Advanced Optical Materials

Liu, Bin; Chu, Bo; Wang, Ya‐Ling; Chen, Zheng; Zhang, Xing‐Hong

doi: 10.1002/adom.201902176pmid: N/A

Nonconjugated luminescent polymers with white light emission are promising for a wide range of applications in display and lighting devices, but their preparation remains a big challenge. Herein, a white‐light‐emitting nonconjugated poly(hydroxyurethane) microsphere (PHUM) synthesized from the crosslinking reaction of trimethylolpropane tri(cyclic carbonate) ether and 1,6‐hexanediamine in chloroform is reported. The resultant PHUMs possess uniform sizes ranging from 12.6 to 21.5 µm. It is proposed that a high crosslinking degree and various hydrogen‐bonding strengths induce the formation of carbamate clusters with different sizes and broad distributions, which result in a broad emission spectrum. The cluster‐size distribution effect leads to multiple n–π* transitions from various carbamate clusters via through‐space conjugation of carbamates, realizing white light emission. In addition, the application of PHUMs as single phosphor combined with a 365 nm UV chip is also demonstrated, with which a white‐light‐emitting diode with a high color rendering index of up to 95 is obtained. This work confirms that crosslinking can induce multiple emissions, which provides a new clusteroluminescence and polymerization‐induced emission system for tunable luminescence emission.

Yin, Wei; Li, Yue; Li, Nan; Yang, Weiyao; An, Hao; Gao, Jinrui; Bi, Yu; Zhao, Na

doi: 10.1002/adom.201902027pmid: N/A

Aggregation‐induced emission luminogens (AIEgens) with excited‐state intramolecular proton transfer (ESIPT) process have attracted significant attention in bioimaging applications owing to their high solid‐state emission efficiencies and large Stokes shifts. Herein, a series of simple AIEgens with ESIPT process, referred to as triphenylamine salicylaldehyde (TS) derivatives, are designed and synthesized by a rational hybridization of triphenylamine and salicylaldehyde units as the intramolecular rotor and ESIPT generator, respectively. Owing to the AIE and ESIPT effects, TS derivatives exhibit intense emission and large Stokes shifts (>140 nm) in the aggregated state. By altering the substituents in the triphenylamine units, their solid‐state emission varies from 490 to 590 nm. Owing to their excellent biocompatibilities and suitable lipophilicities, the TS derivatives are able to specifically and rapidly (<5 min) stain the lipid droplets in the cells in a wash‐free manner and successfully image the lipid‐rich tissue in vivo. Moreover, owing to their suitable hydrophilicity, TS and methoxyl substituted TS (TS‐OMe) are shown to stain gram‐positive bacteria with high selectivity.

Zhang, Miao‐Miao; Li, Kai; Zang, Shuang‐Quan

doi: 10.1002/adom.201902152pmid: N/A

Materials with circularly polarized luminescence (CPL) are especially fascinating due to the widespread potential applications in 3D displays, biological probes, security encoding, encrypted information transmission, and storage. Among these CPL‐active materials, the ones based on atomically precise coinage, namely, the metal coinage clusters, have attracted increasing attention due to their fascinating chiral structures and intriguing luminescence characteristics. Meanwhile, these clusters provide an ideal platform at the nanoscale for understanding the chiral transfer across the organic–inorganic interface. In this report, the recent progress in constructing enantiomerically pure chiral coinage metal clusters and the luminescent mechanism of coinage metal clusters in aggregated state are reviewed, respectively. Moreover, CPL‐active atomically precise coinage metal clusters and their design strategies are discussed in detail. Finally, challenges and opportunities for constructing atomically precise coinage metal clusters with excellent CPL properties are discussed.

