Aggregation-induced Emission Enhancement Research Articles

Halogen-modulated mechanical force-induced luminescence enhancement and chromism of AIE-active tetraphenylethylene-based chalcone derivatives

In this paper, four new tetraphenylethylene-based chalcone derivatives (E)-1-phenyl-3-(4-(1,2,2-triphenylvinyl)phenyl)prop-2-en-1-one (PLPE), (E)-1-(4-fluorophenyl)-3-(4-(1,2,2-triphenylvinyl)phenyl)prop-2-en-1-one (PLPE-F),(E)-1-(4-chlorophenyl)-3-(4-(1,2,2-triphenylvinyl)phenyl)prop-2-en-1-one (PLPE-Cl), (E)-1-(4-bromophenyl)-3-(4-(1,2,2-triphenylvinyl)phenyl)prop-2-en-1-one (PLPE-Br) with different halogen substitutions were reported, and the effects of halogens on their photophysical properties, aggregation-induced emission behaviors and mechano-responsive luminescent properties were systematically investigated. Interestingly, aggregation-induced emission enhancement (AIEE) behaviors were observed for PLPE, PLPE-F, PLPE-Cl, and PLPE-Br. Moreover, upon grinding, all of the four compounds displayed mechanical force-induced luminescence enhancement and red-shifted behaviors, which was found to be reversible in the case of fuming with dichloromethane (DCM) vapors or heat treatment. In particular, upon grinding, PLPE-F showed the highest contrast fluorescence response behaviors (red-shifted 49 nm and solid fluorescence quantum yield increased 20-fold). Furthermore, the results of powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and field emission scanning electron microscopy (FESEM) measurements indicated that reversible phase transitions between the ordered crystalline state and the disordered amorphous form was crucial to their interesting mechanical force-induced luminescence enhancement and chromism. And the obvious red shifts of fluorescence emission are ascribed to the increased molecular conjugations via the planarization of molecular conformations. Moreover, halogen-substituted PLPE-F, PLPE-Cl, PLPE-Br have more twisted conformations than PLPE, which are responsible for their higher contrast mechanical force-induced luminescence chromism. Hence, the present study provides a new strategy to construct new advanced high-contrast mechanical force-induced luminescence enhancement and chromism luminescent materials with the introduction of halogen atoms.

Chromo-Fluorogenic Rhodamine-Based Amphiphilic Probe as a Selective and Sensitive Sensor for Intracellular Cu(I) in Living Cells.

Fluorescent probes are widely studied for metal ion detection because of their multiple favorable properties such as high sensitivity and selectivity, quick response, naked eye detection, and in situ monitoring. However, optical probes that can effectively detect the Cu(I) level in cell interiors are rare due to the difficulty associated with selectively and sensitively detecting this metal ion in a cell environment. Therefore, we designed and synthesized three water-soluble probes (1-3) with a 1,3,5-triazine core decorated by three substituents: a hydrophobic alkyl chain, a hydrophilic maltose, and a rhodamine B hydrazine fluorophore. Among the probes, probe 1, which has an octyl chain and a branched maltose group, was the most effective at sensing Cu+ in aqueous solution. Upon addition of Cu+, this probe showed a dramatic color change from colorless to pink in daylight and displayed an intense yellow fluorescence emission under 365 nm light. The limit of detection and dissociation constant (Kd) of this probe were 20 nM and 1.1 × 10-12 M, respectively, which are the lowest values reported to date. The two metal ion-binding sites and the aggregation-induced emission enhancement effect, endowed by the branched maltose group and the octyl chain, respectively, are responsible for the high sensitivity and selectivity of this probe for Cu+ detection, as demonstrated by 1H NMR, dynamic light scattering, and transmission electron microscopy studies. Furthermore, the probe successfully differentiated the Cu(I) level of cancer cells from that of the normal cells. Thus, the probe holds potential for real-time monitoring of Cu(I) level in biological samples and bioimaging of cancer cells.

