2-benzothiazoleacetonitrile based two-photon fluorescent probe for hydrazine and its bio-imaging and environmental applications

Bis-chalcone Fluorescent Probe for Hydrazine Ratio Sensing in Environment and Organism

In this paper, four novel hydrazine fluorescent probes X1-X4 with bis-chalcone structure were designed and synthesized. Through the measurement of its optical properties, it is found that it can quickly identify hydrazine, high sensitivity, low detection limit, and good anti-interference ability. The recognition of hydrazine by probes X1-X4 is not affected in the pH range of 4-10, X2 has the highest sensitivity, and the detection limit is as low as 0.336 × 10-7 M. Through Gaussian quantization calculation of probe molecules and their reaction products with hydrazine, it is speculated that the recognition mechanism is the closure of intramolecular charge transfer effect. In addition, the cytotoxicity and imaging of HeLa cells were tested, which showed that probes X1-X4 could be used to detect hydrazine in cells.

Engineering a "turn-on" NIR fluorescent sensor-based hydroxyphenyl benzothiazole with a cinnamoyl unit for hydrazine and its environmental and in-vitro applications

Hydrazine (N2H4), a chemical compound widely used in various industrial applications, causes significant environmental and biological hazards. Therefore, it is crucial to develop methodologies for the visualization and real time tracking of N2H4. In this regard, we have constructed a novel near-infrared fluorescent probe (HBT-Cy) that can effectively detect N2H4 in various samples. HBT-Cy contains 2-(2'-hydroxyphenyl)benzothiazole (HBT), cinnamoyl (Cy), and pyridinium (Py) moieties. Importantly, HBT-Cy exhibits a rapid, selective, and highly sensitive response to N2H4. This response results in the release of HBT-Py and the generation of considerable colorimetric changes along with a significant NIR (near infrared) fluorescence signal, peaking at 685 nm. Advantages of this system include turn on NIR fluorescence with large Stokes shift, (approximately 171 nm), low limit of detection (LOD = 0.11 μM) and quantum yield (0.211). The probe with low cytotoxic behavior demonstrates strong NIR fluorescence imaging capabilities to visualize endogenous and exogenous N2H4 in live cells. This mitochondria-targetable probe shows effective subcellular localization. These results suggest that HBT-Cy is a valuable probe for tracking and investigating the behavior of N2H4 in biological systems and environmental samples.

Advances in Optical Probes for the Detection of Hydrazine in Environmental and Biological Systems

Hydrazine, as a crucial raw material in the fine chemical industry, plays an indispensable role in fuel, catalyst, pesticide and drug synthesis. Due to its good water solubility and high toxicity, hydrazine can cause irreparable damage to water and soil in the environment, and it can also be released by taking certain drugs, which brings potential risks to human health. Therefore, it is vital to develop a method that can specifically detect hydrazine in the environment and in vivo. As an effective analysis and detection tool, fluorescence probe has attracted extensive attention in recent years. In this review, we summarized and classified hydrazine fluorescence probes based on various reaction mechanisms, and discussed their structures and applications in the past ten years. At least, we briefly outline the challenges and prospects in this field.

Theoretical Insights on the Sensing Performance for Newly-synthesized Two-photon Fluorescent N2H4 Probes Based on Spirobifluorence

The development of fluorescent probe for hydrazine (N2H4) detection has attracted much attention due to the important role of N2H4 plays in the fields of medicine, agriculture, biology and environments. In this paper, the optical properties and water solubility of two novel two-photon fluorescent molecular probes (Probe1 and Probe2) before and after the reaction with N2H4 are studied by using the density function theory. The results show that electronic distribution and transition dipole moment of the probes are obviously changed after the reaction with N2H4, thus the optical properties of the molecules are influenced and the detection of N2H4 are realized. In addition, photoinduced electron transfer processes for Probe1 and Probe2 in the presence of N2H4 are theoretically characterized, which explains the experimental observations from the microscopic mechanism. Special attention has been paid on the analysis of the two-photon absorption for the probes with the absence and presence of N2H4 by the response theory method. Both probes with good water solubility show large variation on the two-photon absorption cross section when reacts with N2H4. In particular, the two-photon absorption response of Probe2 is more obvious, so it possesses preferable two-photon fluorescence microscopic imaging ability. More importantly, the receptor effect on the sensing performances of the probes are demonstrated, providing a theoretical reference for the design and synthesis on more efficient two-photon fluorescence N2H4 probes. Our study provides necessary information on the response mechanism of the studied chemosensors and helps to establish the relationship between the structure and optical properties of two-photon fluorescence N2H4 probes.

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.

Synthesis and optical properties of Schiff base derivatives based on 2-(2-hydroxyphenyl)benzothiazole (HBT) and application in the detection of N2H4

Four 2-(2-hydroxyphenyl)benzothiazole-based Schiff base derivatives incorporating different substituents were synthesized. Their optical properties were characterized by UV-visible and fluorescence spectra. The electron-withdrawing and electron-donating actions of substituents can change the orbital energy level distributions of molecules resulting in the difference of their luminescence properties. And the fluorescence microscopic images showed that these derivatives had different aggregation behaviors to form aggregates of different shapes. Furthermore, compound HBT-4 has been proved to have excellent recognition performance for N₂H₄ in real aqueous solution. Finally, HBT-4 could be prepared into a simple test paper as an efficient tool for the rapid detection of N₂H₄.

