Aggregation-induced Emission Properties Research Articles

A Fluorescent Hydrogel with AIE Emission for Dehydration-Visualizable Wearable Sensors.

Hydrogel-based wearable sensors eventually experience dehydration, which negatively impacts their function, leading to decreased sensitivity. Monitoring the real-time water retention rate and sensing performance of wearable flexible sensors without dismantling them remains a significant difficulty. In this study, we develop and produce a molecule having aggregation-induced emission (AIE) properties in an aqueous environment, which can combine with anionic guar gum (GG) and acrylic acid (AAc) to create an AIE hydrogel. Wearable sensing electronic devices have the capability to track motion signals at various joints of the human body. Additionally, they can effectively and visually monitor dehydration status during extended periods of operation. The fluorescence intensity of the hydrogel is primarily influenced by the level of aggregation of luminous monomers inside the network. This level of aggregation is predominantly governed by the hydrogel's water retention rate. Hence, the extended duration of hydrogel dehydration can be manifested through alterations in their fluorescence characteristics, which are employed for strain sensing. This approach enables users to assess the water retention of hydrogels with greater efficiency, eliminating the requirement for disassembling them from the completed electrical gadget. In summary, the use of AIE-based fluorescent hydrogels will advance the progress of intelligent wearable electronics. This article is protected by copyright. All rights reserved.

Electronic structure modulation in quinoline derivatives through substituent-mediated effects: Development of AIE fluorescent probes for Fe3+ detection in water samples

Iron (Fe3+) is an essential trace element in biological organisms. Abnormal concentrations of Fe3+ in aquatic possess the potential to disrupt normal physiological and metabolic processes in living organisms. Consequently, the pursuit of developing fluorescent probes for detecting Fe3+ concentrations in water samples is highly significant. The lone electron pair on the nitrogen atom of quinoline demonstrates outstanding coordination capabilities, enabling the selective detection of metal ions through coordination. Nevertheless, the interaction between metal ions and quinoline-based fluorescent probes tends to lead to nanoparticle aggregation, causing aggregation-caused quenching (ACQ) phenomena. This severely restricts the practical application of these probes. To address this challenge, the study utilizes quinoline as the foundational framework and modulates the excited-state electronic structure of quinoline derivatives through substituent effects. This facilitates the transition from ACQ to aggregation-induced emission (AIE). By integrating theoretical calculations, the paper proposes a comprehensive strategy for designing AIE molecules based on quinoline. This contribution provides innovative perspectives on AIE molecule design. Ultimately, the AIE property of the 8-MQB molecule is harnessed to develop a fluorescent probe capable of detecting Fe3+ in water samples. The fluorescence intensity exhibits a robust linear correlation with Fe3+ concentrations within the range of 5.0 μM to 0.3 mM. Moreover, the probe demonstrates exceptional resistance to interference from other metal ions. In conclusion, this research presents a universal strategy for designing AIE molecules and introduces an AIE probe for the rapid detection of Fe3+ concentrations in water samples.

The complexometric behavior of selected aroyl-S,N-ketene acetals shows that they are more than AIEgens

Using the established synthetic methods, aroyl-S,N-ketene acetals and subsequent bi- and multichromophores can be readily synthesized. Aside from pronounced AIE (aggregation induced emission) properties, these selected examples possess distinct complexometric behavior for various metals purely based on the underlying structural motifs. This affects the fluorescence properties of the materials which can be readily exploited for metal ion detection and for the formation of different metal-aroyl-S,N-ketene acetal complexes that were confirmed by Job plot analysis. In particular, gold(I), iron(III), and ruthenium (III) ions reveal complexation enhanced or quenched emission. For most dyes, weakly coodinating complexes were observed, only in case of a phenanthroline aroyl-S,N-ketene acetal multichromophore, measurements indicate the formation of a strongly coordinating complex. For this multichromophore, the complexation results in a loss of fluorescence intensity whereas for dimethylamino-aroyl-S,N-ketene acetals and bipyridine bichromophores, the observed quantum yield is nearly tripled upon complexation. Even if no stable complexes are formed, changes in absorption and emission properties allow for a simple ion detection.

