A novel full-conjugated 4-(2,2′:6′,2′′-terpyrid-4′-yl) benzenediazonium tetrafluoroborate (diazo-tpy) was synthesized and used for surface modification of materials, such as quartz wafers, ITO glass, silicon, and multiwalled carbon nanotubes (MWCNTs). Under UV irradiation, the diazonium group of diazo-tpy is decomposed and the residual terpyridine group is covalently anchored to the surface of substrates. The obtained tpy-modified MWCNTs (tpy-MWCNTs) have good solubility in common organic solvents. TGA and HRTEM analyses confirmed that terpyridine groups have been symmetrically grafted on MWCNTs. The thickness of the tpy-modified monolayer is about 2.3 nm, which is approximately 2 times the axial length of the 4-(2,2′:6′,2′′-terpyrid-4′-yl)phenyl group. The introduction of terpyridine groups on the surface of MWCNTs provides a coordination site to complex with metal ions. Multilayer films were fabricated from tpy-MWCNTs and ruthenium ions [Ru(III)] via the layer-by-layer self-assembled (LBL SA) technique on the tpy-modified quartz wafer, ITO glass, or silicon. The UV−vis results indicate that (1) Ru(III)-tpy-MWCNT SA multilayer films are successfully formed based on the coordination interaction between ruthenium ions and terpyridine groups, and (2) a progressive assembly occurred regularly with almost an equal amount of deposition in each cycle. The SEM image showed a highly covered Ru(III)-tpy-MWCNT film on the substrate. Moreover, the optoelectronic conversion was also studied by assembling Ru(III)-tpy-MWCNT multilayer films on ITO substrates. Under illumination, the LBL SA films on ITO showed an effective photoinduced charge transfer because of their conjugated structure and the ITO current density changed with the number of bilayers. As the number of bilayer increases, the photocurrent intensity increases and reaches its maximum (∼65 nA/cm2) at six bilayers. These results allow us to design novel materials for applications in optoelectronic devices by using LBL SA techniques.

The charge distribution, molecular structure, and morphological packing significantly affect the photophysical properties of organic photoluminescent materials. In this work, two triphenylpyrrole isomers, 1,2,5- (TPP1) and 1,3,4- (TPP2), were first synthesized and characterized. Because of their different substituent positions, TPP1 possesses aggregation-caused emission quenching (ACQ) behavior while TPP2 exhibits aggregation-induced emission (AIE). Their different photoluminescent properties were systematically investigated by using UV–vis absorption spectroscopy, fluorescence spectroscopy, density functional theory (DFT) calculations, and single-crystal structure analysis. The results indicate that substituent position of the two phenyl groups predominately affects the charge distribution of the isomers and determines their molecular packing structures, which further cause the different restriction of intramolecular rotation (RIR) capabilities of phenyl rings, thus resulting in different luminescence properties of these two triphenylpyrrole isomers under different aggregate states.

•AIE dyes could exhibit three-color switching via reversible chemical reactions.•These reactions can tune the emission color repeatedly between cyan, yellow and red.•The switching cycle among three colors is stable after several repeated times.A multicolor switching was achieved via simple reversible coordinationand acetalation reaction between aldehydes, tri(pentafluorophenyl)borane (BCF) and methanol. The coordination [HPB → BCF] of 4,4′-[(1E,3E)-1,2,3,4-tetraphenylbuta-1,3-diene-1,4-diyl]- dibenzaldehyde (E,E-HPB) to tri(pentafluorophenyl)borane can change the emissive wavelength from 550 to 630 nm, while transformation of the aldehyde into acetal can change the emissive wavelength from 550 to 530 nm in the presence of methanol. More important, these reactions can access reversibility easily and tune the emission color repeatedly between cyan, yellow and red. All of these dyes show typical aggregation-induced emission (AIE) or aggregation-enhanced emission (AEE) characteristics. In addition, a tunable photoluminescence mechanism is proposed based on the characterization data including NMR, XRD, MS and IR. The result may provide a new design strategy for the multicolor switches and their related applications.Download high-res image (255KB)Download full-size image

A series of para-substituted phenylacetylenes bearing various amine-containing pendant groups 1–4 can serve as both a monomer and cocatalyst in the polymerization catalyzed by [Rh(norbornadiene)Cl]2 alone in CH2Cl2, affording polyphenylacetylenes (PPAs) with different stereoselectivities and molecular weights. The polymerization of monomer 4 having a long and flexible pendant group produces high molecular weight PPAs with high cis-transoid configurations, similar to those obtained from the coordination–insertion polymerization of these monomers 1–4 by using the [Rh(norbornadiene)Cl]2/cocatalyst systems. However, the stereospecific transformation from the cis-transoid to the trans-cisoid configuration and the growth limitation of the polymer chain are observed in the polymerization of monomers 1–3 containing short and rigid pendant groups. The resulting PPAs have trans-cisoid selectivities of up to 66% and low molecular weights. A metathesis mechanism is suggested, in which the steric repulsion between the pendant group of the monomer and the propagation chain originates from the successive 1,2-insertion of monomers 1–3 to the Rh–carbene active species gives a rational explanation for the tendency of stereospecific transformation and the growth limitation of the polymer chain.

