A fluorescent sensor based on aggregation-induced emission: highly sensitive detection of hydrazine and its application in living cell imaging

Chromaticity sensor for discriminatory identification of aliphatic and aromatic primary amines based on conformational changes of polyacetylene

The design and construction of suitable sensors that can selectively recognize chemically similar substances such as aliphatic and aromatic amines remain challenging. In this work, we reported a poly(phenylacetylene) bearing two aldehyde pendants as the color indicator for discriminative identification of amines. Reversible Schiff-base reaction of the aldehyde group with the amine resulted in a conformational transition of the polyacetylene backbone from cis-cisoid to cis-transoid, which further achieved a colorimetric change. Thirteen aliphatic amines and aromatic amines had been studied. Compared with aromatic amines, aliphatic amines generally caused the polyene backbone to display perceivable colorimetric change. Steric and electronic effect played a significant role in the colorimetric response. In addition, external environment, including amine content, polymer concentration, and temperature, had influence on the sensitivity of this colorimetric indicator system. The amines-induced colorimetric variation was further demonstrated by the CIELAB color space. Moreover, the colorimetric sensor exhibited excellent reversibility and recyclability.

A near-infrared fluorescent probe for detecting hydrazine metabolized from isoniazid in living cells

Isoniazid is a drug for treating tuberculosis, but hydrazine (N2 H4 ), the major metabolite of isoniazid, can cause hepatotoxicity. Therefore, monitoring the content of N2 H4 in time is of great significance for studying the hepatotoxicity induced by isoniazid. In this study, a near-infrared fluorescent probe (BC-N) was designed and synthesized based on the specific reaction of acetyl ester with N2 H4 . BC-N exhibits excellent selectivity, sensitivity, and biocompatibility. In addition, BC-N is applied in the visualization of N2 H4 produced from isoniazid in living cells and is a potential tool for monitoring hepatotoxicity induced by isoniazid.

A nucleophilic addition-elimination based ratiometric fluorescent probe for monitoring N2H4 in biological systems and actual samples

Hydrazine (N₂H₄) is an important reagent in the field of fine chemical engineering. However, its accumulation in the environment and food chain could pose a great threat to food safety and human health. Therefore, designing a fluorescent probe with good cell penetration and high selectivity and sensitivity to detect N₂H₄ in actual samples and in vivo is a meaningful project. Herein, due to the nucleophilicity of hydrazine, we utilized naphthalimide as the fluorescence chromophore and pyrone as the recognition site to achieve the ratiometric detection of hydrazine by ring opening. In addition, we introduced the ester to improve the lipid solubility of the probe, which allowed the probe to better penetrate the cell membrane to realize the fluorescent imaging of probes in cells. Meanwhile, to our delight, the probe showed high selectivity and sensitivity to N₂H₄ in the test system, so we further applied the probe in water samples and food, in vitro and in vivo.

Cyanostilbene-based fluorescent paper array for monitoring fish and meat freshness via amino content detection

The detection of biogenic amines released from degraded meats is an effective method for evaluating meat freshness. However, existing traditional methods like titration are deemed tedious, while the use of sophisticated analytical instruments is not amenable to field testing. Herein, a cyanostilbene-based fluorescent array was rapidly fabricated using macroarray synthesis on a cellulose paper surface to detect amines liberated from spoiled beef, fish, and chicken. The fluorescence changes of immobilized molecules from the interaction with gaseous amines were used to monitor changes in freshness levels. Thanks to the high-throughput nature of macroarray synthesis, a set of highly responsive molecules such as pyridinium and dicyanovinyl moieties were quickly revealed. Importantly, this method offers flexibility in sensing applications including (1) sensing by individual sensor molecules, where the fluorescence response correlated well with established titration methods, and (2) collective sensing whereby chemometric analysis was used to provide a cutoff of freshness with 73-100% accuracy depending on meat types. Overall, this study paves the way for a robust and cost-effective tool for monitoring meat freshness.