Mechanofluorochromic behaviors and latent fingerprint detection of triphenylamine-based compounds with mono-/bis-BF2 fluorophores

To better understand the relationship between molecular structure of the mono-/bis-BF2-core compounds and mechanofluoroboron behaviors, two pyridine-based difluoroboron compounds with triphenylamine group (TPA-ts-BF2 and TPA-ts-2BF2) were designed and successfully synthesized, which TPA-ts-BF2 including a BF2 fluorophore and TPA-ts-2BF2 containing the bisBF2 fluorophores. Based on the photophysical properties measurements results, it was found that TPA-ts-2BF2 had more excellent intramolecular charge transfer characteristics than that of TPA-ts-BF2, and exhibited significant aggregation-induced emission activity, however, TPA-ts-BF2 displayed typical aggregation-caused quenching phenomenon. Meanwhile, the emission spectrum of the solid powders of TPA-ts-2BF2 was red-shifted 52 nm after grinding, that of TPA-ts-BF2 was red-shifted 46 nm, which was resulted from crystalline state switching to amorphous state. According to the theoretical calculations, we conjectured that TPA-ts-BF2 with uncoordinated amide linkage moiety had a tendency to forming a more twisted conformance and higher molecular polarity, which made that mechanofluorochromic behavior was worse than that of TPA-ts-2BF2. Additionally, TPA-ts-2BF2 was applied to latent fingerprint detection due to its prime aggregation-induced emission property.

Aggregation-Induced Emission (AIE) in Polymers: Effect of Polymer size on the Fluorescence of Low Molecular Weight PEG and PPG.

Aggregation-induced emission (AIE) is a fascinating phenomenon where specific molecules exhibit enhanced fluorescence upon aggregation. This unique property has revolutionized the design and development of new fluorescent materials for different applications, from biosensors and organic light-emitting diodes (OLEDs) to biomedical imaging and diagnostics. Researchers are creating sensitive and selective sensing platforms, opening new avenues in material science and engineering by harnessing the potential of AIE. To expand the knowledge in this field, this study explored the aggregation-induced emission (AIE) properties of two polymers, namely polyethylene glycol (PEG) and polypropylene glycol (PPG) of low molecular weight (MW) using fluorescence spectroscopy and absorbance (UV). PEG-300 and PPG-725 were the most fluorescent polymers at UV of the ten investigated. Interestingly, AIE did not correlate linearly with molecular weight (MW), and monobutyl ether substitution in PEG with a similar MW substantially altered its AIE. Furthermore, fluorescence precisely quantified low polymer concentrations in water, and non-aqueous solvents suppressed AIE, suggesting potential for AIE manipulation. These findings enhance our understanding of AIE in polymers, fostering the development of novel materials for applications such as biosensors.

AIE-based fluorescent sensing of ciprofloxacin using non-fluorescent 2D silver dimolybdate nanosheets: The synergistic sensor method (SGSM) to switch on non-fluorescent 2D nanosheets into an effective fluorescent biosensor

The development of an efficient method for detecting ciprofloxacin (CIP) is critical due to the potential for significant harm to humans, including the danger of severe liver damage and hematuria associated with increased levels of this drug. In this study, we offer a highly sensitive and highly selective method for fluorescence sensing of the antibiotic ciprofloxacin employing the properties of Aggregation-Induced Emission (AIE) with silver dimolybdate nanosheets (Ag2Mo2O7 NSs). Outstanding structural characteristics of the Ag2Mo2O7 NSs achieved using the hydrothermal method. By carefully controlling the aggregation of the Synergistic Sensor Method (SGSM), we are able to produce a very bright fluorescence response with the ciprofloxacin concentration range from 0 to 250 nM with a low detection limit of 1.1 nM. Quick and ultrasensitive detection has been achieved by the Synergistic effect (SGE) and AIE from the current approach. The SGSM has been shown to be a novel platform for human health monitoring and pharmaceutical quality control. With broad-ranging practical implications, the combination of AIE and silver dimolybdate nanosheets offers a platform for reliable and ciprofloxacin detection. We believe the SGSM is a role model paper for future nano-biosensor detection methods due to the synergistic effect resulting in the AIE and turn-on sensor approach for many non-fluorescent 2D nanosheets. This can open many new doors for the intensive development of 2D nanosheets for future fluorescent sensors without the need to produce fluorescence by the nanosheet itself.

