Publications by authors named "Haoke Zhang"

49 Publications

Through-Space Interactions in Clusteroluminescence.

JACS Au 2021 Nov 30;1(11):1805-1814. Epub 2021 Sep 30.

Shenzhen Institute of Aggregate Science and Technology, School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen 518172, China.

Conventional π-conjugated luminophores suffer from problems such as emission quenching, biotoxicity, environmental pollution, etc. The emerging nonconjugated and nonaromatic clusteroluminogens (CLgens) are expected to overcome these stubborn drawbacks, so research of CLgens shows great significance not only for practical application but also for the construction of fundamental photophysical theories. This perspective summarizes the unusual features of CLgens in comparison to traditional chromophores, such as nonconjugated molecular structures, unmatched absorption and excitation, excitation-dependent luminescence, multiple emission peaks, and room-temperature phosphorescence. Different from the theory of through-bond conjugation in π-conjugated luminophores, through-space interactions, including through-space n···n interaction and through-space n···π interaction, are regarded as the emitting sources of nonconjugated CLgens. In addition, the formation of network clusters is proposed as an efficient strategy to improve the performance of CLgens, and their potential applications of anticounterfeiting, photoelectronic devices, and bioimaging are prospected.
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http://dx.doi.org/10.1021/jacsau.1c00311DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8611663PMC
November 2021

A synergy between the push-pull electronic effect and twisted conformation for high-contrast mechanochromic AIEgens.

Mater Horiz 2021 Feb 15;8(2):630-638. Epub 2020 Dec 15.

AIE Research Center, Shaanxi Key Laboratory of Phytochemistry, College of Chemistry and Chemical Engineering, Baoji University of Arts and Sciences, Baoji 721013, China.

Mechanochromic (MC) luminogens in response to external stimulus have shown promising applications as pressure sensors and memory devices. Meanwhile, research on their underlying mechanism is still in the initial stage. Here, three pyridinium-functionalized tetraphenylethylenes bearing n-pentyloxy, hydrogen and nitro groups, namely TPE-OP, TPE-H and TPE-NO, are designed to systematically investigate the influence of the push-pull electronic effect and molecular conformation on MC luminescence. Upon anisotropic grinding and isotropic hydrostatic compression, TPE-OP with strong intramolecular charge transfer (ICT) affords the best MC behavior among them. Analysis of three polymorphs of TPE-H clearly indicates that planarization of the molecular conformation plays an important role in their bathochromic shifts under mechanical stimuli. Theoretical calculations also verify that high twisting stress of AIEgens can be released under high pressure. This study presents a mechanistic insight into MC behaviour and an effective strategy to achieve high-contrast MC luminescence.
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http://dx.doi.org/10.1039/d0mh01251cDOI Listing
February 2021

Altering Chain Flexibility of Aliphatic Polyesters for Yellow-green Clusteroluminescence in 38% Quantum Yield.

Angew Chem Int Ed Engl 2021 Nov 25. Epub 2021 Nov 25.

The Hong Kong University of Science and Technology, Department of Chemistry, CHINA.

Preparation of non-conjugated polymers with long-wavelength emission and high quantum yield (QY) is still a huge challenge. Herein, we report the first example of linear non-conjugated polyester exhibiting yellow-green clusteroluminescence (CL) and a high QY of 38%. We discovered that the polyester P3 with balanced flexibility and rigidity showed the longest CL wavelength and highest QY. Systematically photophysical characterization unravel the key role of ester cluster in the CL and the cluster formation via the aggregate of ester units was visualized. Moreover, P3 was demonstrated to be a highly selective, quick-responsive (~1.2 min) and sensitive detector (detection limit is 0.78 μM) for irons owing to the fast disassociation of clusters by irons. This work not only gains further mechanistic insight into CL but also provides a new strategy to design high-efficiency and long-wavelength CL, meanwhile, enlightens the glorious application prospect of luminescent polyester.
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http://dx.doi.org/10.1002/anie.202114117DOI Listing
November 2021

A Mitochondria-targeted AIEgen Labelled with F for Breast Cancer Cell Imaging and Therapy.

Chem Asian J 2021 Dec 20;16(23):3963-3969. Epub 2021 Oct 20.

Department of Nuclear Medicine and PET-CT Center, The Second Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, 310009, P. R. China.