A color-change fluorescence sensor for oleanolic acid based on chiral camphanic decorated bis-cyanostilbene

Although various fluorescent sensors for biomolecules had been extensively reported, the effective fluorescent sensor was seldom reported for detecting oleanolic acid up to now. This work reports the first color-change fluorescence sensor for oleanolic acid based on a bridging bis-cyanostilbene derivative with chiral camphanic groups (C-BCS). C-BCS possessed the chartreuse fluorescence in aqueous media, which transferred to strong blue fluorescence in the presence of oleanolic acid. This sensing ability of C-BCS for oleanolic acid exhibited the high selectivity among all kinds of biomolecules and ions. The good linearity between the fluorescence intensity and concentration of oleanolic acid was acquired in the range of 0.2 × 10^-6 to 8.0 × 10^-6 M with the detecting limitation of 0.0582 μM. The 1:1 binding process was clarified as oleanolic acid located in the opening cavity composed of two bridging cyanostilbene units and two chiral camphanic groups based on multiple hydrogen bonds and hydrophobic interaction. The detecting ability of C-BCS was applied on sensing oleanolic acid in thin-layer chromatography analysis, imprinting experiment, tap water, and tea samples, suggesting the effective on-site sensing abilities of C-BCS for oleanolic acid in real samples and daily life.

Robust ERα-Targeted Near-Infrared Fluorescence Probe for Selective Hydrazine Imaging in Breast Cancer

Breast cancer is the most common malignancy in women and may become worse when a high concentration of hydrazine is absorbed from the environment or drug metabolite. Therefore, rapid and sensitive detection of hydrazine in vivo is beneficial for people's health. In this work, a novel estrogen receptor α (ERα)-targeted near-infrared fluorescence probe was designed to detect hydrazine levels. The probe showed good ERα affinity and an excellent fluorescence response toward hydrazine. Selectivity experiments demonstrated that the probe had a strong anti-interference ability. Mechanistic studies, including mass spectrometry (MS) and density functional theory (DFT) calculation, indicated that intermolecular charge transfer (ICT) progress was hindered when the probe reacted with hydrazine, resulting in fluorescent quenching. In addition, the probe could selectively bind to MCF-7 breast cancer cells with excellent biocompatibility. The in vivo and ex vivo imaging studies demonstrated that the probe could rapidly visualize hydrazine with high contrast in MCF-7 xenograft tumors. Therefore, this probe can serve as a potential tool to robustly monitor hydrazine levels in vivo.

An effective long-wavelength fluorescent sensor for Cu2+ based on dibenzylidenehydrazine-bridged biphenylacrylonitrile

Although numerous fluorescence sensors for Cu²⁺ have been presented, a long-wavelength sensor in aqueous media has rarely been reported as expected due to practical application requirements. In this work, a novel AIE molecule (DHBB) containing two biphenylacrylonitrile units bridged by dibenzylidenehydrazine was prepared. It possessed the merits of long-wavelength emission, good emission in aqueous media, and multiple functional groups for binding Cu²⁺. It exhibited good sensing selectivity for Cu²⁺ among all kinds of tested metal ions. The detection limit was as low as 1.08 × 10^-7 M. The sensing mechanism was clarified as 1:1 stoichiometric ratio based on the binding cooperation of O and N functional groups of DHBB. The selective sensing ability for Cu²⁺ remained stable at pH = 5-9 and was influenced little by other metal ions. The Cu²⁺ sensing ability of DHBB was applied in real samples with 96% recovery rate. The bio-imaging experiment of living cells suggested that DHBB possessed not only good bio-imaging performance but also sensing ability for Cu²⁺ in living environments. This work suggested the good application prospect of DHBB to sense Cu²⁺ in real samples and living environment.