Novel biocompatible N-rich AIE fluorescent probe for live cell imaging and visual onsite detection of uranium.

A sensitive and biocompatible N-rich probe for rapid visualuranium detectionwas constructed by grafting two trianiline groups to 2,6-bis(aminomethyl)pyridine. Possessing excellent aggregation-induced emission (AIE) property and the advantages to form multidentate chelate with U selectively, the probe has been applied successfully to visualize uranium in complex environmental water samples and living cells, demonstrating outstanding anti-interference ability against large equivalent of different ions over a wide effective pH range. A large linear range (1.0 × 10-7-9.0 × 10-7mol/L) and low detection limit (72.6nmol/L, 17.28ppb) were achieved for the visual determination of uranium. The recognition mechanism, photophysical properties, analytical performance and cytotoxicity were systematically investigated, demonstrating highpotential for fast risk assessment of uranium pollution in field and in vivo.

Fast and easy detection of hypochlorite by a smartphone-based fluorescent turn-on probe: Applications to water samples, zebrafish and plant imaging

We have developed a fluorescent probe DBT-Cl ((E)-2-(2-(4-(diphenylamino)benzylidene) hydrazinyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride) for ClO− with an aggregation-induced emission (AIE) strategy depending on solvent polarity. DBT-Cl possessed a prominent solvatochromic emission property with intramolecular charge transfer (ICT) from the TPA (triphenylamine) to the amide group, which was studied by spectroscopic analysis and DFT calculations. These unique AIE properties of DBT-Cl led to the recognition of ClO− with high fluorescent selectivity. DBT-Cl quickly detected ClO− in less than 1 sec with a fluorescent color change from green to cyan. DBT-Cl had a low detection limit of 9.67 μM to ClO−. Detection mechanism of DBT-Cl toward ClO− was illustrated to be oxidative cleavage of DBT-Cl by 1H NMR titrations, ESI-mass, and DFT calculations. We established the viability for dependable detection of ClO− in actual water samples, as well as zebrafish and plant imaging. In particular, DBT-Cl was capable of easily monitoring ClO− through a smartphone application. Therefore, DBT-Cl assured a promising approach for a fast-responsive and multi-applicable ClO− probe in environmental and living organism systems.

Blue aggregation-induced emission bipolar materials consisting of diphenylsulfone or benzophenone core and triphenylethene-carbazole fragments for highly efficient OLEDs

Bipolar derivatives having aggregation-induced emission (AIE) properties were synthesized in reactions of 4,4′-difluorobenzophenone, 4-fluorophenyl-phenylsulfone or bis(4-fluorophenyl)sulfone with prepared key starting materials: 1,1,2-triphenyl-2-(9H-carbazol-2-yl)ethylene or 1-(9H-carbazol-2-yl)-4-(1,2,2-triphenylethenyl)benzene. The objective materials have shown high thermal stabilities and can form amorphous layers having high glass transition temperatures in the region of 110–173 °C. The photoluminescence spectra of the prepared derivatives registered using tetrahydrofuran-water solutions demonstrated strong blue emissions, confirming their AIE property. Thin films of the compounds were tested in multilayer organic light-emitting diodes. The device using bis(4-{2-[4-(1,1,2-triphenylethylenyl)phenyl]carbazol-9-yl}phenyl)sulfone emitter (EM3) outperformed the other devices, achieving a peak efficiencies of 3.4 % (5.6 cd/A and 4.7 lm/W) with maximum luminance of about 11000 cd/m2. However OLED using 4-{2-[4-(1,1,2-triphenylethylenyl)phenyl]carbazol-9-yl}phenyl-phenylsulfone (EM2) as emitter demonstrated higher efficiency at higher luminance values. The maximum efficiencies of the device were obtained at a luminance value of about 100 cd/m2 and were recorded as 3.2 % (5.2 cd/A and 4.1 lm/W) with luminance of 17515 cd/m2.

