized by various noncovalent interactions, especially hydrophobic effect and hydrogen bonds. The helicity of the polymer was further amplified in its higher-order self-assemblies as the formation of helical fibers on the surface of mica upon natural evaporation of its THF solution. By LB technique, the polymer chains were guided to form ordered parallel ridges and highly aligned, with their helical conformation still remaining. The reorganization of the chiral polymer chains on air/water interface was associated with the additional hydrophobic effect of PPA-Ala on an air/water interface. The polymer backbones had to adopt different arrangements to minimize their contact with water, and this adjustment led to the formation of aligned polymer ridges under proper surface pressure.

Triphenylamine (TPA)-based conjugated hyperbranched poly(aryleneethynylene)s (PAEs), hb-P1/2, hb-P1/3, and hb-P1/4, were synthesized with high molecular weights and good solubilities through Sonogashira coupling reactions. These PAEs exhibited outstanding thermal stabilities and different emission behaviors. Tetraphenylethene (TPE)-containing hb-P1/2 fluoresced faintly in THF, although its light emission was enhanced by aggregate formation in aqueous media or in thin films, thereby exhibiting an aggregation-induced emission-enhancement (AIEE) effect. Whereas 1,1,2,3,4,5-hexaphenylsilole (HPS)-bearing hb-P1/3 showed no significant change in emission intensity with increasing water content in aqueous media, hb-P1/4, which consisted of TPAfluorenone donoracceptor groups, presented almost identical absorptions, but both positive and negative solvatochromic emissions in various solvents. A superquenching effect was observed in the picric-acid-detection process by using nanosuspensions of hb-P1/2. All of the polymers possessed good film formability. UV irradiation of the thin films induced simultaneous photobleaching and cross-linking, thus making them applicable in the fabrication of 2D and 3D patterns. Furthermore, the polymer films also showed high refractive indices, which were tunable upon exposure to UV light.

A facile route for the synthesis of luminescent and light refractive polymers is proposed. Silole-containing diyne and halogenated tetraphenylethene derivatives are synthesized and their coupling reactions furnish poly(arylene ethynylene)s with high molecular weights in high yields. All of the polymers are soluble and film-forming and possess a high thermal stability. They emit strong green lights when their solutions and nanoparticle suspensions are photoexcited. The polymers show high refractive indices with low chromatic dispersions. Their RI values can be modulated and their thin films can be crosslinked using UV irradiation, generating negative photoresist patterns.

Hydrosilylation polymerizations of 1,1-dimethyl-2,5-bis(4-ethynylphenyl)-3,4-diphenylsilole with aromatic silylhydrides including 1,4-bis(dimethylsilyl)benzene, 4,4'-bis(dimethylsilyl) biphenyl, 2,5-bis(dimethylsilyl) thiophene, and 2,7-bis(dimethylsilyl)-9,9-dihexylfluorene in the presence of Rh(PPh3)(3)Cl catalyst in refluxed tetrahydrofuran afford a series of silole-containing poly(silylenevinylene)s. Under optimum condition, the alkyne polyhydrosilylation reactions progress efficiently and regioselectively, yielding polymers with high molecular weights (M-w up to 95,300) and good stereoregularity (E content close to 99%) in high yields (up to 92%). The polymers are processable and thermally stable, with high decomposition temperatures in the range of 420-449 degrees C corresponding to 5% weight loss. They are weakly fluorescent in the solution state but become emissive in the aggregate and film states, demonstrating their aggregation-enhanced emission characteristics. The explosive sensing capabilities of the polymers are examined in both solution and aggregate states. The emissions of the polymers aggregates in aqueous mixture are quenched more efficiently by picric acid in an exponential pattern with high quenching constants (up to 27,949 L mol(-1)), suggesting that the polymers aggregates are sensitive chemosensors for explosive detection. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 2265-2274, 2012