A lack of efficient diagnostic tools for early and noninvasive diagnosis of breast cancer has restricted the clinical treatment effect. This problem might be addressed by the combination of aggregation-induced emission (AIE) fluorescence imaging and positron emission tomography (PET) with the dual advantages of high resolution and easy operation, and unlimited penetration and high sensitivity. Here, a mitochondria-targeted AIE luminogen (AIEgen) radiolabeled with F was developed through a two-step radiochemical reaction by virtue of a prosthetic group. The obtained F-Bz-CP imaging probe was examined by in vitro cell uptake and cell proliferation inhibition in two breast cancer cell lines, showing that the probe can efficiently target and locate in the mitochondria through the analysis of fluorescence imaging and PET simultaneously. Additionally, the probe can induce cancer cell apoptosis with the half maximal inhibitory concentration (IC50) of 4.8 μM for MCF-7 cells and 7.2 μM for T47D cells, indicating its potential application for breast cancer therapy.
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http://dx.doi.org/10.1002/asia.202101029DOI Listing
December 2021

Visualization and Manipulation of Solid-State Molecular Motions in Cocrystallization Processes.

J Am Chem Soc 2021 06 21;143(25):9468-9477. Epub 2021 Jun 21.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Department of Chemical and Biomedical Engineering, Institute for Advanced Study, and Guangdong Hong Kong Macro Joint Laboratory of Optoelectronic and Magnetic Functional Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Solid-state molecular motions (SSMM) play a critical role in adjusting behaviors and properties of materials. However, research on SSMM, especially for multicomponent systems, suffers from various problems and is rarely explored. Herein, through collaboration with cocrystal engineering, visualization and manipulation of SSMM in two-component systems, namely, FSBO (()-2-(4-fluorostyryl)benzo[]oxazole)/TCB (1,2,4,5-tetracyanobenzene) and PVBO (()-2-(2-(pyridin-4-yl)vinyl)benzo[]oxazole)/TCB, were realized. The obtained yellow-emissive F/T (FSBO/TCB) cocrystal displayed turn-on fluorescence, and the green-emissive P/T (PVBO/TCB) cocrystal presented redder emission, both of which exhibited an aggregation-induced emission property. At varied pressure and temperature, the grinding mixtures of FSBO/TCB and PVBO/TCB displayed different molecular motions that were readily observed through the fluorescence signal. Notably, even without grinding, FSBO and TCB molecules could move over for 4 mm in a 1D tube. The unique emission changes induced by SSMM were applied in information storage and dynamic anticounterfeiting. This work not only visualized and manipulated SSMM but offered more insights for multicomponent study in aggregate science.
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http://dx.doi.org/10.1021/jacs.1c02594DOI Listing
June 2021

Stimuli-Responsive AIEgens.

Adv Mater 2021 Aug 17;33(32):e2008071. Epub 2021 Jun 17.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

The unique advantages and the exciting application prospects of AIEgens have triggered booming developments in this area in recent years. Among them, stimuli-responsive AIEgens have received particular attention and impressive progress, and they have been demonstrated to show tremendous potential in many fields from physical chemistry to materials science and to biology and medicine. Here, the recent achievements of stimuli-responsive AIEgens in terms of seven most representative types of stimuli including force, light, polarity, temperature, electricity, ion, and pH, are summarized. Based on typical examples, it is illustrated how each type of systems realize the desired stimuli-responsive performance for various applications. The key work principles behind them are ultimately deciphered and figured out to offer new insights and guidelines for the design and engineering of the next-generation stimuli-responsive luminescent materials for more broad applications.
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http://dx.doi.org/10.1002/adma.202008071DOI Listing
August 2021

How to Manipulate Through-Space Conjugation and Clusteroluminescence of Simple AIEgens with Isolated Phenyl Rings.

J Am Chem Soc 2021 Jun 11;143(25):9565-9574. Epub 2021 Jun 11.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China.

Apart from the traditional through-bond conjugation (TBC), through-space conjugation (TSC) is gradually proved as another important interaction in photophysical processes, especially for the recent observation of clusteroluminescence from nonconjugated molecules. However, unlike TBC in conjugated chromophores, it is still challenging to manipulate TSC and clusteroluminescence. Herein, simple and nonconjugated triphenylmethane (TPM) and its derivatives with electron-donating and electron-withdrawing groups were synthesized, and their photophysical properties were systematically studied. TPM was characterized with visible clusteroluminescence due to the intramolecular TSC. Experimental and theoretical results showed that the introduction of electron-donating groups into TPM could red-shift the wavelength and increase the efficiency of clusteroluminescence simultaneously, due to the increased electronic density and stabilization of TSC. However, TPM derivatives with electron-withdrawing groups showed inefficient or even quenched clusteroluminescence caused by the vigorous excited-state intramolecular motion and intermolecular photoinduced electron transfer process. This work provides a reliable strategy to manipulate TSC and clusteroluminescence.
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http://dx.doi.org/10.1021/jacs.1c03882DOI Listing
June 2021

An Air-Stable Organic Radical from a Controllable Photoinduced Domino Reaction of a Hexa-aryl Substituted Anthracene.

