Highly Sensitive and Selective Detection of Nitrophenolic Explosives by Using Nanospheres of a Tetraphenylethylene Macrocycle Displaying Aggregation-Induced Emission

Preparation of Langmuir-Blodgett Films from Quinoxalines Exhibiting Aggregation-Induced Emission and Their Acidochromism

The development of aggregation-induced emission (AIE)-exhibiting compounds heavily relies on our evolving comprehension of their behavior at interfaces, an understanding that still remains notably limited. In this study, we explored the preparation of two-dimensional (2D) sensing films from 2,3-diphenylquinoxaline-based diazapolyoxa- and polyazamacrocycles displaying AIE via the Langmuir-Blodgett (LB) technique. This systematic investigation highlights the key role of the heteroatom-containing tether of 2,3-diphenylquinoxalines in the successful fabrication of Langmuir layers at the air-water interface and the transfer of AIE-emitting supramolecular aggregates onto solid supports. Using both diazapolyoxa- and polyazamacrocycles, we prepared AIE-exhibiting monolayer films containing emissive supramolecular aggregates on silica, mica, and quartz glass and characterized them using ultraviolet-visible (UV-vis) and photoluminescence (PL) spectroscopies, atomic force microscopy (AFM) imaging, and fluorescence microscopy. We also obtained multilayer AIE-emitting films through the LB technique, albeit with increased complexity. Remarkably, by employing the smallest macrocycle N2C3Q, we successfully prepared LB films suitable for the visual detection of acidic vapors. This sensing material, which contains a much lesser amount of organic dye compared with traditional drop-cast films, can be regenerated and utilized for real-life sample analysis, such as monitoring the presence of ammonia in the air and the freshness of meat.

Hydrazone-linked covalent organic framework functionalized with cysteine as a fluorescence sensor and Exploration of paper chip for p-nitrophenol detection

The large use and emission of p-nitrophenol (p-NP) seriously pollute the environment and endanger human health. In this work, a hydrazone-linked fluorescent covalent organic framework (BATHz-COF) was simply synthesized at room temperature and covalently linked N-acetyl-L-cysteine (NALC) via the "thiol-ene" click reaction, where carboxyl groups were introduced to improve dispersion and fluorescence intensity. As a rapid, good selectivity and reusability fluorescence sensor, the obtained COF-NALC has been used for quantitative analysis of p-NP predicated on the internal filtering effect (IFE). Under optimal conditions, COF-NALC enabled quantitative detection of p-NP with a linear range of 5-50 μM and the detection limit was 1.46 μM. The application of COF-NALC to the detection of p-NP in river water samples was successful, and the satisfactory recoveries were 98.0%-109.3%. Furthermore, the fluorescent COF paper chips constructed by in situ growth were combined with a smartphone to build a visual platform for the quick and real-time detection of p-NP, providing an excellent illustration for the development of intelligent fluorescence sensing in environmental analysis.

Urea-Promoted Neat Synthesis of Fused Dihydroisoquinolines and Disubstituted Pyridines: A Mechanistic Observation with Molecular-Sensing Studies

An efficient and short synthesis of fused dihydroisoquinolines, diaryl substituted pyridine derivatives in good to high yields has been established by using an environmentally safe, solvent-metal-oxidant-free tandem approach. In this article, we discuss how the electrocyclic reaction is more pronounced in the solid phase in the presence of urea, whereas the typical aza-Michael addition is more prominent in presence of arylamine in the solution phase for 3-(2-formylcycloalkenyl)acrylic ester derivative substrates. The wide range of substrates and urea-promoted neat synthesis made our approach more significant in medical and also analytical science. Moreover, an isoquinoline alkaloid decumbenine B analogue has been synthesized by using our newly developed neat methodology. We have also investigated the photophysical properties of the synthesized fused dihydroisoquinoline derivatives. One of the synthesized molecules was used as a sensor for the selective detection of toxic picric acid. Therefore, the effective neat synthesis and molecular sensing applications of these compounds made our approach more exciting in the field of heterocyclic chemistry.

