Hydrazine In Aqueous Solution Research Articles

A novel pyrazoline-based fluorescent probe for detection of hydrazine in aqueous solution and gas state and its imaging in living cells

A novel fluorescent probe 4 for hydrazine based on pyrazoline-derived was designed and synthesized. The selective deprotection of phthalimide group of the probe by hydrazine led to a dramatic fluorescent enhancement (∼84.7 folds) at 490nm within 4min in the aqueous solution. The limit of detection is 0.0622μM (1.99ppb) which is much lower than the U.S. Environmental Protection Agency standard (10ppb). Notably, probe 4 could be used to detect hydrazine in gas state with different concentrations through color changes from readily prepared strips. Additionally, probe 4 could also be applied to monitor hydrazine in living cells by biological imaging.

Synthesis of octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals and their structure-activity relationship for the decomposition of hydrazine in aqueous solution to hydrogen.

We developed a co-reduction method to synthesize octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals. The shape/size distribution, structural characteristics, and composition of the Rh2Ni nanocrystals are investigated, and their possible formation mechanism at high temperatures in margaric acid/1-aminoheptadecane solution in the presence of tetraethylgermanium and borane trimethylamine complexes is proposed. A preliminary probing of the structure-activity dependence of the surface "clean" Rh2Ni nanocrystals supported on carbon towards hydrazine (N2H4) in aqueous solution dehydrogenation revealed that the higher the percentage of {111} facets, the higher is the activity and H2 selectivity of the nanocrystals. This result was attributed to the {111} facets not only introducing more basic sites, but also weakening the interaction between the produced adspecies (including H2 and NHx) and surface metal atoms in comparison with those of {100} facets. Furthermore, the as-prepared Rh2Ni nanooctahedra exhibited 100% H2 selectivity and high activity at room temperature for H2 generation via N2H4 decomposition. The activation energy of the Rh2Ni nanooctahedra was 41.6 ± 1.2 kJ mol(-1). The Rh2Ni nanooctahedra were stable catalysts for the hydrolytic dehydrogenation of N2H4, providing 27 723 total turnovers in 30 h. Our work provides a new perspective concerning the possibility of constructing hydrogen-producing systems based on N2H4 and surface "clean" Rh2Ni nanocrystal catalysts with defined shapes supported on carbon that possess a competitive performance in comparison with NaBH4 and NH3BH3 hydrogen-producing systems for fuel cell applications.

Phosphine- and copper-free palladium catalyzed one-pot four-component carbonylation reaction for the synthesis of isoxazoles and pyrazoles

The palladium catalyzed one-pot synthesis of isoxazoles and pyrazoles from aryl iodides, terminal alkynes, chromium hexacarbonyl and hydroxylamine hydrochloride or aqueous hydrazine solution is described. The Sonogashira carbonylative coupling intermediate was trapped in situ by hydroxylamine hydrochloride or aqueous hydrazine to deliver isoxazoles or pyrazoles, respectively, in high yields. This efficient method proceeds at atmospheric pressure and moderate temperature and does not require the use of copper, phosphine ligands or gaseous carbon monoxide.

2D-GaS as a Photocatalyst for Water Splitting to Produce H₂.

Using first-principles local and hybrid density functional theoretical calculations, a thickness-dependent electronic structure of layered GaS is determined, and it is shown that 2D GaS has an electronic structure with valence and conduction bands that straddle the redox potentials of hydrogen evolution reaction and oxygen evolution reaction up to a critical thickness (<5.5 nm). Here, simulations of adsorption of H2O on nanoscale GaS reveal that localized electronic states at its edges appear in the gap and strengthen the interaction with H2O, further activating the surface atomic sites. It is thus predicted that GaS synthesized with a controlled thickness and preferred edges may be an efficient catalyst for photocatalytic splitting of water. Experiments that verify some of the predictions in this study are presented, and it is shown that GaS is effective in absorption of light and evolution of H2 (887 μmol h(-1) g(-1)) in the presence of aqueous solution of hydrazine (1% v/v). This study should open up the use of nanoscale GaS in conversion of solar energy into environment-friendly chemical energy in the form of hydrogen.