A novel approach for creating efficient solid-state emitters is proposed. In this approach, various polyaromatic hydrocarbon groups are attached to tetraphenylethene, generating a series of luminogens that possess aggregation-induced emission characteristics. These luminogens are highly emissive in the solid state, with emission efficiencies equaling unity. High-performance OLEDs using these luminogens as light-emitting layers are fabricated, exhibiting efficiencies up to 5.6 lm W -1, 7.3 cd A -1, and 3.0 %. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-assembly of fluorescent functional materials has attracted increasing interest in the fabrication of optoelectronic and biological nanodevices. Tetraphenylethene (TPE) is a typical dye molecule with aggregation-induced-emission (AIE) characteristics. Melding TPE carrying triple-bond functionality with diazide-containing biphenyl through "click'' chemistry generates AIE-active luminogens [1,1'-biphenyl]- 4,4'-diyl bis(6-(4-(4-(1,2,2-triphenylvinyl)phenyl)-1H-1,2,3-triazol-1-yl) hexanoate) [1(5)] and [1,1'-biphenyl]-4,4'-diyl bis(11-(4-(4-(1,2,2-triphenylvinyl)phenyl)-1H-1,2,3-triazol-1-yl) undecanoate) [1(10)] with solid state efficiencies up to unity. Slow addition of dilute THF solutions of 1(m) (m 5, 10) into nonsolvents such as n-hexane and water yields self-assembled white wooly solids. TEM and SEM observations reveal the (helical) nanofibrous structure of the aggregates. Upon cooling from their concentrated hot solutions, 1(m) readily precipitate. Meanwhile, they can also form gels at high concentrations. Both precipitates and gels of 1(m) exhibit structures similar to those of the aggregates formed in nonsolvents. These results indicate that 1(m) can facilely self-assemble into high emission efficiency (helical) nanofibers, thus paving the way for their optoelectronic and biological applications.

Luminogenic molecules [(TPE)3 (1), TPE-C = C-TPE-C = C-TPE (2), and TPE-C≡C-TPE-C≡C-TPE (3)] and their polymers P1-P3 are constructed from tetraphenylethene (TPE) building blocks in high yields by Suzuki, Witting, and Sonogashira coupling reactions. All the compounds are soluble and enjoy high thermal stability, losing little of their weights when they are heated to 290-528 °C under nitrogen or 288-436 °C in air. Analyses by UV spectroscopy and cyclic voltammetry as well as theoretical calculations show that the conjugation of the luminophores is in the order of 2 > 3 > 1, P2 > P3 > P1, and P1-P3 > 1-3. All the molecules and polymers are weakly emissive in solutions. They, however, become strong emitters in the aggregate state with fluorescence quantum yields up to 90%. Both 1-3 and P1-P3 exhibit the feature of aggregation-enhanced two-photon excited fluorescence. Large two-photon absorption cross sections (up to ∼900 GM) are observed in the nanoaggregates of the polymers. Thin solid films of the polymers show high refractive indices (RI = 1.7649 - 1.6873) in a wide wavelength region of 400-1700 nm, high modified Abbé numbers (v D′ up to 3436), and low optical dispersions (D′ down to 2.9 × 10-4). The light emissions of the polymers can be quenched exponentially by picric acid with large quenching constants, suggesting that they can be utilized as efficient chemosensors for explosive detection.

Aggregation-induced emission (AIE) is a newly developed phenomenon that is exactly opposite to the aggregation-caused emission quenching effect observed with some conventional luminophores. The AIE phenomenon was first realized in propeller-like small molecules and now has extended to polymeric systems. In this review, we summarize the recent progress on the preparation of luminogenic polymers with AIE or aggregation-enhanced emission (AEE) characteristics, which are generally prepared by attaching AIE-active luminogens, such as tetraphenylethene and silole, as pendants to the polymer backbones or utilizing them as skeletons for main chain polymers. An AIE phenomenon was observed in succinic anhydride-containing nonconjugated polymers bearing no luminogens, presumably due to the agglomeration of carbonyl groups. The AIE/AEE-active polymers show unique properties, such as emission superquenching, high and tunable light refractivity, and aggregation-enhanced two-photon excited fluorescence, and have found potential applications as fluorescent sensors, biological probes, and active layers for the fabrication of light-emitting diodes. © 2011 Elsevier Ltd. All rights reserved.

