A dual-color ESIPT-based probe for simultaneous detection of hydrogen sulfide and hydrazine

Hydrogen sulfide (H2S) and hydrazine (N2H4) are toxic compounds in environmental and living systems, and hydrogen sulfide is also an important signaling molecule. However, in the absence of dual-color probes capable of detecting both H2S and N2H4, the ability to monitor the crosstalk of these substances is restricted. Herein, we developed an ESIPT-based dual-response fluorescent probe (BDM-DNP) for H2S and N2H4 detection via dually responsive sites. The BDM-DNP possessed absorbing strength in the detection of H2S and N2H4, with a large Stokes shift (156 nm for H2S and 108 nm for N2H4), high selectivity and sensitivity, and good biocompatibility. Furthermore, BDM-DNP can be utilized for the detection of hydrogen sulfide and hydrazine in actual soil, and gaseous H2S and N2H4 in environmental systems. Notably, BDM-DNP can detect H2S and N2H4 in living cells for disease diagnosis and treatment evaluation.

A deep-red xanthene-based highly sensitive fluorescent probe for detection of hypochlorite

As an oxidant, deodorant and bleaching agent, the hypochlorous acid (HClO) and hypochlorite (ClO- ) are widely used in corrosion inhibitors, textile dyes, pharmaceutical intermediates and in our daily lives. However, excess usage or aberrant accumulation of ClO- leads to tissue damage or some diseases and even cancer. Therefore, it is necessary to develop a fluorescent probe that specifically identifies ClO- . In this article, we synthesized a deep-red xanthene-based fluorescent probe (XA-CN). The strong electron deficient group dicyano endows the probe XA-CN deep-red fluorescent emission with high solubility, selectivity and sensitivity for ClO- detection. Studies showed that the probe demonstrated turn-off fluorescence (643 nm) at the presence of ClO- in dimethylsulfoxide/phosphate-buffered saline 1:1 (pH 9) solution with a limit of detection of 1.64 μM. Detection mechanism investigation revealed that the electron deficient group -CN and the hydroxyl group was oxidized into aldehyde or carbonyl groups at the presence of ClO- , resulting ultraviolet-visible absorption of the probe blue shifted and turned-off fluorescence. Furthermore, XA-CN was successfully used for the detection of ClO- in tap water samples.

Synthesis and applications of a corrole-based dual-responsive fluorescent probe for separate detection of hydrazine and hydrogen sulfide

Here, a corrole-based dual-responsive fluorescent probe DPC-DNBS was rationally designed and synthesized for the separate detection of hydrazine (N₂H₄) and hydrogen sulfide (H₂S) with high selectivity and sensitivity. The probe DPC-DNBS is intrinsically none fluorescent due to PET effect, however, addition of increasing amount of N₂H₄ or H₂S to DPC-DNBS turned on an excellent NIR fluorescence centered at 652 nm and thereby provided a colorimetric signaling behavior. The sensing mechanism was verified by HRMS, ¹H NMR and the DFT calculations. Common metal ions and anions do not interfere with the interactions of DPC-DNBS with N₂H₄ or H₂S. Furthermore, the presence of N₂H₄ does not affect the detection of H₂S; however, the presence of H₂S interferes with the detection of N₂H₄. Hence, quantitative detection of N₂H₄ must occur in an H₂S-free environment. The probe DPC-DNBS displayed some fascinating merits in separate detection of these two analytes, including large Stokes shift (233 nm), fast response (15 min for N₂H₄, 30 s for H₂S), low detection limit (90 nM for N₂H₄, 38 nM for H₂S), wide pH range (6-12) and outstanding biological compatibility. Significantly, DPC-DNBS was utilized to detect hydrazine in real water, soil and food samples. And its favorable performances for separate detection N₂H₄ and H₂S were successfully demonstrated in HeLa cells and zebrafish, indicating its value of practical application in biology.