Synthesis and antimicrobial activity of novel coumarin derivatives from 4-methylumbelliferone

Considering the potential interest of heterocyclic compounds, the aim of the present study is to synthesize new coumarin derivatives, to provide their full chemical characterization and to evaluate their antimicrobial activities. The reaction of ethyl 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetate 2 with sodium hydroxide afforded the corresponding 2-(2-oxo-4-methyl-2H-chromen-7-yloxy) acetic acid 3 which was esterified using a series of alcohols in the presence of iodine to yield a new series of coumarin esters 4a–j. On the other hand, treatment of the key intermediate 2 with an aqueous solution of hydrazine in ethanol at reflux gave the corresponding hydrazide 5 which further converted into coumarin derivatives 6a–f and 7a–c by condensation with a series of aromatic aldehydes and cyclic anhydrides, respectively. The synthesized compounds were completely characterized by 1H NMR, 13C NMR, IR and HRMS. The antibacterial and antifungal activities of the new synthesized compounds were evaluated using the disc diffusion method and seemed to be significant.

Controlled growth of thermally stable uniform-sized Ag nanoparticles on flat support and their electrochemical activity

A method consisting of spin coating of Ag+ ions (AgNO3) solution followed by chemical reduction in aqueous hydrazine solution has been presented for controlled growth of thermally stable uniform-sized Ag nanoparticles on flat substrate. Scanning electron microscopy images and local surface plasmon resonance absorption studies imply that most of the Ag nanoparticles grow with unique preferable size. This preferable size can be controlled by changing AgNO3 solution characteristics (drop size and concentration), spin-coating parameters (rpm and ramp) and annealing temperatures. With increase in rpm or ramp, particle size decreases with enhanced particles density. The Ag nanoparticles are thermally stable up to 450 °C, and the preferable size is increased with annealing temperature. The grown particles are catalytic active for oxygen reduction reaction, and activity was found to be dependent on size and density of Ag nanoparticles.

An ESIPT-based fluorescent probe for sensitive detection of hydrazine in aqueous solution.

A fluorescent probe for sensitive detection of hydrazine based on an ESIPT mechanism and a substitution-cyclization-elimination cascade was developed. After the addition of hydrazine, an approximately 50-fold enhancement in fluorescence intensity at 465 nm was observed and the subsequent decrease at 375 nm was observed in 10 min with a detection limit of 0.147 μM. We also detected hydrazine in HeLa cells successfully.

Metal Nanoparticles Immobilized on Carbon Nanodots as Highly Active Catalysts for Hydrogen Generation from Hydrazine in Aqueous Solution

AbstractWell‐dispersed PtNi nanoparticles (NPs) grown on carbon nanodots (CNDs) derived from a metal–organic framework (ZIF‐8) are synthesized by a simple reduction of metal precursors in the presence of CNDs, wherein the CNDs prove to be a powerful dispersion agent and distinct support for the PtNi NPs. The resultant PtNi‐CND catalyst exerts almost 100 % H2 selectivity and a high activity for the decomposition of hydrous hydrazine at room temperature. This excellent catalytic performance might be a result of the synergistic effect of the CND support and the PtNi NPs. The utilization of CNDs as a support to anchor the active component NPs and thus to facilitate the electron transfer and mass transport kinetics during the catalytic reaction process opens up new avenues to design high‐performance catalysts.

Magnetic and Structural Study of FeNi3 Nanoparticles: Effect of Calcination Temperature

Bimetallic Fe–Ni alloy nanoparticles (NPs) with molar ratio of Fe to Ni 1:3 were synthesized via chemical reduction using hydrazine in aqueous solution and then calcined at different temperatures. The prepared NPs have been characterized utilizing X-ray diffraction (XRD), energy-dispersive X-ray (EDS) spectroscopy, and vibrating sample magnetometer (VSM). XRD results show that FeNi3 NPs with face-centered cubic (FCC) crystalline structure were formed. FeNi3 phase completely disappeared and pure NiO and NiFe2O4 phases observed on further heating at 550° C. VSM results reveal a superparamagnetic characteristic for the synthesized NPs when calcined at 50° C. An increased coercivity and decreased saturation magnetization has been observed with increasing calcination temperature up to 550° C.