Synthesis of Bis-tetraphenylethene as a Novel Turn-On Selective Zinc Sensor

The main purpose of this study is the synthesis of novel fluorescent Bis-TPE and the investigation of its wide range of photochemical behaviors. For this purpose, initially, Bis-TPE was synthesized. Following this, the interactions of Bis-TPE with a wide range of ions were studied in EtOH using ultraviolet-visible (UV-vis) and fluorescence spectroscopy. As a result of all UV-vis and fluorescence studies, it was determined that Bis-TPE showed turn-on sensor features against Zn²⁺ ions. Moreover, the limit of detection (LOD) and K_a values of Bis-TPE/Zn²⁺ were calculated as 0.97 μM (970 nM) and 3.76 × 10⁵ M^-1, respectively. Moreover, all reversal studies resulted in switchable on/off variation of the alternative addition of ZnCl₂ and [Bu₄N]OH to Bis-TPE. This result also implies that the probe Bis-TPE also exhibits specific OH^- sensor properties in the presence of zinc.

A tetraphenylethene-based Schiff base AIEgen with a large Stokes shift as probe for highly sensitive and selective detection of aqueous Cu2+ ions and its application in cell imaging

In this work, an AIE-active tetraphenylethene-based Schiff base fluorescent probe 3 with a large Stokes shift (247 nm) was designed and synthesized. It was found that the aggregated probe 3 exhibited very high selectivity and anti-interference ability for Cu²⁺ in PBS buffer (70% f_w) through a fluorescence "turn-off" strategy. Job's plot and NMR analysis indicated the two phenolic hydroxyl groups of the benzene ring and the N atom (-CH=N-) on probe 3 interacted with Cu²⁺ ions in a 1:1 stoichiometric ratio. A comprehensive analysis of the Stern-Volmer and binding constant indicated a rather strong interaction between probe 3 and Cu²⁺ ions. Probe 3 illustrated excellent sensitivity toward Cu²⁺ under ppb level (4.5 nM) and achieved more than 95% recovery in river, lake and tap water toward estimation of Cu²⁺ ions in the analytical applications. Moreover, probe 3 was able to realize bioimaging of HepG2 cells and be quenched by intracellular Cu²⁺ ions, making it promising as a sensitive Cu²⁺ sensor for organisms.

Deciphering the ultrafast dynamics of a new tetraphenylethylene derivative in solutions: charge separation, phenyl ring rotation and CC bond twisting

Tetraphenylethylene (TPE) derivatives are one of the fundamental units for developing aggregation induced emission (AIE) scaffolds. However, the underlying mechanisms implicated in the relaxation of the excited TPE remain a topic of ongoing discussion, while the effect of bulky substituents on its photobehaviour is still under scrutiny. Here, we report a detailed study of the photophysical properties of a new symmetrical and bulky TPE derivative with terphenyl groups (TTECOOBu) in solvents of different polarities and viscosities. Using femto- to nanosecond (fs-ns) time-resolved absorption and emission techniques, we elucidated the role of the phenyl group rotations and core ethylene bond twisting in its behaviour. We demonstrate that TTECOOBu in DCM solutions undergoes a 600 fs charge separation along the ethylene bond leading to a resonance structure with a lifetime of ∼1 ns. The latter relaxes via two consecutive events: a twisting of the ethylene bond (∼ 9 ps) and a rotation of the phenyl rings (∼ 30 ps) leading to conformationally-relaxed species with a largely Stokes-shifted emission (∼ 12 500 cm^-1). The formation of the red-emitting species clearly depends on the solvent viscosity and rigidity of the medium. Contrary to the photobehavior in the highly viscous triacetin or rigid polymer matrix of PMMA, a reversible mechanism was observed in DCM and DMF solutions. These results provide new findings on the ultrafast mechanisms of excited TPE derivatives and should help in the development of new molecular rotors with interesting AIE properties for photonic applications.