An effective dual sensor for Cu2+ and Zn2+ with long-wavelength fluorescence in aqueous media based on biphenylacrylonitrile Schiff-base

Although some sensors for Cu²⁺ and Zn²⁺ had been reported, the sensor with long-wavelength emission in aqueous media for in-situ detecting Cu²⁺ and Zn²⁺ was always expected. Herein, a biphenylacrylonitrile Schiff-base (OPBS) with large aromatic conjugated system was designed and synthesized in yield of 82%. OPBS possessed excellent long-wavelength fluorescence at 550-750 nm in aqueous media, which selectively response to sense Cu²⁺ with quenched fluorescence and Zn²⁺ with chromotropic fluorescence from red to yellow. The detection of Cu²⁺ and Zn²⁺ were realized without mutual interference in their coexistence system by means of the assistance of ATP. The detection limits were 2.3 × 10^-7 M for Cu²⁺ and 1.8 × 10^-6 M for Zn²⁺, respectively. The sensing mechanism was elucidated by binding MS spectra, fluorescence Job's plot and ¹H NMR spectra. Moreover, OPBS exhibited good bioimaging performance and the in-situ sensing abilities for Cu²⁺ and Zn²⁺ in living cells, suggesting the application potential for detecting Cu²⁺ and Zn²⁺ in both vitro assay and vivo environment.

A novel colorimetric and ratiometric fluorescence probe based on 'C-CN' for detection of hydrazine and its imaging in living cells and mouse

Hydrazine plays an important role in chemistry, pharmaceuticals, agriculture and aerospace. However, it is not to be underestimated and has been identified as harmful to the human body. Therefore, it is significant and urgent to develop the detection of hydrazine in vivo and in vitro. Here, the probe TAN was synthesized by using benzothiazole derivatives as the fluorophore and 2,3-diaminomaleonitrile as the identified group to detect hydrazine. The presence of hydrazine resulted in a colorimetric and ratiometric fluorescence response of the probe based on the formation of hydrazone. The detection limit of TAN was 0.31 µM for hydrazine. In addition, the probe TAN was successfully used to visualize hydrazine in living HepG-2 cells and mouse with low cytotoxicity and excellent biocompatibility.

Environment-sensitive emission of anionic hydrogen-bonded urea-derivative-acetate-ion complexes and their aggregation-induced emission enhancement

Anions often quench fluorescence (FL). However, strong ionic hydrogen bonding between fluorescent dyes and anion molecules has the potential to control the electronic state of FL dyes, creating new functions via non-covalent interactions. Here, we propose an approach, utilising ionic hydrogen bonding between urea groups and anions, to control the electronic states of fluorophores and develop an aggregation-induced emission enhancement (AIEE) system. The AIEE ionic hydrogen-bonded complex (IHBC) formed between 1,8-diphenylnaphthalene (p-2Urea), with aryl urea groups at the para-positions on the peri-phenyl rings, and acetate ions exhibits high environmental sensitivities in solution phases, and the FL quantum yield (QY) in ion-pair assemblies of the IHBC and tetrabutylammonium cations is more than five times higher than that of the IHBC in solution. Our versatile and simple approach for the design of AIEE dye facilitates the future development of environment-sensitive probes and solid-state emitting materials.

An effective fluorescent sensor for ClO- in aqueous media based on thiophene-cyanostilbene Schiff-base

Although some reports on sensing ClO^- had been presented, the ClO^- sensor with high selectivity and sensitivity in aqueous media was still expected. Herein, an effective fluorescent sensor for ClO^- in aqueous media was designed and synthesized by simple procedure based on cyanostilbene derivative (TCS). TCS exhibited strong fluorescence in aqueous media, which could be selectively quenched by ClO^- among various species. The detection limit was as low as 3.2 × 10^-8 M. The sensing mechanism of the oxidation of sulfur in thiophene unit was confirmed by the FT-IR spectrum, fluorescence Job's plot, ¹H NMR spectrum and MS spectrum. This sensor was successfully applied on detecting ClO^- in real sample and living-cell imaging, suggesting its potential application for sensing ClO^- in both vitro assay and vivo environment.

