1:30pm - 1:45pmOral
Clusteroluminescence of Thienylethenes
Department of Chemistry and Hong Kong Branch of Chinese National Engineering, Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Hong Kong (S.A.R.) China
Tetrathienylethene, TTE in which four thiophene rings as rotors linked to a central double bond stator trough single bond, exhibits the aggregation-induced emission (AIE) phenomenon. Such behaviour can be explained by the mechanism of restriction of intramolecular rotations which prevents the energy loss of the excitation trough non-radiative relaxation channel. Closer investigation of its light emitting property, reveals a remarkable emission red-shift of 35 nm from the aggregate state to the crystal state. A similar emission red-shift of 37 nm from the aggregate to the crystal state, was also observed for trans-dithienylethene, DTE. Analasys of their crystals suggest that such phenomenon is ascribable to the presence of strong S···S intra- and intermolecular interactions with distances of 3.669 Å for TTE and 3.679 Å for DTE. These interactions could help explain the photoluminescence of unconventional luminophores and luminescence of non-conjugated biomacromolecules.
1:45pm - 2:00pmOral
Aggregation-Induced Emission of Hexaphenyl-1,3-butadiene Deriveatives
Beijing Institute of Technology, China
E/Z isomers of dialdehyde-containing hexaphenyl-1,3-butadiene (HPB), EE-HPB-CHO, EZ-HPB-CHO and ZZ-HPB-CHO, were firstly synthesized in one-pot and readily separated by silica gel column chromatography. Among them, EE-HPB-CHO with dense molecular packing and strong intermolecular interaction was a better AIEgen while the EZ- and ZZ-isomers exhibited aggregation-enhanced emission (AEE) behavior. Experimental results revealed that the restriction of intramolecular rotations (RIR) is the primary cause of the AIE/AEE behavior of HPB-CHO luminogens. Compared with two other HPB-CHO isomers, the ZZ-HPB-CHO isomer displayed the most remarkable mechanochromic effects because of its twisting conformation and relative loose packing.
A novel nitrile-containing HPB deriveative, ZZ-HPB-CN, was furtherly prepared by the reaction of ZZ-HPB-CHO with malononitrile via Knoevenagel condensation for the one-to-more amine recognition. ZZ-HPB-CN exhibits the excellent AEE property. The ZZ-HPB-CN strip can be used to detect amine via fluorescence, UV and naked-eye detections. The the limit of detection of the ZZ-HPB-CN sensor for amine vapors reached 1 ppb by fluoresence detection.
The coordination compound [HPB→BCF] based on EE-HPB-CHO and tri(pentafluorophenyl)borane (BCF) 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 AIE or AEE characteristics.
We believe our works can considerably contribute to the understanding of the AIE phenomenon and mechanism, and to expanding the application fields of AIE-based materials.
2:00pm - 2:30pmInvited
Fluorescent Systems for Sensing and Imaging Biomolecules
South China University of Technology, China
The detection of biomarkers is of great significance in terms of early diagnosis of major diseases and pathological analysis, as well as monitoring disease progression and evaluating therapeutic efficacy. Functional fluorescent systems could enable a non-invasive, convenient and clinically translatable way for detecting biomarkers, as well as offer such advantages as high sensitivity and easy operation, hence they hold great promise as versatile scaffolds for the development of new tunable and multifunctional sensing and imaging systems. Some biomolecules can serve as biomarkers for related diseases. Herein, amphiphilic polymers, charged polymers and neutral polymers were employed to fabricate functional fluorescent systems for sensing and imaging biomolecules. On one hand, responsive-unit-containing AIE fluorophores were encapsulated by using amphiphilic polymers, so that AIE-based nanoprobes can be obtained for detecting some biomarkers (e.g. γ-glutamyltranspeptidase and ROS species); and the nanoprobes are operable in biological samples. On the other hand, we adopted carbon dots as the carriers for some multifunctional fluorescent systems combining sensing, targeting and/or therapeutic capabilities. For example, carbon dots were adopted as the scaffold for building the therapeutic nanoparticle which is capable of releasing a photosensitizer bioprecursor under two-photon irradiation for photodynamic therapy. The strategies mentioned herein could offer new approaches for fabricating functional fluorescent systems for bio-related applications.