A Highly Efficient Fluorescent Sensor Based on AIEgen for Detection of Nitrophenolic Explosives

The detection of nitrophenolic explosives is important in counterterrorism and environmental protection, but it is still a challenge to identify the nitroaromatic compounds among those with a similar structure. Herein, a simple tetraphenylethene (TPE) derivative with aggregation-induced emission (AIE) characteristics was synthesized and used as a fluorescent sensor for the detection of nitrophenolic explosives (2, 4, 6-trinitrophenol, TNP and 2, 4-dinitrophenol, DNP) in water solution and in a solid state with a high selectivity. Meanwhile, it was found that only hydroxyl containing nitrophenolic explosives caused obvious fluorescence quenching. The sensing mechanism was investigated by using fluorescence titration and ¹H NMR spectra. This simple AIE-active probe can potentially be applied to the construction of portable detection devices for explosives.

Non-aqueous onion like nano-carbons from waste diesel-soot used as FRET-based sensor for sensing of nitro-phenols

Herein, a simple-functionalization method is described to prepare the oleylamine functionalized non-aqueous version of onion-like nanocarbons (ONC-OA), where ONC was isolated from the waste pollutant soot exhausted from the diesel engine. The surface group analysis of ONC-OA has been investigated via Nuclear Magnetic Resonance and X-ray Photoelectron Spectroscopy. ONC-OA shows blue fluorescence with a quantum yield of ∼6% in tetrahydrofuran (THF). The fluorescence-based sensing applications of ONC-OA has been investigated for selective sensing of toxic aromatic nitro-phenols compounds (para-nitro, dinitro, and trinitro phenols) from the tested many nitro organic compounds. Based on the limit of detection values, ONC-OA shows much better results for tri-nitro phenol compared to di and mono nitrophenol. To understand the quenching mechanism, a time-resolved photoluminescence analysis of the sensor with and without the addition of quenchers is performed. The effective lowering in fluorescence lifetime of the sensor after the addition of quenchers concludes that the quenching observed is majorly due to the Förster Resonance Energy Transfer (FRET) mechanism. The real-life application of ONC-OA was analyzed by external spiking of N-PhOHs in soil samples.

Fluorescent cyclophanes and their applications

With the serendipitous discovery of crown ethers by Pedersen more than half a century ago and the subsequent introduction of host-guest chemistry and supramolecular chemistry by Cram and Lehn, respectively, followed by the design and synthesis of wholly synthetic cyclophanes-in particular, fluorescent cyclophanes, having rich structural characteristics and functions-have been the focus of considerable research activity during the past few decades. Cyclophanes with remarkable emissive properties have been investigated continuously over the years and employed in numerous applications across the field of science and technology. In this Review, we feature the recent developments in the chemistry of fluorescent cyclophanes, along with their design and synthesis. Their host-guest chemistry and applications related to their structure and properties are highlighted.

Novel Self-assembly Pd(II)-Schiff Base Complex Modified Glassy Carbon Electrode for Electrochemical Detection of Paracetamol

A self-assembly Pd-Schiff base complex was synthesized and used as an electrochemical sensor in phosphate buffer solution, where it enhanced the electrocatalytic activity toward the paracetamol detection. The Schiff base {(HL) = (4-(((Z)-3-(hydroxyimino) butan-2-ylidene) amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one)} was selected to prepare Pd-based complexes due to its high antimicrobial activity. A linear calibration curve was constructed using GC/Pd-SB in paracetamol concentration range of 1–50 μM and its detection limit was calculated as 0.067 μM. The modified electrode, GC/Pd-SB, could successfully determine the paracetamol concentration in human blood serum and commercial drug tablets with high sensitivity. The prepared metal complex was characterized using techniques, namely, X-ray diffraction (XRD) and scanning electron microscope (SEM). In addition, electrochemical studies were performed using different electrochemical techniques like cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). DFT calculations were used to estimate the equilibrium geometry, molecular orbital, ground-state properties, and interaction energy between paracetamol and palladium.

