A fluorescence "turn-on" sensor for detecting hydrazine in environment

Phenanthroimidazole-based fluorescence probe for discriminative detecting of hydrazine and bisulfite and its applications in environmental samples

Hydrazine (N2H4) and bisulfite (HSO3-) detection methods are urgently needed due to its harmful to the human health and environment safety. Herein, we reported a dual-response fluorescence probe EPC, which is capable of sequential detection of N2H4 and HSO3- by two different fluorescence signals. The probe EPC itself showed yellow florescence. In presence of N2H4, probe EPC exhibited an obviously fluorescence change (from yellow to green). However, a new addition product came into being after probe EPC mixed with HSO3-, followed with weak yellow emission. More important, probe EPC exhibited excellent fluorescence response properties for N2H4 and HSO3-, such as high sensitivity (0.182 µM for N2H4, 0.093 µM for HSO3-), rapid response (55 s for N2H4, 45 s for HSO3-), excellent selectivity and anti-interference performance. The sensing mechanisms for N2H4 and HSO3- were proved by 1H NMR and MS spectra. Practical applications were studied. EPC based test paper can be utilized for quantitative detecting N2H4 in actual water samples. And, probe EPC has been successfully applied to recognize N2H4 contaminant in soil samples. Moreover, EPC has great potential to be used to detect HSO3- in real food samples.

Construction of Co-ZIF-derived CoS2@Cu hollow heterogeneous nanotube array for the detection of hydrazine in environmental water samples

As a neurotoxin, it is necessary to establish a low cost, stable and sensitive method for the quantitative detection of hydrazine. Using Co-ZIF (zeolite imidazole framework) nanorods as precursor, CoS2 hollow nanotube array heterogeneous structure loaded with Cu nanoparticles were prepared on carbon cloth (CC) by etching, calcination and plasma magnetron sputtering (CoS2@Cu HNTA/CC). As a self-supporting electrode, its hollow heterogeneous structure provides a large area of electron transfer channel for the oxidation of the food pollutant hydrazine. In addition, bimetallic synergies and in situ N doping regulated the electronic structure of CoS2@Cu HNTA/CC, and thus significantly improved the electrical conductivity and catalytic activity. As an efficient hydrazine sensor with a wide linear range of 1 μM L-1-10 mM (1 μM-1 mM and 1 mM-10 mM), its sensitivity and the limit of detection are 7996 μA mM-1 cm-2, 3772 μA mM-1 cm-2 and 0.276 μM (S/N = 3), respectively. This study provides a new strategy for the construction of MOFs (Metal Organic Framework)-derived bimetallic composites and their application in electrochemical sensing.

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 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.

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.

Multi-scene visual hydrazine hydrate detection based on a dibenzothiazole derivative

Hydrazine (N₂H₄) produced by industries is distributed into different environments, and seriously threatens ecology and human security. Hence, it is important to develop probes that detect N₂H₄ in various environments. In this study, a novel N₂H₄ fluorescent probe was prepared based on a dibenzothiazole derivative (DBTD). The obtained DBTD probe demonstrated a strong ratio of colorimetric detection of N₂H₄, a rapid response, and good selectivity and sensitivity (detection limit 0.438 μM). Based on its good performance, the DBTD probe was successfully applied for the determination of trace N₂H₄ in water, cells, and zebrafish. In addition, the results of the fluorescence colocalization experiment demonstrated the lysosomal-targetable ability of DBTD.

The syntheses, photophysical properties and pH-sensitive studies of heterocyclic azo dyes bearing coumarin-thiophene-thiazole

This study reports the synthesis of two novel thiazolylazo dyes (4 and 5) bearing coumarin-thiophene moiety. UV-Vis spectroscopy was used to investigate the photophysical properties of 4 and 5 in different solvents. The dyes displayed good potential for hydroxide sensing in different mediums. The reversibility was also studied, and it was found that 4 and 5 could be reverted to their original state by adding acid. Furthermore, the acidochromic properties were studied in protic and aprotic media. Both dyes displayed a good acidochromic response in DCM. Moreover, 4 and 5 were investigated for pH sensing, and it was found that both compounds displayed changes in absorption spectra in a basic media. The theoretical calculations were carried out to investigate the deprotonation and protonation mechanisms using density functional theory (DFT). The thermal properties of the dyes were investigated using thermogravimetric analysis (TGA). The results showed good thermal stability up to around 200 °C.

