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Chemical warfare agents (CWAs) such as phosgene and nerve agents pose serious threats to our lives and public security, but no tools can simultaneously screen multiple CWAs in seconds. Here, we rationally designed a robust sensing platform based on 8-cyclohexanyldiamino-BODIPY (BODIPY-DCH) to monitor diverse CWAs in different emission channels.

Meat's freshness is closely related to food safety and human health and has received increasing attention nowadays. To on-site visually screen meat freshness in a fast and non-destructive manner, we rationally constructed a series of fluorescent probes (

Biogenic amines (BAs) are a family of nitrogen-bearing natural organic molecules with at least one primary amine, which play an important role in living organisms. Elevated concentration of BAs may cause neuron disorder, Parkinson's disease and many other diseases. Therefore, it is essential to monitor BAs in living organisms. Herein, we reported a resorufin-based fluorescence probe for sensing of various BAs. Upon nucleophilic substitution reaction with BAs, the probe released resorufin, affording to strong fluorescence emission at 592 nm with rapid response (8 min), good selectivity and a low detection limit (LOD = 0.47 μM). The probe has low cytotoxicity and good membrane permeability, and has been successfully used to visualize BAs in living cells and zebrafish with good performance.

The mortality rate of pneumonia increases significantly with the prolongation of illness. In the pursuit of a tool to accurately diagnose pneumonia in its early stages, we designed and synthesized a two-photon near-infrared fluorescent probe (DCQN) to identify increased concentrations of the inflammation marker SO

Hydrazine is an essential chemical in industries, but its high toxicity poses great threats to human health and environmental safety. Hence, it is of great significance to monitor the hydrazine in environment. In this work, we presented a chromogenic and fluorogenic dual-mode sensor RA for the detection of hydrazine based on nucleophilic substitution reaction. A linear relationship was obtained between the fluorescence intensity and the concentrations of N

The reactive oxygen species (ROS) are tightly associated with endoplasmic reticulum (ER) stress. Thus, the deep and visual insight of aberrant ROS fluctuations in the ER can help us better investigate the ER stress-associated pathology. In this work, a fluorescent probe ERC for HOCl detection in the ER based on phenothiazine-derived coumarin platform was developed. In the presence of HOCl, ERC exhibited an emission change from 609 nm to 503 nm within seconds. It also showed high sensitivity (0.44 μmol/L) and superb photostability. Significantly, ERC displayed low cytotoxicity, good cell membrane permeability, and appreciable ER-targetability. Ultimately, the probe was successfully utilized to image exogenous and endogenous HOCl in living cells and reveal the HOCl burst in cisplatin-treated cancer cells.

A complex that was composed of β-cyclodextrin (β-CD) and a flavone derivative (compound 5) was designed as a colorimetric and fluorescence turn-on probe to discriminate thiophenol (PhSH) from bioth...

Phosgene is an indispensable industrial gas that has high toxicity, and has been used as a chemical warfare agent, meaning that it poses a great threat to public security in the case of accidental leakage or terrorist attack. To monitor toxic phosgene, herein, we devised a facile and reliable optical sensor (BODIPY–OHA) based on o-hydroxyaniline (OHA) and BODIPY. The adjacent hydroxyl and amino groups in OHA synergistically couple with phosgene to form benzoxazolinone, thus BODIPY–OHA displays a remarkable color change from light green to yellow and a synchronous fluorescence turn-on response towards phosgene. The sensor can be used to specifically sense phosgene, with some favorable merits such as instantaneous response, ultralow detection limit (0.22 nM), noticeable color and fluorescence changes, as well as a high signal-to-noise ratio. Furthermore, this sensor was fabricated as portable membrane strips to serve as an easy-to-handle kit for highly specific, instantaneous, sensitive and visual detection of gaseous phosgene. Moreover, a simple RGB pattern from the fluorescence of test strips was established to allow quantitative determination of the level of phosgene, which was successfully used to monitor the leakage of phosgene. Therefore, these test strips have great potential for monitoring phosgene in public places and industrial production in the case of accidental leakage or terrorist attack.