Switching to a 'turn-on' fluorescent probe for rapid detection of hydrazine in human breast cancer cells using a test-strip

A fluorescent probe TPSBT was developed to monitor hydrazine detection with a "turn on" response, converting from a "non-responsive" probe by a simple structural modification. The probe shows very weak fluorescence due to the strong ICT process and upon treatment with hydrazine, green fluorescence appears due to the blocking of this ICT by the formation of a hydrazone. The probe TPSBT can detect hydrazine with a very low detection limit (1.22 × 10^-7 M) and within a very short time period of 50 s. Additionally, the probe is able to give a response in live cell imaging (MDA-MB 231) and also in the solid phase.

A benzothiazole-based dual reaction site fluorescent probe for the selective detection of hydrazine in water and live cells

As hydrazine is an environmental pollutant and highly toxic to living organisms, selective and rapid detection is highly needed for the benefit of living organisms as well as the environment. Here, we first introduced a novel benzothiazole conjugated methyldicyanovinyl coumarin probe BTC, with dual recognition sites for hydrazine detection. The incorporation of the methyldicyanovinyl group into the benzocoumarin fluorophore increased the electrophilicity of the lactone ring of the probe BTC facilitating the nucleophilic attack of hydrazine and rapid (within 1 min, low detection limit = 1.7 nM) turn-on sky blue fluorescence with 700-fold fluorescence intensity enhancement was observed via hydrazine-induced lactone ring-opening followed by selective cleavage of the dicyanovinyl group. According to the literature, dicyanovinyl group assisted lactone ring opening has revealed the possibility of hydrazine recognition with a large Stokes shift (140 nm) and a high fluorescence quantum yield (0.67). Here, the DFT study and practical applications of the probe BTC in different water samples have been presented. The probe BTC was also successfully applied for the detection of hydrazine in the vapor phase using paper strips and in live MDA-MB 231 cells.

A novel colorimetric fluorescent probe for detecting hydrazine in living cells and zebrafish

Hydrazine (NH₂ NH₂ ) is a highly toxic organic substance that poses threat to human health. Monitoring hydrazine with high sensitivity and selectivity is very important. Herein, a simple colorimetric fluorescent probe for hydrazine detection, which is a seminaphthorhodafluor derivative containing thiophene-2-carboxylic acid ester reaction site, was rationally constructed. The probe itself exhibits weak fluorescence. The fluorescence is significantly enhanced when hydrazine is added. The probe exhibited a broad linear range (0-1 mM) with satisfactory selectivity and sensitivity (LOD 36.4 nM), which turns out to be an excellent fluorescent probe for monitoring hydrazine. Additionally, the probe was used to track hydrazine in living cells and zebrafish with great success, and the detection performance was satisfying. These results proved that this type of fluorescent probe with the thiophene-2-carboxylic acid ester structure can detect hydrazine with higher selectivity and sensitivity.

A bis-pyrene chalcone based fluorescent material for ratiometric sensing of hydrazine: An acid/base molecular switch and solid-state emitter

In this work, we have designed and synthesized a new fluorescent molecular probe, DPY comprising of pyrene-diacetylpyridine conjugate, which was found to be sensitive to hydrazine as well as protonation. DPY is characterised by a strong emission both in solution (λ_em = 530 nm) as well as in solid state (λ_em = 610 nm), attributed to intramolecular charge-transfer. The probe responds to hydrazine with a ratiometric fluorescence emission change from yellow to blue, due to chalcone cyclisation reaction of α, β-unsaturated carbonyl group resulting in the pyrazoline compound, DPY-Hy, imparting a strong greenish-blue emission in solution. Further, the strong fluorescence emission of DPY in powder and thin film was quenched upon exposure to TFA, and revived upon exposure to TEA. For developing on-site detection protocol, when DPY was drop-casted on nonfluorescent silica plate a vivid naked-eye colour change from orange-red to dark blue was realized. Interestingly, in the aggregated state, DPY exhibited a broad range emission from green to orange in a mixed solvent system of THF:H₂O. A plausible explanation of the photophysical events is substantiated with theoretical calculations.