Herein, a pair of enantiomers, (S)-PPPtriAm and (R)-PPPtriAm, with three chiral substituents and their raceme rac-PPPtriAm derived from conjugated luminogen pentaphenylpyrrole were prepared by covalently attaching (R)-/(S)- or racemic 1-phenylethylamine to conjugated 1-biphenyl-2,3,4,5-tetraphenyl pyrrole. The compounds exhibit obvious aggregation-induced emission enhancement (AIEE) features, and the chiral substituents have little effect on the photophysical properties. More importantly, the introduction of chiral substituents endows the chiral compounds (S)-PPPtriAm and (R)-PPPtriAm with distinct aggregation-induced circular dichroism (AICD) with mirror-image Cotton effects and chiral-polarized luminescence (CPL) properties with an emission dissymmetry factor (gem) in the range of 0.5 × 10−3 to 5 × 10−3 for (S)-PPPtriAm and −1 × 10−3 to −6 × 10−3 for (R)-PPPtriAm in a DMSO–water mixture with the water fraction of 40%. The chiral compounds (S)-PPPtriAm and (R)-PPPtriAm can self-assemble into nanofibers, and the lank nanofibers orderly weave and align together to form a regular arrangement of aggregates. The raceme rac-PPPtriAm exhibits AIEE features without any AICD and CPL signals and can self-assemble to form nanoparticle blocks. The enantiomers (S)-PPPtriAm and (R)-PPPtriAm, as AIEE-active luminogens with a multichiral substituent, are expected to have potential applications in photoelectronic materials or in the design of optically active fluorophores for sensitive enantiomer recognition.

A Light/Temperature-Enhanced Emission (LTEE) based fluorescence turn-on probe was prepared via the photocyclization/crystallization of a malononitrile-containing hexaphenyl-1,3-butadiene derivative (HPB-CN) on filter paper. The HPB-CN-coated filter paper exhibited stronger PL intensity as the exposure time under UV light prolonged and the heating temperature increased, indicating the hotter, the brighter.

The surfaces of semiconductor nanocrystals have been known to be a very important factor in determining their optical properties. The introduction of functionalized ligands can further enhance the interactions between nanocrystals, which is beneficial for the assembly of nanocrystals. In a previous report, we developed a ligand-assisted reprecipitation method to fabricate organometal halide perovskite nanocrystals capped with octylamine and oleic acid. Here, a TPE derivative 3-(4-(1,2,2-triphenylvinyl)phenoxy)propan-1-amine, which shows a typical aggregation induced emission feature, is applied to replace octylamine to fabricate CH3NH3PbBr3 nanocrystals. The obtained CH3NH3PbBr3 nanocrystals were nanocubes (average diameter ∼ 11.1 nm) and are likely to assemble into ordered superstructures. By adjusting the chain length of the TPE derivative, we found that the assembly of the CH3NH3PbBr3 nanocrystals was correlated with the interactions between the TPE groups. This provides a new platform to investigate the ligand effects in nanocrystal solids and may potentially achieve enhanced optical and electrical properties.

A novel multi-mode probe consisting of a hexaphenyl-1,3-butadiene derivative, 2,2′-((((1Z,3Z)-1,2,3,4-tetraphenylbuta-1,3-diene-1,4-diyl)bis(4,1-phenylene))bis(methanylylidene))dimalononitrile (ZZ–HPB–CN), with typical aggregation-enhanced emission (AEE) features was easily prepared for the highly sensitive and rapid detection of amine vapors. The ZZ–HPB–CN sensor, which was prepared by simply depositing ZZ–HPB–CN on filter paper, could detect low concentration vapors of volatile amines using fluorescence, ultraviolet and naked-eye detection. The limit of detection of the sensor was as low as 1 ppb for the fluorescence detection. The color change of the sensor caused by 1–10 ppm amine vapors could be observed under UV light or with the naked eye. The high sensitivity, quick response and easy operation of the probe give it great potential for real-life applications.

•A novel pyrrolopyrrole derivative DPPCN exhibited aggregation- and crystalline-induced emission properties.•DPPCN showed three types of polymorphism with blue, cyan-blue and yellow-green emissive, respectively.•The structure-property relationships were investigated based on X-ray single crystal diffraction analysis.•The mechano- and thermo-stimulus fluorescence switching behaviors of the three crystals were investigated.Bis(4-cyanophenyl)-4,4′-(2,5-diphenylpyrrolo[3,2-b] pyrrole-1,-4-diyl) dibenzoate (DPPCN) was synthesized and exhibited aggregation-induced emission properties. DPPCN was cultivated in different solvents getting three kinds of crystals, A, B and C. Crystals of A and B were respectively blue and cyan-blue emissive, while C was yellow-green emissive. They all displayed crystalline-induced emission behaviors. According to X-ray single crystal diffraction analysis, the intermolecular interactions account for restricted internal rotations, leading to fluorescence enhancement. The different kinds of co-effects of the solvent, intermolecular forces, molecular conformations and molecular packing modes endow DPPCN polymorphisms with multi-color emissions (from blue to yellow and up to 60 nm) and different fluorescence efficiencies. The fluorescence of A can be reversibly tuned by grinding and exposing to chloroform vapor with a 46 nm wavelength change. The crystal of C can blue shifted the fluorescence that matches with B upon fumed by chloroform for about 12 h and further blue shifted the fluorescence emission that matches with A when fumed by chloroform for about 24 h. Multi-color fluorescence tuning and switching is attributed to the nature of polymorphs, that is, a change of molecular conformation and intermolecular packing modes. The crystal of A also exhibited thermo-stimulus fluorescence switching behavior due to the co-crystallization with solvent chloroform. The properties of A show promising applications in temperature monitoring and volatile organic compound detecting devices.Download high-res image (283KB)Download full-size image

ABSTRACTA series of new mononuclear neutral and water-soluble cationic rhodium (Rh) complexes bearing strong π-acidic dibenzo[a,e]cyclooctatetraene (dbcot) diene ligand have been synthesized and structurally characterized. In the polymerization of phenylacetylene, the dbcot Rh complex exhibits higher catalytic activity than the corresponding cod-based Rh complex in both of organic solvent and aqueous media, affording the high cis-transoidal PPAs with up to 99% of cis-contents, moderate molecular weights, and moderate to broad molecular weight distributions. Moreover, on-water polymerization of substituted phenylacetylenes is achieved by these complexes under air atmosphere, in which 3- to 163-fold acceleration of the polymerization rate is observed in aqueous polymerization compared to that in organic solvents. The nature of the Rh complex, solvent, polymerization temperature, and substituted group on the phenylacetylene impact on the polymer's yield, stereoselectivity, molecular weight, and molecular weight distribution. In addition, the water-soluble cationic Rh complexes can be reused for three times. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 716–725