Construction of a mitochondria-targeted ratiometric fluorescent probe for monitoring hydrazine in soil samples and culture cells

Isoniazid and its major metabolite, hydrazine (N₂H₄), may interfere with mitochondrial function and have negative effects on cells. Consequently, an understanding of the role of N₂H₄ in mitochondria is highly desirable for protecting human health. Herein, we report a novel mitochondria-targeted ratiometric fluorescent probe (Mitro-N₂H₄) for N₂H₄ detection. Mitro-N₂H₄ exhibited an attenuation of green emission at 521 nm and an enhancement of yellow emission at 590 nm in the presence of N₂H₄ because of hydrazinolysis, indicating that it can be used as a ratiometric chemosensor for N₂H₄ with high selectivity and sensitivity. Such on-site monitoring of N₂H₄ vapour using test strips and N₂H₄-moistened soil analysis demonstrated its advantages in potential application for the convenient sensing of N₂H₄. Moreover, the rationally designed probe has many potential applications for imaging N₂H₄ produced in situ during the metabolism of isoniazid in living cells based on the ratio of the fluorescent signal.

"Turn-on" fluorescent sensor for Th4+ in aqueous media based on a combination of PET-AIE effect

Previously reported fluorescent sensors for Th⁴⁺ experienced emission quenching or generated false positive signal upon aggregate formation in aqueous media. Herein, a simple and novel thorium sensor (CDB-BA) based on cyanodistyrene structure was designed and synthesized, which integrated the highly emitting characteristic of AIE effect and off-on response of PET modulation for the first time to construct the "turn-on" fluorescent probe for Th⁴⁺. Besides excellent selectivity, CDB-BA exhibited remarkable fluorescent enhancement which was linearly related to the concentration of Th⁴⁺ in the range of 0.25-8 μM. The detection limit was attained 0.074 μM, which was lower than that of most previously reported sensors. The mechanism of tris-chelate complex of CDB-BA with Th⁴⁺ was confirmed by mass spectra, IR spectra and DFT calculation. The excellent Th⁴⁺ sensing ability of CDB-BA was successfully applied to detecting Th⁴⁺ on TLC plates, in real water samples and living-cell imaging. This work suggested that the combination of AIE and PET photophysical mechanism could offer the merits of minimized background and enhanced signal fidelity to develop novel "turn-on" fluorescent probe in complicated aqueous environment and biological research.

The aqueous dependent sensing of hydrazine and phosphate anions using a bis-heteroleptic Ru(II) complex with a phthalimide-anchored pyridine-triazole ligand

Selective turn-on luminescence properties are shown by a non-luminescent metalloreceptor upon the addition of phosphate anions in CH3CN and hydrazine in CH3CN/H2O (6/4, v/v). The non-luminescent metalloreceptors [RuII(phen)2(TpH)]2PF6- (RtpH) and [RuII(Phen)2(TpI)]2PF6- (RtpI) {phen = 1,10-phenanthroline; TpH = 2-(2-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)ethyl)isoindoline-1,3-dione; and TpI = 2-(2-(5-iodo-4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)ethyl)isoindoline-1,3-dione} were synthesized and characterized. Both metalloreceptors have excellent sensing properties for phosphate anions (H2PO4- and H2P2O72-) over other anions in CH3CN. The limit of detection (LOD) values were calculated to be 79 nM and 48 nM for H2PO4- upon addition to RtpH and RtpI, respectively. Noncovalent interactions play a key role in the sensing of phosphate anions, among which the halogen-anion interaction showed superior recognition properties over the hydrogen-anion interaction. Comparative electrochemical experiments, 1H NMR titration, 31P NMR titration, and lifetime studies also show that RtpI has better sensing properties, as evidenced by its more drastic emission response to H2PO4- anions compared with RtpH. Moreover, the metalloreceptors showed a remarkable fluorescence increase (at ∼584 nm) upon the addition of hydrazine, without the interference of other amines in CH3CN/H2O (6/4, v/v). Interestingly, fluorescence enhancement was observed within live HeLa cells upon hydrazine addition, which is caused by the efficient photoinduced electron transfer process.