J Org Chem 2021 Jun 25;86(11):7359-7369. Epub 2021 May 25.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Air-stable organic radicals and radical ions have attracted great attention for their far-reaching application ranging from bioimaging to organic electronics. However, because of the highly reactive nature of organic radicals, the design and synthesis of air-stable organic radicals still remains a challenge. Herein, an air-stable organic radical from a controllable photoinduced domino reaction of a hexa-aryl substituted anthracene is described. The domino reaction involves a photoinduced [4 + 2] cycloaddition reaction, rearrangement, photolysis, and an elimination reaction; H/C NMR spectroscopy, high resolution mass spectrometry, single-crystal X-ray diffraction, and EPR spectroscopy were exploited for characterization. Furthermore, a photoinduced domino reaction mechanism is proposed according to the experimental and theoretical studies. In addition, the effects of employing push and pull electronic groups on the controllable photoinduced domino reaction were investigated. This article not only offers a new blue emitter and novel air-stable organic radical compound for potential application in organic semiconductor applications, but also provides a perspective for understanding the fundamentals of the reaction mechanism on going from anthracene to semiquinone in such anthracene systems.
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http://dx.doi.org/10.1021/acs.joc.1c00233DOI Listing
June 2021

Clusteroluminescence from Cluster Excitons in Small Heterocyclics Free of Aromatic Rings.

Adv Sci (Weinh) 2021 04 11;8(7):2004299. Epub 2021 Feb 11.

Department of Chemistry The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong 999077 China.

The study of nonconventional luminescence is important for revealing the luminescence of natural systems and has gradually drawn the attention of researchers in recent years. However, the underlying mechanism is still inexplicable. Herein, the luminescence behavior of two series of simple, heteroatom-containing small molecules without aromatic rings, i.e., maleimide and succinimide derivatives, are studied to gain further mechanistic insight into the nonconventional luminescence process. It has been unveiled that all the molecules exhibit bright and visible luminescence in concentrated solution and solid state and the formation of clusters is the root cause for such behaviors, which can effectively increase the possibility of both the nonradiative n-* and favorable -* transitions and stabilize the excitons formed in the excited state. The distinctive luminescent phenomena and intriguing mechanism presented in this work will be significant for understanding the mechanism of clusteroluminescence and provide new strategies for the rational design of novel luminescent materials.
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http://dx.doi.org/10.1002/advs.202004299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025018PMC
April 2021

Chemiluminescence Resonance Energy Transfer Efficiency and Donor-Acceptor Distance: from Qualitative to Quantitative.

Angew Chem Int Ed Engl 2021 06 5;60(23):13029-13034. Epub 2021 May 5.

State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, China.

Since its birth in 1967, the utilization of chemiluminescence resonance energy transfer (CRET) has made substantial progress in a variety of fields for its unique features. However, the quantitative relationship between CRET efficiency and donor-acceptor distance has not yet been determined owing to the difficulty in designing the variable lengths between chemiluminescent donors and acceptors. Herein, we synthesized three kinds of tetraphenylethene (TPE)-anchored cationic surfactants with aggregation-induced emission (AIE) characteristics. For the first time, it is quantitatively demonstrated that the CRET efficiency is inversely proportional to the sixth power of distance between luminol donors and TPE acceptors. The details disclosed in this contribute have provided the solid evidence that CRET follows Förster resonance theory. Our strategy would build a promising platform to control donor-acceptor distance, allowing to the interdisciplinary applications of CRET.
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http://dx.doi.org/10.1002/anie.202102999DOI Listing
June 2021

Sulfur Conversion to Multifunctional Poly(-thiocarbamate)s through Multicomponent Polymerizations of Sulfur, Diols, and Diisocyanides.

J Am Chem Soc 2021 03 3;143(10):3944-3950. Epub 2021 Mar 3.

MOE Key Laboratory of Macromolecules Synthesis of Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China.

Sulfur, which is generated from the waste byproducts in the oil and gas refinery industry, is an abundant, cheap, stable, and readily available source in the world. However, the utilization of excessive amounts of sulfur is mostly limited, and developing novel methods for sulfur conversion is still a global concern. Here, we report a facile one-step conversion from elemental sulfur to functional poly(-thiocarbamate)s through a multicomponent polymerization of sulfur, diols, and diisocyanides, which possesses a series of advantages such as mild condition (55 °C), short reaction time (1 h), 100% atom economy, and transition-metal free in the catalyst system. Seven poly(-thiocarbamate)s are constructed with high yields (up to 95%), large molecular weight (up to 53100 of ), good solubility in organic solvents, and completely new polymer structures. The poly(-thiocarbamate)s possess a high refractive index above 1.7 from 600 to 1700 nm by adjusting the sulfur content. By incorporating tetraphenylethene (TPE) moieties into the polymer structure, the poly(-thiocarbamate)s can also be designed as fluorescent sensors to detect harmful metal cation of Hg in a turn-on mode with high sensitivity (LOD = 32 nM) and excellent selectivity (over interference cations of Pb, Au, Ag). Different from the previous reports, the exact coordination structure is first identified by single-crystal X-ray diffraction, which is revealed in a tetracoordination fashion (two sulfur and two chloride) using a model coordination compound.
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http://dx.doi.org/10.1021/jacs.1c00243DOI Listing
March 2021

Recent Advances in Clusteroluminescence.