Kim, Hyung Jong; Godumala, Mallesham; Kim, Seong Keun; Yoon, Jiwon; Kim, Chae Yeong; Park, Hanun; Kwon, Jang Hyuk; Cho, Min Ju; Choi, Dong Hoon

doi: 10.1002/adom.201902175pmid: N/A

Three new color‐tunable (deep‐blue to sky‐blue) and solution‐processable emitters—9′‐(2,12‐di‐tert‐butyl‐5,9‐dioxa‐13b‐boranaphtho[3,2,1‐de]anthracen‐7‐yl)‐9′H‐9,3′:6′,9″‐tercarbazole (TB‐3Cz), 9′‐(2,12‐di‐tert‐butyl‐5,9‐dioxa‐13b‐boranaphtho[3,2,1‐de]anthracen‐7‐yl)‐9,9″‐diphenyl‐9H,9′H,9″H‐3,3′:6′,3″‐tercarbazole (TB‐P3Cz), and 9‐(2,12‐di‐tert‐butyl‐5,9‐dioxa‐13b‐boranaphtho[3,2,1‐de]anthracen‐7‐yl)‐N3,N3,N6,N6‐tetraphenyl‐9H‐carbazole‐3,6‐diamine (TB‐DACz)—are demonstrated, which are cleverly designed and synthesized by appending a boron‐fused entity as an electron acceptor to different electron‐rich entities containing carbazole derivatives as donors. The thermal, photophysical, electrochemical, and electroluminescent characteristics of all the new materials are extensively investigated. Comprehensive photophysical investigations reveal that these emitters exhibit not only thermally activated delayed fluorescence (TADF) but also aggregation‐induced emission (AIE) properties. Consequently, solution‐processable organic light‐emitting diodes (OLEDs) fabricated using these new materials as nondoped emitters in the emissive layer exhibit a maximum external quantum efficiency (EQE) and Commission Internationale de l'Éclairage (CIE) color coordinates of 9.90% and (0.17, 0.07), respectively, for TB‐3Cz; 6.13% and (0.15, 0.08), respectively, for TB‐P3Cz; and 6.04% and (0.18, 0.40), respectively, for TB‐DACz. As far as it is known, the performance and ultrahigh color purity satisfying the deep‐blue CIE coordinates of the National Television System Committee (NTSC) for TB‐3Cz and TB‐P3Cz are the highest reported thus far for nondoped solution‐processable TADF emitters, indicating the great potential of these materials as deep‐blue luminogens in OLED applications.

Li, Yang; Zhang, Jinjin; Li, Hui; Fan, Yiqi; He, Tian; Qiu, Huayu; Yin, Shouchun

doi: 10.1002/adom.201902190pmid: N/A

Fluorescent supramolecular assemblies have attracted significant attention for their application as bioimaging agents, biological and chemical sensors, light‐emitting materials, and gene and drug vectors. The introduction of supramolecular coordination complexes constructed by the spontaneous formation of dative metal–ligand bonds through coordination‐driven self‐assembly into fluorescent supramolecular assemblies is of particular interest. This is because the introduction of metal coordination renders the synthesized assemblies excellent stability in addition to providing unique emissions that are different from the fluorescent ligands or metal ions. The discovery of aggregation‐induced emission (AIE), wherein the fluorophores are nonfluorescent in the molecular state, but become highly emissive in the aggregate state, presents new chances for fluorescent supramolecular assemblies since such assemblies are often required to be employed at high concentrations or in the solid state. This progress report provides a summary of the recent design, construction, and application of metallacycle/metallacage‐cored fluorescent supramolecular assemblies based on coordination‐driven self‐assembly, wherein the assemblies exhibit AIE properties. Example applications discussed in detail include light‐emitting materials, chemical and biological sensors, bioimaging agents, and cancer therapy. Moreover, several unsolved issues related to metallacycle/metallacage‐cored fluorescent supramolecular assemblies are discussed in the context of possible future applications of this field.