Graphical Abstract

Chiral assembly of organic luminogens with aggregation-induced emission

Chirality is important to chemistry, biology and optoelectronic materials. The study on chirality has lasted for more than 170 years since its discovery. Recently, chiral materials with aggregation-induced emission (AIE) have attracted increasing interest because of their fascinating photophysical properties. In this review, we discussed the recent development of chiral materials with AIE properties, including their molecular structures, self-assembly and functions. Generally, the most effective strategy to design a chiral AIE luminogen (AIEgen) is to attach a chiral scaffold to an AIE-active fluorophore through covalent bonds. Moreover, some propeller-like or shell-like AIEgens without chiral units exhibit latent chirality upon mirror image symmetry breaking. The chirality of achiral AIEgens can also be induced by some optically active molecules through non-covalent interactions. The introduction of an AIE unit into chiral materials can enhance the efficiency of their circularly polarized luminescence (CPL) in the solid state and the dissymmetric factors of their helical architectures formed through self-assembly. Thus, highly efficient circularly polarized organic light-emitting diodes (CPOLEDs) with AIE characteristics are developed and show great potential in 3D displays. Chiral AIEgens are also widely utilized as "turn on" sensors for rapid enantioselective determination of chiral reagents. It is anticipated that the present review can entice readers to realize the importance of chirality and attract much more chemists to contribute their efforts to chirality and AIE study.

A metal complex based fluorescent chemodosimeter for selective detection of 2,4-dinitrophenol and picric acid in aqueous medium

The work in this report describes the syntheses, characterization, crystal structures, absorption and emission spectra and DFT calculations of three dizinc(II) compounds of composition [ZnII2L(μ1,1-N3)(N3)2] (1), [Zn2L'(2,4-dinitrophenolate)2] (2) and [Zn2L'(picrate)2]...

Design of an AIE-Active Flexible Self-Assembled Monolayer Probe for Trace Nitroaromatic Compound Explosive Detection

In this work, a series of molecules TPE-PA-n (n = 3-11) were designed with classic aggregation-induced emission (AIE) 1,1,2,2-tetraphenylethene (TPE) for self-assembled monolayers (SAMs), which are applied for the detection of trace nitroaromatic compound (NAC) explosives. Phosphoric acid that acts as an anchor is used to connect with TPE through alkyl chains of various lengths. It is found that the alkyl chains play a role in pulling TPE luminogens to aggregate for light emission, which can affect the fluorescence and sensing performance of the SAMs. Ulteriorly, a model is built to explore the influence of the alkyl chain length on the device performance, which is determined by the three effects of the alkyl chain: flexibility, the coupling effect, and the odd-even effect. By comparison, the functional molecules with the chain length of 8 were finally selected and further applied for NAC sensors. By means of fluorescence spectra, the SAM sensor was proved to have good stability, reversibility, selectivity, and sensitivity, and its detection limits for trinitrotoluene, dinitrotoluene, and nitrobenzene were 1.2, 6.0, and 35.7 ppm, respectively. This work provides new ideas for the design and preparation of flexible sensors for trace NAC detection with high performance, low cost, and easy operation.

Y-shaped ferrocene/non-ferrocene conjugated quinoxalines for colorimetric and fluorimetric detection of picric acid

New Y-shaped ferrocene and non-ferrocene conjugated quinoxaline derivatives {[R-(CH)₂-N=CH-)₂C₁₀H₄], R = C₅H₅-Fe-C₅H₅ (1) and R = C₆H₄-OCH₃ (2)} have been synthesized and characterized using analytical and spectroscopic techniques. The thermal stability of the compounds 1 and 2 were examined by thermogravimetric analysis (TGA), both were stable up to 250 °C. The optical properties were studied using UV-Visible and fluorescence spectroscopic methods and Y-shaped ferrocene appended quinoxaline derivative 1 show a weak emission due to the quenching nature of ferrocene. The compound 2 shows enhanced fluorescence intensity in their aggregation state due to Restricted Intramolecular Rotation (RIR). Hence, the compound 2 have further utilized for the detection of picric acid (PA) by fluorimetric method and the detection limit of 1.37 × 10^-6 M was obtained. Further, paper sensor was made using compound 2 which resulted in the instant 'naked eye' response for trace detection of picric acid. Consequently, the compound 2 acts as a colorimetric sensor and can be used as a new probe for the detection of nitro aromatic explosives.

