Aggregation-induced Fluorescence Research Articles

An Aggregation-Induced Fluorescence Probe for Detection H2S and Its Application in Cell Imaging.

Monitoring hydrogen sulfide (H2S) in living organisms is very important because H2S acts as a regulator in many physiological and pathological processes. Upregulation of endogenous H2S concentration has been shown to be closely related to the occurrence and development of tumors, atherosclerosis, neurodegenerative diseases and diabetes. Herin, a novel fluorescent probe HND with aggregation-induced emission was designed. Impressively, HND exhibited a high selectivity, fast response (1 min) and low detection limit (0.61 μM) for H2S in PBS buffer (10 mM, pH = 7.42). Moreover, the reaction mechanism between HND and H2S was conducted by Job's plot, HR-MS, and DFT. In particular, HND was successfully employed to detect H2S in HeLa cells.

Interfacial compatible PolyMOF membranes as ratiometric fluorescence temperature sensors

Cryogenic temperature sensors play significant roles in manufacturing, metallurgy, and aerospace. Metal-organic frameworks (MOFs) as emerging crystal materials exhibited inherent advantages as fluorescence temperature sensors and researchers have shifted their focus toward incorporating MOFs materials into mixed matrix membranes (MMMs) for broader practical applications. However, the poor interfacial compatibility between MOFs particles and the polymer matrix would cause aggregation-induced fluorescence quenching and reduced energy transfer efficiency, thereby compromising temperature sensing performances. Herein, we adopt a post-synthetic copolymerization strategy to realize an interfacial-compatible membranous ratiometric luminescent thermometer based on the emissions of ligands and lanthanide ions. Benefiting from the controllable covalent cross-linking structures, the designed polyMOF membrane exhibited excellent interfacial compatibility and avoided MOFs irregular morphology agglomeration and phase separation, which contributed to outstanding fluorescence temperature sensing performance with excellent sensitivity ranging from 0.300 to 0.745 %·K−1 within the temperature range of 80–300 K, superior to recent reported MOFs-based thermometers. This research presents a promising approach for the design and fabrication of interfacial compatible MOFs-based membranes with excellent fluorescence temperature sensing properties, advancing the understanding of structure-property relationships and accelerating the practical applications.

Paper-based fluorescence sensor array with functionalized carbon quantum dots for bacterial discrimination using a machine learning algorithm

The rapid discrimination of bacteria is currently an emerging trend in the fields of food safety, medical detection, and environmental observation. Traditional methods often require lengthy culturing processes, specialized analytical equipment, and bacterial recognition receptors. In response to this need, we have developed a paper-based fluorescence sensor array platform for identifying different bacteria. The sensor array is based on three unique carbon quantum dots (CQDs) as sensing units, each modified with a different antibiotic (polymyxin B, ampicillin, and gentamicin). These antibiotic-modified CQDs can aggregate on the bacterial surface, triggering aggregation-induced fluorescence quenching. The sensor array exhibits varying fluorescent responses to different bacterial species. To achieve low-cost and portable detection, CQDs were formulated into fluorescent ink and used with an inkjet printer to manufacture paper-based sensor arrays. A smartphone was used to collect the responses generated by the bacteria and platform. Diverse machine learning algorithms were utilized to discriminate bacterial types. Our findings showcase the platform's remarkable capability to differentiate among five bacterial strains, within a detection range spanning from 1.0 × 103 CFU/mL to 1.0 × 107 CFU/mL. Its practicality is further validated through the accurate identification of blind bacterial samples. With its cost-effectiveness, ease of fabrication, and high degree of integration, this platform holds significant promise for on-site detection of diverse bacteria.Graphical abstract

In situ coupling of carbon dots with zeolitic imidazolate frameworks enabling highly red emission in solid state

In this work, an extraordinary solid red emissive phosphor was prepared based on red-emitting carbon dots (R-CDs). The synthesis was conducted under an in-situ strategy, with assistance of zeolitic imidazolate frameworks. The obtained phosphor possesses a stronger red emission located at 630 nm in solid state, with CIE coordinate of (0.63, 0.35) and quantum yield of ∼ 45 %. As a consequence, not only aggregation-induced fluorescence quenching of R-CDs is avoided in solid state, but also an enhanced emission with high quantum yield is presented. Fluorescence properties were further explored in detail. The emission is found to be responsive to temperature and applied pressure. Based on the excellent emissive performance, the material has great potentials in anti-counterfeiting, latent fingerprint imaging, and temperature/pressure-sensing. This work provides a facile and promising way of preparing solid carbon-based phosphors for special applications.