Top Curr Chem (Cham) 2021 Mar 3;379(2):14. Epub 2021 Mar 3.

Department of Chemistry, City University of Hong Kong, Hong Kong, China.

Clusteroluminescence is a phenomenon whereby the aggregation or clustering of non-conjugated electron-rich units leads to the emission of light at long wavelengths. This phenomenon was first discovered in poly(amido amine) (PAMAM) dendrimers. In recent years, clusteroluminescence has attracted growing research interest and its photophysical properties and mechanism have been thoroughly studied. In this review, we first briefly introduce the development of different types of clusteroluminogens. Then we highlight recent developments in clusteroluminescence, including mechanistic studies, the disclosure of room-temperature phosphorescence, and the extension of emission to the longer-wavelength region. Lastly, we demonstrate a few applications in various fields. With advantages such as being earth-abundant, biocompatible and biodegradable, clusteroluminogens are envisioned to be commonplace in the future.
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http://dx.doi.org/10.1007/s41061-021-00326-wDOI Listing
March 2021

Facilitation of molecular motion to develop turn-on photoacoustic bioprobe for detecting nitric oxide in encephalitis.

Nat Commun 2021 02 11;12(1):960. Epub 2021 Feb 11.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering and Institute of Molecular Functional Materials, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.

Nitric oxide (NO) is an important signaling molecule overexpressed in many diseases, thus the development of NO-activatable probes is of vital significance for monitoring related diseases. However, sensitive photoacoustic (PA) probes for detecting NO-associated complicated diseases (e.g., encephalitis), have yet to be developed. Herein, we report a NO-activated PA probe for in vivo detection of encephalitis by tuning the molecular geometry and energy transformation processes. A strong donor-acceptor structure with increased conjugation can be obtained after NO treatment, along with the active intramolecular motion, significantly boosting "turn-on" near-infrared PA property. The molecular probe exhibits high specificity and sensitivity towards NO over interfering reactive species. The probe is capable of detecting and differentiating encephalitis in different severities with high spatiotemporal resolution. This work will inspire more insights into the development of high-performing activatable PA probes for advanced diagnosis by making full use of intramolecular motion and energy transformation processes.
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http://dx.doi.org/10.1038/s41467-021-21208-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7878857PMC
February 2021

Aggregation-Induced Generation of Reactive Oxygen Species: Mechanism and Photosensitizer Construction.

Molecules 2021 Jan 7;26(2). Epub 2021 Jan 7.

MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China.

Luminogens with aggregation-induced emission (AIEgens) have been widely applied in the field of photodynamic therapy. Among them, aggregation-induced emission photosensitizers (AIE-PSs) are demonstrated with high capability in fluorescence and photoacoustic bimodal imaging, as well as in fluorescence imaging-guided photodynamic therapy. They not only improve diagnosis accuracy but also provide an efficient theranostic platform to accelerate preclinical translation as well. In this short review, we divide AIE-PSs into three categories. Through the analysis of such classification and construction methods, it will be helpful for scientists to further develop various types of AIE-PSs with superior performance.
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http://dx.doi.org/10.3390/molecules26020268DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7827197PMC
January 2021

Enantiomeric Switching of the Circularly Polarized Luminescence Processes in a Hierarchical Biomimetic System by Film Tilting.

ACS Nano 2021 01 4;15(1):1397-1406. Epub 2020 Dec 4.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Circularly polarized luminescence (CPL) switching has attracted great attention due to the potential applications in chiral photonics and electronics. However, the lack of examples to achieve switchable CPL within a single material in the dry solid state hampers the scope of applications. Herein, we demonstrate a crystalline chiral polymer film as a polarizing medium consisting of radially assembled twisted crystallites, where achiral aggregation-induced emissive luminogens (AIEgens) are confined between the twisted crystalline stacks, eventually yielding handedness-switchable CPL by simple film tilting. Hierarchically organized twisted crystallites create the selective reflection activity of the polarizing medium. Upon film tilting, enantiomeric switching is realized by selectively collecting transmitted and reflected CPL components. The confined AIEgens in the crystalline polarizing system show a great enhancement of the luminescence efficiency. Moreover, the approach is general with broadband activity, and various AIEgens could be applied to generate full-color-tunable CPL. Additionally, the rigid and continuous nature of this polarizing system affords enhanced optical stability and facile modulation, developing a general route for designing chiroptical materials.
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http://dx.doi.org/10.1021/acsnano.0c08665DOI Listing
January 2021

Incorporation of Planar Blocks into Twisted Skeletons: Boosting Brightness of Fluorophores for Bioimaging beyond 1500 Nanometer.