Supramolecular assemblies of glycoclusters with aggregation-induced emission for sensitive phenol detection

Hypercrosslinked AIE-active glycocluster nano aggregates are facilely synthesized as fluorescent probes for the detection of phenols.

Dynamic Covalent Switches and Communicating Networks for Tunable Multicolor Luminescent Systems and Vapor-Responsive Materials

Molecular switches are an intensive area of research, and in particular, the control of multistate switching is challenging. Herein we introduce a general and versatile strategy of dynamic covalent switches and communicating networks, wherein distinct states of reversible covalent systems can induce addressable fluorescence switching. The regulation of intramolecular ring/chain equilibrium, intermolecular dynamic covalent reactions (DCRs) with amines, and both permitted the activation of optical switches. The variation in electron-withdrawing competition between the fluorophore and 2-formylbenzenesulfonyl unit afforded diverse signaling patterns. The combination of switches in situ further enabled the creation of communicating networks for multistate color switching, including white emission, through the delicate control of DCRs in complex mixtures. Finally, reversible and recyclable multiresponsive luminescent materials were achieved with molecular networks on the solid support, allowing visualization of different types of vapors and quantification of primary amine vapors with high sensitivity and wide detection range. The results reported herein should be appealing for future studies of dynamic assemblies, molecular sensing, intelligent materials, and biological labeling.

A silicon-cored tetraphenyl benzene derivative with aggregation-induced emission enhancement as a fluorescent probe for nitroaromatic compounds detection

Two benzene with multiple contiguous phenyl substituent derivatives, namely, 1, 2, 3, 4-tetraphenyl benzene (TPB) and bis(1,2,3,4-tetraphenylbenzene-yl) diphenylsilane (TPB-Si), were synthesized by the Knoevenagel/Diels-Alder method. TPB and TPB-Si both showed aggregation-induced emission enhancement (AIEE) properties in tetrahydrofuran/water mixtures. The fluorescence-quenching behaviors of the two compounds with different nitroaromatic compounds were also investigated. TPB and TPB-Si both showed low detection limit, high sensitivity, and high quenching efficiency in detecting nitroaromatic compounds. Furthermore, the two compounds in aggregate state exhibited much better detection abilities than in THF solution. And TPB-Si exhibited better detection ability than TPB in both solution and aggregate state. The reason could be attributed to the special tetrahedral molecular structure of TPB-Si, which was demonstrated by theoretical calculations and crystal structures. Moreover, TPB-Si in solid film also exhibited excellent detection performance to nitroaromatic explosive vapor. This work may serve as a basis for designing new organic materials with great efficiency and sensitivity in fluorescence detection.

Aggregation-Induced Emission (AIE)-Labeled Cellulose Nanocrystals for the Detection of Nitrophenolic Explosives in Aqueous Solutions

