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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.

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.

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

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.

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.

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 (

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.

In this study, an organic–inorganic temperature-sensitive polymer encapsulating tetraphenylethene (TPE) was designed. Its fluorescence intensity is sensitive to temperature changes and reaches a maximum at normal cell temperature. Firstly, the organic–inorganic hybrid polymer, polyhedral oligomeric silsesquioxane-based-poly(N-isopropylacrylamide) (POSS-b-PNIPAM) with a particular LCST of 37.5 °C, was synthesized by atom transfer radical polymerization. POSS-b-PNIPAM self-assembled in aqueous solutions to form stable micelles and then TPE was assembled into the micelles in water. The fluorescence intensity of TPE encapsulated in POSS-b-PNIPAM can be tuned by changing the temperature. The fluorescence intensity of TPE encapsulated in POSS-b-PNIPAM reached a maximum at 37 °C, which is much higher than the TPE fluorescence intensity at the same temperature. TPE encapsulated in POSS-b-PNIPAM still showed high fluorescence intensity after entering HeLa cells at 37 °C.

A colorimetric and ratiometric fluorescent probe was developed for the detection of sulfite in sugar. The probe underwent a Michael addition reaction with sulfite, which resulted in significant changes in fluorescence ratios. The probe displayed a fast response (within 30 s) and high selectivity towards sulfite over other anions and bio-thiols. The fluorescence intensity ratios were linearly related to the concentration of SO32− ranging from 0 to 15 μM, and the limit of detection was determined to be as low as 12 nM. The probe was employed to determine the concentration of sulfite in sugar with good recovery.

Abnormal levels of glutathione (GSH) and cysteine (Cys) are associated with some diseases, thus monitoring the dynamic changes and the quantification of GSH/Cys is of great significance in clinical diagnosis. Herein, a smart fluorescent probe was developed for the detection of Cys and GSH, which was constructed with a far-red emitting indole-BODIPY and 7-nitrobenzofurazan (NBD) linked via an ether bond. Upon substitution of the ether with nucleophilic thiolate of GSH/Cys, the probe released indole-BODIPY fluorophore, which gave rise to a significant fluorescence “turn-on” signal at 635 nm. Moreover, Cys induced an intramolecular rearrangement reaction on electrophilic site of NBD, resulting in another emission band at 540 nm. Therefore, this probe can be used to simultaneously detect Cys and GSH in different emission channel. Such capability of the probe has been demonstrated for the measurement of Cys and GSH in human plasmas with fast response and low detection limit (0.64 μM). Furthermore, fluorescence imaging of HeLa cell indicated that the probe was cell membrane permeable and could be used for visualizing GSH and Cys in living cells.

A ratiometric fluorescent probe for ClO− has been developed based on coumarin–hemicyanine, which displayed a colorimetric and fluorescence response to ClO− with high selectivity, fast response (within 2 min) and an extremely low detection limit (0.08 μM). This probe was successfully used to visualize hypochlorite in living cells.

Two simple intramolecular charge transfer compounds (BzBMN and BzFAN), derived from 2-benzyloxy-4-diethylaminobenzaldehyde, have been synthesized. Unlike typical AIEE molecules, the enhanced emission of these compounds in the solid state is accompanied by large red shifts in emission wavelength. Absorption and photoluminescence (PL) spectra of the compounds in solution, film and the X-ray single crystal structures were investigated to understand the mechanism of enhanced emission in the solid state. The results indicate that the bathochromic shift excimer-like emissions originated from dimers induced by the dipole–dipole interaction and long-range ordered arrangement (e.g. J-aggregation), and the enhanced emission is attributed to the restriction of intramolecular rotations caused by multiple intermolecular hydrogen bonding interactions. In addition, it was also observed that BzBMN and BzFAN can facilely form single crystal microbelts and microtubes by a simple reprecipitation method.