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Multi-stimuli Responsive Supramolecular Gels Based on a D-π-A Structural Cyanostilbene Derivative with Aggregation Induced Emission Properties
摘要： Developing multi-stimuli responsive fluorescent gel materials in a single system remains challenging. Gelator molecules with classical fluorophores suffer from aggregation-caused quenching (ACQ) effect, limiting their applications further. Herein, a novel V-shaped cyanostilbene-based molecule (BAPBIA) with aggregation induced emission (AIE) characteristics and great gelation ability was synthesized and was found to exhibit multi-stimuli responsive behaviors. Reversible gel-sol phase transitions together with emission quenching are realized in response to external stimuli including heating, light and fluoride ion. Especially, the introduction of dimethylaniline group (donor) and cyano group (acceptor) generates a D-π-A structure, further leading to an intramolecular charge transfer (ICT) effect, which enlarges the emission contrast with the variations of the distribution of charge. Thus, upon trifluoroacetic acid (TFA) triggered protonation of dimethylaniline group, not only gel-sol transition but also emission color switching (yellow-to-blue) is achieved due to the loss of the ICT effect. This work paves an easy way to construct fully reversible multi-stimuli responsive fluorescence modulation smart materials.
关键词： supramolecular gels,aggregation induced emission,multi-stimuli responsive,fluorescence switching,cyanostilbene derivative
更新于2025-11-14 15:14:40
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Excited-state intramolecular proton transfer-based multifunctional solid-state emitter: a fluorescent platform with ‘write-erase-write’ function
摘要： The excited-state intramolecular proton transfer (ESIPT)-based molecular probes have drawn significant attention owing to their environment-sensitive fluorescence properties, large Stokes shift and emerged as building blocks for the development of molecular sensors and switches. However, most of the ESIPT-based fluorophores exhibit weak emission in the solid state limiting the scope of real-time applications. Addressing such issues, herein, we presented a C3-symmetric like molecular architecture employing a simple one-step Schiff base condensation between triaminoguanidinium chloride and 3,5-di-tert-butyl-2-hydroxybenzaldehyde (TGHB). The temperature-dependent fluorescence studies including at 77 K indicated the strong emission from the keto tautomer compared to that of the enol. The facile ESIPT in TGHB in the solid-state led to a remarkable enhancement of fluorescence quantum yield of 1600-times compared to that of the solution (λem = 545 nm) by restricting the intramolecular rotation and subsequently suppressing the nonradiative deactivation. The excited–state processes were further elucidated through time-resolved fluorescence measurements. TGHB exhibited turn on-off fluorescence upon exposure to acid /base vapor in the form of powder as well as transparent, free-standing thin film. A rewritable and erasable fluorescent platform was demonstrated using TGHB as molecular ink, which offers a potential testbed for performing multiple times ‘write-erase-write’ cycles. In addition, TGHB, possessing multiple binding sites (O and N donors) involving the central core of triaminoguanidinium cation, displayed selective turn-on fluorescence with Zn2+. The structure-property relationship revealed in the present study provides insight towards the development of novel cost-effective multifunctional materials promising for stimuli-responsive molecular switches.
关键词： molecular ink,thin film,ESIPT,multifunctional,solid-state emission,fluorescence switching
更新于2025-09-23 15:21:21
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Cu2+-mediated Fluorescence Switching of Graphene Quantum Dots for Highly Selective Detection of Glutathione
摘要： As a short peptide containing active thiol group, glutathione (GSH) participates in many cellular reactions, so it is of great significance to detect cellular GSH. In this work, amino-rich graphene quantum dots (GQDs) were synthesized, which could coordinate with copper ions (Cu2+) and yield aggregation-induced fluorescence quenching. However, GSH owns stronger coordination ability with Cu2+, so that GSH could promote the dissociation of Cu2+ from the surface of GQDs, and then led to the fluorescence recovery of GQDs. In BR buffer medium at pH 6.8, GSH was able to gradually recover the fluorescence of GQDs (1 μg/mL) that was quenched by Cu2+ (250 μmol/L), which could be finished within 20 min. Additionally, the recovery degree of fluorescence was linear to the concentration of GSH in the range of 20─500 μmol/L with a detection limit of 3.4 μmol/L. This method was applicable to the detection of GSH in cell lysate by the switchable function of Cu2+ to improve the selectivity.