Aggregation-Induced Fluorescence Upconversion of Pyrene under Low Fluence: In Solutions and Polymeric Nanoparticles.

In this study, aggregation-induced photon upconversion (iPUC) is demonstrated in the small polyaromatic molecule, pyrene. In binary-solvent mixtures, water, which induces the aggregation of polyaromatic molecules, assisted in triplet-triplet annihilation-based upconversion. No upconverted emission was observed in a dry solvent. Although upconverted emission in the absence of a triplet sensitizer was assigned to pyrene-aggregate-induced sensitization, the presence of a triplet sensitizer enhanced the upconversion efficiency. This experimental finding was further simulated to explore the possibility of iPUC in the condensed-phase polymer matrix. We studied 2-aminoethyl methacrylate hydrochloride-polystyrene copolymer nanoparticles embedded with the molecular upconversion system. The nanoparticle iPUC agreed with the proposition that water domains were present in polymer nanoparticles and helped aggregate pyrene in the host polymer. Despite the low systemic upconversion efficiency, this study provides a method for achieving fluorescence upconversion in relatively simple systems.

Machine learning-assisted visual sensor array for identifying the origin of Lilium bulbs

In this work, we constructed a machine learning-assisted dual-channel visual sensor array for identifying the origin of Lilium bulbs (BH). Nanogold clusters (AuNCs) and quantum dots (QDs) were selected and combined into sensor arrays. The amino acids existed in lilium bulbs could induce aggregation-induced fluorescence enhancement effect (AIEE) of AuNCs through hydrogen bonding. The hydrogen protons released from the amino acids and phenolic acids could interact with the COO- group of QDs, resulting in aggregation-caused quenching (ACQ) of QDs. Due to the different contents of amino acids and phenolic acids in BH from different origins, the sensor array can produce distinct and different fluorescent colors, such as red, blue, green and purple. In conjunction with pattern recognition by the RF model, the sensor array clearly identifies the origin of BH with 94.4% prediction accuracy. The visual sensor array constructed in this work exhibited the advantages of simplicity, speed, accuracy and portability, showing potential application prospects in identifying the origin of food and traditional Chinese medicine.

High-loading of organosilane-grafted carbon dots in high-performance luminescent solar concentrators with ultrahigh transparency

Carbon dots (CDs) generally suffer from aggregation-induced fluorescence quenching effect in solid-state, which significantly limits their application in photoelectric devices. Due to this effect, it is a great challenge to achieve high-transparency and high-performance luminescent solar concentrators (LSCs) based on CDs. Here, the synthesis of organosilane-grafted carbon dots (Si-CDs) is rationally designed by hydrothermal method using anhydrous citric acid, ethanolamine and KH-792 as the reaction precursors. The obtained Si-CDs can be uniformly dispersed in the polyvinyl alcohol (PVA) matrix through the dehydration condensation reaction and hydrogen bonding between the silicon hydroxyl group of Si-CDs and the hydroxyl group of PVA. Based on this property, Si-CDs/PVA thin-film LSCs (5 ×5 ×0.2 cm3) with ultrahigh CD loading (25 wt%) and high transparency can be fabricated, exhibiting excellent absorption in the UV spectral region and about 90 % transmission in the visible range. Furthermore, the power conversion efficiency (PCE) of the LSCs can reach 2.09 % under a standard solar light and shows excellent stability even over 12 weeks. This synthetic design is expected to be beneficial for future development of CD synthesis and paves the way for the development of CDs-based photoelectric devices.

A Smart Responsive Fluorescence-MR Nanoprobe for Monitoring Tumor Response to Immunotherapy.

Accurately evaluating tumor responses to immunotherapyis clinically relevant. However, non-invasive, real-time visualization techniques to evaluate tumor immunotherapy are still lacking. Herein, a smart responsive fluorescence-MR dual-modal nanoprobe, QM(GP)-MZF(CP), is reported that can be targeted for cleavage by the cytotoxic T cell activation marker granzyme B and the apoptosis-related marker cysteine-aspartic acid-specific protease 3 (Caspase-3). The probe uses quinoline-malononitrile (QM), an aggregation-induced emission luminogen, and Mn-Zn ferrite magnetic nanoparticles (MZF-MNPs), a T2-weighted imaging (T2WI) contrast agent, as imaging molecules that are linked with the substrate peptides specific to granzyme B and Caspase-3. Therefore, both granzyme B and Caspase-3 can target and cleave the substrate peptides in QM(GP)-MZF(CP). Via aggregation-induced fluorescence imaging of QM and the aggregation-induced T2WI-enhanced imaging effect of MZF-MNPs, the status of T cells after tumor immunotherapy and the subsequent triggering of tumor cell apoptosis can be determined to identify tumor responsiveness to immunotherapy and thereby evaluate the effectiveness of this therapy in the early stages of treatment.