In this contribution, we conceptually present a new avenue to construction of molecular functional materials with high performance of circularly polarised luminescence (CPL) in the condensed phase. A molecule (1) containing luminogenic silole and chiral sugar moieties was synthesized and thoroughly characterized. In a solution of 1, no circular dichroism (CD) and fluorescence emission are observed, but upon molecular aggregation, both the CD and fluorescence are simultaneously turned on, showing aggregation-induced CD (AICD) and emission (AIE) effects. The AICD effect is supported by the fact that the molecules readily assemble into right-handed helical nanoribbons and superhelical ropes when aggregated. The AIE effect boosts the fluorescence quantum efficiency (phi(F)) by 136 fold (phi(F), similar to 0.6% in the solution versus similar to 81.3% in the solid state), which surmounts the serious limitations of aggregation-caused quenching effect encountered by conventional luminescent materials. Time-resolved fluorescence study and theoretical calculation from first principles conclude that restriction of the low-frequency intramolecular motions is responsible for the AIE effect. The helical assemblies of 1 prefer to emit right-handed circularly polarised light and display large CPL dissymmetry factors (g(em)), whose absolute values are in the range of 0.08-0.32 and are two orders of magnitude higher than those of commonly reported organic materials. We demonstrate for the first time the use of a Teflon-based microfluidic technique for fabrication of the fluorescent pattern. This shows the highest g(em) of -0.32 possibly due to the enhanced assembling order in the confined microchannel environment. The CPL performance was preserved after more than half year storage under ambient conditions, revealing the excellent spectral stability. Computational simulation was performed to interpret how the molecules in the aggregates interact with each other at the molecular level.

A facile approach to thermally stable and efficient solid-state emitters is proposed. By hooking up tetraphenylethene (TPE) units through aryl linkers under Suzuki coupling conditions, a series of arylene bis(tetraphenylethene)s (TPE-Ar-TPE Ar = 2, 5-dimethyl-1, 4-phenylene, 2, 5-bis(hexyloxyl)-1, 4-phenylene, 1, 5-naphthylene, and 9, 10-anthracenylene) are prepared in satisfactory to high yields (67-96%). These molecules are nonluminescent when dissolved in solutions but become highly emissive when aggregated in poor solvents or fabricated as thin film in the solid state, displaying a phenomenon of aggregation-induced emission. Fluorescence quantum yields of 100% were achieved in the amorphous films of the luminogens. The luminogens exhibit mechano-, vapo-, and thermochromism: their emissions can be repeatedly switched between blue and blue-green colors by simple grinding-fuming and grinding-heating cycles owing to the morphological change from a crystalline to an amorphous state and vice versa. These compounds are thermally stable, losing little of their weight at high temperatures of 421-452°C. All the luminogens are morphological stable with high glass transition temperatures. Multilayer light-emitting diodes with a device configuration of ITO/NPB/dye/TPBi/Alq 3/LiF/Al are fabricated, which emit sky-blue electroluminescence with maximum luminance and external quantum efficiency of 7900 cd mr -2 and 2.1 %, respectively. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Benzene-cored luminogens with multiple triarylvinyl units are designed and synthesized. These propeller-shaped molecules are nonemissive when dissolved in good solvents, but become highly emissive when aggregated in poor solvents or in the solid state, showing the novel phenomenon of aggregation-induced emission. Restriction of intramolecular motion is identified as the main cause for this effect. Thanks to their high solid-state fluorescence quantum yields (up to unity) and high thermal and morphological stabilities, light-emitting diodes with the luminogens as emitters give sky-blue to greenish-blue light in high luminance and efficiencies of 10800 cd m -2, 5.8 cd A -1, and 2.7%, respectively. The emissions of the nanoaggregates of the luminogens can be quenched exponentially by picric acid, or selectively by Ru 3+, with quenching constants up to 10 5 and ∼2.0 × 10 5 L mol -1, respectively, making them highly sensitive (and selective) chemosensors for explosives and metal ions. Benzene-cored luminogens with multiple triarylvinyl units exhibit aggregation-induced emission. The high solid-state fluorescence quantum yields and high thermal and morphological stabilities of such emitters gave light-emitting diodes with sky-blue to greenish-blue light in high luminance and efficiencies. The emission could be quenched exponentially by picric acid, or selectively by Ru 3+, making them highly sensitive (and selective) chemosensors for explosives and metal ions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbazole-containing 1-phenyl-1-alkynes with different spacer lengths [C6H5C C(CH2)(m)Car 1(m) (m = 3, 4, 9), Car = 9-carbazolyl] were synthesised in high yields by consecutive substitution and coupling reactions of n-chloro-1-alkynes. Polymerisation of the monomers was effected by NbCl5- and WCl6-Ph4Sn catalysts, furnishing soluble polymers P1(m) with high molecular weights in high yields. All the polymers were thermally stable, commencing to lose their weights at high temperatures (>= 400 degrees C). Photoexcitation of their THF solutions induced strong blue light emissions with high quantum efficiencies up to 92 %. Multilayer electroluminescence devices with configurations of ITO/P1(m)(:PVK)/BCP/Alq(3)/LiF/Al were constructed, which gave blue light with maximum luminance and external quantum efficiency of 438 cdm(-2) and 0.63 %. UV irradiation of a thin film of P1(4) through a mask oxidized and quenched the light emission of the exposed parts, generating a two-dimensional luminescent photopattern.

