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Journal ArticleDOI

Recent advances in excited state intramolecular proton transfer mechanism-based solid state fluorescent materials and stimuli-responsive fluorescence switching

TL;DR: In this article, the authors presented the recent developments in ESIPT-based solid state fluorescent materials and external stimuli-induced fluorescence switching and showed that the substitutional unit, molecular conformation and supramolecular interactions played a significant role in transforming planar ESIPt fluorophores to stimuli-induced fluorescent switching materials either between two states or off-on states.
Abstract: Stimuli-responsive organic solid state fluorescent materials are considered as potential candidates for optoelectronic application as well as in the biomedical field. Molecular design and supramolecular interaction controlled organization in the solid state played an important role in producing switchable and tunable fluorescent materials. Excited state intramolecular proton transfer (ESIPT) mechanism-based solid state fluorescent materials showed unique photophysical properties such as a large Stokes shift and local environment (pH, polarity, ions and viscosity) responsive fluorescence modulation. The unique photophysical properties of ESIPT molecules made them interesting for various fields including laser dyes, molecular probes, optoelectronics, white emissive materials and optical information storage materials. Systematic fluorophore structural engineering has been performed over the years to gain insight on the ESIPT mechanism in order to improve the quantum efficiency and introduce desirable material attributes for functional applications. The substitutional unit, molecular conformation and supramolecular interactions played a significant role in transforming planar ESIPT fluorophores to stimuli-induced fluorescence switching materials either between two states or off–on states. In this review article, we have presented the recent developments in ESIPT-based solid state fluorescent materials and external stimuli-induced fluorescence switching.
Citations
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Journal ArticleDOI
TL;DR: A comprehensive review of the recent development and applications of excited-state intramolecular proton transfer-based (ESIPT-based) aggregation-induced emission luminogens (AIEgens) can be found in this paper .
Abstract: In this review, we present a systematic and comprehensive summary of the recent development and applications of excited‐state intramolecular proton transfer‐based (ESIPT‐based) aggregation‐induced emission luminogens (AIEgens), a type of promising materials that inherit the advantages of ESIPT and AIE, such as large Stokes shift, excellent photostability, and low self‐quenching. We first summarize the backbones that have been used to construct the ESIPT‐based AIEgens and classify the constructed ones based on the relation between ESIPT and AIE unit. According to the sensing mechanisms and design strategies, we have reviewed the applications of ESIPT‐based AIEgens in bioimaging, drug delivery systems, organic light‐emitting diodes, photo‐patterning, liquid crystal, and the detection of metal cations, anions, small molecules, biothiols, biological enzymes, latent fingerprinting, and so on. We have also reviewed the recent advances in the development of new theoretical methods for investigating molecular photochemistry in crystals and their applications in ESIPT‐based AIEgens. We discussed the remaining challenges in this field and the issues that need to be addressed. We anticipate that this review can provide a comprehensive picture of the current condition of research in this field, and promote researchers to make more efforts to develop novel ESIPT‐based AIEgens with new applications.

55 citations

Journal ArticleDOI
TL;DR: In this paper , a brief overview on the exploitation of ESIPT luminescence for the optimization of dual-state emissive (DSE) dyes properties is presented, where a synergistic approach between organic synthesis and ab initio calculations has proven to be an efficient tool for the construction and optimization of DSE-ESIPT fluorophores.
Abstract: Dual-state emissive (DSE) fluorophores are organic dyes displaying fluorescence emission both in dilute and concentrated solution and in the solid-state, as amorphous, single crystal, polycrystalline samples or thin films. This comes in contrast to the vast majority of organic fluorescent dyes which typically show intense fluorescence in solution but are quenched in concentrated media and in the solid-state owing to π-stacking interactions; a well-known phenomenon called aggregation-caused quenching (ACQ). On the contrary, molecular rotors with a significant number of free rotations have been engineered to show quenched emission in solution but strong fluorescence in the aggregated-state thanks to restriction of the intramolecular motions. This is the concept of aggregation-induced emission (AIE). DSE fluorophores have been far less explored despite the fact that they are at the crossroad of ACQ and AIE phenomena and allow targeting applications both in solution (bio-conjugation, sensing, imaging) and solid-state (organic electronics, data encryption, lasing, luminescent displays). Excited-State Intramolecular Proton Transfer (ESIPT) fluorescence is particularly suitable to engineer DSE dyes. Indeed, ESIPT fluorescence, which relies on a phototautomerism between normal and tautomeric species, is characterized by a strong emission in the solid-state along with a large Stokes’ shift, an enhanced photostability and a strong sensitivity to the close environment, a feature prone to be used in bio-sensing. A drawback that needs to be overcome is their weak emission intensity in solution, owing to detrimental molecular motions in the excited-state. Several strategies have been proposed in that regard. In the past few years, a growing number of examples of DSE-ESIPT dyes have indeed emerged in the literature, enriching the database of such attractive dyes. This review aims at a brief but concise overview on the exploitation of ESIPT luminescence for the optimization of DSE dyes properties. In that perspective, a synergistic approach between organic synthesis, fluorescence spectroscopy and ab initio calculations has proven to be an efficient tool for the construction and optimization of DSE-ESIPT fluorophores.

30 citations

Journal ArticleDOI
04 Aug 2021
TL;DR: From cell imaging with precise subcellular localization to the fabrication of low-cost, more efficient optoelectronic devices for room illumination, Dual-State Emitter molecules (DSEgens) can be considered as fine-tuned, tailored molecular entities capable of intensely fluorescing both in solution and in the solid state.
Abstract: From cell imaging with precise subcellular localization to the fabrication of low-cost, more efficient optoelectronic devices for room illumination, Dual-State Emitter (DSE) molecules (DSEgens) can be considered as fine-tuned, tailored molecular entities capable of intensely fluorescing both in solution and in the solid state. The synthesis of these new kind of fluorophores requires innovative molecular blueprints as their successful development will enable a whole spectrum of possibilities for future uses in the fields of energy, analytical chemistry, or molecular biology.