A Michael addition reaction-based fluorescent probe for malononitrile detection and its applications in aqueous solution, living cells and zebrafish

It is highly desirable to detect malononitrile in organisms and human bodies owning to its inherent toxicity. With dicyanovinyl as the recognition site, a Michael addition reaction-based fluorescent probe Hcy-DCV was developed for malononitrile detection. A notable advantage of this probe is that it responds quickly to malononitrile without any additive to speed the sensing reaction. It has a good water solubility and the detection limit was determined to be 6.92 ppb in 100% aqueous solution. In particular, Hcy-DCV exhibited good selectivity towards malononitrile over other interfering substances including hydrazine and other active methylene compounds. The probe was applied successfully to quantitate malononitrile in pure water with satisfying recovery and relative standard deviation. Additionally, the ability of visualizing malononitrile by using probe-coated strip papers was displayed, which may facilitate the on-site detection of malononitrile. Moreover, the bioimaging of malononitrile in living H1975 cells and zebrafish larvae was also demonstrated. All the experimental results suggested the potential of Hcy-DCV for practical detection of malononitrile in both environmental and biological samples.

Hydrazine Detection during Ammonia Electro-oxidation Using an Aggregation-Induced Emission Dye

Ammonia electro-oxidation is an extremely significant reaction with regards to the nitrogen cycle, hydrogen economy, and wastewater remediation. The design of efficient electrocatalysts for use in the ammonia electro-oxidation reaction (AOR) requires comprehensive understanding of the mechanism and intermediates involved. In this study, aggregation-induced emission (AIE), a robust fluorescence sensing platform, is employed for the sensitive and qualitative detection of hydrazine (N₂H₄), one of the important intermediates during the AOR. Here, we successfully identified N₂H₄ as a main intermediate during the AOR on the model Pt/C electrocatalyst using 4-(1,2,2-triphenylvinyl)benzaldehyde (TPE-CHO), an aggregation-induced emission luminogen (AIEgen). We propose the AOR mechanism for Pt with N₂H₄ being formed during the dimerization process (NH₂ coupling) within the framework of the Gerischer and Mauerer mechanism. The unique chemodosimeter approach demonstrated in this study opens a novel pathway for understanding electrochemical reactions in depth.

A simple "turn-on" fluorescence sensor for salicylaldehyde skeleton based on switch of PET-AIE effect

The selective detection of salicylaldehyde skeleton is of great significance in phytochemistry and biological research but rarely reported. In this research, a simple and highly selective "turn-on" fluorescence sensor (CDB-Am) for salicylaldehyde skeleton was developed based on switch of photoinduced electron transfer (PET) and aggregation-induced emission (AIE). CDB-Am bearing amino-cyanodistyrene structure responded to salicylaldehyde in the range of 3.1 to 40 μM with a detection limit of 0.94 μM. The sensing process of formation of Schiff-base adduct CDB-SA was confirmed by ¹H NMR, MS, and FT-IR spectra, revealing that a recovered AIE property accounted for the turn-on fluorescence response of CDB-Am and the intramolecular hydrogen bonding played a crucial role in the disruption of PET process. This sensing ability was successfully applied for both fluorescence qualitative test of salicylaldehyde skeleton on TLC analysis and quantitative detection of salicylaldehyde skeleton with good accuracy in the root bark of Periploca sepium, suggesting the extensive applications in phytochemistry and traditional Chinese herbal medicine. Furthermore, CDB-Am exhibited the first excellent fluorescence imaging ability in detecting salicylaldehyde skeleton in a living system. This work supplied a new strategy of preparing a novel "turn-on" fluorescence probe for detecting salicylaldehyde skeleton in complex environments and living bodies.

A “turn-on” fluorescent sensor for cytosine in aqueous media based on diamino-bridged biphenyl acrylonitrile

A “turn-on” fluorescent sensor for cytosine in aqueous media was prepared.

