Conference Programme

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Overview
Session
T2-05: Symp T
Time:
Tuesday, 20/Jun/2017:
4:00pm - 6:15pm

Session Chair: Deqing Zhang, Chinese Academy of Sciences, Beijing
Location: Nicoll 3

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Presentations
4:00pm - 4:15pm
Oral

Chemo-/biosensing and Imaging with Aggregation Induced Emission Luminogens

Deqing ZHANG

Institute of Chemistry, Chinese Academy of Sciences, China

Normally, luminogens become weakly emissive after aggregation either in the solution or solid state. This feature limit their applications in various areas. However, there are luminogens referred as to “aggregation-induced emission” (AIE) by Tang and his coworkers exhibit abnormal fluorescence behavior; they are almost non-emissive in solution, but they show strong emission after aggregation. We and others have disclosed series of chemo/biosensors by manipulating the aggregation and deaggregation of AIE luminogens including silole and tetraphenylethylene molecules. In this presentation, I will introduce AIE-based bio-/chemosensors for nuclease and AChE assay, screening of inhibitors, and detections of various analytes including charged biopolymers and ionic species. In comparison with conventional fluorophores AIE luminogens enable us to realize fluorescence turn-on detection of biomolecules and on-site, label-free enzyme assays as well as high-throughout inhibitor screening. Moreover, these AIE luminogens were successfully utilized for fluorescence turn-on cell imaging after conjugation with appropriate targeting groups. This fluorescence imaging can be carried out without multiple washing steps with rather low background fluorescence.


4:15pm - 4:30pm
Oral

Highly Emissive Pentagonal Phenyl-Expanded Radialene: Synthesis, Structure, and the Precursor for Carbon Nanosheet

Zikai HE1, Ben Zhong TANG2

1Harbin Institute of Technology Shenzhen, China; 2Department of Chemistry, The Hong Kong University of Science and Technology, Hong Kong S.A.R. (China)

Shape-persistent, conjugated macrocycles have attracted continuous interest because of their synthetic challenges, fantastic topologies, unique self-assembly behavior as well as optical properties. A unique family of these macrocycles are the radialenes, which are containing only sp2-hybridized carbons. Although [3]-, [4]-, and [6]-radialenes have been prepared and studied for decades, the attempts to synthesize the [5]-radialene was successful until 2015 due to its high reactivity. On the other hand, expanded radialenes arising from the insertion of acetylene units into the framework of a radialene molecule have been well investigated, but phenyl-expanded radialenes (PERs) are rarely reported to the best of our knowledge. Here we present the synthesis and characterization of the first phenyl-expanded [5]radialene macrocycle (MC5-PER).

Careful examination of the structure of PER reveals the tetraphenylethylene subunit embedding in the macrocycle, which is an archetypal aggregation-induced emissive (AIE) luminogen. Luminescent materials with AIE characteristics have recently been extensively applied in chemo/biosensors. PERs would be potentially highly luminescent at aggregated states and function as the promise fluorescent sensor. Oxidation coupling the TPE affords the dibenzo[g,p]chrysene, a twisted polycyclic aromatic hydrocarbon used as functional materials in electronic and optoelectronic devices. Selective oxidation coupling of MC5-PER would afford a carbon holey-nanosheet with well-defined structure, which is about 2 nm in diameter. The holey-nanosheets play an essential role in applications, such as supercapacitors, electrode materials, and energy storage. Thus, the synthesis of specific graphene segments with holes is of importance to investigate the influence of the holes on the electronic properties.

Herein we describe a facile synthesis of the first macrocylic phenyl-expanded radialene that becomes highly emissive upon aggregation due to AIE effect. Unexpected pentagonal architecture results in smaller ring strain and better conjugation. Its interesting self-assembly behaviour leads polymorphism-dependent emission. Features of the explosive sensor and precursor for carbon nanosheet demonstrated its promising applications.