Identification of multi-component metal ion mixtures in complex systems using fluorescence sensor arrays

The growing co-contamination of multiple metal ions seriously influences human health due to their synergistic and additive toxicological effects, whereas the rapid discrimination of multiple heavy metal ions in complex aquatic systems remains a major challenge. Herein, a high- throughput fluorescence sensor array was fabricated based on three gold nanoclusters (GSH-Au NCs, OVA-Au NCs, and BSA-Au NCs) for the direct identification and quantification of seven heavy metal ions (Pb2+, Fe3+, Cu2+, Co2+, Ag+, Hg2+ and As3+) from environmental waters without sample pretreatment other than filtration. At the detection system, three gold nanoclusters with various ligands possessed distinct binding capacities against metal ions and induced aggregation-induced fluorescence enhancement and quenching, resulting in a unique pattern of fluorescence variations. Meanwhile, integrated the collected fluorescence fingerprints with linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA), a discrete database was obtained for the accurate recognition and sensitive detection of metal ions. Under the optimized conditions, the limit of detection (LOD) of the proposed fluorescence sensor array for metal ions detection at nM concentration level along with a satisfactory accuracy. Importantly, our study indicated that the fluorescence sensor array could be widely used as a general platform in environmental monitoring against multiple targets at low concentrations.

A novel portable smart phone sensing platform based on a supramolecular fluorescence probe for quick visual quantitative detection of picric acid.

Picric acid (PA) is a lethal explosive substance that is easily soluble in water and harmful to the environment. Here, a supramolecular polymer material BTPY@Q[8] with aggregation induced emission (AIE) was prepared by supramolecular self-assembly of cucurbit uril (Q[8]) and 1,3,5-tris[4-(pyridin-4-yl) phenyl] benzene derivative (BTPY), which exhibited aggregation-induced fluorescence enhancement. To this supramolecular self-assembly, the addition of a number of nitrophenols was found to have no obvious effect on the fluorescence, however on addition of PA, the fluorescence intensity underwent a dramatic quench. For PA, BTPY@Q[8] had sensitive specificity and effective selectivity. Based on this, a quick and simple on-site visual PA fluorescence quantitative detection platform was developed using smart phones, and the platform was used to monitor temperature. Machine learning (ML) is a popular pattern recognition technology, which can accurately predict the results from data. Therefore, ML has much more potential for analyzing and improving sensing data than the widely used statistical pattern recognition method. In the field of analytical science, the sensing platform offers a reliable method for the quantitative detection of PA that can be applied to other analytes or micropollutant screening.

Multi-Stimuli-Responsive Amphiphilic Pyridinium Salt and Its Application in the Visualization of Level 3 Details in Latent Fingerprints.

Organic luminescent materials that can simultaneously achieve multimode mechanochromism and its water-vapor-induced recovery are desirable for practical applications but rarely reported. Herein, an amphiphilic compound, 4-(9H-carbazol-9-yl)-1-(2-hydroxyethyl)pyridin-1-ium bromide (CPAB), was designed by integrating a lipophilic aromatic unit and hydrophilic end in the molecular architecture. Self-recovered mechanochromism from brown to cyan was observed upon mechanical grinding in air. Comprehensive research by X-ray diffraction, infrared spectroscopy, and single-crystal analysis revealed that the photoluminescence switch originated from the variation in intermolecular hydrogen bonds and molecular packing mode. The amphiphilic nature of CPAB allowed water molecules to enter the crystalline lattice, forming two polymorphs of the crystalline phase, namely CPAB-D and CPAB-W. The hydrosoluble CPAB exhibited excellent capability in probing the level 3 details of fingerprints because its lipophilic part could target the fatty acid residues of fingerprints, leading to strong aggregation-induced fluorescence. The research may inspire the design of latent fingerprint developers and application in forensics/anti-counterfeiting. This article is protected by copyright. All rights reserved.