Monitoring cell viability in N-nitrosodiethylamine induced acute hepatitis and detection of hydrazine in solution and gas phase with Dual-function fluorescent probes

The highly toxic N-nitrosodiethylamine (NDEA) and hydrazine (N₂H₄) caused severe environmental contamination and serious health risks. Herein, we designed the two-photon ratiometric fluorescent probe (Nap-2), emission maximum shifted from 466 nm to 571 nm, to monitor cell viability of NDEA induced acute hepatitis via esterase activity detection. Furthermore, the probe Nap-2 evaluate the hydrazine (N₂H₄) content in the solution and gas phase. It is worth mentioning that we used NDEA induced acute hepatitis in the mice and evaluated the negative correlation of esterase activity in the tissue cells and serum with Nap-2. The probe Nap-2 exhibited that acute hepatitis induced by NDEA decreased cell viability. Furthermore, we made convenient test papers using Nap-2 to detect N₂H₄ in solution and gas phase. After adding N₂H₄, the fluorescence color changed from blue to yellow and was visible to the naked eye. This work provides a convenient tool and method for evaluating the toxicity of NDEA induced acute hepatitis and detecting N₂H₄ in the environment.

Smartphone-assisted microfluidic and spectrophotometric recognition of hydrazine: a new platform towards rapid analysis of carcinogenic agents and environmental technology

Hydrazine (Hyd), a poisonous substance, is frequently employed in agriculture and industry as a scavenger to remove residues of oxygen from boiler feed water, electrical power plants, etc. Even at trace amounts, these chemicals are hazardous to humans. To limit the risks of exposure, there is a critical need for sensors for the monitoring of Hyd concentration to guarantee they are below harmful levels. In comparison to other approaches, the colorimetric method has garnered a great deal of interest due to its high sensitivity, speed, convenience, and simple optical color change detection. This study's primary purpose is to develop a portable tool for the colorimetric and spectrophotometric detection of Hyd using silver nanoparticles (silver nanoprism (AgNPr), silver nanowires (AgNW), and silver citrate (AgCit)). In addition, UV-visible spectroscopy was utilized for the quantitation evaluation of Hyd in real samples. The proposed approach demonstrated a linear range of 0.08 M to 6 M for Hyd by AgNW and 0.02 to 5 M by AgNPr as optical probes, whereas AgCit exhibited no color change (negative response). Using AgNPr and AgNW, the low limit of detection of Hyd was 200 μM and 800 μM, respectively. In addition, a novel method was employed for the first time to explore the effect of time on the determination of the candidate analyte. Consequently, the proposed method can be utilized to detect Hyd in real samples. Therefore, our method shows both qualitative and quantitative measurement of Hyd with high sensitivity, low cost, and fast analysis time and promisingly it can be industrialized for quick detection of Hyd in aquatic real samples.

A Novel Turn-On Fluorescent Sensor Based on Sulfur Quantum Dots and MnO2 Nanosheet Architectures for Detection of Hydrazine

In this paper, the SQDs@MnO2 NS as the probe was applied to construct a novel “turn-on” fluorescent sensor for sensitive and selective detection of hydrazine (N2H4). Sulfur quantum dots (SQDs) and MnO2 nanosheets (MnO2 NS) were simply mixed, through the process of adsorption to prepare the architectures of SQDs@MnO2 NS. The fluorescent emissions of SQDs@MnO2 NS play a key role to indicate the state of the sensor. According to the inner filter effect (IFE) mechanism, the state of the sensor at the “off” position, or low emission, under the presence of MnO2 NS, is which the ultraviolet and visible spectrum overlaps with the fluorescence emission spectrum of SQDs. Under the optimal conditions, the emission was gradually recovered with the addition of the N2H4, since the N2H4 as a strong reductant could make the MnO2 NS converted into Mn2+, the state of the sensor at the “on”. Meanwhile, the fluorescent sensor possesses good selectivity and high sensitivity, and the detection concentration of N2H4 with a wide range from 0.1 µM to 10 mM with a detection limit of 0.072 µM. Furthermore, actual samples were successful in detecting certain implications, indicating that the fluorescent sensor possesses the potential application ability to monitor the N2H4 in the water.

An ICT-Based Coumarin Fluorescent Probe for the Detection of Hydrazine and Its Application in Environmental Water Samples and Organisms

As an inorganic small molecule pollutant, the toxicity and potential carcinogenicity of hydrazine (N₂H₄) are of increasing concern. In this work, A water-soluble fluorescent probe (OCYB) based on the intramolecular charge transfer (ICT) mechanism for the detection of hydrazine was designed and synthesized. Taking the advantage of 4-bromobutyryl as the recognition group, the high selectivity of OCYB to N₂H₄ was confirmed by steady-state fluorescence spectroscopy. The limit of detection (LOD) was calculated to be 78 nM in the DMSO-HEPES (pH 7.4) system. The detection mechanism was verified by NMR, HRMS and density functional theory (DFT) calculations. In addition, OCYB exhibits strong anti-interference ability and an “Off-On” fluorescence enhancement effect. Importantly, OCYB can be used to effectively monitor the fluorescence distribution of N₂H₄ in environmental water samples and organisms.