ACS Nano 2020 10 1;14(10):14228-14239. Epub 2020 Oct 1.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Division of Life Science and State Key Laboratory of Molecular Neuroscience, and Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong China.

The brightness of organic fluorescence materials determines their resolution and sensitivity in fluorescence display and detection. However, strategies to effectively enhance the brightness are still scarce. Conventional planar π-conjugated molecules display excellent photophysical properties as isolated species but suffer from aggregation-caused quenching effect when aggregated owing to the cofacial π-π interactions. In contrast, twisted molecules show high photoluminescence quantum yield (Φ) in aggregate while at the cost of absorption due to the breakage in conjugation. Therefore, it is challenging to integrate the strong absorption and high solid-state Φ, which are two main indicators of brightness, into one molecule. Herein, we propose a molecular design strategy to boost the brightness through the incorporation of planar blocks into twisted skeletons. As a proof-of-concept, twisted small-molecule TT3-CB with larger π-conjugated dithieno[3,2-:2',3'-]thiophene unit displays superb brightness at the NIR-IIb (1500-1700 nm) than that of TT1-CB and TT2-CB with smaller thiophene and thienothiophene unit, respectively. Whole-body angiography using TT3-CB nanoparticles presents an apparent vessel width of 0.29 mm. Improved NIR-IIb image resolution is achieved for femoral vessels with an apparent width of only 0.04 mm. High-magnification through-skull microscopic NIR-IIb imaging of cerebral vasculature gives an apparent width of ∼3.3 μm. Moreover, the deeply located internal organ such as bladder is identified with high clarity. The present molecular design philosophy embodies a platform for further development of bioimaging.
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http://dx.doi.org/10.1021/acsnano.0c07527DOI Listing
October 2020

Planar and Twisted Molecular Structure Leads to the High Brightness of Semiconducting Polymer Nanoparticles for NIR-IIa Fluorescence Imaging.

J Am Chem Soc 2020 09 19;142(35):15146-15156. Epub 2020 Aug 19.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Division of Life Science and State Key Laboratory of Molecular Neuroscience, and Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong, China.

Semiconducting polymer nanoparticles (SPNs) emitting in the second near-infrared window (NIR-II, 1000-1700 nm) are promising materials for deep-tissue optical imaging in mammals, but the brightness is far from satisfactory. Herein, we developed a molecular design strategy to boost the brightness of NIR-II SPNs: structure planarization and twisting. By integration of the strong absorption coefficient inherited from planar π-conjugated units and high solid-state quantum yield (Φ) from twisted motifs into one polymer, a rise in brightness was obtained. The resulting pNIR-4 with both twisted and planar structure displayed improved Φ and absorption when compared to the planar polymer pNIR-1 and the twisted polymer pNIR-2. Given the emission tail extending into the NIR-IIa region (1300-1400 nm) of the pNIR-4 nanoparticles, NIR-IIa fluorescence imaging of blood vessels with enhanced clarity was observed. Moreover, a pH-responsive poly(β-amino ester) made pNIR-4 specifically accumulate at tumor sites, allowing NIR-IIa fluorescence image-guided cancer precision resection. This study provides a molecular design strategy for developing highly bright fluorophores.
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http://dx.doi.org/10.1021/jacs.0c07193DOI Listing
September 2020

Aggregate Science: From Structures to Properties.

Adv Mater 2020 Sep 30;32(36):e2001457. Epub 2020 Jul 30.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

Molecular science entails the study of structures and properties of materials at the level of single molecules or small interacting complexes of molecules. Moving beyond single molecules and well-defined complexes, aggregates (i.e., irregular clusters of many molecules) serve as a particularly useful form of materials that often display modified or wholly new properties compared to their molecular components. Some unique structures and phenomena such as polymorphic aggregates, aggregation-induced symmetry breaking, and cluster excitons are only identified in aggregates, as a few examples of their exotic features. Here, by virtue of the flourishing research on aggregation-induced emission, the concept of "aggregate science" is put forward to fill the gaps between molecules and aggregates. Structures and properties on the aggregate scale are also systematically summarized. The structure-property relationships established for aggregates are expected to contribute to new materials and technological development. Ultimately, aggregate science may become an interdisciplinary research field and serves as a general platform for academic research.
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http://dx.doi.org/10.1002/adma.202001457DOI Listing
September 2020

Platinum-AIEgen coordination complex for imaging-guided annihilation of cisplatin-resistant cancer cells.

Chem Commun (Camb) 2020 Jul;56(56):7785-7788

Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China.