Investigating structural dynamics and sensing capabilities: Spectroscopic and DFT analysis of novel AIEE active deferasirox based organic sensor

A deferasirox based sensor DPA was rationally designed through single step amidation reaction. Sensor DPA exhibited aggregation induced emission enhancement (AIEE) property that was attributed to restriction in intramolecular rotation (RIR). Moreover, the sensor DPA displayed remarkable bathochromic shift (red-shift) of 110 nm in wavelength, ascribed to formation of J-aggregates. Furthermore, sensor DPA was employed for the selective and sensitive fluorescence based sensing of hazardous and carcinogenic nitrobenzene (NB). The sensor DPA successfully detected NB in solution through the quenching of emission intensity. The quenching of sensor fluorescence intensity was ascribed to photoinduced electron transfer (PET) mechanism. The sensing mechanism was investigated by 1H NMR titration experiment, Job's plot and density functional theory (DFT) calculations. Additionally, the existence of non-covalent interactions between sensor DPA and NB were examined by Bader's Quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analysis. Finally, sensor DPA was employed for the detection of volatile nitrobenzene in vapor phase.

Multi-stimuli fluorescence responsiveness of α-cyanostilbene derivative: AIEE, stimuli response to polarity, acid, force and light, applications in anti-counterfeiting and single phosphor w-OLED

Recently, the small molecule functional materials with a simple synthesis have attracted more and more attention. A multi-stimuli-responsive aggregation-induced emission (AIE) molecule is expected to have great applications in the near future. Identically, the single-component white organic light diode (w-OLED) has a good application field. Herein, a cyanostilbene derivative (TSC) was efficiently synthesized by Vilsmeier and Knoevenagel reactions with only 2 steps under mild conditions. TSC was characterized by NMR (1H, 13C), FT-IR, HRMS and elemental analysis. TSC has aggregation-induced enhanced emission (AIEE) effect, and significant polar-, acid-, force- and light-stimuli fluorescence responsiveness properties. The AIE effect and four different stimulus responses are all simultaneously presented in TSC. This phenomenon is relatively rare in small molecule fluorescent compounds. The results of SEM and DLS reveal the AIEE of TSC is mainly due to the fact that molecular self-assembly into nanofiber networks in the aggregated state limiting the distortion of molecules. DFT calculations show that the polarity stimuli-response (fluorescence from green to orange) is closely related to intramolecular charge transfer (ICT). Acid/base 1H NMR titration proves that the acidochromism results from reversible protonation/deprotonation. The results of DSC, SEM, PXRD and POM prove that the essence of mechanical force stimuli-response is the change of crystallinity. The results of 1H NMR, UV–vis and fluorescence spectra, DFT calculations and SEM reveal that the light stimuli-response is attributed to the Z/E configuration transformation. Based on multi-stimuli responsive properties, TSC can be used for recognition of solvents polarity by naked eyes or fluorophotometer, used as an acid indicator and also used to quantitatively test the concentration of trace acids, used in anti-counterfeiting including safty ink, data rewriting, even can be used to construct supramolecular liquid crystals materials. In addition, TSC can be used to fabricate single phosphor w-OLED, avoiding using multicomponent composite materials.

UiO-66-NH2 initiated cascade reaction: Constructing a ratiometric fluorescence sensor for ultrasensitive detection of nerve agent simulant