•Three isomers of HPB-CHO were synthesized in one-pot.•Three E/Z isomers exhibited differences in the fields of AIE or AEE behavior.•ZZ-HPB-CHO isomer displayed the most remarkable mechanochromic effects.E/Z isomers of hexaphenyl-1,3-butadiene (HPB) derivative containing dialdehyde groups, 4,4’-((1E,3E)-1,2,3,4-tetraphenylbuta-1,3-diene-1,4-diyl)dibenzaldehyde (EE-HPB-CHO), 4,4’-((1Z,3E)-1,2,3,4-tetraphenylbuta-1,3-diene-1,4-diyl)-dibenzaldehyde (EZ-HPB-CHO) and 4,4’-((1Z,3Z)-1,2,3,4-tetra-phenylbuta-1,3-diene-1,4-diyl)dibenzaldehyde (ZZ-HPB-CHO), were firstly synthesized in one-pot and readily separated by silica gel column chromatography. The E/Z isomers containing conjugated diene exhibited remarkable differences in the fields of aggregation-induced emission (AIE) or aggregation-enhancement emission (AEE) behavior, thermostability, and mechanochromic performance. Among them, EE-HPB-CHO with dense molecular packing and strong intermolecular interaction was a better AIEgen while the EZ- and ZZ-isomers exhibited AEE behavior. Moreover, EE-HPB-CHO hardly displayed the mechanochromic performance. EZ-HPB-CHO irreversibly exhibited a blue-shift of 23 nm by grinding treatment, which could not be restored by fuming with organic solvents or heating. In contrast, owing to its twisting conformation and relative loose packing, ZZ-HPB-CHO reversibly displayed a red-shift of 20 nm during multiple repeating cycles of grinding and fuming treatments, showing superior mechanochromic performance.

A pair of enantiomers ((R)-TPPBAm and (S)-TPPBAm) and their raceme (rac-TPPBAm) were designed and prepared by conjugating (R)-, (S)- or racemic 1-phenylethylamine to an aggregation-induced emission enhancement (AIEE) active triphenylpyrrole fluorophore. The three target compounds were thoroughly characterized and their optical properties were systematically investigated. The fluorescence analyses indicate that they all retain the AIEE activities originating from the triphenylpyrrole moiety, irrespective of the attaching groups. More importantly, both the enantiomers containing (R)- or (S)-1-phenylethylamine attachment exhibit aggregation-induced circular dichroism (AICD) features with mirror-image signals. Besides, they also exhibit circularly polarized luminescence (CPL) with an emission dissymmetry factor (gem) from 1.5 × 10−4 to 3 × 10−3 for (R)-TPPBAm and −1.3 × 10−4 to −4 × 10−3 for (S)-TPPBAm in aggregate states. As expected, consistent with the variations of their CD signals, (R)-TPPBAm and (S)-TPPBAm could self-assemble into helical nanofibers with the opposite screw direction during the aggregation process in the THF–water mixed solution, while the racemic compound rac-TPPBAm exhibits no CD and CPL signals, and self-assembles to form nanoparticles blocks. These results demonstrate that the morphologies and optical activities can be controlled simultaneously without losing the solid-state emission performance of the material by attaching a chiral group to an AIEE fluorophore, which could shed light on the design of optical active fluorophores for sensitive and time-efficient enantiomer determination.

A flame retardant TAD constructed by phosphaphenanthrene and triazine-trione groups was synthesized via addition reaction between triallyl isocyanurate (TAIC) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Then, the molecular structure and thermal stability of TAD were characterized. To research its flame-retardant behaviors, TAD was incorporated into epoxy resin, diglycidyl ether of bisphenol-A, cured by 4,4′-diamino-diphenyl sulfone (DDS). TAD obviously increased the LOI values and UL94 rating of epoxy resin thermosets. TAD also reduced the values including peak of heat release rate (pk-HRR), total heat release (THR), average effective heat of combustion (av-EHC), average CO2 yield and total mass loss (TML), and increased average CO yields of epoxy thermosets. Further, the different decrease ratio of av-EHC and TML from thermoset containing TAD reveals that TAD exerted more gas-phase flame-retardant effect than condensed-phase effect. The opinion also was testified by the TAD/EP residues with loosen morphology from the cone calorimeter test. The analyzed pyrolysis route of TAD reveals that phosphaphenanthrene group mainly exerted quenching effect and the triazine-trione group exerted gas dilution effect. The excellent flame-retardant performance of TAD is resulted by the group synergistic effect from the two typical flame-retardant groups: phosphaphenanthrene and triazine-trione.

A novel fluorescent probe, tris (2-(dimethylamino) ethyl)-4,4′,4″-(1H-pyrrole-1,2,5-triyl) tribenzoate (TPP-TMAE), with aggregation-enhanced emission (AEE) feature showed a simple, highly selective, specific, and instant response to trace amount carbon dioxide (CO2). Because of this special characteristic, TPP-TMAE is ideal to be a biomarker for in-situ monitoring of the CO2 generation rate during the metabolism of single living cell. The rates in single living HeLa cell, MCF-7 cell, and MEF cell were 6.40 × 10−6 ± 6.0 × 10−8 μg/h, 5.78 × 10−6 ± 6.0 × 10−8 μg/h, and 4.27 × 10−7 ± 4.0 × 10−9 μg/h, respectively. The distinct responses of TPP-TMAE to CO2 generated from cancer cells and normal cells suggested TPP-TMAE as a useful tool for deeper understanding metabolism process and distinguishing cancer cells from normal cells during the early diagnosis of cancers.