We report the synthesis and comprehensive characterization of a new platinum-AIEgen coordination complex. Possessing a high 1O2 quantum yield of 0.75 in water, the complex efficiently kills cisplatin-resistant cancer cells under mild white light irradiation. Its strong fluorescence upon binding with proteins also enables direct visualization of its intracellular distribution.
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http://dx.doi.org/10.1039/d0cc00821dDOI Listing
July 2020

Solid-state intramolecular motions in continuous fibers driven by ambient humidity for fluorescent sensors.

Natl Sci Rev 2021 Apr 17;8(4):nwaa135. Epub 2020 Jun 17.

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, International Joint Laboratory for Advanced Fiber and Low-Dimension Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.

One striking feature of molecular rotors is their ability to change conformation with detectable optical signals through molecular motion when stimulated. However, due to the strong intermolecular interactions, synthetic molecular rotors have often relied on fluid environments. Here, we take advantage of the solid-state intramolecular motion of aggregation-induced emission (AIE) molecular rotors and one-dimensional fibers, developing highly sensitive optical fiber sensors that respond to ambient humidity rapidly and reversibly with observable chromatic fluorescence change. Moisture environments induce the swelling of the polymer fibers, activating intramolecular motions of AIE molecules to result in red-shifted fluorescence and linear response to ambient humidity. In this case, polymer fiber provides a process-friendly architecture and a physically tunable medium for the embedded AIE molecules to manipulate their fluorescence response characteristics. Assembly of sensor fibers could be built into hierarchical structures, which are adaptive to diverse-configuration for spatial-temporal humidity mapping, and suitable for device integration to build light-emitting sensors as well as touchless positioning interfaces for intelligence systems.
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http://dx.doi.org/10.1093/nsr/nwaa135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8288334PMC
April 2021

ACQ-to-AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two-Photon NIR Bioimaging.

Angew Chem Int Ed Engl 2020 07 4;59(31):12822-12826. Epub 2020 Jun 4.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, State Key Laboratory of Molecular Neuroscience and Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

The traditional design strategies for highly bright solid-state luminescent materials rely on weakening the intermolecular π-π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid-state fluorescence. TBP-e-TPA with a molecular rotor in the end position of a planar core adopts a long-range cofacial packing mode, which in the solid state is almost non-emissive. By shifting molecular rotors to the bay position, the resultant TBP-b-TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid-state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP-b-TPA nanoparticles were used for two-photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid-state fluorophores.
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http://dx.doi.org/10.1002/anie.202005785DOI Listing
July 2020

Design of AIEgens for near-infrared IIb imaging through structural modulation at molecular and morphological levels.

Nat Commun 2020 03 9;11(1):1255. Epub 2020 Mar 9.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Department of Chemical and Biological Engineering and Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Fluorescence imaging in near-infrared IIb (NIR-IIb, 1500-1700 nm) spectrum holds a great promise for tissue imaging. While few inorganic NIR-IIb fluorescent probes have been reported, their organic counterparts are still rarely developed, possibly due to the shortage of efficient materials with long emission wavelength. Herein, we propose a molecular design philosophy to explore pure organic NIR-IIb fluorophores by manipulation of the effects of twisted intramolecular charge transfer and aggregation-induced emission at the molecular and morphological levels. An organic fluorescent dye emitting up to 1600 nm with a quantum yield of 11.5% in the NIR-II region is developed. NIR-IIb fluorescence imaging of blood vessels and deeply-located intestinal tract of live mice based on organic dyes is achieved with high clarity and enhanced signal-to-background ratio. We hope this study will inspire further development on the evolution of pure organic NIR-IIb dyes for bio-imaging.
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http://dx.doi.org/10.1038/s41467-020-15095-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7062876PMC
March 2020

Aggregation-Induced Emission: New Vistas at the Aggregate Level.

Angew Chem Int Ed Engl 2020 06 14;59(25):9888-9907. Epub 2020 May 14.

Department of Chemistry, Department of Chemical and Biological Engineering, Institute for Advanced Study, Hong Kong Branch of Chinese National Engineering Research Center, for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

Aggregation-induced emission (AIE) describes a photophysical phenomenon in which molecular aggregates exhibit stronger emission than the single molecules. Over the course of the last 20 years, AIE research has made great strides in material development, mechanistic study and high-tech applications. The achievements of AIE research demonstrate that molecular aggregates show many properties and functions that are absent in molecular species. In this review, we summarize the advances in the field of AIE and its related areas. We specifically focus on the new properties of materials attained by molecular aggregates beyond the microscopic molecular level. We hope this review will inspire more research into molecular ensembles at and beyond the meso level and lead to the significant progress in material and biological science.
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http://dx.doi.org/10.1002/anie.201916729DOI Listing
June 2020

Highly efficient singlet oxygen generation, two-photon photodynamic therapy and melanoma ablation by rationally designed mitochondria-specific near-infrared AIEgens.

