A new selective and sensitive fluorescence turn-on detection of CN(-) is reported by taking advantage of aggregation induced-emission (AIE) behavior of tetraphenylethylene units and the nucleophilic ...attack of CN(-) on the indolium group in compound 1.
Research on materials with pure organic room temperature phosphorescence (RTP) and their application as organic single-molecule white light emitters is a hot area and relies on the design of highly ...efficient pure organic RTP luminogens. Herein, a facile strategy of heavy-atom-participated anion-π
interactions is proposed to construct RTP-active organic salt compounds (1,2,3,4-tetraphenyloxazoliums with different counterions). Those compounds with heavy-atom counterions (bromide and iodide ions) exhibit outstanding RTP due to the external heavy atom effect via anion-π
interactions, evidently supported by the single-crystal X-ray diffraction analysis and theoretical calculation. Their single-molecule white light emission is realized by tuning the degree of crystallization. Such white light emission also performs well in polymer matrices and their use in 3D printing is demonstrated by white light lampshades.
A new convenient and continuous fluorometric assay method for acetylcholinesterase (AChE) and its inhibitor screening is successfully established with the ensemble of 1 a TPE (tetraphenylethylene) ...compound with two sulfonate (−SO3 −) units and myristoylcholine (an amphiphilic compound as a good substrate of AChE). This new assay method is designed by making use of the aggregation-induced emission (AIE) feature of TPE compounds. Both dynamic light scattering (DLS) and fluorescence confocal microscopic measurements indicated the formation of aggregation complex for the ensemble of 1 and myristoylcholine and further disassembly of the aggregation complex after introducing AChE. The analysis for AChE can be carried out continuously, and AChE with concentration as low as 0.5 U/mL can be assayed. The results also clearly demonstrate the usefulness of this convenient assay method for kinetic study of AChE-catalyzed myristoylcholine hydrolysis and screening inhibitors of AChE. Given its simplicity and easy operation, this method may extend to high-throughput screening of AChE inhibitors and relevant Alzheimer’s disease (AD) drug discovery.
White-light emissive materials with stable photophysical properties are of great importance for their potential applications in information display, fluorescent sensors, and optical-recording ...systems. Herein, an amphiphilic tetraphenylpyrazine (TPP)-based cage compound (TPP-Cage) was facilely synthesized by reaction of propeller-like TPP with aggregation-induced emission characteristics and triglycol monomethyl ether-substituted triazine. By immobilizing the twisted conformation of TPP, TPP-Cage showed obvious helical chirality in the solution and aggregated state. TPP-Cage emits strong deep blue fluorescence in solution due to the restriction of intramolecular rotation of the TPP unit. Its amphiphilic nature enables it to serve as an excellent light-harvesting platform to encapsulate diketopyrrolopyrrole (DPP) with aggregation-caused quenching effect in its hydrophobic cavity in aqueous medium, forming the DPP@TPP-Cage complex. Such inclusion prevents π–π stacking of DPP enabling it to emit strong yellow-light emission in the aggregated state. Due to the complementary emission colors of TPP-Cage and DPP, DPP@TPP-Cage exhibited stable white-light emission in the aggregated state and poly(ethylene glycol) film. This work not only introduces a promising strategy for development of chiral compounds through immobilization of propeller-like achiral molecules but also provides a prospective pathway for white-light emission based on supramolecular assembly.
A novel dark through-bond energy transfer (DTBET) strategy is proposed and applied as the design strategy to develop ratiometric Hg2+ sensors with high performance. Tetraphenylethene (TPE) ...derivatives with aggregation-induced emission (AIE) characteristics are selected as dark donors to eliminate emission leakage from the donors. The TBET mechanism has been adopted since it experiences less influence from spectral overlapping than Forster resonance energy transfer (FRET), making it more flexible for developing cassettes with large pseudo-Stokes shifts. In this work, energy transfer from the TPE derivatives (dark donor) to a rhodamine moiety (acceptor) was illustrated through photophysical spectroscopic studies and the energy transfer efficiency (ETE) was found to be up to 99%. In the solution state, no emission from the donors was observed and large pseudo-Stokes shifts were achieved (>280 nm), which are beneficial for biological imaging. Theoretical calculations were performed to gain a deeper mechanistic insight into the DTBET process and the structure-property relationship of the DTBET cassettes. Ratiometric Hg2+ sensors were rationally constructed based on the DTBET mechanism by taking advantage of the intense emission of TPE aggregates. The Hg2+ sensors exhibited well resolved emission peaks. >6000-fold ratiometric fluorescent enhancement is also achieved and the detection limit was found to be as low as 0.3 ppb. This newly proposed DTBET mechanism could be used to develop novel ratiometric sensors for various analytes and AIEgens with DTBET characteristics will have great potential in various areas including light harvesting materials, environmental science, chemical sensing, biological imaging and diagnostics.