BackgroundHighly toxic organophosphorus nerve agents often exist in the form of gas in the environment and can damage human neuroregulatory system by inhibiting the activity of acetylcholinesterase (AChE). However, fluorescent probes based on small organic molecules bring a secondary burden to environment, and their sensitivity and specificity for sarin simulant diethyl chlorophosphate (DCP) detection are unsatisfactory. Nanozyme cascade systems with signal amplification can be used for highly sensitive identification of analytes, but are rarely used in ratiometric analysis of DCP. Combination of enzyme cascades and ratiometric fluorescence ensures the accuracy and sensitivity of the output signal. ResultsWe prepared a self-assembled nanohybrid (Ag–AuNCs@UiO-66-NH2) by metal-organic framework material and gold nanoclusters. On the one hand, UiO-66-NH2 with enzyme-like activity was used to hydrolyze DCP into diethyl phosphate (DEP) and chloridion (Cl−). Cl− hindered aggregation-induced enhanced emission (AIEE) of AuNCs by binding with Ag+ and decreased the fluorescence of AuNCs. On the other hand, ligand metal charge transfer effect (LMCT) of UiO-66-NH2 was blocked by DCP to enhance the fluorescence of UiO-66-NH2. Combining ratiometric analysis and nanozyme cascade reaction, an ultra-sensitive fluorescence sensor for detecting DCP was constructed, and ensured the accuracy of experimental results. In addition, Ag–AuNCs@UiO-66-NH2 was embedded into the agarose hydrogel substrate, the resulting agarose hydrogel film allowed quantitative assessment of DCP vapor and high sensitivity was demonstrated (detection limit as low as 1.02 ppb). SignificanceA strategy combining enzyme cascade with ratiometric fluorescence was proposed, which improved the accuracy and sensitivity of the analysis results. The soft-solid platform based on agarose hydrogel film was constructed to realize the quantitative monitoring of sarin simulant gas. The LOD value obtained in this work is much lower than the immediately life-threatening or health threatening concentration of sarin.

Fluorimetric determination of tetracycline antibiotics in animal derived foods using boron and nitrogen co-doped ceria-based nanoparticles.

Aninnovative synthesis of boron and nitrogen co-doped ceria-based nanoparticles (B/N-CeFNPs) with bright blue fluorescence emission is reportedusing the hydrothermal method. Based on the aggregation-induced emission enhancement (AIEE) effect between B/N-CeFNPs and chlortetracycline (CTC), a rapid detection method for CTC through fluorescence enhancement was developed. In addition, through the electron transfer process (ET), fluorescence resonance energy transfer (FRET) effect and static quenching between B/N-CeFNPs and oxytetracycline (OTC), a ratio fluorescence strategy for detecting OTC was generated. The fluorescence of B/N-CeFNPs at 410nm can be effectively quenched by OTC, and new fluorescence emission appears at a wavelength of 500nm. B/N-CeFNPs showed good linear responses with CTC and OTC in the range 0.1-1 µM and 1-40 µM, respectively. This system was used to simultaneously detect the CTC and OTC in milk and honey, realizing multi-residues detection of TCs in actual samples by using the same ceria-based fluorescence nanomaterial.

Fluorescent Carbon Dots: Aggregation-Induced Emission Enhancement, Application as Probe for CN- and Cr2O7-2, Sensing Strips and Bio-imaging Agent.

Fluorescent carbon dots (Trp-CDs) were prepared using tryptophan as precursor and were characterized on the basis of elemental analysis, powder-XRD, IR, Raman spectroscopy, 13C-NMR, UV-Vis, fluorescence and TEM. Trp-CDs exhibit poor fluorescence in 100% water but showed strong Aggregation Induced Emission (AIE) in ethanol and higher alcohols. The anion sensing study of Trp-CD revealed that it selectively detects CN- and Cr2O7-2 and from fluorescence quenching titration study, quenching constant, LOD and range of detection were evaluated. The emission life-time of Trp-CD before and after addition of CN- and Cr2O7-2 were measured, the decay curve before addition of anion was best fitted with a bi-exponential function with life-time of τ1 2.79ns (10.74%) and τ2 18.93ns (89.26%). The mechanistic study revealed that for CN-, the fluorescence quenching is due to its interaction with protons attached to surface functional groups and for Cr2O7-2, it is due to inner filter effect (IFE). Sensing strips were prepared by coating Trp-CDs onto various solid surfaces including agarose films and were used for detection of CN- and Cr2O7-. Trp-CD was found to be nontoxic and biocompatible and used as staining agent for Artemia and Bacteria (Bacillus Subtilis, Pseudomonas) and detection of CN- and Cr2O7-.