Aggregation-induced emission (AIE) active cellulose nanocrystals (TPE-CNCs) were synthesized by attaching tetraphenylethylene (TPE) to cellulose nanocrystals (CNCs). The structure and morphology of TPE-CNCs were characterized by FT-IR, XRD, ζ-potential measurements, elemental analysis, TEM, atomic force microscopy (AFM), and dynamic laser light scattering (DLS). Fluorescent properties of TPE-CNCs were also further studied. Unlike aggregation-caused quenching (ACQ), TPE-CNCs emitted weak fluorescence in the dilute suspensions, while emitting efficiently in the aggregated states. The AIE mechanism of TPE-CNCs was attributed to the restriction of an intramolecular rotation (RIR) process in the aggregated states. TPE-CNCs displayed good dispersity in water and stable fluorescence, which was reported through the specific detection of nitrophenolic explosives in aqueous solutions by a fluorescence quenching assay. The fluorescence emissions of TPE-CNCs showed quantitative and sensitive responses to picric acid (PA), 2,4-dinitro-phenol (DNP), and 4-nitrophenol (NP), and the detection limits were 220, 250, and 520 nM, respectively. Fluorescence quenching occurred through a static mechanism via the formation of a nonfluorescent complex between TPE-CNCs and nitrophenolic analytes. A fluorescence lifetime measurement revealed that the quenching was a static process. The results demonstrated that TPE-CNCs were excellent sensors for the detection of nitrophenolic explosives in aqueous systems, which has great potential applications in chemosensing and bioimaging.

Electrochemical Sensors Containing Schiff Bases and their Transition Metal Complexes to Detect Analytes of Forensic, Pharmaceutical and Environmental Interest. A Review

Schiff bases and their transition metal complexes are inexpensive and easy to synthesize. These compounds display several structural and electronic features that allow their application in numerous research fields. Over the last three decades, electroanalytical scientists of various areas have developed electrochemical sensors from many compounds. The present review discusses the applicability of Schiff bases, their transition metal complexes and new materials containing these compounds as electrode modifiers in sensors to detect analytes of forensic, pharmaceutical and environmental interest. In forensic sciences, Schiff bases are mainly used to analyze illicit drugs: chemical reactions involving Schiff bases can help to elucidate illicit drug production and to determine analytes in seized samples. In the environmental area, given that most methodologies provide Limit of Detection (LOD) values below the values recommended by regulatory agencies, Schiff bases constitute a promising strategy. As for pharmaceutical applications, Schiff bases represent an approach for analysis of complex biological samples containing low levels of the target analytes in the presence of a large quantity of interfering compounds. This review will show that new highly specific materials can be synthesized based on Schiff bases and applied in the pharmaceutical industry, toxicological studies, electrocatalysis and biosensors. Most literature papers have reported on Schiff bases combined with carbon paste to give a chemically modified electrode that is easy and inexpensive to produce and which displays specific and selective sensing capacity for different applications.

Multiple Emitting Amphiphilic Conjugated Polythiophenes-Coated CdTe QDs for Picogram Detection of Trinitrophenol Explosive and Application Using Chitosan Film and Paper-Based Sensor Coupled with Smartphone

Novel multiple emitting amphiphilic conjugated polythiophene-coated CdTe quantum dots for picogram level determination of the 2,4,6-trinitrophenol (TNP) explosive are developed. Four biocompatible sensors, cationic polythiophene nanohybrids (CPTQDs), nonionic polythiophene nanohybrids (NPTQDs), anionic polythiophene nanohybrids (APTQDs), and thiophene copolymer nanohybrids (TCPQDs), are designed using an in situ polymerization method, which shows highly enhanced fluorescence intensity and quantum yield (up to 78%). All sensors are investigated for nitroexplosive detection to provide a remarkable fluorescence quenching for TNP and the quenching efficiency reached 96% in the case of TCPQDs. The fluorescence of the sensors are quenched by TNP through inner filter effect, electrostatic, π-π, and hydrogen bonding interactions. Under optimal conditions, the detection limits of CPTQDs, NPTQDs, APTQDs, and TCPQDs are 2.56, 7.23, 4.12, and 0.56 × 10-9 m, respectively, within 60 s. More importantly, portable, cost effective, and simple to use paper strips and chitosan film are successfully applied to visually detect as little as 2.29 pg of TNP. The possibility of utilizing a smartphone with a color-scanning APP in the determination of TNP is also established. Moreover, the practical application of the developed sensors for TNP detection in tap and river water samples is described with satisfactory recoveries of 98.02-107.50%.