Fluorescent probes have been widely used in bioimaging as an efficient and convenient analytical tool. From the initial inorganic nanoparticles and small organic molecules to polymeric nanoparticles, scientific researchers have been trying to develop a probe with strong fluorescence and excellent biocompatibility. In this study, a tetraphenylethylene derivative with AIE properties and hyaluronic acid modified by methacrylic anhydride were combined to prepare a novel nanoparticle (HA-Ac-Pha-C) as a fluorescent probe by a photochemical cross-linking reaction. The fluorescence intensity and size of the nanoparticles were characterized by different techniques. It was confirmed that cross-linked nanoparticles not only showed stronger fluorescence, but also had better photostability while still maintaining 85.9% of the initial intensity after seven days. Moreover, cells and zebrafish imaging experiments also demonstrated that nanoparticles show specific fluorescence labeling for cancer cells and excellent biocompatibility in living organisms.

Sulfur dioxide derivatives are intimately involved in some physiological processes in organisms, and high levels of these substances can cause many diseases. Herein, we rationally prepared a mitochondrion-targeting, in situ-activatable near-infrared (NIR) fluorescent probe (DCQN) by coupling 2-(3,5,5-trimethylcyclohex-2-enylidene)malononitrile with 3-quinolinium carboxaldehyde. DCQN displayed a NIR fluorescence turn-on signal to indicate the presence of HSO3-, along with a considerable hyperchromic shift from light yellow to purple via a 1,4-nucleophilic addition reaction. We were able to use DCQN to instantaneously and quantitatively determine the concentration of HSO3- with high specificity, a low detection limit (24 nM), a large Stokes shift (∼110 nm), and a high contrast ratio. Moreover, DCQN displayed good mitochondrion-targeting abilities and was in situ-activated by HSO3- to produce NIR fluorescence for imaging HSO3- in the mitochondria of live breast cancer cells. Furthermore, DCQN was used to monitor HSO3- in zebrafish with a high contrast ratio.

Spoiled meat contains many pathogenic bacteria; hence, the intake of spoiled food can lead to various illnesses. To screen the freshness of food, in this study, we devised a ratiometric fluorescence sensor dicyanovinyl coumarin (CMDC) for the determination of cadaverine, an important biomarker for the spoilage of meat. CMDC underwent aza-Michael addition with cadaverine, exhibiting high sensitivity, fast response (50 s), and distinct fluorescence color transition. Test strips fabricated using CMDC showed a noticeable color change from red to green when exposed to cadaverine vapor. The test strips were successfully used to visually monitor the spoilage of beef based on the fluorescence color change. Furthermore, the as-developed test strip coupled with a smartphone provides a simple tool for consumers and suppliers to obtain information about meat quality.

Nanoprobes with biocompatibility and strong fluorescence have unique advantages in tumor detection and diagnosis. A nanoparticle with dual fluorescent signals for detecting and imaging of tumor cells was prepared, in which the outer layer of the particle is a hyaluronic acid-modified molecule with aggregation-induced emission properties, and the inner content is the boron-dipyrromethene (BODIPY) derivative. This nanoparticle has low critical micelle concentration, small size, and high fluorescence intensity. Cell imaging experiments showed that it is capable of stable cell imaging with a red and blue fluorescence conversion in response to cancer cells. Furthermore, the zebrafish experiment confirmed that it can be used for biological imaging. Nanoparticles with dual fluorescence response properties of the coated structure provide an effective way for detecting cancer cells.

A near-infrared (NIR) fluorescent probe (Cys-AN) for selective and sensitive detection of cysteine (Cys) was designed and synthesized. The fluorescent probe was water-soluble and had a large Stokes shift of 150 nm, whose detection limit could reach to 0.96 μM in PBS buffer. After we analyzed the HRMS, TLC and optical data, a proposed sensing mechanism for the detection of Cys could result from the Michael addition and intramolecular cyclization reactions between the probe and Cys, followed by intramolecular charge transfer (ICT) process to afford the NIR fluorescent signal at 674 nm. Meanwhile, Cys-AN exhibited low cytotoxicity, and was successfully applied for bioimaging of Cys in living cells.