A high-performance organic fluorescent probe with aggregation-induced emission properties for long-term tumor monitoring

Near-infrared organic fluorescent probes have great need in biological sciences and medicine but most of them are still largely unable to meet demand. In this work, a delicate multipurpose organic fluorescent probe (DPPM-TPA) with aggregation-induced emission performances is designed and prepared by facile method to reflect fluorescence labeling, two-photon imaging, and long-term fluorescent tracking. Specifically, DPPM-TPA NPs was constructed from 4-(diphenylamino)phenylboronic acid and DPPM-Br by classical Suzuki coupling reaction and then coated with F127. Such nanoprobe possessed high stability in diverse medium under ambient temperatures, low cytotoxicity, and brilliant fluorescence performance. More importantly, DPPM-TPA NPs showed excellent two-photon imaging and extraordinary long-term fluorescence tracing capacity to malignant tumor, and it can last up to 9 days. These results indicated that DPPM-TPA NPs is expected to serve as a fluorescent probe for photodiagnostic and providing a new idea for the development of long-term fluorescent tracker.

Photorewriting, Time-Resolved Encryption, and Unclonable Anticounterfeiting with Artificial Intelligence Authentication via a Reversible Photoswitchable System.

In the fields of photolithographic patterning, optical anticounterfeiting, and information encryption, reversible photochromic materials with solid-state fluorescence are emerging as a potential class of systems. A design strategy for reversible photochromic materials has been proposed and synthesized through the introduction of photoactive thiophene groups into the molecular backbone of aryl vinyls, compounds with unique aggregation-induced emission properties, and solid-state reversible photocontrollable fluorescence and color-changing properties. This work develops novel photochromic inks, films, and cellulose hydrogels for enhancing the security of information encryption and anticounterfeiting technologies. They achieve rapid and reversible color change under ultraviolet light irradiation. Dependent upon the rate of color change, higher levels of time-resolved security can be achieved. This feature is important for enhancing the confidentiality of encrypted information and the reliability of security labels. Color-changing cellulose hydrogels, inks, and films consisting of three photochromic fluorescent molecules have quick photoactivity, great photoreversibility and photostability, and good processability, making them ideal for time-delayed anticounterfeiting and smart encryption. Furthermore, specialized algorithms are used to construct convolutional neural networks, and image analysis is performed on these systems, thus solving the current problem of the time-consuming information decryption process. This artificial intelligence method offers new opportunities for enhanced data encryption.

A Novel Enhanced-Fluorescent Probe Based on DHLA-Stabilized Red-Emitting Copper Nanoclusters for Methimazole Detection Via Aggregation-Induced Emission Effect.

Herein, an aqueous phase synthesis approach was presented for the fabrication of copper nanoclusters (Cu NCs) with aggregation-induced emission (AIE) property, utilizing lipoic acid and NaBH4 as ligands and reducing agent, respectively. The as-synthesized Cu NCs exhibit an average size of 3.0 ± 0.2nm and demonstrate strong solid-state fluorescence upon excitation with UV light. However, when dissolved in water, no observable fluorescent emission is detected in the aqueous solution of Cu NCs. Remarkably, the addition of Methimazole induced a significant red fluorescence from the aqueous solution of Cu NCs. This unexpected phenomenon can be ascribed to the aggregation of negatively charged Cu NCs caused by electrostatic interaction with positively charged imidazole groups in Methimazole, resulting in enhanced fluorescence through AIE mechanism. Therefore, there exists an excellent linear correlation between the fluorescent intensities of Cu NCs aqueous solution and the concentration of Methimazole within a range of 0.1-1.5 mM with a low limit of detection of 82.2 µM. Importantly, the designed enhanced-fluorescent nanoprobe based on Cu NCs exhibits satisfactory performance in assaying commercially available Methimazole tablets, demonstrating its exceptional sensitivity, reliability, and accuracy.

Controllable Synthesis of Furan-Based Poly(ester amide)s and Its Study on Adhesive and Aggregation-Induced Emission Properties

Controllable Synthesis of Furan-Based Poly(ester amide)s and Its Study on Adhesive and Aggregation-Induced Emission Properties

Effects of a Larger N‐Heterocyclic Ring in Rofecoxib Analogues on AIE Activity and Multifunctional Applications

