Nonlinear optical microscopy has become a powerful tool in bioimaging research due to its unique capabilities of deep optical sectioning, high-spatial-resolution imaging, and 3D reconstruction of biological specimens. Developing organic fluorescent probes with strong nonlinear optical effects, in particular third-harmonic generation (THG), is promising for exploiting nonlinear microscopic imaging for biomedical applications. Herein, a simple method for preparing organic nanocrystals based on an aggregation-induced emission (AIE) luminogen (DCCN) with bright near-infrared emission is successfully demonstrated. Aggregation-induced nonlinear optical effects, including two-photon fluorescence (2PF), three-photon fluorescence (3PF), and THG, of DCCN are observed in nanoparticles, especially for crystalline nanoparticles. The nanocrystals of DCCN are successfully applied for 2PF microscopy at 1040 nm NIR-II excitation and THG microscopy at 1560 nm NIR-II excitation, respectively, to reconstruct the 3D vasculature of the mouse cerebral vasculature. Impressively, the THG microscopy provides much higher spatial resolution and brightness than the 2PF microscopy and can visualize small vessels with diameters of ≈2.7 µm at the deepest depth of 800 µm in a mouse brain. Thus, this is expected to inspire new insights into the development of advanced AIE materials with multiple nonlinearity, in particular THG, for multimodal nonlinear optical microscopy.

Zheng Zheng;Dongyu Li;Zhiyang Liu;Hui Qing Peng;Herman H.Y. Sung;Ryan T.K. Kwok;Ian D. Williams;Jacky W.Y. Lam;Jun Qian;本忠 唐

Advanced Materials

2019-11-1

In this contribution, we conceptually present a new avenue to construction of molecular functional materials with high performance of circularly polarised luminescence (CPL) in the condensed phase. A molecule (1) containing luminogenic silole and chiral sugar moieties was synthesized and thoroughly characterized. In a solution of 1, no circular dichroism (CD) and fluorescence emission are observed, but upon molecular aggregation, both the CD and fluorescence are simultaneously turned on, showing aggregation-induced CD (AICD) and emission (AIE) effects. The AICD effect is supported by the fact that the molecules readily assemble into right-handed helical nanoribbons and superhelical ropes when aggregated. The AIE effect boosts the fluorescence quantum efficiency (Φ _F) by 136 fold (Φ _F, ∼0.6% in the solution versus ∼81.3% in the solid state), which surmounts the serious limitations of aggregation-caused quenching effect encountered by conventional luminescent materials. Time-resolved fluorescence study and theoretical calculation from first principles conclude that restriction of the low-frequency intramolecular motions is responsible for the AIE effect. The helical assemblies of 1 prefer to emit right-handed circularly polarised light and display large CPL dissymmetry factors (g _em), whose absolute values are in the range of 0.08-0.32 and are two orders of magnitude higher than those of commonly reported organic materials. We demonstrate for the first time the use of a Teflon-based microfluidic technique for fabrication of the fluorescent pattern. This shows the highest g _em of -0.32 possibly due to the enhanced assembling order in the confined microchannel environment. The CPL performance was preserved after more than half year storage under ambient conditions, revealing the excellent spectral stability. Computational simulation was performed to interpret how the molecules in the aggregates interact with each other at the molecular level. Our designed molecule represents the desired molecular functional material for generating efficient CPL in the solid state, and the current study shows the best results among the reported organic conjugated molecular systems in terms of emission efficiency, dissymmetry factor, and spectral stability.