Chem Sci 2020 Jan 21;11(9):2494-2503. Epub 2020 Jan 21.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, Institute of Molecular Functional Materials, Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology (HKUST) Clear Water Bay Kowloon Hong Kong China

Photosensitizers (PSs) with multiple characteristics, including efficient singlet oxygen (O) generation, cancer cell-selective accumulation and subsequent mitochondrial localization as well as near-infrared (NIR) excitation and bright NIR emission, are promising candidates for imaging-guided photodynamic therapy (PDT) but rarely concerned. Herein, a simple rational strategy, namely modulation of donor-acceptor (D-A) strength, for molecular engineering of mitochondria-targeting aggregation-induced emission (AIE) PSs with desirable characteristics including highly improved O generation efficiency, NIR emission (736 nm), high specificity to mitochondria, good biocompatibility, high brightness and superior photostability is demonstrated. Impressively, upon light irradiation, the optimal NIR AIE PS (DCQu) can generate O with efficiency much higher than those of commercially available PSs. The excellent two-photon absorption properties of DCQu allow two-photon fluorescence imaging of mitochondria and subsequent two-photon excited PDT. DCQu can selectively differentiate cancer cells from normal cells without the aid of extra targeting ligands. Upon ultralow-power light irradiation at 4.2 mW cm, mitochondrial photodynamic activation to specifically damage cancer cells and efficient melanoma ablation are demonstrated, suggesting superior potency of the AIE PS in imaging-guided PDT with minimal side effects, which is promising for future precision medicine.
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http://dx.doi.org/10.1039/c9sc06441aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8157451PMC
January 2020

Time-dependent solid-state molecular motion and colour tuning of host-guest systems by organic solvents.

Nat Commun 2020 01 7;11(1):77. Epub 2020 Jan 7.

College of Chemistry, Beijing Normal University, Xinjiekouwaidajie 19, Beijing, 100875, P. R. China.

Host-guest complex solid state molecular motion is a critical but underexplored phenomenon. In principle, it can be used to control molecular machines that function in the solid state. Here we describe a solid state system that operates on the basis of complexation between an all-hydrocarbon macrocycle, D-CDMB-8, and perylene. Molecular motion in this solid state machine is induced by exposure to organic solvents or grinding and gives rise to different co-crystalline, mixed crystalline, or amorphous forms. Distinct time-dependent emissive responses are seen for different organic solvents as their respective vapours or when the solid forms are subject to grinding. This temporal feature allows the present D-CDMB-8⊃perylene-based system to be used as a time-dependent, colour-based 4th dimension response element in pattern-based information codes. This work highlights how dynamic control over solid-state host-guest molecular motion may be used to induce a tuneable temporal response and provide materials with information storage capability.
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http://dx.doi.org/10.1038/s41467-019-13844-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946670PMC
January 2020

Deep-Red Fluorescent Organic Nanoparticles with High Brightness and Photostability for Super-Resolution in Vitro and in Vivo Imaging Using STED Nanoscopy.

ACS Appl Mater Interfaces 2020 Feb 30;12(6):6814-6826. Epub 2020 Jan 30.

School of Science, MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, Xi'an Key Laboratory of Sustainable Energy Material Chemistry , Xi'an Jiao Tong University , Xi'an 710049 , P. R. China.

To achieve super-resolution imaging in biological research using stimulated emission depletion (STED) nanoscopy, organic luminescent materials and their corresponding fluorescent nanoparticles with high brightness and photostability are of great significance. Herein, donor-acceptor-typed DBTBT-4C8 bearing flexible alkyl chains was developed, not only to afford deep-red emission from 600 to 800 nm but also to obtain high fluorescent brightness with the absolute photoluminescence quantum yields of 25%. After that, well-defined and monodispersed spherical nanoparticles using DBTBT-4C8 with bright emission, excellent biocompatibility, and photostability, which can easily mix with amphipathic block polymers, were then produced for super-resolution in vitro and in vivo imaging using STED nanoscopy. The observations showed that in contrast to confocal microscopy with a full width at half-maximum (FWHM) value of ≈400 nm, superior resolution with a significantly improved FWHM value of only 100 nm was achieved in biomedical cell imaging, which was also used to reconstruct three-dimensional images of stained HeLa cells at an ultrahigh resolution. More importantly, by using the prepared fluorescent organic nanoparticles (FONPs) in STED nanoscopy, in vivo imaging in glass catfish with largely enhanced resolution was also successfully achieved, demonstrating that these developed deep-red FONPs here are highly suitable for super-resolution in vitro and in vivo imaging using STED nanoscopy.
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http://dx.doi.org/10.1021/acsami.9b18336DOI Listing
February 2020

Polymorph selectivity of an AIE luminogen under nano-confinement to visualize polymer microstructures.