Subcomponent self-assembled metal-organic nanocages with tunable aggregation-induced fluorescence

The combination of aggregation-induced emission (AIE) luminescence and supramolecular chemistry has attracted great attention recently. However, due to the fluorescence quench ability of coordination metals and the dynamic reversibility of coordination bonds, the construction of supramolecular metal-organic nanocages with AIE properties has been a difficult and challenging problem in this field. Herein, we reported the design and construction of novel tetraphenylethene (TPE)-modified organic tetrahedral nanocages by coordination driven self-assembly. The synthesized organic tetrahedral nanocages exhibited unique AIE properties, stimulus-responsive luminescence features and solvatochromism effect after sub-component self-assembly. This provides a new way to construct selective photoluminescence materials and new information encryption materials.

Protein-directed synthesis of fluorescent sulfur quantum dots for highly robust detection of pyrophosphate

Inorganic pyrophosphate anions (PPi) play a key role in various biological processes and act as an essential indicator for physiological function evaluation and disease diagnosis. However, there is still a lack of available approaches for straightforward, robust, and convenient PPi detection. Herein, we design an on-off-on fluorescent switching nanoprobe employing Fe3+-mediated fluorescent sulfur quantum dots (SQDs) for highly robust detection of PPi. The bovine serum protein (BSA)-capped SQDs with fine water dispersibility and good optical stability are synthesized by an H2O2-assisted chemical etching reaction. Specifically, Fe3+ can strongly induce the aggregation of the SQDs into relatively larger sizes, resulting in aggregation-induced fluorescence quenching behavior. PPi can selectively bind with Fe3+ via emulative coordination and in preventing the aggregation of SQDs this isaccompanied by recovery of fluorescence. The physicochemical properties of aggregated and disaggregated SQDs have been systematically investigated. Aggregation and disaggregation of the SQDs and the corresponding quenching and recovery of fluorescence occurs and guarantees the high-contrast sensing performance of the SQD system in complex and challenging aquatic environments. Our designed on-off-on nanoswitch holds great potential for the design of elemental quantum dot-based biosensors for the highly robust detection of analytes in the near future.

Water-soluble graphene quantum dot‐based polymer nanoparticles with internal donor/acceptor heterojunctions for efficient and selective detection of cancer cells

We present a new, insightful donor–acceptor (D-A) energy transfer-based strategy for the preparation and development of water-soluble multifunctional pH-responsive heterojunction nanoparticles. Hydrophilic tertiary amine-grafted polythiophene (WPT) as a donor and blue fluorescent graphene quantum dots (GQD) as an acceptor spontaneously form co-assembled nanoparticles that function as a highly pH-sensitive and efficient biosensor appropriate for the detection of cancer cells. These WPT/GQD nanoparticles exhibit a number of unique physical characteristics—such as broad-range, tunable GQD-loading contents and particle sizes, extremely low cytotoxicity in normal and cancer cells, and highly sensitive pH-responsiveness and rapid acid-triggered fluorescent behavior under aqueous acidic conditions. We show these features are conferred by self-aggregation of the GQD within the nanoparticles and subsequent aggregation-induced fluorescence of GQD after disassembly of the nanoparticles and dissociation of the D-A interactions under acidic conditions. Importantly, in vitro fluorescence imaging experiments clearly demonstrated the WPT/GQD nanoparticles were gradually taken up into normal and cancer cells in vitro. Selective formation of GQD aggregates subsequently occurred in the acidic microenvironment of the cancer cells and the interior of the cancer cells exhibited strong blue fluorescence; these phenomena did not occur in normal cells. In contrast, pristine WPT and GQD did not exhibit cellular microenvironment-triggered fluorescence transitions in cancer or normal cell lines. Therefore, this newly discovered water-soluble heterojunction system may represent a strongly fluorescent highly pH-sensitive bioprobe for rapid detection of cancer cells.

Lighting up RNA-specific multi-photon and super-resolution imaging using a novel zinc complex.

Ribonucleic acid (RNA) probes are critical for understanding the role of RNA dynamics in cellular function but are in short supply due to the lack of optimized imaging systems and excellent fluorescence emission performance. Here, the terpyridine Zn(II) complex (Zn-T) with D-π-A configuration and bright aggregation-induced fluorescence emission (AIE) has been fabricated for the selective detection and real-time monitoring of RNA. Impressively, Zn-T exhibits a large Stokes shift and three-photon absorption (3PA) activity and responds specifically through hydrophobic interactions with an RNA pocket. The combination of AIE-assisted two-photon fluorescence and stimulated emission depletion (STED) microscopy of Zn-T for imaging nuclear RNA has higher spatial resolution and brightness, thus providing an imaging platform for studying RNA-related physiological or pathological processes.