A fluorescent chemosensor has been developed for discriminative detection of phosgene and a nerve agent mimic diethyl chlorophosphate (DCP), which was comprised of an anthracene-carboxyimide fluorophore and o-phenylenediamine (OPD) reaction site. Upon phosphorylation of OPD, the chemosensor displays an obvious fluorescence turn-on response toward DPC at 588 nm with instant response and a low detection limit (88 nM). By contrast, the chemosensor exhibits a colorimetric and fluorescence enhancement response at 500 nm toward phosgene with fast response (

Thiophenols as high toxic environmental pollutants are poisonous for animals and aquatic organisms. Therefore, it is indispensable to monitor thiophenols in the environment. Herein, a novel near-infrared fluorescent probe was developed for the detection of thiophenols, which was easily prepared by one-step coupling of 2,4-dinitrobenzenesulfonyl chloride with Nile blue. The probe showed a significant near infrared (∼675 nm) fluorescence “turn-on” response to thiophenols with some good features including chromogenic reaction, high sensitivity and selectivity, fast response, near-infrared emission along with low detection limit (1.8 nM). The probe was employed to rapidly and visually determine thiophenols in several industrial wastewaters with good recoveries (90–110%). Moreover, this probe has been demonstrated good capability for imaging thiophenol in HeLa cells.

Fluorescent probes with novel organelle-labeling manner can contribute to verify the unraveling cellular functions of various organelles. In this work, we reported a glutathione (GSH) specific near-infrared fluorescent probe, which was composed of a near-infrared cyanine moiety, a morpholine-containing naphthalimide and a thiol-reactive site. The cationic fluorophore cyanine can be capable of targeting mitochondria while the morpholine group can serve as the lysosome-targeting role. The optical behavior in vitro showed that this probe showed high selectivity toward GSH over other thiol-containing amino acids in near-infrared channel. Similar selectivity was found in bioimaging of living cells. The fluorescence co-localization images confirmed that the probe had a good mitochondria-targeting and lysosome-targeting capability in living cells. Moreover, the probe was endowed with near-infrared emission which was favorable for marking the GSH in vivo. We anticipate that such dual targeting strategy will be helpful to develop multiple organelle-targeting fluorescent probes.

Composite nanomaterials are particularly useful and offer many excellent opportunities for electrochemical sensing application. Depending on the high catalytic activity of bimetallic nanoparticles, the large specific surface area, abundant active edges and co-catalytic function of MoS2 nanosheets, we, for the first time, prepared a novel PtNi bimetallic nanoparticles loaded MoS2 nanosheets (PtNi@MoS2) hybrid material by a co-reduction method for the electrochemical sensing application. The nanocomposite is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), and then casted on a bare glassy carbon electrode (GCE) to fabricate an electrochemical sensor (PtNi@MoS2/GCE). The electrochemical investigation showed that the sensor performed good selectivity and wide linear ranges for the simultaneous detection of dopamine (0.5–150 μM) and uric acid (0.5–600 μM). And the detection limits were down to 0.1 μM (S/N = 3) for both analytes.

Sodium sulfite (Na2SO3) is widely used as a food additive, but the excessive residue of SO32− in food can cause irritative effects and damages to the human body. In this study, we reported a novel near-infrared (NIR) fluorescent probe (DCMQ) for visual detection of SO32− based on a chromogenic reaction. The probe can quantitatively determine SO32− with high specificity and sensitivity, fast response (

A high brightness red fluorescent probe (S-BODIPY) has been developed for the sensitive and specific imaging of HClO/ClO– in vitro and in vivo. This probe exhibits some distinctive features such as excellent resistance to photobleaching, a high fluorescence brightness, high selectivity, as well as a good biocompatibility. Upon oxidation of the thio-ether group into sulfoxide, the probe showed a noticeable ratiometric fluorescence response toward ClO– with fast response (within 30 s) and a low detection limit (59 nM). The probe demonstrated the successful imaging of exogenous and endogenous HClO/ClO– in living HeLa cells, zebrafish, and mice with high signal-to-noise ratios. S-BODIPY allows for the real-time monitoring the level of ClO– in living cells by ratiometric fluorescence imaging, opening up exciting prospects to develop red and even near-infrared BODIPYs with high brightness and good photostability for in vivo imaging.