Ni–Pt nanoparticles supported on MIL-101 as highly efficient catalysts for hydrogen generation from aqueous alkaline solution of hydrazine for chemical hydrogen storage

Highly dispersed bimetallic Ni–Pt nanoparticles with different compositions supported on MIL-101 have been successfully synthesized by a simple liquid impregnation method. The as-synthesized NPs in an average of 1.9 ± 0.4 nm could be isolated by certification and characterized by using PXRD, TEM, EDX, XPS, BET, and ICP-AES. Catalytic activity of the Ni–Pt@MIL-101 was tested in the hydrogen generation from aqueous alkaline solution of hydrazine. These catalysts were composition dependent for the catalytic activity. Among all the Ni–Pt@MIL-101 catalysts tested, the Ni88Pt12@MIL-101 exhibited the highest catalytic activity, with the turnover frequency (TOF) value of 350 molH2molmetal−1h−1 at 50 °C, which is the highest among all the previously reported catalysts.

Split-flow Taylor dispersion technique for diffusivity and concentration measurements of hydrazine in aqueous solution

A sensitive continuous-flow monitoring method is developed for the determination of the diffusion coefficient and concentration of hydrazine in an aqueous solution. The effect of pH on the diffusion coefficient of hydrazine in water was studied at room temperature using the developed split-flow Taylor dispersion technique. The hydrazine calibration curve was linear in the range of 10−1000 ppb and the limit of quantification was 10 ppb. The results showed that the diffusion coefficient of hydrazine does not change significantly over the pH range of 4.01−8.27 but increases in alkaline media of pH greater than 8.27. This method can be used for accurate determination of hydrazine concentration in aqueous flow systems.

Kinetics and Mechanism of Redox Reaction between Tetrachloroaurate(III) Ions and Hydrazine

ABSTRACT: In this work, the kinetics and mechanism of a redox reaction between the [AuCl4]− complex ions and hydrazine in aqueous solution were carried out. Using a combination of the classical UV–vis spectrophotometry and the stopped‐flow technique, the impact of different parameters, such as pH, ionic strength, temperature, the presence of chloride ions, and [AuCl4]− and N2H5+ concentrations on the rate constant of [AuCl4]− reduction was investigated. From the obtained results, the rate law of the reaction was determined and the possible mechanism of a one‐electron inner‐sphere reaction was suggested. It has been found that the reaction is complex and consists of at least two consecutive steps with the gold(I) formation, which can be further reduced to a metallic form as a final product of the reaction.

A fluorescence “switch-on” approach to detect hydrazine in aqueous solution at neutral pH

The fluorescent probe developed here (1) works well in aqueous solution at neutral pH, (2) has excellent specificity and (3) allows visualization of vaporized hydrazine.

New methods of preparation of hydroxy-closo-decaborates [B10H10 − n (OH) n ]2− (n = 1, 2)

New methods of preparation of hydroxy-closo-decaborates [B10H10 − n (OH) n ]2− (n = 1, 2) that are based on the reaction of anions [B10H10 − n (OAc) n ]2− and alkoxyethylidenoxonio-closo-decaborates [2-B10H9OC(OR)CH3]− with aqueous solution of hydrazine are proposed. The obtained compounds were characterized by IR, ESI/MS, and NMR (1H, 11B, 13C) spectroscopy.

Hydrazine and Aqueous Hydrazine Solutions: Evaluating Safety in Chemical Processes

This contribution provides a summary of the hazards of hydrazine and its aqueous solutions and an understanding of the important role dilution plays in increasing the inherent safety of aqueous hydrazine solutions. Rather than provide an extensive description of the hazardous properties of hydrazine, the intent is to provide enough information to allow the reader to decide if hydrazine may be acceptable for a given application, and if so, what concentration range may provide an acceptable safety and environmental risk. Calculations are used to explore the favorable effect of dilution on the risk of fire, explosions, runaway reactions, and toxic exposure. Examples are provided to illustrate the strong effect catalysts can have on decomposition reactions. An analysis indicates the previously published lower flammability limit (LFL) is nonconservative.