•The compound 1,2,4,5-tetraphenyl-1,4-dihydropyrrolo[3,2-b]pyrrole (DPPTP) exhibits aggregation-induced emission enhancement (AEE) and crystalline-induced emission enhancement (CEE) properties.•The DPPTP films show rapid response, excellent selectivity, and sensitivity to chloroform vapor.•The DPPTP solid films have good reversibility and also can be used as a quantitative analysis sensor for the detection of chloroform at as low as 100 ppm level.An one-step synthesized 1,2,4,5-tetraphenyl-1,4-dihydropyrrolo [3,2-b]pyrrole (DPPTP) exhibits aggregation-induced emission enhancement properties. The solid film prepared by spin-coating a DPPTP solution in THF onto a quartz glass showed rapid response and excellent selectivity to chloroform when fumed with different organic solvents. Experimental results show that hydrochloric gas produced from the photodecomposition of chloroform is the main reason for the fluorescent response of the DPPTP film to chloroform. The DPPTP solid films have good reversibility and also can be used as a quantitative analysis sensor for the detection of chloroform as low as 100 ppm.An one-step synthesized 1,2,4,5-tetraphenyl-1,4-dihydropyrrolo [3,2-b]pyrrole (DPPTP) exhibits aggregation-induced emission enhancement properties. The solid film prepared by spin-coating a DPPTP solution in THF onto a quartz glass showed rapid response and excellent selectivity to chloroform when fumed with different organic solvents. Experimental results show that hydrochloric gas produced from the photodecomposition of chloroform is the main reason for the fluorescent response of the DPPTP film to chloroform. The DPPTP solid films have good reversibility and also can be used as a quantitative analysis sensor for the detection of chloroform as low as 100 ppm.

Novel fluorescent probes based on the 1,2,5-triphenylpyrrole core containing a different number of tertiary amine moieties, 2-(dimethylamino)ethyl 4-(2,5-diphenyl-1H-pyrrol-1-yl)benzoate (TPP-DMAE), bis(2-(dimethylamino)ethyl) 4,4′-(1-phenyl-1H-pyrrole-2,5-diyl)dibenzoate (TPP-BDMAE) and tris(2-(dimethylamino)ethyl) 4,4′,4′′-(1H-pyrrole-1,2,5-triyl)tribenzoate (TPP-TDMAE), with an aggregation-enhanced emission (AEE) feature, were prepared for the quantitative detection of low levels of carbon dioxide in the gas mixture with the fraction of carbon dioxide ranging from 0.4% to 5%. Compared with the other two compounds, TPP-TDMAE showed the most selective, fastest and most iterative response to carbon dioxide. A significant fluorescence decrease with a turn-off ratio over 20-fold was triggered by the disaggregation process through the reaction with carbon dioxide. Response time results indicated that the emission intensity of TPP-TDMAE can be quickly decreased to the minimum level in less than 12 s upon bubbling of carbon dioxide. It is desirable to develop a novel method for the selective, real-time and quantitative detection of CO2 for biological and medical applications.

A dye emitted red fluorescence with aggregation-enhanced emission properties was reported here. It can be utilized to specifically recognize the cell membrane of MCF-7 and 293T cell lines during bio-imaging.

An aggregation-enhanced emission active luminogen named as sodium 4,4′4″-(3,4-diphenyl-1H-pyrrole-1,2,5-triyl)tribenzoate (DP-TPPNa) with propeller construction was synthesized and developed as a “turn on” fluorescent probe for in situ quantitation of albumin in blood serum. The DP-TPPNa fluorescence intensity was linearly correlated with the concentration of two serum albumins, bovine serum albumin (BSA) and human serum albumin (HSA), in pure PBS buffer in the ranges of 2.18–70 and 1.68–100 μg/mL, respectively. The detection limits were as low as 2.18 μg/mL for BSA and 1.68 μg/mL for HSA. The response time of fluorescence to serum albumin (SA) was very short (below 6 s), which achieved real-time detection. It also showed high selectivity to SA because other components in serum barely interfere with the detection of DP-TPPNa to SA, enabling in situ quantitative detection of SA without isolation from serum. DP-TPPNa was successfully applied for the quantitative detection of BSA in fetal bovine serum. The mechanism of fluorescent turn-on behavior was elucidated utilizing an unfolding process induced by guanidine hydrochloride, which revealed a capture process via selective hydrophobic interaction and hydrogen bonding between luminogen and SA.Keywords: aggregation-enhanced emission; albumin; aryl-substituted pyrrole; blood serum; in situ detection; real-time quantitation;

A novel blue thermally activated delayed fluorescence (TADF) emitter, CPC (2,6-di(9H-carbazol-9-yl)-4-phenylpyridine-3,5-dicarbonitrile), was designed and synthesized. By directly linking carbazole (to serve as electron-donor) and pyridine-3,5-dicarbonitrile (to serve as electron-acceptor), and distributing cyanogroups and carbazole groups at the para-position of pyridine core, CPC successfully achieves an extremely small singlet–triplet splitting and fairish photoluminescence quantum yield, thus can act as the highly efficient blue TADF emitter. The optimized organic light-emitting diode (OLED) based on 13 wt % CPC doped in mCP (1,3-bis(9H-carbazol-9-yl)benzene) host exhibits maximum current efficiency, power efficiency, and external quantum efficiency of 47.7 cd A–1, 42.8 lm W–1, and 21.2%, respectively, which are the best results in reported blue TADF-based devices up to date and even comparable with the best reported blue phosphorescent OLEDs.Keywords: blue emitter; carbazole; carbonitrile; charge transfer transition; OLEDs; pyridine; TADF;

The emissive properties of fluorophores in aggregated state are important for the development of bio-sensors or bio-imaging reagents. So three water-soluble TPE derivatives with different lengths of side chains have been synthesized and we investigated the effects of side chains on aggregation-induced emission (AIE) properties in the aggregated states. The results indicate that side chains on the fluorophores play a pivotal role in their emission in aggregated state mediated by heparin or solid state, because the coplanarity of these TPE derivatives was affected by side chains. The rates of radiative decay kf and non-radiative decay knr have been obtained through the quantum yields and lifetime, and a larger kf and smaller knr were present for compound TPE-C4N, suggesting that the aggregated TPE-C4N should posses the most remarkable fluorescent property.Three water-soluble TPE derivatives with different lengths of side chains have been synthesized and we investigated the effects of side chains on aggregation-induced emission (AIE) properties in the aggregated states. The results indicate that side chains on the fluorophores play a pivotal role in their emission in aggregated state mediated by heparin or solid state, because the coplanarity of these TPE derivatives was affected by side chains.