Chem Sci 2019 Nov 22;11(4):997-1005. Epub 2019 Nov 22.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China

Despite the huge progress of luminescent molecular assemblies over the past decade, it is still challenging to understand their confined behavior in semi-crystalline polymers for constrained space recognition. Here, we report a polymorphic luminogen with aggregation-induced emission (AIE), capable of selective growth in polymer amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE luminogen embedded within the polymer network are dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE luminogen with green emission is stabilized in the amorphous phase, while a metastable polymorph with yellow emission is confined in the crystalline phase. The information on polymer crystalline and amorphous phases is transformed into distinct fluorescence colors, allowing a single AIE luminogen as a fluorescent marker for visualization of polymer microstructures in terms of amorphous and crystalline phase distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. Our findings demonstrate that confinement of the AIE luminogen in the polymer network can achieve free space recognition and also provide a correlation between microscopic morphologies and macroscopic optical signals. We envision that our strategy will inspire the development of other materials with spatial confinement to incorporate AIE luminogens for various applications.
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http://dx.doi.org/10.1039/c9sc04239cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8146380PMC
November 2019

Dual-Color Emissive AIEgen for Specific and Label-Free Double-Stranded DNA Recognition and Single-Nucleotide Polymorphisms Detection.

J Am Chem Soc 2019 12 11;141(51):20097-20106. Epub 2019 Dec 11.

Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction , The Hong Kong University of Science & Technology , Clear Water Bay , Kowloon , Hong Kong , People's Republic of China.

Simple, rapid, and sensitive assays of DNA sequence hold great importance in genetic analysis, clinical diagnosis, and molecular biology research. Most current methods for DNA detection, based on the complementary base pairing, require hybridization with intricately modified single-stranded DNA (ssDNA) probes or analytes. Herein, we have developed a powerful molecule with aggregation-induced emission (AIE) characteristic, namely, TPBT, which can specifically recognize double-stranded DNA (dsDNA) by emitting out a unique dual-color fluorescent signal of red (∼640 nm) and green (∼537 nm). The red-color emission at around 640 nm is observed when TPBT binds with dsDNA, ssDNA, proteins, and other polyanionic analytes. However, the green emission at around 537 nm is demonstrated to be the exclusive response of TPBT to dsDNA, which is closely related to the conformational change of TPBT upon groove binding. More strikingly, TPBT can distinguish single-nucleotide polymorphisms (SNPs) in a dsDNA sequence and detect the DNA damage suffered from UV light with ultrahigh sensitivity and specificity. This label-free, AIEgen-based dsDNA assay method is facile, robust, and universal, which will lead to major advances in genomic and disease diagnosis.
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http://dx.doi.org/10.1021/jacs.9b09239DOI Listing
December 2019

Visualization and Manipulation of Molecular Motion in the Solid State through Photoinduced Clusteroluminescence.

J Phys Chem Lett 2019 Nov 5;10(22):7077-7085. Epub 2019 Nov 5.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study , The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon , Hong Kong SAR, China.

The development of molecular machines has long been a dream of scientists and is expected to revolutionize many aspects of technology and medicine. As the prerequisite of a practicable molecular machine, studies on the solid-state molecular motion (SSMM) are not only of scientific importance but also practically useful. Herein, two nonconjugated molecules, 1,2-diphenylethane (-DPE) and 1,2-bis(2,4,5-trimethylphenyl)ethane (-DPE-TM), are synthesized, and their SSMM is investigated. Experimental and calculation results reveal that -DPE and -DPE-TM are capable of performing light-driven SSMM to form excited-state through-space complexes (ESTSC). The radiative decay of ESTSC generates an unexpected visible emission termed clusteroluminescence, which serves as a tool to visualize the process of SSMM. Meanwhile, the original packing structure can be recovered from ESTSC after the removal of light irradiation. This work provides a new strategy to manipulate and "see" the SSMM and gains new insights into clusteroluminescence.
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http://dx.doi.org/10.1021/acs.jpclett.9b02752DOI Listing
November 2019

New Wine in Old Bottles: Prolonging Room-Temperature Phosphorescence of Crown Ethers by Supramolecular Interactions.

Angew Chem Int Ed Engl 2020 Jun 20;59(24):9293-9298. Epub 2019 Nov 20.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, and Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Supramolecular macrocyclic hosts have long been used in smart materials. However, their triplet emission and regulation at crystal level is rarely studied. Herein, ultralong and universal room-temperature phosphorescence (RTP) is reported for traditional crown ethers. A supramolecular strategy involving chain length adjustment and morphological locking through complexation with K was explored as a general method to tune the phosphorescence lifetime in the solid state. A maximum 10-fold increase of lifetime after complex formation accompanied with by invisible to visible phosphorescence was achieved. A deep encryption based on this activated RTP strategy was also facilely fabricated. This work thus opens a new world for supramolecular macrocycles and their intrinsic guest responsiveness offers a new avenue for versatile smart luminescent materials.
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http://dx.doi.org/10.1002/anie.201912155DOI Listing
June 2020
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