Jianzhao Liu;Huimin Su;Luming Meng;Yihua Zhao;Chunmei Deng;Jason C.Y. Ng;Ping Lu;Mahtab Faisal;Jacky W.Y. Lam;Xuhui Huang;Hongkai Wu;Kam Sing Wong;本忠 唐

Chemical Science

2012-9

Due to immense potential in using as chemo/biosensors and solid emitters, aggregation-induced emission (AIE) phenomenon is attracting huge interest in scientific community. After endowed with chirality, the resultant chiral AIE luminogens (AIEgen), just like a tiger with added wings, can display more and stronger promising functionalities. Moreover, many classic luminophores can be transformed into AIEgens from notorious aggregation-caused quenching (ACQ) compounds as soon as they are attached with chiral groups. Compared with other chiral fluorescent receptors and chiral emitter, chiral AIEgens have displayed unique and outstanding advantages. Firstly, chiral AIEgen can differentiate two enantiomers of chiral analyte by 1.68 × 10⁴ fold difference and get a chiral magnification up to 2.5 × 10³ times due to aggregation. In addition, two enantiomers of up to 18 chiral carboxylic acids can be recognized just by using only one chiral AIEgen receptor and enantiomeric excess (ee) of chiral analytes at uM level can be measured. Furthermore, accurate ee analysis was carried out for the first time from fluorescence wavelength change rather than intensity change of the chiral AIEgen receptor. Therefore, the chiral AIEgens show unprecedentedly high selectivity, high sensitivity, high applicability, and high accuracy. Secondly, in the area of organic circularly polarized luminescence (CPL) materials, the CPL dissymmetry factor (g_lum) of chiral AIEgen can get to 1.42 that is near to the theoretical value of 2, making a breakthrough progress while the |g_lum| of previous organic luminophores is generally between 10⁻⁵ and 10⁻². Furthermore, the highly efficient circularly polarized organic light-emitting diodes (CPOLEDs) are constructed for the first time by chiral AIEgens. Thirdly, chiral AIEgens enable novel display technology under different lighting conditions to be possible. More importantly, due to AIE effect, AIEgens are very beneficial for disclosing the mechanism of chiral transfer and magnification between molecules, which is thought to be the key for evolution of homochirality in natural world and preparation of chiral materials with hierarchical structures. For the above reason, chiral AIEgens have been brought to extensive attention and a large number of research works about them are reported. To take an overall view on chiral AIEgens and facilitate the development of chiral AIEgens, it is necessary to make a full review on the chiral AIEgens. This review covers the following contents: (1) construction of chiral AIEgens including propeller-like chiral AIEgens, chiral AIEgens with optically pure groups, polymer chiral AIEgens and supramolecular chiral AIEgen system; (2) chiral recognition and ee determination of chiral carboxylic acids, chiral amines, α-amino acids, and chiral neutral molecules by chiral AIEgens; (3) performance of chiral AIEgens in circular dichroism (CD), CPL and CPOLEDs; (4) other versatile application researches related to chiral AIEgens.

Ming Hu;Hai Tao Feng;Ying Xue Yuan;Yan Song Zheng;本忠 唐

Coordination Chemistry Reviews

2020-8-1

Tetraphenylethene derivatives [Ph(PhCH=CHPhR)C=C(PhCH=CHPhR)Ph, R=H, CN, NO₂, NPh₂] with green, yellow-green, and orange emission colours were designed and synthesized. These molecules are practically non-emissive in their dilute solutions but emit intensely as nanoaggregates in poor solvents, demonstrating a novel phenomenon of aggregation-induced emission. Their blended films with poly(methyl methacrylate) also display bright emissions. Restriction of intramolecular motion in the condensed phase may be responsible for such unusual behaviour. Multilayer electroluminescence devices with a configuration of indium tin oxide/N,N′-di(1-naphthyl)-N,N′- diphenylbenzidine/emitter/tris(8-hydroxyquinolinolato)aluminum (Alq ₃)/LiF/Al were constructed, which gave green light with a maximum luminance and current efficiency of 12930 cdcm^-2 and 3.04cd A ^-1 respectively. The tetraphenylethenes can serve as excellent cell staining agents for selectively illuminating the cytoplasm and vesicles of living cells.