Tetraphenylethene-containing diyne (1), named 1,2-bis(4-ethynylphenyl)-1,2-diphenylethene, was synthesized and polymerized by TaBr5 catalyst, affording the hyperbranched polymer hb-P1 with a high molecular weight (M-w up to 157 800) in a nearly quantitative yield. The cyclotrimerization of 1-(4-ethynylphenyl)-1,2,2-triphenylethene was also carried out to give 1,3,5- and 1,2,4-tris[4-(1,2,2-triphenylvinyl)phenyl]benzene (1,3,5-2 and 1,2,4-2) that served as model compounds for structural characterization and properties investigation. The structures of hb-P1 and 2 are characterized by MS, IR, and NMR spectroscopies with satisfactory results. All the molecules and polymer are completely soluble in common organic solvents such as chloroform, toluene and THF. They show high thermal stability with degradation temperatures up to 443 and 446 degrees C, respectively, in nitrogen and air. Whereas their solutions are almost non-emissive or weakly fluorescent, their aggregates in poor solvents and solid powders emit intensely with fluorescence quantum yields up to 81%, demonstrating a novel phenomenon of aggregation-induced or enhanced emission. The unreacted triple bonds on the periphery of hb-P1 allow its thin film to cross-link under UV irradiation, generating well-resolved photopatterns. The hyperbranched polymer can limit harsh laser pulses. Its emission can be quenched efficiently by picric acid in solution and aggregated states with large quenching constants, suggesting that it is a promising fluorescent chemosensor for explosives detection.

9,9-Bis(9-heptyl-3-carbazolyl) fluorenes (BPyBCF, BAnBCF, BTPABCF, and BTPEBCF, where B = Bis, Py = pyrene, C = carbazole, F = fluorene, An = anthracene, TPA = triphenylamine, and TPE = tetraphenylethene) with different chromophoric units at the 2,7-positions are synthesized in moderate to high yields (52-89%) by Suzuki coupling reactions of 9,9-bis(9-heptyl-3-carbazolyl)-2,7-dibromofluorene with the corresponding arylboronic acid and utilized as active layers for the construction of blue organic light-emitting diodes (OLEDs). BPyBCF, BAnBCF and BTPABCF emit intense blue light with high fluorescence quantum yields (ΦF = 75-94%) in solution. However, they exhibit much lower ΦF values (30-61%) in the film state, revealing that aggregate formation has quenched their light emission. On the contrary, BTPEBCF is weakly emissive in solution (ΦF = 0.3%) but becomes a strong emitter (ΦF = 100%) when fabricated into solid film, demonstrating a phenomenon of aggregation-induced emission (AIE). Restriction of intramolecular rotation and suppression of intermolecular interactions due to the propeller-like tetraphenylethene unit are responsible for the AIE phenomenon. All the luminogens are thermally and morphologically stable, showing high glass-transition (Tg = 109-147 °C) and thermal-degradation temperatures (Td = 396-478 °C). Non-doped OLEDs using BPyBCF, BAnBCF, and BTPABCF as light-emitting layers are constructed, which give blue electroluminescence with maximum current (ηC,max) and external quantum (ηext,max) efficiencies of 4.8 cd A-1) and 2.3%. With the same device configuration, BTPEBCF shows higher ηC,max and ηext,max values of 7.9 cd A-1 and 2.9%, respectively, thanks to its AIE feature.

2,5-Bis(triphenylsilylethynyl)-3,4-diphenylsiloles with different 1,1-substituents [XYSi(CPh)(2)(C C=C SiPh(3))(2)] (Ph = phenyl) were synthesized in high yields by the Sonogashira coupling of 2,5-dibromo-3,4-diphenylsiloles with triphenylsilylacetylene, and two of these were characterized crystallographically. Crystal structures and theoretical calculations showed that the new silole molecules had higher conjugation than 2,5-diarylsiloles. They possessed low HOMO and LUMO energy levels due to the electron-withdrawing effect of the triphenylsilylethynyl groups. Cyclic voltammetry analysis revealed low electron affinities, which same conditions. All of the silole molecules possessed high thermal stability. Although, their solutions were weakly emissive, their nanoparticle suspensions and thin films emitted intense blue-green light upon photoexcitation, demonstrating a novel feature of aggregation-induced emission (AIE). Polarized emissions were observed in the silole crystals. The addition of solvents, which did not dissolve the silole molecules, into silole-containing solutions caused self-assembly of the molecules, which produced macroscopic fibrils with strong light emissions.