Fabrication and application of 2,4,6-trinitrophenol sensors based on fluorescent functional materials

2,4,6-Trinitrophenol (TNP) has been widely used for a long time. The adverse effects of TNP on ecological environment and human health have promoted researchers to develop various methods for detecting TNP. Among multifarious technologies utilized for the TNP detection, fluorescence strategy based on different functional materials has become an effective and efficient method attributed to its merits such as preferable sensitivity and selectivity, rapid response speed, simple operation, and lower cost, which is also the focus of review. This review summarizes the development status of fluorescence sensors for TNP in a detailed and systematic way, especially focusing on the research progress since 2015. The sensing properties of fluorescent materials for TNP are the core of this review, including nanomaterials, organic small molecules, emerging supramolecular systems, aggregation induced emission materials and others. Moreover, the development direction and prospect of fluorescence sensing method in the field of TNP detection are introduced and discussed at the end of review.

An ultrasensitive surface-enhanced Raman scattering sensor for the detection of hydrazine via the Schiff base reaction

The development of convenient assays for the determination of hydrazine (N₂H₄) has drawn significant attention due to the high toxicity of this substance. Herein, we developed a concise, rapid and ultrasensitive surface-enhanced Raman scattering (SERS) sensor for N₂H₄ detection based on alpha-cyclodextrin-silver nanoparticles (α-CD-AgNPs) modified by 4-mercaptobenzaldehyde (4-MBA). The 4-MBA molecules can specifically capture the N₂H₄ molecules and undergo a Schiff base reaction. As a result, this induces the aggregation of nanoparticles and generates a new characteristic peak at 1529 cm^-1 that is attributed to CN and CC vibrations. Compared with noble metal nanoparticles, 4-MBA not only formed AgS bonds but could also be fixed in the cavity of cyclodextrin to produce a more stable and stronger SERS signal. The SERS intensity at 1529 cm^-1 and the logarithm of the concentration of N₂H₄ presented a good linear relationship from 10^-9 to 10^-7 M with an unprecedented limit of detection (LOD) of 38 pM. The proposed SERS sensor exhibited satisfactory selectivity and reproducibility and was applied to detect N₂H₄ in real and complex water samples. We expect this assay to be a promising alternative tool for the on-site detection of N₂H₄.

Automated fluorimetric sensor for hydrazine determination in water samples based on the concept of zone fluidics

In the present study, we report an automated fluorescence sensor for the determination of hydrazine in various water samples based on the concept of zone fluidics. Hydrazine and O-phthalaldehyde react through a unique mechanism in acidic medium (pH = 1.5) and without the presence of additional nucleophilic compounds. Another interesting feature of the proposed reaction is that it is not based on the Red/Ox properties of hydrazine, enhancing further the selectivity of the analytical procedure. The produced hydrazone exhibits high fluorescence at Ex = 318/Em = 376 nm. Using 120 s as a stopped flow step and temperature of 70 °C, we achieved satisfactory sensitivity for the determination of the analyte at a microgram per liter level with a limit of detection of 1.4 μg L^-1 and an analysis rate of 12 h^-1. The absence of matrix effect enabled the direct analysis of drinking (tap, mineral, table) and boiler feedwater samples with percent recoveries in the range of 91-111%.

A New Molecular Recognition Concept: Multiple Hydrogen Bonds and Their Optically Triggered Proton Transfer in Confined Metal-Organic Frameworks for Superior Sensing Element

We report a new sensing mechanism based on an indium-dihydroxyterephthalic acid metal-organic framework (MOF, SNNU-153), in which the spatially fitted analyte-MOF hydrogen-bond (H-bond) formation provides selective recognition while the analyte-H-bond assisted excited-state intramolecular proton transfer (ESIPT) and the resulting ratiometric emission act as a superior signal transducer with ultrafast response. The synergy of ESIPT signal transduction and confined MOF pore enables the SNNU-153 sensor selectively sensing hydrazine even among nitrogen-containing hydride analogs such as NH₃, NH₂OH, and (Me)₂NNH₂. The key of H-bond and associated ESIPT was further counter evidenced by an indium-2,5-dimethoxyterephthalic acid MOF (SNNU-152), where the hydroxyl protons were removed by methylation, showing near inertness to N₂H₄. The new molecular recognition concept thus makes SNNU-153 a powerful N₂H₄ sensor, which should be far-reaching to other sensing elements.