AbstractTwo analogues of rofecoxib, 2‐Pyr‐ROF and 2‐Pip‐ROF, were designed according to the strategy of heterocyclic ring enlargement and facilely synthesized in a facile manner by Knoevenagel reactions. The first compound, 2‐Pyr‐ROF, had low quantum yields (QY) of 3.0 % in the solid states. After replacing the pyrrolidinyl with piperidinyl, the resulting 2‐Pip‐ROF had a significantly increased QY, with a value of 28 %. The root‐mean‐square deviation (RMSD) values between S0 and S1 of 2‐Pyr‐ROF and 2‐Pip‐ROF in tetrahydrofuran were 0.51, 0.35 Å, respectively. As compared with 2‐Pyr‐ROF, compound 2‐Pip‐ROF exhibited a smaller RMSD, which indicated a lower non‐radiative transition rate. A single‐crystal X‐ray diffraction study and Hirshfeld surfaces analysis revealed that 2‐Pip‐ROF had a more nonplanar molecule structure and a weaker π‐π interaction, which might result in a higher fluorescence intensity and QY. Owing to its better aggregation‐induced emission (AIE) behavior, compound 2‐Pip‐ROF showed more multi‐functional applications, including mechanochromism, acidochromism, and lipid droplets imaging ability. These results imply that the strategy of heterocyclic ring enlargement provides a new paradigm for the design of new luminogens with AIE properties.

Aggregation-Induced Emission of Naphthalene Diimides: Effect of Chain Length on Liquid and Solid-Phase Emissive Properties.

The aggregation-induced emission (AIE) properties of a systematic series of naphthalene diimides (NDIs) varying the chain length at the imide positions have been studied. A solvophobic collapse of NDI units through the flash injection of THF NDI solutions in sonicating water triggers the formation of stable suspensions with enhanced fluorescence emissions. Shorter chains favor the π-π stacking of NDI units through H-aggregation producing a strong AIE effect showing remarkably high quantum yields that have not been observed for non core-substitued NDIs previously. On the other hand, NDIs functionalized with longer chains lead to more disordered domains where π-π stacking between NDI units is mainly given by J-aggregation unfavoring the AIE effect.

Assessing the Impact of π‐Conjugation Length on Aggregation Induced Emission and Self‐Assembly Formation of α‐Cyanostilbene and Bis‐Cyanostilbene

AbstractIn this work, short π‐conjugated (Z)‐2‐(4‐(2‐cyano‐2‐phenylvinyl)phenoxy)‐N‐(1‐(3‐ethoxy‐4‐methoxyphenyl)‐2‐(methyl sulfonyl)ethyl)acetamide (CYS) and large π‐conjugated 2,2′‐(((1Z,1′Z)‐1,4‐phenylenebis(2‐cyanoethene‐2,1‐diyl))bis(4,1‐phenyl ene))bis(oxy))bis(N‐(1‐(3‐ethoxy‐4‐methoxyphenyl)‐2‐(methyl sulfonyl)ethyl)acetamide (BCYS) compounds were synthesized. Furthermore, the influence of π‐conjugation length on CYS and BCYS absorption, fluorescence, aggregation induced emission (AIE) characteristics, and self‐assembly was examined. The large π‐conjugated BCYS (π‐conjugation length=18.71 Å) exhibits AIE property getting on in the DMSO−Water solvent combination as the volume % of water increases and demonstrated production of self‐assembled bundle of micro fibrous structure of around 5 to 6 microns long and 200 to 500 nm wide. Short π‐conjugated CYS (π‐conjugation length=10.80 Å), on the other hand, exhibits aggregation caused quenching (ACQ) in the DMSO−Water solvent combination as the volume % of water increases and the creation of self‐assembled nanostructured crystalline asymmetrical particles. Moreover, the cytotoxicity study of CYS and BCYS revealed that BCYS had superior biocompatibility than CYS.

A thermochromic salicylaldehyde Schiff bases derivative with AIE properties due to twisted structure

Great attention has been attracted to the salicylaldehyde Schiff base due to its thermochromic and photochromic characteristics in the solid state. However, the boundary between photochromic and thermochromic salicylaldehyde Schiff base structures is still unclear, and few studies have been conducted to investigate their thermochromic behavior and structures in depth and systematically. In the present work, we have synthesized a novel salicylaldehyde Schiff base derivative (2,2′-((1E,1′E)-((2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diyl)-bis(azaneylylidene))bis(methaneylylidene))diphenol, BTB) with twisted structure, which possesses both thermochromic and aggregation-induced emission (AIE) characteristics, and systematically investigated its thermochromic properties, enol-keto isomerization, AIE properties, aggregated state, and excited state intramolecular proton transfer (ESIPT) process. Interestingly, in our study, we found that the color of the BTB molecule changed gradually during the heating process, and it can be found that the thermochromism of BTB is produced by the reversible equilibrium shift of the enol form and the keto forms due to the temperature change by the color difference test, the in-situ IR spectra and the DSC curves. Finally, the pathway of BTB proton transfer was analyzed through quantum chemical calculations, and it was found that enol ketone isomerization is achieved through single excited state intramolecular proton transfer, rather than the expected double excited state intramolecular proton transfer.