27 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reported the first example of 1-hydroxy-1H-imidazole-based ESIPT-fluorophores, 1-H-5-methyl-2,4-di(pyridin-2-yl)-1H -imidrazole (HL), featuring a short intramolecular hydrogen bond.
Abstract: The ability of 1-hydroxy-1H-imidazoles to exist in the form of two prototropic tautomers, the N-hydroxy and the N-oxide forms, can be utilized in the design of new types of ESIPT-fluorophores (ESIPT=excited state intramolecular proton transfer). Here we report the first example of 1-hydroxy-1H-imidazole-based ESIPT-fluorophores, 1-hydroxy-5-methyl-2,4-di(pyridin-2-yl)-1H-imidazole (HL), featuring a short intramolecular hydrogen bond O-H⋅⋅⋅N (O⋅⋅⋅N 2.56 A) as a pre-requisite for ESIPT. The emission of HL originates from the anti-Kasha S2 →S0 fluorescence in the N-oxide form as a result of a large S2 -S1 energy gap slowing down the S2 →S1 internal conversion. Due to an energy barrier between the N-hydroxy and N-oxide forms in the ground state, the HL molecules can be trapped and photoexcited in the N-oxide form leading to the Stokes shift of ca. 60 nm which is the smallest among known ESIPT-fluorophores.

12 citations

References
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Journal ArticleDOI
TL;DR: Aggregation greatly boosts emission efficiency of the silole, turning it from a weak luminophor into a strong emitter.

5,916 citations

Journal ArticleDOI
TL;DR: In this critical review, recent progress in the area ofAIE research is summarized and typical examples of AIE systems are discussed, from which their structure-property relationships are derived.
Abstract: Luminogenic materials with aggregation-induced emission (AIE) attributes have attracted much interest since the debut of the AIE concept in 2001. In this critical review, recent progress in the area of AIE research is summarized. Typical examples of AIE systems are discussed, from which their structure–property relationships are derived. Through mechanistic decipherment of the photophysical processes, structural design strategies for generating new AIE luminogens are developed. Technological, especially optoelectronic and biological, applications of the AIE systems are exemplified to illustrate how the novel AIE effect can be utilized for high-tech innovations (183 references).

4,996 citations

Journal ArticleDOI
TL;DR: This review restricts discussions to purely fluorescence-based methods using conjugated polymers (CPs) and details earlier research in this Introduction to illustrate fundamental concepts and terminology that underpin the recent literature.
Abstract: The field of chemical sensing is becoming ever more dependent upon novel materials. Polymers, crystals, glasses, particles, and nanostructures have made a profound impact and have endowed modern sensory systems with superior performance. Electronic polymers have emerged as one of the most important classes of transduction materials; they readily transform a chemical signal into an easily measured electrical or optical event. Although our group reviewed this field in 2000,1 the high levels of activity and the impact of these methods now justify a subsequent review as part of this special issue. In this review we restrict our discussions to purely fluorescence-based methods using conjugated polymers (CPs). We further confine our detailed coverage to articles published since our previous review and will only detail earlier research in this Introduction to illustrate fundamental concepts and terminology that underpin the recent literature.

3,796 citations

Journal ArticleDOI
TL;DR: A new class of organic nanoparticles (CN-MBE nanoparticles) with a mean diameter of ca.
Abstract: A new class of organic nanoparticles (CN-MBE nanoparticles) with a mean diameter of ca. 30−40 nm, which exhibit a strongly enhanced fluorescence emission, were prepared by a simple reprecipitation method. CN-MBE (1-cyano-trans-1,2-bis-(4‘-methylbiphenyl)ethylene) is very weakly fluorescent in solution, but the intensity is increased by almost 700 times in the nanoparticles. Enhanced emission in CN-MBE nanoparticles is attributed to the synergetic effect of intramolecular planarization and J-type aggregate formation (restricted excimer formation) in nanopaticles. On/off fluorescence switching for organic vapor was demonstrated with CN-MBE nanoparticles.

1,770 citations

Journal ArticleDOI
TL;DR: New fluorescent sensing mechanisms that have emerged in the past five years, such as aggregation-induced emission (AIE) and C=N isomerization, which can be ascribed to fluorescence changes via conformational restriction are focused on.
Abstract: During the past decade, fluorescent chemosensors have become an important research field of supramolecular chemistry and have attracted great attention because of their simplicity, high selectivity and sensitivity in fluorescent assays. In the design of new fluorescent chemosensors, exploration of new sensing mechanisms between recognition and signal reporting units is of continuing interest. Based on different photophysical processes, conventional sensing mechanisms including photo-induced electron transfer (PET), intramolecular charge transfer (ICT), metal–ligand charge transfer (MLCT), twisted intramolecular charge transfer (TICT), electronic energy transfer (EET), fluorescence resonance energy transfer (FRET), and excimer/exciplex formation have been investigated and reviewed extensively in the literature. This tutorial review will mainly focus on new fluorescent sensing mechanisms that have emerged in the past five years, such as aggregation-induced emission (AIE) and CN isomerization, which can be ascribed to fluorescence changes via conformational restriction. In addition, excited-state intramolecular proton transfer (ESIPT) has not been well reviewed yet, although a number of chemosensors based on the ESIPT mechanism have been reported. Thus, ESIPT-based chemosensors have been also summarized in this review.

1,511 citations