Tsutsui, Yusuke; Zhang, Wanying; Ghosh, Samrat; Sakurai, Tsuneaki; Yoshida, Hiroyuki; Ozaki, Masanori; Akutagawa, Tomoyuki; Seki, Shu

doi: 10.1002/adom.201902158pmid: N/A

Use of organic molecules as lasing media has much potential to develop next‐generation optical devices as soft‐matter photonics with wideband tunability and large coherence area. Although mirrorless lasing was theoretically predicted and practically demonstrated in helical cholesteric liquid crystalline (LC) phases of organic compounds, recent studies on optical confinement have been much focused into hard‐crystalline phases of the molecules. Aggregation‐induced emission (AIE) and enhancement (AIEE) provides one of the optimal molecular systems for light amplification in condensed phases, and herein AIEE activity and excited‐state intramolecular proton transfer (ESIPT) are successfully coupled in a room temperature (RT) nematic LC. Suppressing the effect of concentration quenching/self‐absorption and attaining four‐level system for population inversion by the combination of AIEE and ESIPT in LC phases, lead to the amplified spontaneous emission (ASE) from a newly designed molecule: C5Ph‐HBT dispersed in RT LC matrix with the pumping energy threshold of 20 mJ cm–2. Moreover, the nematic LC allows the orientation of the molecular dipoles in response to external electric fields. Hence, the fluorescence as well as the ASE switching is attained at RT, demonstrating the potential of these composite materials as “switchable” ASE media for technological progress.

Das, Gourab; Thirumalai, Rajasekaran; Vedhanarayanan, Balaraman; Praveen, Vakayil K.; Ajayaghosh, Ayyappanpillai

doi: 10.1002/adom.202000173pmid: N/A

Optical properties of π‐systems are of great significance for a wide range of applications in materials and biology. Aggregation and self‐assembly induced emission are one of such phenomena. Herein, the self‐assembly induced modulation of the emission of p‐phenyleneethynylene (PE) chromophores bearing linear achiral (1) or branched chiral (2) alkoxy chains is reported. Self‐assembled structures of both 1 and 2 from n‐decane exhibit enhanced emission with fluorescence quantum yield (ΦF) values of 0.34 and 0.25, respectively, whereas these molecules are less‐emissive in chloroform (ΦF = 0.02). Transmission electron microscopy and fluorescence microscopy studies reveal the formation of entangled blue‐emissive fibers for 1 and supercoiled helical blue‐emissive fiber bundles for 2. At higher concentrations (8.8 × 10−3 m for 1 and 23.6 × 10−3 m for 2) in n‐decane, intense blue‐emitting gels are formed. Significant shift in the emission toward longer wavelength can be seen from solution state to aggregates to the gel state. The wide‐angle X‐ray scattering and fluorescence data indicate that the interdigitated lamellar assembly with weaker π‐stacking and the resultant restriction of rotation of the PE chromophores are responsible for the enhanced emission of the self‐assembled gel state.

Liu, Haixiang; Xiong, Ling‐Hong; Kwok, Ryan Tsz Kin; He, Xuewen; Lam, Jacky Wing Yip; Tang, Ben Zhong

doi: 10.1002/adom.202000162pmid: N/A

Fluorescence‐based techniques have found potential biomedical applications owing to their high sensitivity, rapid response, and in situ characteristics. Traditional fluorescent probes suffer from aggregation‐caused quenching effects, which limit their usage at high concentrations or in nanoparticles. Aggregation‐induced emission (AIE), on the other hand, is a phenomenon wherein luminogens are non‐emissive in dilute solutions but highly emissive in the aggregate and solid states. AIE bioconjugates formed by covalent linkage of AIE luminogens to biomolecules are especially promising candidates for biomedical applications because they show excellent biocompatibility, good water solubility, high specificity to the target of interest, wide functionality, and smart responsiveness. This review summarizes the methodologies in synthesizing AIE bioconjugates and their intricate applications in biosensing, bioimaging, image‐guided therapy, and “Lab‐in‐cell” over the past 20 years. Perspectives are also shared to inspire enthusiasm and motivate researchers to further develop this emerging field.

Aparin, Ilya O.; Melnychuk, Nina; Klymchenko, Andrey S.

doi: 10.1002/adom.202070058pmid: N/A

Tsutsui, Yusuke; Zhang, Wanying; Ghosh, Samrat; Sakurai, Tsuneaki; Yoshida, Hiroyuki; Ozaki, Masanori; Akutagawa, Tomoyuki; Seki, Shu

doi: 10.1002/adom.202070056pmid: N/A