Pyrene-substituted ethenes, 1,2,2-tripheny-1-pyrenylethene (TPPyE) and 1,2-diphenyl-1,2-dipyrenylethene (DPDPyE), are synthesized and characterized. Whereas they are weakly emissive in solution they become strong emitters when aggregated in the condensed phase. In contrast to the general observation that excimer formation quenches the light emission of fluorophores, TPPyE and DPDPyE exhibit efficient excimer emissions in the solid state with high fluorescence quantum yields up to 100%. The pi-pi intermolecular interactions between the pyrene rings, coupled with multiple C-H center dot center dot center dot pi hydrogen bonds, efficiently restrict intramolecular rotations, which block the nonradiative energy decay channel, and hence make the dye molecules highly emissive in the solid state. Non-doped organic light-emitting diodes using TPPyE and DPDPyE as emitters are fabricated, which give green light at low turn-on voltages (down to 3.2 V) with maximum luminance and power, current, and external quantum efficiencies of 49830 cd m(-2), 9.2 lm W(-1), 10.2 cd A(-1) and 3.3%, respectively.

Fluorescent liquid crystals (LCs) have wide applications in optoelectronic devices. However, the synthesis of high solid-state emission efficiency LCs is difficult. On one hand, impeding the aggregation of traditional luminogens is the pre-requisite for high efficiencies; on the other hand, self-organization is an inherent attribute for LCs in the mesomorphic states. Because of such irreconcilable conflict, new strategy toward efficient fluorescent LCs is highly desirable. Herein, a conceptually new approach toward high efficiency fluorescent LCs is developed. Through rational design and combination of biphenyl-containing diazides and diynes carrying tetraphenylethylene units, soluble, regioregular, and liquid crystalline polytriazoles with high solid-state emission efficiencies (up to 63.7%) are obtained. The photophysical properties of the polymers are sensitive to their molecular structures and their solid-state quantum yields decrease with increasing spacer length. The spacer length also impacts on the mesomorphic properties. While polymers with rigid main chains exhibit nematicity, those with longer spacer lengths show better mesogenic packing and hence form smetcic phases.

Introduction of freely rotatable tetraphenylethene (TPE) to conventional luminophors quenches their light emissions in the solutions but endows the resultant molecules (TPEArs) with aggregation-induced emission characteristics in the condensed phase due to the restriction of intramolecular rotation. High fluorescence quantum yields up to 100% have been achieved in the films of TPEArs.

The atom-economical alkyne polyhydrothiolations of aromatic diynes (1) and dithiol (2) catalyzed by rhodium complexes proceed smoothly under mild conditions at room temperature in a regioselective manner, producing sole anti-Markovnikov products of poly(vinylene sulfide)s (3) with high molecular weights (M(w) up to 31500) and stereoregularities (E content up to 100%) in high yields (up to 95.2%). The stereostructures of the polymers are readily tuned by engineering control on the sequential addition of monomers during the polymerization process and postmanipulation by light irradiation. All the poly(vinylene sulfide)s are soluble in common organic solvents and exhibit good film-forming ability and high optical transparency. The functional pendants in 1 have endowed 3 with novel properties such as aggregation-enhanced emission characteristics, optical limiting to harsh laser pulses, and ceramization capability to semiconducting nanoparticles. The polymers are thermal and UV curable, enabling the fabrication of fluorescent photopatterns. Their thin films show high refractive indices (n(D) = 1.75-1.70) and low optical dispersions (down to 0.006) at telecom important wavelengths. Their refractive indices vary with their stereostructures and can be modulated by UV irradiation.

Simple molecule possesses high power: 1,3,6,8-Tetrakis[(triisopropylsilyl) ethynyl]pyrene (TTIPSEPy), a simple-structured molecule, shows strong solid-state photoluminescence with unity emission efficiency. Highly efficient non-doped organic light-emitting diodes are fabricated using TTIPSEPy as emitter, exhibiting stable yellow light (CIE = 0.41, 0.56) with high luminance and efficiency up to 26,400 cd/m2 and 9.2 cd/A, respectively. © 2011 Elsevier B.V. All rights reserved.