2:30pm - 2:45pmOral
Effective Methods to Improve the Fluorescence Properties of Organic Materials in their Aggregated States
Xi'an JiaoTong University, China
Currently, the organic materials for bio-imaging are under intensive research for their advantages of good chemical stability, tailorability, high quantum yield and also good biocompatibility. However, for these mentioned organic dyes, the main challenge is that their fluorescent intensity of organic fluorophores tends to decrease seriously when they are in close contact caused by the aggregation-caused quenching (ACQ) effect. Therefore, to solve this problems, effective methods should be proposed and aggregation induced emission (AIE) strategy by developing the non-planar structures containing several rotors are widely used now. On the other hand, the method that "isolating" and "fastening" the fluorescent moieties into a stable cross-linked polyphosphazene (PPZ) to form the fixed networks is also proposed. Meanwhile, a facile method that grown an alkyl "cocoon" on fluorescent organic molecules can also be developed to improve their fluorescence properties, which do not need the careful molecular design to obtain the special molecular structures. When the alkyl "cocoon" were grafted in the molecular backbone, remarkably enhanced fluorescence intensity together with much increased quantum yield was achieved in the thin solids, indicating the great potentials for application in the bio-imaging.
2:45pm - 3:15pmInvited
Through-Space Conjugated AIEgens for Single-Molecule Wires with Multichannel Conductance
South China University of Technology, China
Deciphering charge transport through single-molecule junction is of high importance to rationally design and construct future bottom-up electronic devices. However, the widely studied molecular junctions are confined to the through-bond conjugated rod-like molecules, which is likely to reach the limit where efficient and reliable molecular devices are out of feasibility. Herein, we developed a series of novel luminogens with aggregation-induced emission (AIEgens) featuring through-space conjugation. The presence of through-space conjugation rigidifies the molecular structures and enhances emission efficiencies of the AIEgens in solutions, which provides direct evidences for AIE mechanism of restriction of intramolecular motions. Single-molecule wires are constructed based on through-space conjugated AIEgens, and their conductance is measured in metal-molecule-metal junctions using the scanning tunneling microscope-based break-junction (STM-BJ) technique. The new molecular wires exhibit advanced conductance relative to traditional π‒conjugated linear ones. It is demonstrated that their high conductance is achieved by the cooperative effect of the through-space and through-bond tunneling pathways, which can improve the charge transfer probability. The construction of single-molecule junction with multiple tunneling channels is not only of conceptual advance but also of significant importance to obtain molecular wires with excellent charge transport ability and stability.
3:15pm - 3:30pmOral
Understanding Heavy Metal Ions Bioaccumulation in Small Aquatic Organisms by a Specified Aggregation-induced Emission Fluorogen (AIEgen)
1Flinders University, Australia; 2The Hong Kong University of Science and Technology, Hong Kong S.A.R. (China)
Bioaccumulationis a process of gradual build-up of pollutants in living organisms through which the concentration of a chemical in an organism exceeds that in the medium. Bioaccumulation occurs within a trophic level. Aquatic organisms accumulate, retain and transform toxic substances inside their bodies and longer lived organisms usually accumulate more toxic substances. Toxic substance accumulation can cause mutation of genetic materials and even death of aquatic organisms. Traditional methods for describing toxic bioaccumulation are limited because they usually provide only a “snapshot” of organisms for a particular season, life history stage or location, and the mechanism of toxic substance transfer along time is largely unknown, especially in small organisms. Small organisms at the lower levels are important trophic links between primary producers and larger zooplankton because they begin the accumulation of toxic substances at the base of food chains. Therefore, there is a compelling need to develop new methodology to detect and quantify toxic substances in aquatic organisms in vivo to understand the mechanisms. Since bioaccumulation are naturally occurring aggregation processes, AIEgens with specific design can provide new tools for tracking and understanding the processes of toxic substance transfer and enrichment in bioaccumulation in small aquatic organisms. Consequently, a novel methodology can be established based on the study of bioaccumulation.
In this study, Euglena gracilis, a model algal for nutrient absorption and rotifers, an important part of the zooplankton and a major food source were selected as the small aquatic organisms and Hg2+ was used as the pollutant. A novel methodology was developed using a specified AIEgen to monitor and quantify the complex bioaccumulation process in a microcosm aquatic ecosystem. Bioaccumulation, bioaccumulation efficiency, and in situ Hg2+ transfer kinetics were carefully characterized by this novel method and results were validated with the existing analytical method.