The preparation of a special fluorescent probe with an aggregation-induced emission effect for detecting hydrazine in water

A novel phenyl-carbazole fluorescent molecule, PCBI, with an AIE effect is used as an excellent special probe for the detection of N2H4 in a DMF–H2O system.

A practical pH-compatible fluorescent sensor for hydrazine in soil, water and living cells

The excellent water solubility of hydrazine (N₂H₄) allows it to easily invade the human body through the skin and respiratory tract, thereby damaging human organs and the central nervous system. To realize the monitoring of N₂H₄ effectively, first, coumarin was used to construct an inner alicyclic ring as the reaction site, extending the conjugation and strengthening the rigidity of the probe Co-Hy to improve its luminescence performance and enhance its ability to resist acids and alkalis. Second, we introduced a carboxyl group at the ortho position of the inner alicyclic ring to improve the water solubility of Co-Hy, and its strong electron pulling effect increased the activity of the reaction site. Spectroscopy experiments showed that Co-Hy featured excellent water solubility, high pH resistance (pH 4-11), excellent selectivity, fast analysis speed (within 5 minutes), and a low detection limit toward N₂H₄ (69 nM, 2.2 ppb). In addition, test-strip, spray, and cell-imaging experiments confirmed the outstanding application potential of Co-Hy for convenient N₂H₄ analysis in a variety of environments.

A coumarin-fused 'off-on' fluorescent probe for highly selective detection of hydrazine

Hydrazine is a kind of widely used industrial raw material and a toxic biochemical reagent. Due to its toxic to organisms, hydrazine has been classified to be a hazardous environmental pollutant. It is urgent to develop fluorescent probe tools for selective sensitivity detection of hydrazine in the environment and the body. We developed here a new coumarin-based fluorescent probe for hydrazine detection. The probe can selectively detect hydrazine over other environmental and endogenous interfering analytes with a large off-on fluorescence response. The detection limit is 8.55 ppb, which is well below the allowed threshold limit value. The sensing mechanism is hydrazine-induced pyrazole ring formation, which is confirmed by HRMS and DFT calculation methods. Additionally, the probe could also be applied for hydrazine imaging in living HeLa cells.

An ICT-based fluorescent probe with a large Stokes shift for measuring hydrazine in biological and water samples

As a strong reductant and highly active alkali, hydrazine (N₂H₄) has been widely used in chemical industry, pharmaceutical manufacturing and agricultural production. However, its high acute toxicity poses a threat to ecosystem and human health. In the present study, a ratiometric fluorescent probe for the detection of N₂H₄ was designed, utilizing dicyanoisophorone as the fluorescent group and 4-bromobutyryl moiety as the recognition site. 4-(2-(3-(dicyanomethylene)-5,5-dimethylcyclohex-1-enyl) phenyl 4-brobutanoate (DDPB) was readily synthesized and could specially sense N₂H₄ via an intramolecular charge transfer (ICT) pathway. The cyclization cleavage reaction of N₂H₄ with a 4-bromobutyryl group released phenolic hydroxyl group and reversed the ICT process between hydroxy group and fluorophore, turning on the fluorescence in the DDPB-N₂H₄ complexes. DDPB exhibits a low cytotoxicity, reasonable cell permeability, a large Stokes shift (186 nm) and a low detection limit (86.3 nM). The quantitative determination of environmental water systems and the visualization fluorescence of DDPB test strips provides a strong evidence for the applications of DDPB. In addition, DDPB is suitable for the fluorescence imaging of exogenous N₂H₄ in HeLa cells and zebrafish.

A seminaphthorhodafluor-based near-infrared fluorescent probe for hydrazine and its bioimaging in living systems

Hydrazine (N₂H₄) has been classified as a potential carcinogen with its high toxicity, which can be readily absorbed through the skin or via breathing directly. Although some fluorescent probes have been developed for imaging of N₂H₄, very little can be used for imaging of N₂H₄ in vivo because of its short emission wavelength. In this study, a new colorimetric and near-infrared (NIR) fluorescent probe CF-1 based on a seminaphthorhodafluor dye was successfully designed and used for hydrazine determination. Upon reaction with N₂H₄, probe CF-1 showed obvious off-on NIR emission spectrum centered at 657 nm, as well as a distinct color change that can be distinguished by the naked eye. The results of fluorescence spectrum experiments indicated that probe CF-1 has high selectivity and low detection limitation (40.6 nM in the solution). Probe CF-1 has low cytotoxicity and was applied to imaging hydrazine in mitochondria of HeLa cells and in zebrafish.

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.

A novel dicyanoisophorone based red-emitting fluorescent probe with a large Stokes shift for detection of hydrazine in solution and living cells

A novel dicyanoisophorone based fluorescent probe HP was developed to detect hydrazine. Upon the addition of hydrazine, probe HP displayed turn-on fluorescence in the red region with a large Stokes shift (180nm). This probe exhibited high selectivity and high sensitivity to hydrazine in solution. The detection limit of HP was found to be 3.26ppb, which was lower than the threshold limit value set by USEPA (10ppb). Moreover, the probe was successfully applied to detect hydrazine in different water samples and living cells.

A renewable test strip combined with solid-state ratiometric fluorescence emission spectra for the highly selective and fast determination of hydrazine gas

We developed a new technique combining a renewable test strip and solid-state ratiometric fluorescence readout for the fast capture and quantification of N₂H₄ gas.