π-Extended Tetraphenylethylene Containing a Dicyanovinyl Group as an Ideal Fluorescence Turn-On and Naked-Eye Color Change Probe for Hydrazine Detection

A π-extended tetraphenylethylene derivative 1 was developed as a fluorescent "turn-on" and "naked-eye" color change probe for hydrazine detection. Probe 1 was composed of the representative AIE luminogen (AIEgen), tetraphenylethylene, and a dicyanovinyl group was adopted for hydrazine recognition. Upon exposure of hydrazine, probe 1 immediately gave a significant aggregation-induced emission around 575 nm and excellent photostability. A naked-eye color change was also observed from red to yellow. Moreover, probe 1 was simply coated with a glass-backed silica gel-coated thin-layer chromatography plate, showing rapid and on-site detection of hydrazine vapor.

A novel triphenylamine-based bis-Schiff bases fluorophores with AIE-Activity as the hydrazine fluorescence turn-off probes and cell imaging in live cells

Developing a specific and sensitive method for endogenous hydrazine detection in living systems is valuable to understand its various pathological events. In this work, two novel fluorescent chemosensors (C1, C3) based on triphenylamine Schiff-base derivative and reference dyes (C2, C4) were prepared in relatively high yield (more than 72% yield). The aggregation induced emission (AIE) properties of sensors were investigated through UV-Visible, dynamic light scattering, X-ray diffraction, fluorescence spectrophotometric analyses as well as scanning electron microscope images (SEM). The results indicated that probes C1 and C3 exhibited strong AIE property in DMF/H₂O (1:1, v/v) mixture system with brilliant yellow fluorescence emission (560 nm) observed under 365 nm UV lamp. The experiments of sensing indicated that probes C1 and C3 possessed the sequentially detecting abilities for hydrazine with high sensitivity, specificity as well as an extremely low detection limit (55.1 nM), which was due to blocking of AIE process of probes C1 and C3 by special chemical reaction (-CHN- moiety transformed into -CH₂-NH- group) after hydrazine addition, resulting in the increase in water solubility and a weak emission in aqueous media. Furthermore, ¹H NMR, SEM and fluorescence titration experiment was also conducted to confirm the sensing mechanism. For biological application, probes C1 and C3 presented a good bio-imaging performance and showed the similar fluorescence quenching after adding hydrazine. Therefore, the probes are suitable for the fluorescence imaging of exogenous hydrazine in HeLa cells.

Cellulose-based fluorescent sensor for visual and versatile detection of amines and anions

It is practical and challenging to construct ultrasensitive and multi-responsive sensors for visual and real-time monitoring of the environment. Herein, a cellulose-based multi-responsive fluorescent sensor (Phen-MDI-CA) is fabricated, and realizes a visual and ultrasensitive detection of not only various amines but also three anions based on the change of the fluorescence and/or visible colors. Once exposure to various amines in both the solution and vapor state, the Phen-MDI-CA solution and test paper exhibit different fluorescence colors, which can be used to distinguish triethylamine, ethylenediamine, methylamine, aniline, hydrazine and pyrrolidine from other amines. Moreover, via combining the Phen-MDI-CA with the Phen-MDI-CA/malachite green ratiometric system, phosphate (PO₄^3-), carbonate (CO₃^2-) and borate (B₄O₇^2-) can be visually and accurately recognized depending on the change of the visible and fluorescence colors. In fluorescent mode, the LOD for B₄O₇^2-, PO₄^3- and CO₃^2- ions is as low as 0.18 nmol, 0.69 nmol and 0.86 nmol, respectively. Significantly, the Phen-MDI-CA can readily make a qualitative and quantitative detection of B₄O₇^2-, PO₄^3- and CO₃^2- anions in the mixture of anions. The state-of-the-art responsive behavior of Phen-MDI-CA originates from the amplification effect of cellulose polymer chain and the differentiated interactions between the sensor and analytes.