High-Efficiency Circularly Polarized Light-Emitting Diodes Based on Chiral Metal Nanoclusters.

Circularly polarized light-emitting diodes (CP-LEDs) are critical for next-generation optical technologies, ranging from holography to quantum information processing. Currently deployed chiral luminescent materials, with their intricate synthesis and processing and limited efficiency, are the main bottleneck for CP-LEDs. Chiral metal nanoclusters (MNCs) are potential CP-LED materials, given their ease of synthesis and processability as well as diverse structures and excited states. However, their films are usually plagued by inferior electronic quality and aggregation-caused photoluminescence quenching, necessitating their incorporation into host materials; without such a scheme, MNC-based LEDs exhibit external quantum efficiencies (EQEs) < 10%. Herein, we achieve an efficiency leap for both CP-LEDs and cluster-based LEDs by using novel chiral MNCs with aggregation-induced emission enhancement. CP-LEDs using enantiopure MNC films attain EQEs of up to 23.5%. Furthermore, by incorporating host materials, the devices yield record EQEs of up to 36.5% for both CP-LEDs and cluster-based LEDs, along with electroluminescence dissymmetry factors (|gEL|) of around 1.0 × 10-3. These findings open a new avenue for advancing chiral light sources for next-generation optoelectronics.

A Rational Design of Electrochemically and Photophysically Tunable Triarylamine Luminophores by Consecutive (Pseudo-)Four-Component Syntheses.

The concatenation of Suzuki coupling and two-fold Buchwald-Hartwig amination in sequentially palladium-catalyzed consecutive multicomponent syntheses paves a concise, convergent route to diversely functionalized para-biaryl-substituted triarylamines (p-bTAAs) from simple, readily available starting materials. An extensive library of p-bTAAs permits comprehensive investigations of their electronic properties by absorption and emission spectroscopy, cyclic voltammetry, and quantum chemical calculations, which contribute to a deep understanding of their electronic structure. The synthesized p-bTAAs exhibit tunable fluorescence from blue to yellow upon photonic excitation with quantum yields up to 98 % in solution and 92 % in the solid state. Furthermore, a pronounced bathochromic shift of the emission maxima by increasing solvent polarity indicates positive emission solvatochromism. Aggregation-induced enhanced emission (AIEE) in dimethyl sulfoxide (DMSO)/water mixtures causes the formation of intensely blue fluorescent aggregates. Cyclic voltammetry shows reversible first and second oxidations of p-bTAAs at low potentials, which are tunable by variation of the introduced para substituents. 3D Hammett plots resulting from the correlation of oxidation potentials and emission maxima with electronic substituent parameters emphasize the rational design of tailored p-bTAAs with predictable electrochemical and photophysical properties.

A simple vitamin B6-based fluorescent chemosensor for selective and sensitive Al3+ recognition in water: A spectral and DFT study

This paper describes the development and characterization of a hydrazone-type chemosensor for the detection of Al3+ ions. Hydrazone is based on pyridoxal 5′-phosphate and pyrazine-2-carbohydrazide and exhibits a blue emissive turn-on response upon binding to Al3+. The aggregation-induced emission enhancement phenomenon of the sensor and its Al3+ complex was investigated in mixed DMSO/H2O solvents. The sensor is capable of detecting extremely low levels of Al3+ ions (8 nM) in almost pure water, making it suitable for analyzing water with good ion recovery. Quantum chemical calculations were used to optimize the structure and electron absorption spectra of the sensor and its Al complex. The chemosensor has low toxicity levels (up to 50 μM) on tumor and non-tumor cell lines, which makes it a potential candidate for bioimaging use. This study provides valuable insights into the development of fluorescence sensors for precise recognition of metal ions.