A novel colorimetric and ratiometric fluorescent probe (Cou-BPO) was readily prepared for specific detection of harmful benzoyl peroxide (BPO). The probe Cou-BPO reacted with BPO via a selective oxidation cleavage-induced cascade reaction of the pinacol phenylboronate group, which resulted in an observable colorimetric and ratiometric fluorescence response towards BPO with a fast response time (

Organic compounds with bright solid-state emission are emerging as versatile materials in many fields. However, traditional fluorescent dyes generally show high-emissive fluorescence in solution but faint or quenched emission in the solid state. Therefore, it remains a great challenge to develop bright solid-state emissive materials based on traditional fluorescent dyes. Herein, we report several solid-state emissive meso-substituted BODIPYs (PhMe3-BODIPY, PhMe-BODIPY, Ph-BODIPY and Me-BODIPY) obtained by using a simple two-step synthesis. Interestingly, these BODIPYs exhibit bright dual-state emission (DSE) with green fluorescence (512–520 nm, fluorescence quantum yield ΦF is up to 85%) in THF and solid-state red emission (601–632 nm, ΦF is up to 32.2%) in the crystalline state. The highly emissive fluorescence in the crystalline state is demonstrated to be due to the formation of J-aggregation. More importantly, the single crystals of the meso-aryl-substituted BODIPYs exhibit an unusual high-contrast mechanochromic property, which displays remarkable fluorescence color changes from red to yellow upon gentle grinding due to the transition from single crystals to microcrystals. Furthermore, strong grinding completely destroys the J-aggregation and leads to the transformation from microcrystals to a free state, hence the fluorescence color becomes green after strong grinding.

An anthracene carboxyimide derivative was synthesized as a colorimetric and fluorogenic sensor to determine NO2- with a rapid response (

An europium functionalized metal-organic fluorescent probe, Eu3+@UiO-66-FDC was constructed by post-synthetic modification through coordination interactions. Eu3+@UiO-66-FDC displayed high selectivity and sensitivity toward Tryptophan (Trp) among all the 20 natural amino acids and other general compounds in food and biological samples, with a wide linear concentration range (0–1000 μM), low detection limit (0.29 μM), and a rapid response (

Two-photon excitation (TPE) photodynamic therapy (PDT) has attracted great interest due to its distinctive properties, e.g., good penetration ability of biological tissues and less damage to healthy tissues. However, the conventional photosensitizers (PSs) for PDT have poor subcellular location capability and low two-photon absorption (TPA) cross section in the phototherapeutic window. Herein, we report a fascinating multi-functional TPE PS, polythiophene nanoparticles (PT NPs), for simultaneous lysosome-targetable fluorescence imaging and PDT. PT NPs show bright yellow fluorescence, good water solubility as well as excellent photo- and pH-stability. Moreover, PT NPs exhibit high singlet oxygen generation quantum yield (∼42%) and large TPA cross section (∼3420 GM). A fluorescence imaging penetration depth of 1800 μm could be reached in the tissue phantom under the TPE mode. Due to these outstanding merits and their unique clathrin- and caveola-independent intracellular uptake pathway, PT NPs have great potential for application in TPE fluorescence imaging and photodynamic therapy.

In this work, a metal-organic framework UiO-66-(COOH)

Photosensitizers (PSs) with aggregation-induced emission (AIE) feature show promising applications in fluorescence imaging-guided photodynamic therapy (PDT) in virtue of their enhanced fluorescence and phototoxicity in aggregate state. Seeking the ideal AIE luminogens (AIEgens) with good capability of generating reactive oxygen species is still urgent. Here we rationally synthesized an acceptor-donor-acceptor (A-D-A) structured AIEgen (BTZPP) and then prepared it into nanoparticles (NPs) through a simple re-precipitation procedure. The obtained BTZPP NPs show a deep-red emission peaked at 635 nm, a large Stokes shift of 195 nm, and a high 1O2 generation quantum yield of 72.3%. Moreover, these NPs can selectively target lysosomes in live cells and image mouse tumor with a high contrast and long-term tracking (up to 14 days) capability. The high-efficiency imaging-guided PDT against cancer cells and tumors is successfully demonstrated in vitro and in vivo.

Doping is an effective approach to regulate the physicochemical properties of carbon dots (CDs) and has received increasing attention in recent years. After CDs are doped with heteroatoms, their electronic structure, nanostructure, and chemical composition will be changed due to the overlapping atomic orbitals of the heteroatoms and carbon atoms, as well as the push/pull electron effect of heteroatoms. As compared with the non-metallic atoms, metal ions have more electron and unoccupied orbitals, and larger atomic radius, doping CDs with metal ions may induce noticeable alterations of the optical, electronic, and magnetic properties by changing the electron density distribution and energy gap of the CDs. In this review, we summarize the synthesis methods of metal ions-doped CDs (M−CDs), discuss the novel physicochemical properties originating from the doping of metal ions, and provide examples of applications in sensing, imaging, phototherapy, optoelectronics, and catalysis. Furthermore, we describe challenges in preparing M−CDs and provide an outlook for their future development.