A tripodal supramolecular sensor to successively detect picric acid and CN− through guest competitive controlled AIE

Herein, we report a simple and efficient method for the selective and sensitive detection of picric acid (PA) and CN⁻via a novel guest competitive controlled aggregation-induced emission (AIE) mechanism based on a tris-naphthalimide derivative TG.

A porous β-cyclodextrin-based terpolymer fluorescence sensor for in situ trinitrophenol detection

Permanent porosity plays a key role in fluorescent-based polymers with “on–off” emissive properties due to the role of guest adsorption at accessible fluorophore sites of the polymer framework. In particular, we report on the design of a porous fluorescent polymer (FL-PFP) composed of a covalently cross-linked ternary combination of β-cyclodextrin (β-CD), 4,4′-diisocyanato-3,3′-dimethyl biphenyl (DL) and tetrakis(4-hydoxyphenyl)ethene (TPE). The textural properties of FL-PFP were evaluated by the gas uptake properties using N₂ and CO₂ isotherms. The BET surface area estimates according to N₂ uptake ranged from 100–150 m² g⁻¹, while a lower range of values (20–30 m² g⁻¹) was estimated for CO₂ uptake. Model nitroarenes such as trinitrophenol (TNP) and nitrobenzene (NB) were shown to induce turn-off of the fluorescence emission of the polymer framework at concentrations near 50 nM with ca. 50% fluorescence quenching upon TNP adsorption and detection. The strong donor–acceptor interaction between the nitroarenes and the TPE reporter unit led to fluorescence quenching of FL-PFP upon nitroarene adsorption. The fluorescence lifetime (τ) for FL-PFP (τ = 3.82 ns) was obtained along with a quantum yield estimate of 0.399 relative to quinine sulphate. The β-CD terpolymer reported herein has significant potential for monitoring the rapid and controlled detection of nitroarenes (TNP and NB) in aquatic environments and other complex media.

Permanent porosity plays a key role in fluorescent-based polymers with “on–off” emissive properties due to the role of guest adsorption at accessible fluorophore sites of the polymer framework.

Chiral molecular face-rotating sandwich structures constructed through restricting the phenyl flipping of tetraphenylethylene

Chiral tetraphenylethylene (TPE) derivatives have great potential in chiral recognition and circularly polarized luminescence. However, they were mainly constructed through introducing chiral substituents at the periphery of the TPE moiety, which required additional chemical modifications and limited the variety of chiralities of products. Herein, we constructed a series of chiral face-rotating sandwich structures (FRSs) through restricting the phenyl flipping of TPE without introducing any chiral substituents. In FRSs, the complex arrangements of TPE motifs resulted in a variety of chiralities. We also found that non-covalent repulsive interactions in vertices caused the facial hetero-directionality of FRSs, and the hydrogen bonds between imine bonds and hydroxy groups induced excited-state intramolecular proton transfer (ESIPT) emission of FRSs. In addition, the fluorescence intensity of FRSs decreases with the addition of trifluoroacetic acid. This study provides new insights into the rational design of chiral assemblies from aggregation-induced emission (AIE) active building blocks through restriction of intramolecular rotation (RIR).

Organic core-shell-shaped micro/nanoparticles from twisted macrocycles in Schiff base reaction

A series of organic core–shell-shaped micro/nanoparticles from twisted enantiomeric macrocycles could be obtained in Schiff base reaction with high yield at room temperature.

Functional self-assemblies derived from noncovalent interactions such as lipid vesicles and DNA chiral double helices are a typical feature of natural life activity. Because of this phenomenon, a self-assembly approach for various functional organic particles is a desirable objective in supramolecular chemistry. Here, we report the discovery of enantiomeric conformers from a twisted macrocyclic host (MH), which was obtained from an achiral precursor by Schiff base reaction. Further studies suggest that a series of unexpected and stable core–shell-based organic micro/nanospheres can be directly precipitated from a simple reaction solution with high yield. A single-crystal X-ray diffraction analysis of MH revealed that the unusual C–H···π interaction triggered self-assembly of the enantiomeric forms in the solid state plays an important role in the formation of the core–shell-shaped organic particles.