Yuning Hong;Jacky Wing Yip Lam;Sijie Chen;本忠 唐

Australian Journal of Chemistry

2011

A facile approach to thermally stable and efficient solid-state emitters is proposed. By hooking up tetraphenylethene (TPE) units through aryl linkers under Suzuki coupling conditions, a series of arylene bis(tetraphenylethene)s (TPE-Ar-TPE Ar = 2, 5-dimethyl-1, 4-phenylene, 2, 5-bis(hexyloxyl)-1, 4-phenylene, 1, 5-naphthylene, and 9, 10-anthracenylene) are prepared in satisfactory to high yields (67-96%). These molecules are nonluminescent when dissolved in solutions but become highly emissive when aggregated in poor solvents or fabricated as thin film in the solid state, displaying a phenomenon of aggregation-induced emission. Fluorescence quantum yields of 100% were achieved in the amorphous films of the luminogens. The luminogens exhibit mechano-, vapo-, and thermochromism: their emissions can be repeatedly switched between blue and blue-green colors by simple grinding-fuming and grinding-heating cycles owing to the morphological change from a crystalline to an amorphous state and vice versa. These compounds are thermally stable, losing little of their weight at high temperatures of 421-452°C. All the luminogens are morphological stable with high glass transition temperatures. Multilayer light-emitting diodes with a device configuration of ITO/NPB/dye/TPBi/Alq ₃/LiF/Al are fabricated, which emit sky-blue electroluminescence with maximum luminance and external quantum efficiency of 7900 cd mr ^-2 and 2.1 %, respectively.

Carrie Yin Kwan Chan;Jacky Wing Yip Lam;Zujin Zhao;Chunmei Deng;Shuming Chen;Ping Lu;Herman H.Y. Sung;Hoi Sing Kwok;於光 马;Ian D. Williams;本忠 唐

ChemPlusChem

2012-10

Efficient organic photosensitizers (PSs) have attracted much attention because of their promising applications in photodynamic therapy (PDT). However, guidelines on their molecular design are rarely reported. In this work, a series of PSs are designed and synthesized based on a triphenylamine-azafluorenone core. Their structure-property-application relationships are systematically studied. Cationization is an effective strategy to enhance the PDT efficiency of PSs by targeting mitochondria. From the molecularly dispersed state to the aggregate state, the fluorescence and the reactive oxygen species generation efficiency of PSs with aggregation-induced emission (AIE) increase due to the restriction of the intramolecular motions and enhancement of intersystem crossing. Cationized mitochondrion-targeting PSs show higher PDT efficiency than that of nonionized ones targeting lipid droplets. The ability of AIE PSs to kill cancer cells can be further enhanced by combination of PDT with radiotherapy. Such results should trigger research enthusiasm for designing and synthesizing AIE PSs with better PDT efficiency and properties.

Zhiyang Liu;Hang Zou;Zheng Zhao;Pengfei Zhang;Guo Gang Shan;Ryan T.K. Kwok;Jacky W.Y. Lam;Lei Zheng;本忠 唐

ACS Nano

2019-10-22

Acridone (ADO) is an anthracene-based derivative that plays an important role in the construction of organic light-emitting diode emitters. However, ADO suffers from an aggregation-caused quenching (ACQ) effect because of its strong intermolecular stacking and tendency to form excimers. In this work, we appended some electron-donating moieties with different rotors and substitution patterns on ADO to prepare six ADO-based derivatives. In addition, a benzonitrile group was introduced onto the nitrogen atom of the ADO unit to fabricate a high-energy charge-transfer (CT) state that formed a reverse intersystem crossing (RISC) channel. Systematic spectral measurements revealed that the rotors effectively suppressed the ACQ effect. In addition, aggregation-enhanced emission (AEE) was observed for the ADO derivatives modified with triphenylamine (TPA) because of the existence of multiple rotors and propeller-like conformation in TPA block. Theoretical calculations and the performance of electroluminescent devices containing the derivatives confirmed that the exciton conversion channel was constructed at the high-energy level and activated during device operation. Although the performance of these ADO-based derivatives was not ideal in terms of efficiency, the results confirmed the feasibility of this structure modification strategy to simultaneously inhibit the ACQ effect and construct excitons conversion channels.