Excessive sulfite is harmful to human health. To monitor the sulfite level in food, living cells, and organisms, we herein present a high-performance near-infrared (NIR) fluorescent probe DCQN that exhibits chromogenic and NIR fluorescence turn-on response towards sulfite with a rapid response time of 4.5 s, unique specificity, a low detection limit of 24 nM, and a large Stokes shift. DCQN was used for the facile and accurate determination of the sulfite level in real food with high sensitivity and good recoveries (93–105%). In particular, the sulfite present in food samples can be in situ visually detected by DCQN in terms of chromogenic reaction along with fluorescence turn-on indicator. Moreover, DCQN was incorporated into agar hydrogel to serve as a convenient, cheap and portable device for the fast and visual on-site detection of sulfite in food. Furthermore, DCQN was used to achieve in situ tracking and imaging of sulfite in MCF-7 cells and zebrafish with a high contrast ratio and high sensitivity.

Hydrazine and bisulfite are poisonous to the environment and human health, hence it is necessary to monitor hydrazine and bisulfite in the environment and living cells. In this study, we reported a smart fluorescent probe (CMCA) for discriminative detection of hydrazine and bisulfite. The single fluorescent probe can respond to hydrazine and bisulfite with two different sets of colorimetric and ratiometric fluorescence signals together with high selectivity, fast response and low detection limit. The discriminative sensing behaviors of the probe for hydrazine and bisulfite were ascribed to different reaction mechanisms, which were confirmed by 1H NMR and HR-MS spectra. The probe has been successfully used to discriminatively determine hydrazine and bisulfite in industrial wastewater with good recoveries. Furthermore, the probe was employed to visualize hydrazine and bisulfite in live cells from different fluorescence channels with good performance. Therefore, this probe has great potential applications for discriminative detection of hydrazine and bisulfite in the environment and living cells.

A series of highly photostable, lysosome-targeted BODIPYs with tunable fluorescence from green to the near-infrared region was developed. The probes were found to show an accurate lysosome-targeting ability with high selectivity and high photostability under continuous excitation irradiation. The results show that these lysosome-targeted BODIPYs offer a simple and convenient tool for fluorescence imaging of lysosomes, which will be valuable for understanding the activity and function of lysosomes in related cells.

DNA apurinic/apyrimidinic site (AP site) has received much attention due to its importance in disease evolution and development of selective genetic drugs. Fluorescence technique has been widely employed in identifying the AP sequence environment using fluorophores as the AP site-targeting probes. However, the sequence effect on the AP site binding of a ligand should be fully understood for illustrating the binding behavior. Triplex-forming oligonucleotide (TFO) can bind with its partner ds-DNA via specific hydrogen bonding interactions different from the canonical Watson-Crick pattern to form a triplex DNA structure. Due to its wide bioactivity, triplex has been recently investigated using small molecules as the structure identifiers and tuners. In this work, we spectroscopically characterized a novel fluorescent benz[e]indolium probe of BIFS and found that BIFS can selectively target the AP site and its fluorescence is significantly enhanced only when the TFO strand binds to the AP site-containing duplex DNA. The TFO binding restricts the non-radiative twist relaxation process of the excited state BIFS and results in the emissive BIFS. Because BIFS alone in aqueous solution is non-fluorescent, this selective lighting-up emission is advantageous for developing a practical sensor to target the triplex AP site with a weak fluorescence background. This selective recognition of the AP site by the lighting-up fluorescent probe would find wide applications including fluorescently evaluating the triplex-based small molecular binders.

Four thermoresponsive silica-poly(N-isopropylacrylamide-co-butyl methacrylate) materials were prepared by grafting (N-isopropylacrylamide-co-butyl methacrylate) at different ratios on multimodal po...