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 dual-analytes responsive fluorescent probe for discriminative detection of ClO- and N2H4 in living cells

Hydrazine (N₂H₄) and ClO^- are very harmful for public health, hence it is important and necessary to monitor them in living cells. Herein, we rationally designed and synthesized a dual-analytes responsive fluorescent sensor PTMQ for distinguishing detection of N₂H₄ and ClO^-. PTMQ underwent N₂H₄-induced double bond cleavage, affording colorimetric and green fluorescence enhancement with good selectivity and a low detection limit (89nM). On the other hand, PTMQ underwent ClO^--induced sulfur oxidation and displayed red fluorescence lighting-up response towards ClO^- with good selectivity, rapid response (<0.2min) and a low detection limit (58nM). Moreover, PTMQ was successfully employed for in-situ imaging of N₂H₄ and ClO^- in living cells.

Name reactions: strategies in the design of chemodosimeters for analyte detection

The design and synthesis of suitable chemodosimeters for the detection of toxic analytes has become challenging for new researchers nowadays in the molecular recognition field.

A sensitive TICT Probe exhibiting ratiometric fluorescence repose to detect hydrazine in solution and gas phase

A twisted intramolecular charge transfer (TICT) based probe, dicyanovinyl-9-phenylanthracene (DPA) has been designed and synthesized for the detection of hydrazine (N₂H₄) with good limit of detection (LOD, 7.85 nM (0.25 ppb)). Upon interaction with hydrazine the terminal electron withdrawing dicyanovinyl function is changed to electron donating amino/hydrazone function. Consequently, the significant change in the photophysical property of the probe is attributed to a change in orientation of charge propagation. The probe with hydrazine shows ratiometric fluorescence "turn-on" response as well as naked-eye sensitive color change in the medium. The surface morphology studies (SEM and TEM) suggested about amorphousness and crystalline nature of the probe DPA and derivative DPA-HDz, respectively. The conducting behavior of the probe decreases upon interaction with hydrazine because of decrease in amorphousness of the matrix and increase in relatively more rigid crystalline structure. Additionally, the probe been utilized to detect hydrazine vapor in solution and on test paper strip with good naked-eye sensitive responses.

A benzyl carbazate-based fluorescent chemosensor for detecting Zn2+: Application to zebrafish

A benzyl carbazate-based fluorescent chemosensor BCS was designed and synthesized for detection of Zn²⁺ in aqueous media. BCS displayed a notable fluorescence increase with Zn²⁺. Detection limit (1.12 μM) of BCS for zinc ion was much lower than the standard of World Health Organization. BCS was used to analyze the amounts of Zn²⁺ in water samples. Importantly, sensor BCS could be used to image Zn²⁺ in zebrafish, and a fluorescent test strip of sensor BCS for detecting Zn²⁺ could be useful for practical purpose. Sensing process of Zn²⁺ by BCS was demonstrated by DFT calculations, based on an effect of chelation-enhanced fluorescence.

A new "turn-on" fluorescence probe based on hydrazine-triggered tandem reaction

Hydrazine is extremely harmful to the human body. The leakage of hydrazine is liable to cause potential safety hazards. Here, we reported a new fluorescence probe based on the tandem reaction. The hydrazine-triggered hydrazinolysis-cyclization resulted in the formation of the iminocoumarin. The fluorescence intensity at 522 nm of the probe increased after the reaction with hydrazine. There was a linear relationship between the fluorescence intensity and the concentration of hydrazine (0.14-120.00 μM). The LOD of the probe to N₂H₄ was 1.36 ppb. Notably, the probe could detect hydrazine in BT474 cells and tap water.

Rapid switch-on fluorescent detection of nanomolar-level hydrazine in water by a diacetoxy-functionalized MOF: application in paper strips and environmental samples

A diacetoxy-functionalized Zr-based metal–organic framework was employed for the selective, ultra-sensitive, turn-on fluorescent detection of hydrazine in an aqueous medium.