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.

Reversible piezochromic luminescence and aggregation induced emission properties of 4,4′-((Z,Z)-1,4-diphenylbuta-1,3-diene-1,4-diyl)dibenzoic acid are reported. The photoluminescent color of it changes from blue to yellow-green upon grinding, which can be restored upon exposure to a solvent. Intermolecular hydrogen bonding plays a key role in the altered emission.

Tetraphenylethylene (TPE) derivatives have been proved to be typical aggregation-induced emission (AIE) luminogens when they were aggregated in the free three-dimensional space. In order to reveal the effect of the dimensional degree on AIE property of TPEs, we utilized tetra(4-hydroxyphenyl)ethylene (TPE-4OH) and 1,4-benzenediamine diazonium salt (BD) to fabricate the ultra-thin films (TPE-4OH/BD LBL SA film) through layer-by-layer self-assembled technique. The interaction between TPE-4OH and BD in the films was converted from electrostatic force and hydrogen-bond to covalent bonds through photodecomposition of diazonium groups under UV irradiation. Fluorescence emission spectroscopy, UV-Vis absorption spectroscopy and atomic force microscope were carried out to evaluate the relationship between bilayer number and photoluminescence of the TPE-based self-assembled films. The experimental results showed that the TPE-based film with three bilayers only displayed AIE character, whereas the fluorescence of the film became randomly changed if the bilayer number was above three. It is supposed that the fluorescence property of the TPE-4OH/BD LBL SA film with limited molecular length in z-axis and infinite aggregation space in x- and y-axis is dominated by two competitive effects, one is the partial restriction of intramolecular rotation through short intermolecular interactions in cross-linked structure of TPE-4OH/BD, and the other is deactivation of its excited state through unrestricted intramolecular rotations or π-π interactions.

Polyelectrolyte PTPEPyH, containing tetraphenylethene (TPE) and pyridinium, was synthesized. Its optical properties were investigated with spectroscopies and the results showed that there were two emission-enhanced stages in the interaction between positive-charged PTPEPyH and negative-charged biomacromolecule heparin. The mechanism was very different due to the reduced non-radiative energy loss and the change of surroundings. The polyelectrolyte PTPEPyH, compared with ChS and HA, also showed high selectivity for heparin in the buffer solution and could be used as a potential bio-probe for heparin quantification in the clinical full range.

Fully conjugated metallosupramolecular self-assembled multilayer films were controllably fabricated based on bibenzonitril-phthalocyaninato ruthenium(II) (BBPR) and 4,4′-bipyridine (BP) via axially coordination interaction between ruthenium ions and the pyridine groups on the modified substrates. The substrates were first functionalized by 4-(pyridine-4-ylethynyl)benzenic diazonium salt (PBD) through photodecomposition of diazonium group under UV irradiation. As a result, the pyridine-containing functional groups were vertically and covalently anchored onto the surface of substrate and got a stable monolayer. Soluble ruthenium phthalocyanine, axially coordinated by labile benzonitrile groups, was used to fabricate the layer-by-layer self-assembled films with BP through ligand-exchanging reaction between benzonitrile and pyridine in each self-assembled cycle. The UV–vis analysis results demonstrated the successful fabrication of bi(4,4′-bipyridine)phthalocyaninato ruthenium(II) (BPPR) metallosupramolecular ultrathin films with definite structures on PBD-modified substrate. Under illumination, the BPPR self-assembled multilayer films displayed a quick response to light. The maximum current density reached 120 nA/cm2 at six bilayers. The Eg, HOMO, and LUMO of the six-bilayer were quantitatively measured to be 1.68, −5.29, and −3.61 eV, respectively. This strategy supplies a facile method to get full-conjugated metallosupramolecules and a platform for developing higher performance solar cell from the point of adjusting dye aggregate state structure.

A “turn-on” fluorescent sensor, sodium 4,4′,4′′-(1H-pyrrole-1,2,5-triyl)tri-benzoate (Py(PhCOO-Na)3), has been prepared for the detection of Al3+ in aqueous solution. The detection mechanism, as well the mechanism specific to Al3+, was studied by fluorescence spectroscopy, UV-vis spectroscopy and dynamic light scattering (DLS) measurement. Py(PhCOONa)3 exhibited an aggregation-induced emission (AIE) characteristic and was found to show a specific affinity to Al3+, as indicated by the enhanced and bathochromically shifted emission of the AIE fluorogen. Upon binding Al3+, a significant fluorescence enhancement with a turn-on ratio of over 10-fold was triggered by the AIE process. Moreover, this sensor is highly selective for Al3+ over other metal ions with a detection limit of 5 μM and a quantitative detection range of 5–120 μM, and is able to be used in the determination of Al3+ in drinking water. The time-response investigation indicates that the emission intensity of (Py(PhCOO−)3) can be quickly boosted to reach the maximum intensity in less than 10 s upon titration of Al3+.

A water-soluble, ‘turn-on’ fluorescent chemosensor based on aggregation-induced emission (AIE) has been developed. It exhibits rapid response, excellent selectivity, and sensitivity to Al3+.