关键词： Graphene quantum dots,Fluorescence switching,Copper ions,Glutathione
更新于2025-09-19 17:13:59
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Green-light-induced melting of self-assembled azobenzene nano/microstructures
摘要： We report the formation of green-light-responsive fluorescent aggregates composed of trigonal molecules having three ortho-dialkylated azobenzene wings at the periphery (a green-light-responsive 3BuES and an aggregation-induced emission/aggregation-induced emission enhancement [AIE/AIEE]-active 3BuAz). Exposure of the respective (3BuES and 3BuAz) spheres to green light leads to color tuning and/or fluorescence switching. The results can be rationalized in terms of green-light-induced molecular conformational changes of the trigonal azobenzene molecules and the resulting phase transition of the self-assembled structures. For instance, irradiation of 3BuES with green light produces B35% of U-shaped cis forms (i.e., approximately one-third of the trans-azobenzene units isomerizes to the cis forms), which seems to be su?cient to weaken the degree of the molecular packing of the trigonal azobenzene frameworks and lower the melting temperatures. Moreover, to apply the excellent fluorescence switching functions of 3BuAz aggregates to create new fluorescent organic materials, we used a co-assembly of 3BuES–3BuAz binary mixtures. Our important approach for obtaining green-light-responsive fluorescent nano/microstructures from the binary mixtures is phase separation based on the structural difference between 3BuES (having a planar central core) and 3BuAz (having a distorted conformation), which helps retain the fluorescence functions of the AIE/AIEE-active 3BuAz chromophore. Scanning electron microscopy (SEM), optical microscopy (OM), and fluorescence optical microscopy (FOM) observations prove apparent green-light-induced melting, color tuning and fluorescence switching of the phase-separated structures (i.e., microspheres and nanoparticles).
关键词： green-light-responsive,AIE/AIEE,azobenzene,fluorescent aggregates,fluorescence switching,phase separation
更新于2025-09-16 10:30:52
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Highly cooperative fluorescence switching of self-assembled squaraine dye at tunable threshold temperatures using thermosensitive nanovesicles for optical sensing and imaging
摘要： Thermosensitive fluorescent dyes can convert thermal signals into optical signals as a molecular nanoprobe. These nanoprobes are playing an increasingly important part in optical temperature sensing and imaging at the nano- and microscale. However, the ability of a fluorescent dye itself has sensitivity and accuracy limitations. Here we present a molecular strategy based on self-assembly to overcome such limitations. We found that thermosensitive nanovesicles composed of lipids and a unique fluorescent dye exhibit fluorescence switching characteristics at a threshold temperature. The switch is rapid and reversible and has a high signal to background ratio (>60), and is also highly sensitive to temperature (10–22%/°C) around the threshold value. Furthermore, the threshold temperature at which fluorescence switching is induced, can be tuned according to the phase transition temperature of the lipid bilayer membrane forming the nanovesicles. Spectroscopic analysis indicated that the fluorescence switching is induced by the aggregation-caused quenching and disaggregation-induced emission of the fluorescent dye in a cooperative response to the thermotropic phase transition of the membrane. This mechanism presents a useful approach for chemical and material design to develop fluorescent nanomaterials with superior fluorescence sensitivity to thermal signals for optical temperature sensing and imaging at the nano- and microscales.
关键词： fluorescence switching,optical sensing,nanovesicles,thermosensitive fluorescent dyes,imaging
更新于2025-09-11 14:15:04
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A Highly Fluorescent and Photoresponsive Polymer Gel Consisting of Poly(acrylic acid) and Supramolecular Cyanostilbene Crosslinkers
摘要： A poly(acrylic acid)-based polymer gel exhibiting strong fluorescence and high photoresponsibility is prepared by using a cyanostilbene derivative as a self-assembling supramolecular crosslinking agent, which generates conceptually new multiple hydrogen bonds in the gel system. This polymer gel in ethanol shows the gel-to-sol transition upon UV light irradiation with concomitant fluorescence color and intensity changes, which are attributed to the trans-to-cis photoisomerization of the supramolecular crosslinkers. Aggregation-induced enhanced emission (AIEE) behavior of the trans-cyanostilbene derivative enables a highly fluorescent polymer gel (ΦF = 0.68) with green color (λem = 541 nm), which can be switched into a blue fluorescent sol (λem = 506 nm and ΦF = 0.12) upon UV irradiation.
关键词： polymer gels,fluorescence switching,photoisomerization,gel-to-sol transition,hydrogen bonding
更新于2025-09-04 15:30:14