Jianbing Shi

Aggregation-Induced Emission Enhancement of Aryl-Substituted Pyrrole Derivatives

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.

A highly sensitive, single selective, real-time and “turn-on” fluorescent sensor for Al3+ detection in aqueous media

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+.

Crystallization-Induced Emission Enhancement in a Phosphorus-Containing Heterocyclic Luminogen

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.

Mechanochromic Behavior of Aryl-Substituted Buta-1,3-Diene Derivatives with Aggregation Enhanced Emission

Three tetra-aryl substituted 1,3-butadiene derivatives with aggregation enhanced emission (AEE) and mechanochromic fluorescence behavior have been rationally designed and synthesized. The results suggest an effective design strategy for developing diverse materials with aggregation induced emission (AIE) and significant mechanochromic performance by employing D-π-A structures with large dipole moments.

DMF-induced emission of an aryl-substituted pyrrole derivative: a solid thermo-responsive material to detect temperature in a specific range

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 ( 85 °C), good reversibility and solvent-free procedure make TPPA a thermo-responsive material for use in temperature monitoring devices.

A fluorescent probe with an aggregation-enhanced emission feature for real-time monitoring of low carbon dioxide levels

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.

Fabrication and optoelectronic properties of novel films based on functionalized multiwalled carbon nanotubes and (phthalocyaninato)ruthenium(II) via coordination bonded layer-by-layer self-assembly.

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/cm(2)) at nine bilayers. These results allow us to design novel materials for applications in optoelectronic devices by using LBL self-assembly techniques.

Diaminomaleonitrile-based Schiff bases: aggregation-enhanced emission, red fluorescence, mechanochromism and bioimaging 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.

Aggregation-induced emission enhancement in poly(phenylene-ethynylene)s bearing aniline groups

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.

An AIEE polyelectrolyte as a light-up fluorescent probe for heparin sensing in full detection range

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.