An aggregation-induced emission (AIE)-active chromophore 1,2-bis[4-(3-hydroxyphenyl)phenyl]-1,2-diphenylethene (TPE-2PhOH) was synthesized from 1,2-bis[4-bromophenyl]-1,2-diphenylethene (TPE-2Br) and 3-hydroxylphenylboronic acid via Suzuki coupling reaction. TPE-2PhOH nanoaggregates can be obtained from the nonsolvent-induced aggregation process. By alternately depositing 4,4′-biphenyldiazonium (BPD) salts and TPE-2PhOH nanoaggregates, layer-by-layer self-assembled films based on hydrogen-bonding interactions were successfully fabricated onto modified quartz slides. A more stable film was further prepared by subsequent decomposition of diazonium group (–N2+) under irradiation of UV light, which induces the conversation of the hydrogen-bond interaction between the hydroxyl groups on the surface of TPE-2PhOH nanoaggregates and diazonium groups into covalent bonds. The covalently linked self-assembled film exhibited highly fluorescence quenching sensitivity towards volatile of solid nitroanilines (2-nitroaniline (2-NA), 3-nitroaniline (3-NA) and 4-nitroaniline (4-NA)) and 2,4,6-trinitrotoluene (TNT) at normal atmospheric temperature and pressure. This strategy can provide a platform for developing highly sensitive and efficient chemosensors for harmful compounds and warfare explosives.

Poly(phenylene ethynylene)s (P1) with 4-vinylaniline pendant groups were successfully prepared by the Sonogashira coupling polymerization between 1,4-diethynyl-2,5-bis(pentyloxy)benzene and 4-[2-(2,5-dibromophenyl)vinyl]-aniline. In comparison with its analogue P2 without amino group, the emission of P1 is only enhanced by aggregation when adding n-hexane into its THF solution, exhibiting an aggregation-induced emission enhancement (AIEE) effect. When methanol or water instead of hexane was added into THF solution, P1, however, didn’t show AIEE. The results indicated that amino groups strengthen the inter-chain and intra-chain interactions in P1 and restrict the non-radiative energy transition. This strategy can provide a platform for developing highly sensitive and efficient bio- and chemosensors.

Transition metal ions (Pb2+, Zn2+, Cd2+, Co2+, Mn2+, Cu2+, Ni2+, Hg2+, Ag+, Fe3+) in water are used to quench emission of 2-(6-oxido-6H-dibenz 〈c,e〉 〈1,2〉 oxaphosphorin-6-yl)-1,4-phenylene-bis(p-pentyloxylbenzoate)s (MD5) with aggregation-induced emission enhancement (AIEE) in water-acetonitrile (AN) mixture (80:20 by volume). Among all metal ions, Fe3+ exhibits the highest quenching efficiency on AIEE of MD5 even when the concentration of Fe3+ is lower than 1×10−6 mol/L. The quenching efficiency of Hg2+ is lower than that of Fe3+ at the same concentration, though MD5 is used to detect Hg2+ efficiently, too. To other metal ions, low quenching efficiency has few relations with a wider concentration range. The UV absorbance spectra show only red shift of absorbance wavelength in the presence of Hg2+ and Fe3+, which indicates a salt-induced Jaggregation. SEM photos reveal larger aggregation and morphological change of nanoparticles of MD5 in water containing Hg2+ and Fe3+, which reduce the surface area of MD5 emission for further aggregation. The selective quenching effect of transition metal ions to emission of MD5 has a potential application in chemical sensors of some metal ions.

4-(2-(4-pyridinyl)Ethynyl)benzenic diazonium salt (PBD) was used to modify multiwalled carbon nanotubes (MWCNTs) by the self-assembly technique. After the decomposition of the diazonium group in PBD under UV irradiation, the PBD monolayer film covalently anchored on multiwalled carbon nanotubes is very stable. The obtained pyridine-modified MWCNTs (Py(Ar)-MWCNTs) have good solubility in common organic solvents. Furthermore, the layer-by-layer (LBL) self-assembled fully conjugated films of Py(Ar)-MWCNTs and (phthalocyaninato)ruthenium(II) (RuPc) were fabricated on the PBD-modified substrates, and characterized using UV−vis absorption spectroscopy, scanning electron microscopy (SEM), and electrochemistry. The UV−vis analysis results indicate that the LBL RuPc/Py(Ar)-MWCNTs self-assembled multilayer films with axial ligands between the ruthenium atom and pyridine group were successfully fabricated, and the progressive assembly runs regularly with almost equal amounts of deposition in each cycle. A top view SEM image shows a random and homogeneous distribution of Py(Ar)-MWCNTs over the PBD-modified silicon substrate, which indicates well independence between all Py(Ar)-MWCNTs. Moreover, the opto-electronic conversion was also studied by assembling RuPc/Py(Ar)-MWCNTs multilayer films on PBD-modified ITO substrate. Under illumination, the LBL self-assembled films on ITO showed an effective photoinduced charge transfer because of their conjugated structure and the ITO current density changed with the number of bilayer. As the number of bilayers was increased, the photocurrent increases and reaches its maximum value (∼300 nA/cm2) at nine bilayers. These results allow us to design novel materials for applications in optoelectronic devices by using LBL self-assembly techniques.

The stability of full-conjugated self-assembled (SA) multilayer films based on partially doped polyaniline (PANI) as a polycation and poly(o-aminobenzoic acid) (PCAN), poly(aniline-2-sulfonic acid) (PSAN) as polyanions is investigated in alkali aqueous solutions. The self-assembled PANI-PCAN films keep their stability within 24 h in 1 mol/L NaOH solution, -the PANI-PSAN films, however, maintain the stability for 20 min in the same condition because the solubility of PSAN in alkali solutions is much higher than that of PCAN. The electrochemical properties of the SA films are determined, and the film-CdS composites formed in situ are also reported.

The relationship between the structures and light emission properties of five aryl-substituted pyrrole derivatives was studied during aggregation in THF−water mixtures. Only pentaphenylpyrrole clearly shows, however, an aggregation-induced emission enhancement (AIEE) phenomenon. On comparison of the optical properties and single-crystal structures of these pyrrole derivatives, it is suggested that the more twisted configuration which prevented parallel orientation of conjugated chromophores combined with the restricted intramolecular rotation (RIR) effect was the main cause of the AIEE phenomenon.