Effect of Polymer Host on Aggregation-Induced Enhanced Emission of Fluorescent Optical Brighteners.

Fluorophores displaying concentration-dependent luminescence are becoming increasingly valuable in stress-sensing, tagging, and dyeing applications, including the quantification of recycled content in plastic packaging. In this work, we investigate the effects of the polymer matrix, dye structure, and crystallinity on aggregation-induced enhanced emission (AIEE). We demonstrate that the aggregation threshold required for successful quantification can be adjusted through modulation of guest-host (dye-polymer) interactions and monitored using an array of fluorescence characterization. Modification of guest-host interactions is realized through choice of host, change of guest, and tuning of the crystallinity of the host system. Increasing the number of guest-host interactions and solubility between guest and host, loosely predicted through the calculation of the solubility parameter, increases the aggregation threshold relative to other low-polarity and low-interacting systems. We demonstrate that issues, such as loading level and cost, associated with high aggregation thresholds, can be circumvented by increasing system crystallinity, improving spectral intensities, and subsequent quantification. These insights explore the fundamental understanding of supramolecular interactions that govern dye-polymer systems.

Tetraphenylethylene fused pyrrolo[3,2-b]pyrrole derivatives with reversible mechanofluorochromic and aggregation-induced emission enhancement characteristics

Modification on typical of molecular unit with aggregation-induced emission (AIE)/aggregation-induced emission enhancement (AIEE) can play a important role in obtaining solid-state fluorescence materials and mechanofluorochromic (MFC) materials. We utilize the multicomponent reaction of TPE-containing aldehyde, arylamine and butane-2,3-dione in the presence of iron(III) perchlorate to design and synthesize two novel MFC materials by combination of the tetraphenylethylene (TPE) and pyrrolo [3,2-b]pyrrole core units. Investigation of CHW-1 and CHW-2 aggregation-induced emission behaviors indicated that these materials all exhibited AIEE properties. Subsequent mechanochromic luminescence tests exhibited reversible mechanochromism natures that involve fluorescent color change from green to yellow (Grinding-induced spectral shift (△λ): 35 nm and 38 nm, respectively). Then the datas (including SEM, PXRD and DSC) revealed that this mechanofluorochromism was ascribed to the transformation of crystal state to the amorphous form. Moreover, CHW-1 and CHW-2 could be applied for optical recording devices and security printing.

Substituent Position Dependent Photophysical Properties of Indole – Barbituric and Thiobarbituric Acid based Molecular Rotors

AbstractA series of 2‐ and 3‐methylindole (MI)‐based barbituric acid (BA) and thiobarbituric acid (TBA) derivatives (2MIBA, 2MITBA, 3MIBA and 3MITBA) in Donor (D)‐π‐Acceptor (A) configuration having strong intramolecular charge transfer (ICT) interactions were synthesized by the simple and efficient route. Methyl substituent at the 2‐ and 3‐ position alters the coplanarity of the DA systems leaving 2MI derivatives as nonplanar whilst 3MI derivatives as planar one and the latter forms an intramolecular hydrogen bond between indole N−H and −C=O of BA or TBA, which facilitates the excited state intramolecular proton transfer (ESIPT) emission in 3MIBA and 3MITBA. Comparing the UV‐visible absorption spectra in the solution phase reveals that the ICT band of 2MITBA and 3MITBA are red‐shifted from the 2MIBA and 3MIBA due to the stronger electron‐accepting nature of C=S than the C=O. Since these molecules exert photo‐induced intramolecular charge transfer followed by a rotation around the bridging methylene group, only weak fluorescence is noted. Nevertheless, in an aggregated state, both 3MIBA and 3MITBA exhibit significant aggregation‐induced enhanced emission (AIEE) characteristics in their THF/water mixture, but the effect is not promising for 2MIBA and 2MITBA. Further, melamine‐3MITBA co‐assembly aided through an intermolecular hydrogen bonding network can also be used as a solid‐state emitter.

