Fluorescent probe for imaging N2H4 in plants, food, and living cells and for quantitative detection of N2H4 in soil and water using a smartphone

Hydrazine is volatile and highly toxic, causing severe harm to water, soil, air, and organisms. Therefore, real-time detection and long-term monitoring of hydrazine are crucial for environmental protection and human health. Herein, an "OFF-ON" fluorescent probe 5-((10-ethyl-2-methoxy-10 H-phenothiazin-3-yl)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione (MPD) for hydrazine detection through a nucleophilic addition reaction was developed. MPD could exclusively identify hydrazine through colorimetric and fluorescent dual-channel responses within 30 s, which also demonstrated high sensitivity (detection limit, 12 nM) and a wide pH range (6 -12). The sensing mechanism of MPD was confirmed using theoretical calculations, where fluorescence was emitted following the recognition of hydrazine because of the disappearance of the photoinduced electron transfer (PET) process. Using a smartphone, MPD enabled the quantitative detection of hydrazine in real water samples and sandy soil. Notably, in the process of detecting hydrazine in actual water samples, the establishment of analytical methods and the completion of rapid quantitative detection only required a smartphone and built-in apps. Additionally, we showed that MPD could recognize hydrazine in various environmental samples, including plants, food, hydrazine vapors, and cells. We believe that the fluorescent probe MPD developed in this study and the established smartphone visualization platform will provide a convenient and effective tool for detecting hydrazine in environmental monitoring, food safety assessment, biological system safety, and other fields.

A Pyrazine-Based Chromophore Photophysical Properties and its Detection for Hydrazine and Acid Vapors

Designed and synthesized linear pyrazine-based D-π-A-π-A probe is investigated to study the colorimetric and emission properties with different polarity index solvents. Their molar extinction coefficients were estimated for each solvent. This TLP probe was investigated in THF/water binary solution aggregates, and a redshifted AIE was observed reaching a water fraction of 70%. Also, this TLP probe was applied to the multifunctional, rapid, sensitive and selective detection of acid-base (TFA/TEA) and hydrazine (N2H4) in colorimetric and fluorimetric sensors. The pyrazine unit probe demonstrated an acidochromic effect and explored the acid-sensing behavior. The TLP probe containing malononitrile functional groups has extensively detected hazardous hydrazine species due to nucleophilic attack of hydrazine at the α-position of dicyano. This TLP probe allowed the quick and fast-sensitive detection of hydrazine hydride with a low detection limit of 1.08 nM. According to the results, the mechanism was confirmed by UV-Vis, PL, NMR and MS spectra for the detection of hydrazine, and further evidence of the protonation-deprotonation process in added TFA/TEA was made by titration studies by 1H NMR. Therefore, this work can be used for test strip kits for multifunction applications.

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.

A thiomorpholine substituted malonyl-coumarin dye for discriminative detection of hydrazine and strong acidity

Detection of toxic hydrazine and harmful strong acidity is of great importance for survival of organisms. In the present paper, a new thiomorpholine substituted malonyl-coumarin dye was synthesized for discriminative detection of hydrazine and strong acidity. At pH 7.4, the fluorescence at 560 nm decreased and that at 496 nm increased upon reaction with hydrazine, which was used for on-site detection of hydrazine vapor and endogenous hydrazine in live cells. From pH 2.0 to 1.2, the fluorescence at 563 nm increased greatly, which could be ascribed to the PET process from thiomorpholine to malonyl-coumarin. The probe was desirable for discriminative detection of toxic hydrazine and strong acidity.

A Ratiometric Fluorescent Probe for N2H4 Having a Large Detection Range Based upon Coumarin with Multiple Applications

Although hydrazine (N2H4) is a versatile chemical used in many applications, it is toxic, and its leakage may pose a threat to both human health and environments. Consequently, the monitoring of N2H4 is significant. This study reports a one-step synthesis for coumarin-based ratiometric fluorescent probe (FP) CHAC, with acetyl as the recognition group. Selected deprotection of the acetyl group via N2H4 released the coumarin fluorophore, which recovered the intramolecular charge transfer process, which caused a prominent fluorescent, ratiometric response. CHAC demonstrated the advantages of high selectivity, a strong capacity for anti-interference, a low limit of detection (LOD) (0.16 μM), a large linear detection range (0-500 μM), and a wide effective pH interval (6-12) in N2H4 detection. Furthermore, the probe enabled quantitative N2H4 verifications in environmental water specimens in addition to qualitative detection of N2H4 in various soils and of gaseous N2H4. Finally, the probe ratiometrically monitored N2H4 in living cells having low cytotoxicity.

A lysosomal targeted fluorescent probe based on coumarin for monitoring hydrazine in living cells with high performance

A lysosomal targeted fluorescent probe based on coumarin for monitoring hydrazine (N₂H₄) in living cells was designed and synthesised. The novel fluorescent probe Cou-Lyso-N2H4, in response to N₂H₄, exhibited good selectivity, low cytotoxicity, and lysosomal localization, which could be suitable for studying the harmfulness of N₂H₄ in subcellular organelles during various physiological processes.

A xanthene-based novel colorimetric and fluorometric chemosensor for the detection of hydrazine and its application in the bio-imaging of live cells

An efficient xanthene-based colorimetric and fluorometric probe (MXI) for the selective detection of hydrazine in solution and in living cells.

A colorimetric and near-infrared ratiometric fluorescent probe for hydrazine detection and bioimaging

Hydrazine (N₂H₄) is extensively used in industry but highly toxic; hence, highly sensitive detection of N₂H₄ is extremely meaningful. Herein, a colorimetric and near-infrared (NIR) ratiometric fluorescent probe named DXM-OH was rationally designed and synthesized based on oxanthrene malononitrile derivative for the specific detection of N₂H₄. The dicyanovinyl group in DXM-OH was served as the recognition unit for N₂H₄. DXM-OH showed high sensitivity to N₂H₄ in the range of 1-900 μM, with the limit of detection (LOD) of 0.09 μM (2.87 ppb), which is much lower than the U.S. Environmental Protection Agency standard (10 ppb). Furthermore, the practical applications of DXM-OH in detecting N₂H₄ in real water samples and imaging of N₂H₄ in living cells were demonstrated, indicating its potential utility for N₂H₄ sensing in environmental and biological samples.

A mitochondrion-targeting fluorescent probe for hypochlorite anion in living cells

As momentous reactive oxygen species (ROS), it is necessary to develop high-sensitivity and high-specificity fluorescent probes for tracking hypochlorite anion (ClO^-) in environmental and biological systems. Herein, a kind of red luminescent carbon dots (NS-dots) was synthesized by one-step solvothermal method to detect ClO^- in PBS buffer solution (V_PBS:V_EtOH = 100:1, pH = 7.4). The NS-dots has high sensitivity and low detection limit (13.3 μmol/L) for detecting ClO^- with linear range from 6.7 × 10^-5 mol/L to 26.7 × 10^-5 mol/L. Using Rhodamine B (31% at 520 nm in water) as a reference, the NS-dots have a fluorescence quantum yield of 7.2%. Intracellular photostability, mitochondrial targeting properties and the fluorescence imaging towards intracellular ClO^- were demonstrated.

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.

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.

In situ generated chromophore as the indicator for background-free sensing strategy of hydrazine with high sensitivity with in vitro and in vivo applications

A background-free sensing assay for hydrazine was developed by using a fluorescent chromophore generated in situ as the signal indicator.