New catalyst systems for diyne polycyclotrimerization were developed. E-1-[2-(2,5-Diethynylphenyl)vinyl]ferrocene (1), a ferrocene-containing diyne, was polymerized by ruthenium- and rhodium-based catalysts, affording hyperbranched polyphenylenes (hb-P1) with high molecular weights (Mw up to ∼1.4 × 105) in high yields (up to 100%). Effects of reaction conditions on the polymerization process were investigated, and structures of the resultant polymers were characterized by spectroscopic methods. The polymers were soluble, thermally stable, and redox active. Complexation with cobalt carbonyls further metalized the polymers. Both the polymers and their cobalt complexes showed high refractive indices (RI up to ∼1.81) at 300−1700 nm, large Abbé numbers (νD′ up to ∼681), and low optical dispersions (D′ down to ∼0.0015) in the telecommunication wavelength region. Pyrolyses of the polymers and their complexes furnished magnetic ceramics with high magnetizabilities (Ms up to ∼83 emu/g).

4-(2-(4-Pyridinyl)ethynyl)benzenic diazonium salt (PBD) was synthesized and used to modify the substrate by self-assembly (SA) technique. Following decomposition of the diazonium group in PBD under UV irradiation, the ionic bonds between the diazonium salt and substrate are converted to covalent bonds. The PBD monolayer film anchored on substrates is very stable. Furthermore, the layer-by-layer (LBL) self-assembled films of bis(4,4′-bipyridine)(phthalocyaninato)ruthenium(II) (RuPc(bipy)2, BPR) and triruthenium dodecacarbonyl (Ru3(CO)12, TRDC) were fabricated on the PBD-modified substrates and characterized using UV−vis absorption spectroscopy, atomic force microscopy (AFM), and electrochemistry. The UV−vis analysis results indicate that the LBL TRDC-BPR self-assembled multilayer films with axial ligands between ruthenium atoms and pyridine groups were successfully fabricated and the progressive assembly runs regularly with almost equal amounts of deposition in each cycle. The AFM images of the seven-bilayer TRDC-BPR film on silicon wafer showed round-shaped small domains with sizes of 30−40 nm. The values of the energy band gap (Eg), the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) of six-bilayer TRDC-BPR on indium-tin-oxide (ITO) glass slides were measured using the UV−vis absorption spectrum and a cyclic voltammogram with values of 1.8, −5.0, and −3.2 eV, respectively. Under illumination, the self-assembled film on ITO showed effective photoinduced charge transfer and changed the current density. As the number of bilayers was increased, the photocurrent increased and reached its maximum value (∼150 nA/cm2) at six bilayers. A further increase in the number of bilayers led to a decrease in current due to the increase in cell resistance. The results allow us to design new materials with higher performance for optoelectronic applications.

Whereas aggregation often quenches luminescence, the emission of a heterocyclic luminogen, 10-[2,5-bis(4-pentyloxyphenylcarbonyloxy)phenyl]-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (3), is greatly enhanced by aggregate formation. Crystallization further boosts the emission of 3, turning it from a weak emitter in the solution state to a strong emitter in the crystalline state. The emission of 3 is changed in response to the exposure to vapors of volatile organic compounds (VOCs). The morphology of the thin film of 3 is reversibly and repeatedly modulated between amorphous and crystalline phases by simple fuming−heating and heating−cooling cycles, leading to an emission switching between bright and dark states. The novel attributes of the crystallization-induced emission enhancement, the VOC-responsive emission change, and the morphology-tunable emission switching of 3 could enable it to find applications in an array of technological areas, including chemosensing, optical display, and rewritable information storage.

Polyelectrolyte-layered films containing β-cyclodextrin (β-CD) were fabricated by a layer-by-layer deposition of carboxymethyl-β-cyclodextrin (CM-β-CD) as a polyanion and cationic photosensitive diazoresin (DR) on a solid surface. Under UV irradiation, following the decomposition of diazonium group between the adjacent interfaces of the multilayers, the ionic bonds of the self-assembly film convert to covalent bonds and the film become stable toward many common organic solvent. When a high-ionic-strength buffer is employed as a bathing solution, the film is thicker than that deposited from water solution. And the deposition increases with the increase of the carboxymethylated degree of CM-β-CD. The CM-β-CD/DR film can bind methylene blue (MB), and the durability of MB-adsorbing films to reductive glucose indicates that MB molecules not only diffuse into the film, but also load to the cavity of β-CD through a host–guest complexation assisted by electrostatic interactions. The binding quantity of MB increases linearly with increasing the number of bilayers, and is influenced obviously by the pH value of MB aqueous solution. MB molecules can desorb from the 12-bilayer MB-absorbing CM-β-CD/DR films when being immersed in water/ethanol mixture, and the released quantity of MB increases a little with increasing the concentration of water when it is below 30%, while decreases evidently over 30%.The UV–vis spectra of MB-adsorbing CM-β-CD(7.4)/DR film before and after being immersed in reductive glucose solution.

A novel multilayer film was assembled from water-soluble poly(4-carboxyphenyl)acetylene sodium salt (PCPA) and diazoresin (DR) in aqueous solution via electrostatic attraction. Under UV irradiation, following the decomposition of the diazonium group between the adjacent interfaces of the multilayers, the ionic bonds of the self-assembled film convert to covalent bonds and the film becomes very stable toward electrolyte aqueous solutions. Thus, the photoelectric conversion property of PCPA-containing film can be measured in a conventional three-electrode photoelectrochemical cell, and 0.5 mol/l KCl solution can be used as the supporting electrolyte. The photocurrent spectroscopy response coincides with the absorption spectrum of the irradiated self-assembled film, which indicates that the irradiated DR/PCPA film is responsible for the photocurrent generation.