Preparation of silicon quantum dots@star like bloc-copolymer (SiQD@S-BP) colloidal nanoclusters through in-situ reduction and confined growth

Here in this work, colloidal nanocrystal clusters (CNCs) formed by silicon quantum dots and star-like block-copolymers (SiQDs@S-BP) were prepared through in-situ reduction and confined growth method. Water-soluble star-like block copolymer β-CD-g-PAA-b-POEGA (unimolecular micelle) was precisely synthesized through ATRP and used as the templates for SiQDs@S-BP. Owing to the electrostatic interaction, the amino groups functionalized silicon can be adsorbed to the carboxyl groups in the polymer chains. After in-situ reduction and confined growth, silicon quantum dots were formed and monodispersed in the unimolecular micelles. Benefitting from the CNCs structure, the fluorescence emission of the SiQDs enhanced due to the aggregation induced emission enhancement (AIEE) effect. The inner structure and outer polymer brushes of the CNCs avoided the coalescence of SiQDs during application and collection, and made it more efficient in recycling and reusing.

AIEE active novel chalcone based fluorescent probe for sensitive detection of drotaverine in solid state and real samples through fluorescence enhancement

A novel chalcone based probe OBP with exquisite aggregation induced emission enhancement (AIEE) has been rationally synthesized through simple two-step process. Owing to remarkable emission characteristics, probe OBP has been employed for selective and sensitive detection of drotaverine (DV) in solution and solid state. Significant fluorometric and colorimetric enhancement in fluorescence emission was displayed by probe OBP at λmax 455 nm after exposure to DV. Photo induced electron transfer (PET) process is responsible for detection of DV through OBP down to nanomolar level. OBP-DV interaction was elucidated through fluorescence and UV–Vis. spectroscopy along with 1H NMR titration experiments. Moreover, density functional theory (DFT) calculations were performed to analyze thermodynamic stability, density of states (DOS), frontier molecular orbitals (FMO), non-covalent interactions (NCI), quantum theory of atom in molecule (QTAIM), electron density difference (EDD) and natural bond orbital (NBO). Additionally, OBP was investigated for DV detection in blood samples as well as in solid state.

An Ultra-low Detection Limit Fe3+ Optical Fiber Fluorescent Sensor Based on a Anti-B18H22 Derivative withAggregation-inducedEmission Enhancement.

A fluorescent Fe3+ probe ((C10H7NO2)2B18H20, M1) by introducing two isoquinoline-1-carboxylic acid group into the 6,9-position of anti-B18H22 was designed and synthesized. The structure of M1 was investigated by 1H NMR, MS, FT-IR and theoretical calculation, and its optical properties were characterized with UV-Vis and PL. M1 showed aggregation induced emission enhancement (AIEE) properties in THF/H2O solution, and exhibited an excellent selectivity toward Fe3+ in THF/H2O (v/v, ƒw = 95%) solution with a detection limit of 1.93 × 10-5M. The interaction mechanism of probe for detecting Fe3+ is attributed to the involvement of intramolecular charge transfer (ICT) process. Furthermore, a optical fiber fluorescent Fe3+ sensor based on M1 sensing film was developed, the detection limit of the optical fiber Fe3+ fluorescent sensor could be improved to13.8pM, the ultra-low detection limit is superior to most reported fluorescent probes (or sensors) towards Fe3+. This method has the advantages of high sensitivity, anti-interference and easy to operate, and has great potential in the field of the analysis of environmental and biological samples.