Cellulose nanofiber-templated metal-organic frameworks for fluorescent detection of methyl parathion pesticides

Methyl parathion is a typical organophosphorus pesticide that poses threats to the global environment and human health. In this study, we developed a portable 2D sensing pad for monitoring methyl parathion based on the aggregation-induced emission (AIE) properties of an innovated hybrid material that integrates cellulose nanofibers (CNFs) with luminescent metal-organic frameworks (LMOFs). The hybrid material enhanced the flexibility and moldability of LMOFs and significantly improved the scalability of sensing material. The resulting CNF/LMOF material was shaped into a 2D pad, exhibiting fluorescent properties under UV exposure. The fluorescence of the pad was quenchable upon exposure to methyl parathion. This host-guest interaction enabled the precise quantification of the pesticide’s concentration by monitoring the intensity variation of the fluorescence at 405 nm wavelength. We further engineered these hybrid pads into a user-friendly and portable sensing prototype, and then validated them with real sample testing. Time-dependent Density Functional Theory calculations were employed to elucidate the underlying fluorescence quenching mechanism triggered by methyl parathion. This work introduces a practical and sustainable sensing platform for pesticide detection.

Aggregation-induced-emission red carbon dots for ratiometric sensing of norfloxacin and anti-counterfeiting

The detection of trace antibiotic residues holds significant importance because it’s related to food safety and human health. In this study, we developed a new high-yield red-emitting carbon dots (R-CDs) with aggregation-induced emission properties for ratiometric sensing of norfloxacin. R-CDs were prepared in 30 min using an economical and efficient microwave-assisted method with tartaric acid and o-phenylenediamine as precursors, achieving a high yield of 34.4 %. R-CDs showed concentration-dependent fluorescence and aggregation-induced-emission properties. A ratiometric fluorescent probe for detecting the norfloxacin was developed. In the range of 0–40 μM, the intensity ratio of two emission peaks (I445 nm/I395 nm) towards norfloxacin show good linear relationship with its concentrations and a low detection limit was obtained (36.78 nM). In addition, complex patterns were developed for anti-counterfeiting based on different emission phenomenon at different concentrations. In summary, this study designed a novel ratiometric fluorescent probe for detection of norfloxacin, which greatly shortens the detection time and improves efficiency compared with high-performance liquid chromatography and other methods. The study will promote the application of carbon dots in anti-counterfeiting and other related fields, laying the foundation for the preparation of low-cost photosensitive anti-counterfeiting materials.

D-π-A type dicyanoethylene derivatives modified by tetraphenylethylene exhibiting aggregation-induced emission and high-contrast mechanofluorochromism

Based on a rational design strategy by combining an electron-withdrawing dicyanoethylene unit and electron-donating tetraphenylethylene moiety, we successfully synthesized two π-conjugated molecules Ph-TPE-MMN and NA-TPE-MMN. According to the optical research and theoretical calculation results, they had highly distorted conformations, D-A type molecular structure and definite intramolecular charge transfer (ICT) properties. Moreover, two molecules Ph-TPE-MMN and NA-TPE-MMN showed aggregation-induced emission (AIE) properties in the THF/water mixture at higher fw (water fraction). Ph-TPE-MMN and NA-TPE-MMN also exhibited fluorescence response to external force. The emitting color of both had changed greatly before and after grinding. The maximum emission wavelengths of Ph-TPE-MMN and NA-TPE-MMN were redshifted by 46 nm and 33 nm, respectively, implying high-contrast mechanofluorochromism. Notably, mechanofluorochromic process also showed a good reversible. XRD experiments indicated that mechanofluorochromic mechanism originated from changes in molecular stacking in solid state.