An aggregation-induced emission (AIE)-active chromophore 1,2-bis[4-(3-hydroxyphenyl)phenyl]-1,2-diphenylethene (TPE-2PhOH) was synthesized from 1,2-bis[4-bromophenyl]-1,2-diphenylethene (TPE-2Br) and 3-hydroxylphenylboronic acid via Suzuki coupling reaction. TPE-2PhOH nanoaggregates can be obtained from the nonsolvent-induced aggregation process. By alternately depositing 4,4′-biphenyldiazonium (BPD) salts and TPE-2PhOH nanoaggregates, layer-by-layer self-assembled films based on hydrogen-bonding interactions were successfully fabricated onto modified quartz slides. A more stable film was further prepared by subsequent decomposition of diazonium group (–N2+) under irradiation of UV light, which induces the conversation of the hydrogen-bond interaction between the hydroxyl groups on the surface of TPE-2PhOH nanoaggregates and diazonium groups into covalent bonds. The covalently linked self-assembled film exhibited highly fluorescence quenching sensitivity towards volatile of solid nitroanilines (2-nitroaniline (2-NA), 3-nitroaniline (3-NA) and 4-nitroaniline (4-NA)) and 2,4,6-trinitrotoluene (TNT) at normal atmospheric temperature and pressure. This strategy can provide a platform for developing highly sensitive and efficient chemosensors for harmful compounds and warfare explosives.

•A novel “turn-on” fluorescent probe was synthesized for in-situ detection of γ-globulins in the blood serum.•This probe achieved quantitative detection of γ-globulins in a wide concentration range (7.89–300 μg/mL).•This probe can detect γ-globulins in-situ without isolating the analyte from the blood serum.•The fluorescence response time of the probe was very short (below 5 s) for real-time detection.As a novel “turn on” fluorescent probe, 4-((1Z,3Z)-1,4-bis(4-(methoxycarbonyl)phenyl)-4-(pyridin-4-yl)buta-1,3-dien-1-yl)-1-methylpyridin-1-ium hexafluorophosphate (TABD-Py-PF6) with an aggregation-induced emission characteristic was synthesized for in-situ quantitation of γ-globulins in the blood serum. It was shown that the TABD-Py-PF6 probe was highly specific for γ-globulins and that other components in the blood serum, including serum albumins, fibrinogen, glucose, urea, and cholesterol, barely interfered with the molecular interactions between TABD-Py-PF6 and γ-globulins. The high specificity of this probe enabled in-situ quantitative detection of γ-globulins without isolation of γ-globulins from the blood serum. The fluorescence intensity of TABD-Py-PF6 was linearly correlated with the concentration of γ-globulins in the ranges of 7.89−300 μg/mL. The detection limit of γ-globulins was determined to be 7.89 μg/mL. The fluorescence response time of TABD-Py-PF6 for detecting γ-globulins was very short (below 5 s), allowing for real-time detection. The mechanism of the fluorescent turn-on behavior of the TABD-Py-PF6 probe was investigated and electrostatic interactions between TABD-Py-PF6 and γ-globulins were identified.

Novel fluorescent probes based on the 1,2,5-triphenylpyrrole core containing a different number of tertiary amine moieties, 2-(dimethylamino)ethyl 4-(2,5-diphenyl-1H-pyrrol-1-yl)benzoate (TPP-DMAE), bis(2-(dimethylamino)ethyl) 4,4′-(1-phenyl-1H-pyrrole-2,5-diyl)dibenzoate (TPP-BDMAE) and tris(2-(dimethylamino)ethyl) 4,4′,4′′-(1H-pyrrole-1,2,5-triyl)tribenzoate (TPP-TDMAE), with an aggregation-enhanced emission (AEE) feature, were prepared for the quantitative detection of low levels of carbon dioxide in the gas mixture with the fraction of carbon dioxide ranging from 0.4% to 5%. Compared with the other two compounds, TPP-TDMAE showed the most selective, fastest and most iterative response to carbon dioxide. A significant fluorescence decrease with a turn-off ratio over 20-fold was triggered by the disaggregation process through the reaction with carbon dioxide. Response time results indicated that the emission intensity of TPP-TDMAE can be quickly decreased to the minimum level in less than 12 s upon bubbling of carbon dioxide. It is desirable to develop a novel method for the selective, real-time and quantitative detection of CO2 for biological and medical applications.

Here we report the synthesis of two diaminomaleonitrile-based Schiff bases with a donor–acceptor structure and an aggregation-enhanced emission feature. By changing the alkyl chain length in the donor unit, a red-emitting material with remarkable mechanochromic properties and applications in bioimaging was generated due to the J-aggregate formation in the solid state.

A “turn-on” fluorescent sensor, sodium 4,4′,4′′-(1H-pyrrole-1,2,5-triyl)tri-benzoate (Py(PhCOO-Na)3), has been prepared for the detection of Al3+ in aqueous solution. The detection mechanism, as well the mechanism specific to Al3+, was studied by fluorescence spectroscopy, UV-vis spectroscopy and dynamic light scattering (DLS) measurement. Py(PhCOONa)3 exhibited an aggregation-induced emission (AIE) characteristic and was found to show a specific affinity to Al3+, as indicated by the enhanced and bathochromically shifted emission of the AIE fluorogen. Upon binding Al3+, a significant fluorescence enhancement with a turn-on ratio of over 10-fold was triggered by the AIE process. Moreover, this sensor is highly selective for Al3+ over other metal ions with a detection limit of 5 μM and a quantitative detection range of 5–120 μM, and is able to be used in the determination of Al3+ in drinking water. The time-response investigation indicates that the emission intensity of (Py(PhCOO−)3) can be quickly boosted to reach the maximum intensity in less than 10 s upon titration of Al3+.

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.

A dye emitted red fluorescence with aggregation-enhanced emission properties was reported here. It can be utilized to specifically recognize the cell membrane of MCF-7 and 293T cell lines during bio-imaging.

Reversible piezochromic luminescence and aggregation induced emission properties of 4,4′-((Z,Z)-1,4-diphenylbuta-1,3-diene-1,4-diyl)dibenzoic acid are reported. The photoluminescent color of it changes from blue to yellow-green upon grinding, which can be restored upon exposure to a solvent. Intermolecular hydrogen bonding plays a key role in the altered emission.

A water-soluble, ‘turn-on’ fluorescent chemosensor based on aggregation-induced emission (AIE) has been developed. It exhibits rapid response, excellent selectivity, and sensitivity to Al3+.