Development of Azo-Based Turn-On Chemical Array System for Hydrazine Detection with Fluorescence Pattern Analysis

A facile turn-on chemical sensor array was developed for hydrazine detection by means of fluorescence pattern recognition. Taking advantage of the unique properties of the azo group, four different fluorogenic probes, Seoul-Fluor (SF)-Azo 01-04, were designed and prepared. SF-Azo 01-04 displayed fluorescence enhancement of up to 800-fold upon reaction with hydrazine, and all probes exhibited excellent selectivity in the presence of various anions and nucleophiles. By employing the probes in a cellulose paper-based array system, the hydrazine concentration was successfully determined by monitoring the change in fluorescent patterns.

A hemicyanine-based fluorescent probe for hydrazine detection in aqueous solution and its application in real time bioimaging of hydrazine as a metabolite in mice

A fluorescent probe, Hcy-Ac, was developed for the monitoring of in situ hydrazine release during the metabolism of isoniazid.

An isophorone-based NIR probe for hydrazine in real water samples and hermetic space

The role of hydrazine in production is not to be underestimated due to its strong reducibility. However, every coin has two sides.

A phthalimide-functionalized UiO-66 metal–organic framework for the fluorogenic detection of hydrazine in live cells

A phthalimide-functionalized Zr(iv) UiO-66 MOF was utilized for fluorogenic detection of hydrazine in HEPES buffer and inside living cells.

A probe with double acetoxyl moieties for hydrazine and its application in living cells

As a common chemical reductant, hydrazine has been widely used in various fields. However, its high toxicity to human and environment have also attracted people's attention. In this work, a new fluorescence "turn-on" probe based on coumarin for hydrazine was successfully synthesized. The probe with double acetoxyl moieties as the reaction sites can obtain the detection limit as low as 2.98 nM for the detection of hydrazine in distilled water, which was lower than the U.S. Environmental Protection Agency standard (10 ppb). In addition, it also responded obvious fluorescence enhancement and high selectivity to hydrazine over other molecules. Furthermore, this probe could visualize the hydrazine in living cells.

Europium ion post-functionalized zirconium metal-organic frameworks as luminescent probes for effectively sensing hydrazine hydrate

We describe a highly sensitive chemical sensor for the detection of the hydrazine hydrate. The chemical sensor was synthesized by simply doping a UiO-66 type metal-organic framework (MOF) with Eu3+ through a well-known post-synthetic modification method. The Eu3+@MOF was characterized by powder X-ray diffraction (PXRD), nitrogen gas adsorption isotherm measurements, FTIR, and ICP-MS. This luminescent probe exhibits strong emission intensity, and more significantly, displays various merits, such as high selectivity with notable photoluminescence quenching effect, rapid response time, and remarkable sensitivity with low detection of limit for hydrazine recognition. Under the optimal experimental conditions, hydrazine hydrate can be detected by this method in concentrations as low as 0.18 μM, which is much lower than the threshold limit value (10 ppb, ≈0.3 μM) of hydrazine exposure recommended by the U.S. Environmental Protection Agency (EPA). More interestingly, a portable film sensing device derived from this MOF display quick response to hydrazine hydrate within 90 s. A possible luminescent quenching mechanism for hydrazine hydrate was also investigated.

A novel fluorescein-based "turn-on" probe for the detection of hydrazine and its application in living cells

We constructed a novel probe for hydrazine detection based on ICT and PET mechanism. Phthalimide and acetyl ester groups were used as the recognition units. Addition of hydrazine produced a turn-on fluorescence at 525nm along with the fluorescent color change from dark to yellow. The probe could selectively detect hydrazine over other related interfering species. The detection limit of the probe for hydrazine was calculated to be 0.057μM which was lower than the EPA standard (0.320μM). Furthermore, the probe could also be applied for the imaging of hydrazine in living cells.