Acting as a Molecular Tailor: Dye Structural Modifications for Improved Sensitivity toward Lysophosphatidic Acids Sensing.

Lysophosphatidic acids (LPA) are key biomarkers for several physiological processes, the monitoring of which can provide insights into the host's health. Common lab-based techniques for their detection are cumbersome, expensive, and necessitate specialized personnel to operate. LPA-sensitive fluorescent probes have been described, albeit for nonaqueous conditions, which impedes their use in biological matrices. In this paper, we explore in detail the influence of structure on the extent of aggregation-induced fluorescence quenching using specially synthesized styrylpyridinium dyes bearing structural adaptations to bestow them enhanced affinity toward LPA in aqueous media. Spectroscopic investigations supported by time-resolved fluorimetry revealed the contribution of excimer formation to the fluorescence quenching mechanism displayed by the fluorescent probes. Experimental observations of the influence of structure on detection sensitivity were supported by DFT calculations.

An abiotic carbon dots@ ZIF-90 fluorescent probe for rapid and reliable detection of adenosine triphosphate

ATP is a high-energy compound that plays a vital role in biological metabolism. Abnormal changes in ATP concentration are related to various diseases and reflect microbial metabolism in biofilms. In this work, we prepared carbon quantum dots (CDs) with aggregation-induced fluorescence inhibition effect using the bacterial culture medium as raw material with a hydrothermal method. Then, an abiotic fluorescent nanoprobe named CDs@zeolitic imidazolate frameworks-90 (ZIF-90) was facilely synthesized by encapsulating CDs into ZIF-90. Owing to the encapsulation of CDs in the hollow structure of ZIF-90, the blue fluorescence emission of CDs@ZIF-90 decreased significantly. In the presence of ATP, the ZIF-90 framework was destroyed due to the strong coordination between ATP and Zn2+. The released CDs exhibited stronger fluorescence intensity, which was closely related to the ATP concentration. The convenient synthesis process and rapid ATP-responsive ability make CDs@ZIF-90 highly promising for clinical and environmental analysis.

Bola-type PEG-linked polyaromatic hydrocarbon-based chemosensors for the “turn-off” excimer fluorescence detection of nitro-analytes/explosives in aqueous solutions

Diesters of 1-pyrenecarboxylic acid with tri- and tetra - ethylene glycols were prepared and characterized for the first time and their photophysical and sensory properties were investigated. In aqueous solutions these compounds exhibited an intensive excimeric emission at 521 nm, which is attributed to the aggregation-induced fluorescence of the dimers, pre-associated in the ground state. In aqueous solutions an intensive “turn-off” fluorescence response towards common nitro-explosive components, such as 2,4-dinitrotoluene (2,4-DNT), 2,4,6-trinitrotoluene (TNT), as well as aliphatic nitro compounds, such as pentaerythritol tetranitrate (PETN), 1,3,5-trinitro-1,3,5-triazinane (RDX) and 2,3-dimethyl-2,3-dinitrobutane (DMDNB) was observed via the excimeric emission quenching. For the most representative chemosensor 4a the highest Stern-Volmer fluorescence quenching constant of 8.75 × 106 M−1 was observed in the presence of TNT.

A thiophenic alkynylplatinum(II) terpyridyl complex: synthesis and photophysical properties

A new thiophenic alkynylplatinum(II) terpyridyl complex [tBuArC≡CPt(tpy)]PF6 (tpy = 2,2′:6′,2″-terpyridine; Ar = [(MeC4H2S)(C≡C)]2C6H2) has been synthesized in five steps in 45% total yield. The photophysical properties were studied by steady-state spectroscopy and transient spectroscopy and obvious metal-metal interactions and π-π stacking were found in a series of solvents. Concentration dependent emission data show that the complex exhibited aggregation-induced fluorescence enhancement at low concentrations while aggregation-induced fluorescence quenching at high concentrations. The complex displayed biexponential decays with lifetimes in the range of nanoseconds in dilute dichloromethane and acetonitrile solutions.

Aggregation-Induced Fluorescence Enhancement for Efficient X-ray Imaging Scintillators and High-Speed Optical Wireless Communication

Aggregation-Induced Fluorescence Enhancement for Efficient X-ray Imaging Scintillators and High-Speed Optical Wireless Communication