Hypochlorous acid (HOCl)/hypochlorite (ClO−), an endogenous reactive oxygen species (ROS), plays an important role in a variety of physiological and pathological processes. Herein, a ratiometric fluorescent probe (BIP) for ClO− was prepared, which exhibited a noticeable color change from purple-red to colorless along with a remarkable fluorescence change from bright red to blue in response to ClO−. The probe could quantitatively determine the concentrations of ClO− with large Stokes shift (107 nm), excellent selectivity, fast response, as well as low limit of detection (182 nM). NMR and mass spectral analysis demonstrated that ClO− triggered the oxidative cleavage of the bridge double bond in BIP, resulting in significant changes in color and fluorescence. In particular, BIP was a specific mitochondria-targeted fluorescent probe with excellent photostability, biocompatibility and cell membrane permeability. BIP was successfully used to image intracellular ClO− and its fluctuation in living HeLa cells (human cervical cancer). Furthermore, the probe was employed to visualize the ClO− mediated redox equilibrium within living cells by a ratiometric fluorescence imaging manner. Therefore, BIP has a great potential application for the detecting HOCl, which also offers an effective tool for the investigation of some HOCl related biological processes.

A naphthalimide-based ratiometric fluorescent probe for determining glutathione (GSH) was constructed by installing two oxidized morpholine (e.g. thiomorpholine-S-dioxide and morpholine-N-oxide) components on the “off-to-on” GSH probe. This probe displayed high selectivity towards GSH. As well, the bioimaging application confirmed that this probe was capable of acting as an indicator to monitor the intracellular GSH. Thus, this work provides a promising strategy to construct the ratiometric fluorescent probe.

A novel fluorescent chemodosimeter for thiophenols has been readily developed from a red emitting Indole-BODIPY . The chemodosimeter displays a significant fluorescence turn-on response towards thiophenols based on nucleophilic substitution reaction. A linear relationship was obtained between the fluorescence intensity and the concentrations of thiophenols ranging from 0 to 1.8 μM. The chemodosimeter can determine thiophenols (4-fluorothiophenol, 4-methoxybenzenethiol, p -toluenethiol) with high selectivity, fast response (within 8 min) and extremely low limit of detection (9.8 nM). The chemodosimeter was successfully used to determine the level of thiophenol (PhSH) in industrial wastewater and Bohai Sea water with good recoveries. Furthermore, the chemodosimeter was employed to image thiophenols in cancer cells with good performance and low cytotoxicity. Therefore, this chemodosimeter has great potential application in environment.

Two naphthalimide-based fluorescent probes containing a thiomorpholine (Np-NS) or a sulfoxide-morpholine (Np-NSO) component are reported. The morpholine unit of non-fluorescent Np-NS and Np-NSO can transform into sulphone-morpholine and be accompanied by blue fluorescence upon oxidative stress, ascribed to the formation of sulphone-morpholine on probes. This sensing behavior displays that they can selectively respond to glutathione to generate a green emission by a sulfonamide-based detection moiety both in vitro and in living cells. Interestingly, the different oxidation states of a sulphur atom on a thiomorpholine ring can be utilized to regulate responsiveness of these probes towards glutathione. Such an oxidation strategy would provide a possibility for enhancing the response rate.

Monitoring sulfur dioxide (SO2) derivatives in environment is of great significance due to their harmful effects to the environment and human health. In this study, a fluorescent probe (CZBT) for SO2 derivatives was prepared from 9-ethyl-9H-carbazole-3,6-dicarboxaldehyde and 2-methyl-benzothiazolium, which displayed a noticeable color change from yellow to colorless along with a remarkable fluorescence change from yellow to blue in response to HSO3-. The probe could quantitatively determine the concentration of HSO3- with excellent selectivity, high sensitivity and low limit of detection. 1H NMR and HR-MS spectra demonstrated that a selective 1, 4-nucleophilic addition occurred on the bridge double bond in CZBT. The probe was successfully used to determine the SO2 derivatives in several real water samples with good recovery. Furthermore, the probe was employed for monitoring the level of intracellular HSO3- in HeLa (human cervical cancer) cells by fluorescence imaging. These results indicated that CZBT has a good capability for monitoring SO2 derivatives in environment and living cells.