Tetraphenylethylene-Based AIE-Active Probes for Sensing Applications

This Review provides a comprehensive analysis of recent development in the field of aggregation-induced emission (AIE)-active tetraphenylethylene (TPE) luminophores and their applications in biomolecular science. It begins with a discussion of the diverse range of structural motifs that have found particular applications in sensing, and demonstrates that TPE structures and their derivatives have been used for a diverse range of analytes such as such as H⁺, anions, cations, heavy metals, organic volatiles, and toxic gases. Advances are discussed in depth where TPE is utilized as a mechanoluminescent material in bioinspired receptor units with specificity for analytes for such as glucose or RNA. The rapid advances in sensor research make this summary of recent developments in AIE-active TPE luminophores timely, in order to disseminate the advantages of these materials for sensing of analytes in solution, as well as the importance of solid and aggregated states in controlling sensing behavior.

A photo-stable fluorescent chiral thiourea probe for enantioselective discrimination of chiral guests

Herein, a chiral thiourea Schiff base derived from (1R,2R)-1,2-cyclohexanediamine and tetraphenylethylene (TPE) was applied as a highly effective chiral sensor for the enantioselective discrimination of various acids and aminesviaion-pair and hydrogen-bond interaction.

A versatile chemosensor for the detection of Al3+ and picric acid (PA) in aqueous solution

The selective detection of Al³⁺ and picric acid in water has been realized by means of a fluorescence spectroscopy-based chemosensor.

Self-agglomerated crystalline needles harnessing ESIPT and AIEE features for the ‘turn-on’ fluorescence detection of Al3+ ions

We report the synthesis of probe 2 for the fluorescence “turn-on” detection of Al³⁺ ions in CH₃OH.

Macrocycles and cages based on tetraphenylethylene with aggregation-induced emission effect

Syntheses, photophysical properties and applications of macrocycles and cages based on tetraphenylethylene with aggregation-induced emission (AIE) effect.

Fluorescent supramolecular hydrogels self-assembled from tetraphenylethene (TPE)/single amino acid conjugates

TPE-Ser molecules exhibit non-covalent interactions necessary for hydrogelation under physiological pH conditions.

Fluorescent sensors based on AIEgen-functionalised mesoporous silica nanoparticles for the detection of explosives and antibiotics

AIEgen-functionalised mesoporous silica nanoparticles can be used for the detection of explosives and antibiotics based on a FRET mechanism.

Conjugated polymers containing tetraphenylethylene in the backbones and side-chains for highly sensitive TNT detection

Polytriphenylamines with tetraphenylethylene (TPE) side groups and bis(tert-butyl)-TPE in the backbones exhibit the AIE effect and high sensitivity in PL-based TNT detection.

Tetraphenylpyrimidine-Based AIEgens: Facile Preparation, Theoretical Investigation and Practical Application

Aggregation-induced emission (AIE) has become a hot research area and tremendous amounts of AIE-active luminogens (AIEgens) have been generated. To further promote the development of AIE, new AIEgens are highly desirable. Herein, new AIEgens based on tetraphenylpyrimidine (TPPM) are rationally designed according to the AIE mechanism of restriction of intramolecular motion, and facilely prepared under mild reaction conditions. The photophysical property of the generated TPPM, TPPM-4M and TPPM-4P are systematically investigated and the results show that they feature the aggregation-enhanced emission (AEE) characteristics. Theoretical study shows the high-frequency bending vibrations in the central pyrimidine ring of TPPM derivatives dominate the nonradiative decay channels. Thanks to the AEE feature, their aggregates can be used to detect explosives with super-amplification quenching effects, and the sensing ability is higher than typical AIE-active tetraphenylethene. It is anticipated that TPPM derivatives could serve as a new type of widely used AIEgen based on their facile preparation and good thermo-, photo- and chemostabilities.