Qing Wan;Bing Zhang;Jialin Tong;Yin Li;Haozhong Wu;Han Zhang;Zhiming Wang;Yuyu Pan;本忠 唐

Physical Chemistry Chemical Physics

2019

Folate functionalized nanoparticles (NPs) that contain fluorogens with aggregation-induced emission (AIE) characteristics are fabricated to show bright far-red/near-infrared fluorescence, a large two-photon absorption cross section and low cytotoxicity, which are internalized into MCF-7 cancer cells mainly through caveolae-mediated endocytosis. One-photon excited in vivo fluorescence imaging illustrates that these AIE NPs can accumulate in a tumor and two-photon excited ex vivo tumor tissue imaging reveals that they can be easily detected in the tumor mass at a depth of 400 μm. These studies indicate that AIE NPs are promising alternatives to conventional TPA probes for biological imaging.

Junlong Geng;Kai Li;Dan Ding;Xinhai Zhang;Wei Qin;Jianzhao Liu;本忠 唐;Bin Liu

Small

2012-12-7

Polymerization of a phenylacetylene monomer containing chiral center and thiolacetate was achieved by using a zwitterionic rhodium complex or Rh+ -C ₆H ₅ ( nbd) B-(C ₆H ₅) ₃] as catalyst. Chemical structure was characterized with infrared (IR) ,nuclear magnetic resonance (NMR),UV-Vis absorption spectroscopic techniques, and the experimental data confirmed the formation of the expected polymer. The obtained polymer was soluble in common organic solvents such as chloroform, dichloromethane, tetrahydrofurran, and its weight-average molecular weight was about 7.32 x 10 ⁴ . The polymer was highly thermally stable; it lost 5% of its original weight at a temperature of 336°C, and about 31% residual weight was measured at 9001 . SEM images showed that rod-like ordered entities were observed for the thin film fabricated by casting polymer solution (a concentration of 5.0 mg/mL in chloroform) under ambient condition; while crystallites were observed when dilute polymer solution (a concentration of 0.5 mg/mL in chloroform) was used to film fabrication. As revealed by TEM images, when the evaporation rate was controlled to be slow and the concentration of polymer in chloroform was higher than 1.0 mg/ mL,a polymer layer spread on the carbon supporting film on copper micro-grid; when polymer concentration was lower than 0.5 mg/mL, microcrystallites with regular shapes were observed. Based on the macromolecular structure, the improvement of the thermal stability and the formation ordered microstructure can be tentatively ascribed to the role of chiral centers on the side chains of the resulted polyphenylacetylene.

Wang Jian;Mao Yu;Xu Haipeng;Yuan Wangzhang;Sun Jingzhi;本忠 唐

Acta Polymerica Sinica

2009-10

The development of novel photosensitizing agents with aggregation-induced emission (AIE) properties has fueled significant advances in the field of photodynamic therapy (PDT). An electroporation method was used to prepare tumor-exocytosed exosome/AIE luminogen (AIEgen) hybrid nanovesicles (DES) that could facilitate efficient tumor penetration. Dexamethasone was then used to normalize vascular function within the tumor microenvironment (TME) to reduce local hypoxia, thereby significantly enhancing the PDT efficacy of DES nanovesicles, and allowing them to effectively inhibit tumor growth. The hybridization of AIEgen and biological tumor-exocytosed exosomes was achieved for the first time, and combined with PDT approaches by normalizing the intratumoral vasculature as a means of reducing local tissue hypoxia. This work highlights a new approach to the design of AIEgen-based PDT systems and underscores the potential clinical value of AIEgens.

Daoming Zhu;Yanhong Duo;Meng Suo;Yonghua Zhao;Ligang Xia;Zheng Zheng;Yang Li;本忠 唐

Angewandte Chemie - International Edition

2020-8-10