First fluorescent sensor for curcumin in aqueous media based on acylhydrazone-bridged bis-tetraphenylethylene

This work designed and synthesized the first organic fluorescent sensor for curcumin in aqueous media based on red-to-green fluorescence change of acylhydrazone-bridged bis-tetraphenylethylene (Bis-TPE). Bis-TPE was prepared by condensation of formyltetraphenylethylene with dihydrazide oxalate in 86% yield. It has the large conjugated electron effect with strong red AIE fluorescence in aqueous solution. It displayed high selective sensing ability for curcumin with red-to-green fluorescence change in THF-H₂O (5:95). The detection limit was as low as 1.15 × 10^-7 M. The sensing mechanism was confirmed as 1:1 stoichiometric ratio based on quadruple hydrogen bonds. Bis-TPE was successfully applied for analyzing curcumin of ginger and living cell imaging, supplying a new detecting strategy for curcumin in real sample and living environment.

Dual-Mode Photonic Sensor Array for Detecting and Discriminating Hydrazine and Aliphatic Amines

Colorimetric chemosensors have attracted tremendous interest for sensing hazardous substances in an uncomplicated and economical manner. Herein, a series of push-pull dicyanovinyl-substituted oligothiophene derivatives were designed, and the impacts of different end-cappers on their photophysical properties were comprehensively investigated. Interestingly, combined with a zinc porphyrin derivative (Zn-TPP), one dicyanovinyl-substituted oligothiophene derivative (NA-3T-CN) can be further developed into colorimetric and fluorescent sensor array for dual-mode detection of aliphatic amines and hydrazine. The obtained sensors showed satisfactory results between optical response and analyte's concentration both in selective single-sensor type and in enhanced multisensory mode. Based on the fluorescence change of the NA-3T-CN system, the detection limit for N₂H₄ was calculated to be around 1.22 × 10^-5 mol/L in THF. The stained TLC-supported sensor array offers obvious optical changes for down to 0.5 wt % hydrazine solution for naked-eye sensing. An aromatic amine like aniline has no obvious effect on the dicyanovinyl-substituted oligothiophene derivatives. We also found that a zinc porphyrin derivative has an obvious colorimetric response to the presence of hydrazine, ethanolamine, and aniline. Furthermore, smartphone-enabled readout system and data treatment based on RGB changes of the sensor array were performed, and the discrimination capability among hydrazine, aliphatic amines, and aromatic amine was satisfactory. In this regard, related push-pull oligothiophene derivatives not only can be regarded as models for a fundamental understanding of the relationship between molecular structure and photophysical properties but also present potential applications in the field of real-time and visual detection of hazardous chemicals.

Double-detecting fluorescent sensor for ATP based on Cu2+ and Zn2+ response of hydrazono-bis-tetraphenylethylene

Although all kinds of sensors with unique detecting ability for one guest were reported, the fluorescence sensor with multiple detecting abilities was seldom presented. This work designed and synthesized a novel AIE fluorescence probe bearing double detecting for ATP based on Cu²⁺ and Zn²⁺ response of hydrazono-bis-tetraphenylethylene (Bis-TPE). Bis-TPE was prepared in 82% yield with simple procedure. It exhibited strong red AIE fluorescence based on the large conjugated electron effect in aqueous media. It showed outstanding selective sensing abilities for Cu²⁺ by strong fluorescence quenching and for Zn²⁺ by red-orange fluorescence change. The sensing mechanism of 1:1 stoichiometric ratios was confirmed by ¹H NMR and MS study. The strong red fluorescence of Bis-TPE + Cu²⁺ system could be recovered by adding ATP. The orange fluorescence of Bis-TPE + Zn²⁺ system could be quenched by adding Cu²⁺ and then was recovered by adding ATP. These double detecting abilities for ATP with the "off-on" red fluorescence in Bis-TPE + Cu²⁺ system and "allochroic-off-on" orange fluorescence in Bis-TPE + Zn²⁺+Cu²⁺ system were successfully applied to test Cu²⁺, Zn²⁺ and ATP in test paper and living cell imaging, displaying the good application prospects for sensing Cu²⁺, Zn²⁺ and double detecting ATP in the complicated environment.