Squaraines (SQs) with tunable emission in the solid state is of great importance for various demands; however a remaining challenge is emission quenching upon aggregation. Herein, a unique SQ, named ...as CIEE‐SQ, is designed to exhibit strong emission in crystal, undergoing crystallization‐induced reverse from dark 1(n+σ,π*) to bright 1(π,π*) excited states. Such an excited state of CIEE‐SQ can be subtly tuned by molecular conformation changes during the unexpected temperature‐triggered single‐crystal to single‐crystal (SCSC) reversible transformation. Furthermore, co‐crystallization between CIEE‐SQ and chloroform largely stabilize the 1(π,π*) state, enhancing the transition dipole moment and decreasing the reorganization energy to boost the fluorescence, which is promising in data encryption and decryption.
A unique squaraine, CIEE‐SQ, exhibits strong emission in the crystal, undergoing crystallization‐induced reversal from dark 1(n+σ,π*) to bright 1(π,π*) excited states. Such an excited state can be tuned by an unexpected temperature‐triggered single‐crystal to single‐crystal reversible transformation. Co‐crystallization between CIEE‐SQ and chloroform largely boosts the fluorescence.
Self-healing gels are emerging as promising materials for various human-interfaced applications. Unveiling microscopic processes for self-healing gels is crucial for not only understanding ...self-healing mechanisms but also guiding material design, which is, however, hardly achieved because of the lack of direct and effective approaches. Herein, covalent bond-induced emission of AIEgen is, for the first time, utilized for establishing a fluorescence turn-on strategy to visualize microscope processes for self-healing gels. Such strategy allows the in situ monitoring of gelation and self-healing processes with extremely low background. Besides, the fluorescence also endows self-healing gels with diverse emission, especially white-light emission. By coding these multicolor fluorescent self-healing gels, fluorescent codes with a stealth effect are successfully fabricated with features of stretchability, wearability, reusability, and diversity, performing superiorly in anticounterfeiting. These results give rise to a deep insight into self-healing mechanism and will potentially boost the development of new multifunctional self-healing gels.
Aggregation-induced emission (AIE) is the long-sought solution to the problem of aggregation-caused quenching that has hampered efficient application of fluorescent organic materials. An important ...goal on the way to fully understand the working mechanism of the AIE process was, for more than a decade, and still remains obtaining more comprehensive insights into the correlation between the ultrafast excited-state dynamics in tetraphenylethylene (TPE)-based molecules and the AIE effect in them. Here we report a number of TPE-based derivatives with varying structural rigidities and AIE properties. Using a combination of ultrafast time-resolved spectroscopy and computational studies, we observe a direct correlation between the state-dependent coupling motions and inhibited fluorescence, and prove the existence of photocyclized intermediates in them. We demonstrate that the dominant non-radiative relaxation dynamics,
formation of intermediate or rotation around the elongated Cdouble bond, length as m-dashC bond, is responsible for the AIE effect, which is strongly structure-dependent but not related to structural rigidity.
A new ratiometric fluorescence detection of heparin is reported with the ensemble of 1 and 2. This method is based on the respective ACQ (aggregation-caused quenched emission) and AIE ...(aggregation-induced emission) features of anthracene and tetraphenylethene. DLS, CLSM and fluorescent spectral investigations suggest that the variation of the fluorescence intensity ratio I(497)/I(421) is due to the formation of aggregates of 1 and 2 with heparin. Moreover, this ratiometric fluorescence method can be used to distinguish heparin from its analogues (HA, Dex). In order to demonstrate the practical utilization of this ratiometric fluorescence method, the fluorescence spectra of the ensemble of 1 and 2 were measured in the presence of serum, and the results indicate that it is possible to eliminate the interferences from other biomolecules by either subtracting the background fluorescence intensities or lowering the pH values of the sample solutions.
Full quantum mechanical (FQM) calculation of the excited state of aggregation‐induced‐emission (AIE) materials is highly sought but still a challenging task. Herein, we employed the recently ...developed electrostatically embedded generalized molecular fractionation (EE‐GMF) method, a method based on the systematic fragmentation approach, to predict, for the first time, the spectra of a prototype AIE fluorophore: di(p‐methoxylphenyl)dibenzofulvene (FTPE). Compared to the single molecular or QM/MM calculations, the EE‐GMF method shows significantly improved accuracy, nearly reproducing the experimental optical spectra of FTPE in both condensed phases. Importantly, we show that the conventional restriction of the intramolecular rotation mechanism cannot fully account for AIE, whereas the two‐body intermolecular quantum mechanical interaction plays a crucial role in AIE.
Reproducing to better understand: The calculational method electrostatically embedded generalized molecular fractionation is a full quantum mechanical (FQM) approach that can nearly reproduce the experimental optical absorption and emission spectra of the prototype fluorophore di(p‐methoxylphenyl)dibenzofulvene, which displays aggregation‐induced emission, in both condensed phases.
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