4:30pm - 4:45pm
Oral

Stimuli-responsive Luminescence of Aggregation Induced Emission Molecules

Bin XU, Wenjing TIAN

State Key Laboratory of Supramolecular Structure and Materials, Jilin University, China

Luminescent materials sensitive to environmental stimuli have been attracted intensive interests over the past decade to their potential applications in fluorescent switches and optical devices. However, organic stimuli-responsive luminescent materials were limited several years ago.

In the past few years, our group has been synthesized many stimuli-responsive luminescent materials, including piezochromic luminescent materials and proton-triggered hypsochromic luminescent chromophore. We have reported piezochromic luminescence of 9, 10-bis(( E )-2-(pyrid-2-yl)vinyl)anthracene (BP2VA), which showed gradually redshifted wavelength and decreased intensity of luminescence due to the enhanced π–π interaction under the hydrostatic pressure, and of AD-TPE, which showed an intriguing turn-on and color-tuned piezochromic luminescence in response to the mechanical grinding and the hydrostatic pressure. For AD-TPE, the almost orthogonal conformation between TPE and AD fully separates the electronic distribution and inhibits the ICT process, leading to the emission from LE state in the D-phase of the molecular crystals. Thus, the switching of excited state characteristics by the mechanical stimuli induced the change in luminescence from the nonemission D-phase to the bright cyan emission B-phase. These studies provide detailed insights into the origin of the color-switchable feature and will inspire the development of a new class of novel functional chromophores for optical-recording and temperature-, pressure- or acid/base sensing materials.

References:

[1] Y. Dong, B. Xu, B. Zou, W. Tian, et al. Angew. Chem. Int. Ed. 2012, 51, 10782.

[2] Qi, Q.; Xu, B.; Zou, B.; Tian, W. et al. Adv. Funct. Mater. 2015, 25, 4005.

[3] J. Chen, B. Xu, W. Tian, et al. J. Phys. Chem. Lett. 2014, 5, 2781.


4:45pm - 5:00pm
Oral

Synthesis and Device Application of an AIE-active Dibenzothiophene Derivative as Thermally Activated Delayed Fluorescence Material with Small ΔEST

Xin HE, Ping LU

Jilin University, China

Organic materials that can emit strongly in visible range have attracted continuously attentions due to their potential application in large-scale flat-panel displaying and solid-state lighting. According to the spin statistics in OLEDs, the ratio of singlet and triplet excitons is 1:3 under electrical excitation. Thus, OLEDs based on traditional fluorescent materials can only harvest singlet excitons which suffer from a superior limit of internal quantum efficiency (IQE) of 25%. Innovatively, Adachi et al arises thermally activated delayed fluorescence (TADF) mechanism for pure organic materials to harvest triplet excitons through reverse intersystem crossing (RISC) from the lowest excited triplet state (T1) to the lowest excited singlet state (S1). TADF is generally observed in charge transfer (CT) system containing electron donor and acceptor with localized states (LE). Only when the LE3 state is close to or even higher than the CT3 state can efficient RISC between the CT1 and CT3 happen. Generally speaking, big torsion angle can be formed when introducing the comparatively large steric hindrance between the electron donor and acceptor, which would lead to a small overlap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and may realize small splitting energy between singlet and triplet eventually. Here, we report the realization of a comparable small ΔEST of 0.10 eV in a pure organic TADF material based on DBTDO and its application in OLEDs. 9,9-Diphenyl-9,10-dihydroacridine (DPAC), which possesses large steric hindrance and a rather high triplet energy when substituted on the 9-site, is adopted as electron donor. The resulting DPAC-DBTDO shows good thermal stability, aggregation-induced emission and a very high quantum efficiency of nearly 100% in solid-state. The small ΔEST guarantees the occurrence of efficient RISC process. A much improved OLEDs performance with a maximum EQE of 13.1% is achieved based on this new DBTDO-based AIEgen.



 
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