Growth of Ag Nanoparticles by Spin Coating

Ag nanoparticles were grown on glass substrate by spin coating of Ag ions (AgNO3) solution followed by either chemical reduction, in aqueous hydrazine or NaBH4 solution, or by thermal reduction in H2 environment. Effects of different reducing agent have been explained. Morphology and absorbance spectra ofAg nanoparticles films, measured by using Scanning Electron Microscopy (SEM) and UV-visible Spectrophotometer techniques, are used to understand effect of reduction process on growth of Ag nanoparticles. To grow uniformly size distributed Ag nanoparticles thermal reduction in H2 is better than chemical reduction by aqueous either NaBH4 orhydrazine hydrate solutions.

Metal–Organic Framework Supported Bimetallic NiPt Nanoparticles as High‐performance Catalysts for Hydrogen Generation from Hydrazine in Aqueous Solution

AbstractHighly dispersed bimetallic NiPt nanoparticles with different NiPt compositions have been successfully immobilized by the zeolitic metal–organic framework ZIF‐8 by a simple liquid impregnation method. These catalysts show high catalytic activity and durability for hydrogen generation from decomposition of hydrazine (H2NNH2) in aqueous alkaline solution at 323 K. Both transmission electron microscopic (TEM) and high‐angle annular dark‐field scanning TEM measurements (HAADF‐STEM) images showed that the ZIF‐8 immobilized NPs were highly dispersed and controlled in small sizes with an average diameter of 2.2±0.3 nm.

Deactivation and regeneration of the supported bimetallic Pd–Pb catalyst in direct oxidative esterification of methacrolein with methanol

The deactivation of the supported bimetallic Pd–Pb catalyst in the repeated runs of direct oxidative esterification of methacrolein with methanol in the atmosphere was investigated. The catalysts before and after stability tests were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma mass spectrometry, Brunauer–Emmett–Teller method and thermogravimetric analysis. The results indicated that the major factor affecting the deactivation of the catalyst was the deposition of organic substances on the surface active sites of the catalyst during batch reaction. Washing the deactivated catalyst with either MeOH or an aqueous hydrazine solution at 80°C could completely recover the initial activity of the catalyst, and calcining the deactivated catalyst in air at 500°C and then reducing in an aqueous hydrazine solution could partly recover its activity. The deactivation and regeneration of the catalyst in the direct oxidative esterification at gas–liquid–solid phase are important and meaningful.

Enhancing effect of hydrazine on chemiluminescence of luminol-H2O2 system

Enhancement in chemiluminescence (CL) signals was obtained when an aqueous alkaline solution of hydrazine was mixed with a luminol–hydrogen peroxide system. The CL intensity is a linear function of hydrazine concentration over a range of 1–10 μg/ml. Several variables on the CL response were examined for the determination of optimum conditions for the system. A possible mechanism of the CL reaction is also discussed.

Gelatin-stabilized copper nanoparticles: Synthesis, morphology, and their surface-enhanced Raman scattering properties

Gelatin-stabilized spherical-shaped copper nanoparticles are synthesized by a simple chemical reaction. The synthesis is performed by the reduction of copper (II) salt with hydrazine in aqueous solution under atmospheric air in the presence of gelatin as capping agent. Advantages of the synthetic method include its production of water dispersible copper nanoparticles at room temperature under no inert atmosphere and making the synthesis more environmental friendly. The synthesized copper nanoparticles are investigated by UV–vis spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and transmission electron microscopy (TEM). The results demonstrate that the amount of gelatin is important for the formation of the copper nanoparticles. The resulting colloidal copper nanoparticles exhibit large surface-enhanced Raman scattering (SERS) signals.