Bis-biphenylacrylonitrile bridged with crown ether chain: a novel fluorescence sensor for Fe3+ in aqueous media

A novel fluorescence sensor for Fe³⁺ in aqueous media was developed and applied for living-cell imaging.

A sensitive and selective fluorescent probe for hydrazine with a unique nonaromatic fluorophore

To achieve sensitive, selective and facile detection of hydrazine in environmental and biological systems, a fluorescent probe (Che-Dcv) with a unique nonaromatic fluorophore was developed. Upon hydrazine addition in 20% DMSO–PBS buffer (pH = 7.4, 10 mM, v/v) at room temperature, the probe displayed a strong emission at 496 nm along with a color change from brown-red to yellow. The response was attributed to the reaction of dicyanovinyl groups with hydrazine to afford hydrazone, which was supported by ¹H NMR and HRMS. The detection limit of Che-Dcv for hydrazine was estimated to be as low as 1.08 ppb and good selectivity over amines including hydroxylamine was observed. Then, the potential of probe-coated test papers to detect hydrazine in solution and vapor phase was demonstrated. Moreover, the bioimaging of hydrazine in living H1975 cells was performed successfully.

A novel fluorescent probe for hydrazine with low detection limit and large Stokes shift was developed.

A novel 'turn-on' coumarin-based fluorescence probe with aggregation-induced emission (AIE) for sensitive detection of hydrazine and its imaging in living cells

An aggregation-induced emission (AIE)- and intramolecular charge transfer (ICT)-based probe 1 (7‑hydroxy‑3‑(3‑methyl‑isoxazol‑5‑yl)‑chromen‑2‑one) that is highly selective for N₂H₄ has been synthesized, exhibiting a 'turn-on' response toward N₂H₄ in CH₃CN/H₂O solution. The detection limit of the probe was 2.90 ppb, which was evidently lower than the threshold limit value (10 ppb) recommended by the Environmental Protection Agency. Notably, the sensor could be used for the detection of N₂H₄ in living cells.

Highly selective Fe3+ and F-/H2PO4- sensor based on a water-soluble cationic pillar[5]arene with aggregation-induced emission characteristic

A water-soluble cationic pillar[5]arene (CWP5) without lager conjugated construction was first reported as a novel pillar[5]arene-based aggregation-induced emission luminogen (AIEgen), which showed a remarkable aggregation-induced emission (AIE) with the concentration increasing. The AIE effect of CWP5 has affected by different solvent, it had the lowest critical aggregation concentration (CAC) value and highest fluoresence emission intensity in DMSO solution. Simultaneously, CWP5 can serve as a chemosensor for the successively fluorescent detection of Fe³⁺ and F^-/H₂PO₄^- with high sensitivity and selectivity. A rewritable portable test kit made from CWP5 provides a possibility to on-site detection and manufacture of encryption and decryption materials.

A fluorescent sensor for folic acid based on crown ether-bridged bis-tetraphenylethylene

Aggregation-induced emission (AIE) provides a new strategy for preparing fluorescent sensors in aggregated state. In this paper, a series of crown ether-bridged bis-tetraphenylethylene compounds were synthesized in 78-84% yield by a simple procedure. The molecules exhibited excellent AIE properties in THF/H2O solutions and solid films. The investigation on sensing abilities for various biomolecules and metal ions suggested that Bis-TPE-1 possessed obvious response to folic acid, with fluorescence enhancement and blue shift of maximum emission wavelength from 380 nm to 365 nm. The detection limit for folic acid was 6.36 × 10-7 M, and the sensor's selectivity for folic acid was little interfered by the other species. The sensor mechanism was studied by FT-IR, 1H NMR, MS spectra and fluorescence Jobs' plot. The selective sensor for folic acid was applied in test paper and the analyses of real samples of mung bean and spinach. The superior bioimaging performance of Bis-TPE-1 for sensing folic acid was confirmed by the live cell imaging experiments, which indicated its good practical application potential for detecting folic acid.