Functional-group-regulated stimuli-responsive banana-shaped α-cyanostilbene derivatives: Dual-state emission, AIEE, acidochromism and their applications in anti-counterfeiting, fingerprint recognition and OLEDs

The research of structure-property relationships is of great significance for exploring the luminescent mechanism, the design of functional materials with desired photoelectric properties and facilitating practical applications. In this paper, a series of cyanostilbene derivatives (TS-R) with different functional groups were synthesized by one step under mild conditions and characterized. Their photoelectric properties and structure-property relationships have been researched. The results indicate that TS-R have solution and solid dual-state emission (DSE) property, aggregation-induced emission enhancement (AIEE) effect, solvatochromism behavior and stimuli-responsive fluorescence characteristic for acid. The photoelectric properties can be changed by introducing different functional groups at the molecular same position of TS-R. The applications of TS-R were also investigated. The results indicate that TS-R can be used in fluorescent anti-counterfeiting, fingerprint recognition and light emitting diode (LED).

Enhancing Fluorescence in Both Solution and Solid States Induced by Imine Cage Formation.

Developing luminescent materials that exhibit strong emissions in both solution and solid phases is highly desirable and challenging. Herein, we report imine-bond directed formation of a rigid organic cage (TPE-cage) that was synthesized by [2+4] imine condensation of a TPE-cored tetra-aldehyde (TPE-TA) with a clip-like diamine (XA) to illustrate confinement-induced fluorescence enhancement. Compared to the non-emissive TPE-TA (ϕF =0.26 %) in the dichloromethane (DCM) solution, the TPE-cage achieved a remarkable (~520-fold) emission enhancement (ϕF =70.38 %). In contrast, a monomeric tetra-imine model compound (TPE-model) showed only a minor enhancement (ϕF =0.56 %) in emission compared to the parent tetra-aldehyde TPE-TA. The emission of TPE-cage was further enhanced by ~1.5-fold (ϕF =80.96 %) in the aggregated state owing to aggregation-induced emission enhancement (AIEE). This approach establishes the potential for synthesizing luminescent materials with high emission in both solution and solid-state by employing a single-step imine condensation reaction.

A ratiometric fluorescence nanosensor for glutathione detection based on spatially confined dual-emission of α-lipoic acid-modified gold nanoclusters and silicon nanoparticles.

The development of dual-emission ratiometric fluorescent probes with aggregation-induced emission enhancement (AIEE) overcomes the limitations of gold nanocluster (Au NC)-based probes, particularly their weak intrinsic fluorescence, in real-world applications. These AIEE probes also exhibit superior detection limits and enhanced sensitivity. A novel combination for the reliable fluorometric detection of glutathione (GSH) was proposed, utilizing aggregation-induced emission enhancement (AIEE) facilitated by electrostatic interaction and spatial confinement. The probe consists of a ratiometric combination of negatively charged α-lipoic acid-modified Au NCs (LA@Au NCs) and positively charged silicon nanoparticles (SiNPs). The addition of SiNPs causes aggregation of LA@Au NCs, enhancing the fluorescence of LA@Au NCs through the AIE effect under electrostatic interaction and spatial confinement. The addition of Cu2+ quenched the emission of LA@Au NCs as a result of charge transfer. The fluorescence emissions of LA@Au NCs were restored upon the addition of GSH due to the interaction between GSH and Cu2+. Simultaneously, the emission signal of SiNPs remains unchanged, serving as an internal reference signal during GSH measurement. It was found that the fluorescence ratio (F680/F465) is directly proportional to the concentration of GSH in the range of 0.05-100 μM, with a detection limit of 1.7 nM (S/N = 3). The proposed system was applied to detect GSH in real samples, including dietary supplements, human serum, and saliva samples. This work opens new avenues for constructing novel sensors based on AIEE for detecting biomolecules.

Dual aggregation-induced emission enhancement (AIEE) and crosslink-enhanced emission (CEE) driven via halogen-bond-assisted cocrystallization and radical solid-phase polymerization

Concurrent emission enhancement was attained by halogen-bond-driven cocrystallization (aggregation-induced emission enhancement, AIEE), followed by halogen-bond-driven (non)covalent crosslinking of polymer (crosslink-enhanced emission, CEE).