Sodium metabisulfite (Na2S2O5) is widely used as a bleaching agent and food preservative. However, excess of S2O52− can irritate and damage the human body. In this study, we report a colorimetric and ratiometric fluorescent probe for visual detection of S2O52−. The probe can quantitatively determine S2O52− with high specificity and sensitivity, fast response (

A family of anthracene carboxyimides with multi-color fluorescence have been successfully prepared, and their spectroscopic properties were investigated by UV–vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy. The photostability and solvatochromic fluorescence in organic solvents were also investigated. The parent anthracene carboxyimide 4a displays very strong green fluorescence (Φ F = 0.91 in EtOH), good pH stability and photostability, as well as a large Stokes shift. By attachment of different substituents at the 10-position of the anthracene carboxyimide, the fluorescence maxima could be effectively modulated from 500 nm to 615 nm. The 10-(picolylamine) substituted anthracene carboxyimides 5a and 5b exhibit large Stokes shifts (>80 nm) and significant positive solvatochromic fluorescence in organic solvents due to their intramolecular charge-transfer (ICT) character. Furthermore, cell staining experiments indicate that anthracene carboxyimides have excellent cell membrane permeability and good photo-bleaching resistance in living cells. Particularly, compound 5a is a specific mitochondria-targeting dye with red fluorescence. All these features enable anthracene carboxyimides to serve as promising candidates for bio-labeling/imaging applications.

Aberrant levels of glutathione (GSH) and cysteine (Cys) are key risk indicators for some diseases, hence monitoring the levels of GSH and Cys is of great significance in clinical diagnosis. Herein, a water soluble near-infrared fluorescent probe (CFL-NDB) was readily prepared for fast, sensitive and discriminative detection of GSH and Cys. The probe was constructed with a near-infrared semi-heptamethine cyanine attached to 7-nitrobenzofurazan (NBD) via an ether bond. Upon substitution of NBD with GSH, this probe exhibits a significant fluorescence “turn-on” signal towards GSH at 702 nm with fast response (within 5 min) and low limit of detection (81 nM). In contrast, the probe not only displays the emission at 702 nm but also shows another emission band at 540 nm in the presence of cysteine (Cys). Therefore, this probe can be used to simultaneously detect Cys and GSH from different emission channels. Such capability of the probe has been demonstrated for quantitative determination of Cys and GSH in human plasmas. Furthermore, fluorescence imaging of HeLa cell indicated that the probe could be used for visualizing GSH and Cys in living cells.

Aberrant levels of cysteine (Cys) in living cells are closely related to some diseases; thus in situ visualization of intracellular Cys is very helpful for the investigation of physiological and pathological processes. Herein, we report a dual-channel responsive near-infrared (NIR) fluorescent probe for multicolour imaging of Cys in living cells. The probe was constructed with a NIR BODIPY attached to 7-nitrobenzofurazan (NBD) via an ether bond. Upon substitution of the ether with the nucleophilic thiolate of Cys, a NIR BODIPY fluorophore was released to produce a significant fluorescence-enhanced signal at 735 nm. Moreover, Cys induced an intramolecular rearrangement reaction on the electrophilic site of NBD, resulting in another emission band at 540 nm. This probe exhibited some favorable properties including a dual-channel response, high fluorescence brightness, good photostability, fast response, low detection limit (22 nM) and low cytotoxicity. Furthermore, the probe was successfully applied for multicolour imaging of Cys in living cells.

A chemosensor containing an o-hydroxyaniline unit as the reaction site was developed for colorimetric and fluorimetric detection of phosgene, which showed fast response (15 s), high specificity, and an extremely low detection limit. The chemosensor was incorporated into paper strips for visual detection of phosgene vapor.

A N-2-phenylethyl-substituted 1,4-dihydropyridine derivative (NDHP) containing 5,5-dimethylcyclohexane-1,3-dione and naphthylethylene was designed and synthesized. NDHP acts as a multifunctional fluorescent sensor in dual phases. The crystal structure analysis confirms that the NDHP molecules have highly twisted conformations. The twisted conformation results in aggregation-induced emission properties and solid-state emission, by restricting the intramolecular free rotation in the aggregated or solid state. In the solid state, NDHP exhibits reversible mechanochromic properties as a result of the transition between the amorphous and crystalline states. NDHP also exhibits a rare phenomenon of acid-fumed solid-state emission enhancement owing to the change in packing mode from a zigzag arrangement to J-aggregation. The solid-state stimuli-responsive fluorescence switching is applied to realize a rewritable optical recording media and a multiple output combinational logic system. In solution, NDHP shows a selective fluorescence response for environmentally harmful Hg2+ , with a limit of detection of 2.7 nm. This results from the "turn-on" responsive behavior owing to the Hg2+ -triggered aggregation of the NDHP molecules. NDHP is also used in the imaging of intracellular Hg2+ in HeLa cells. These findings provide a feasible and attractive route for developing multifunctional fluorescent sensors for use in dual phases.