Copper sulfide|reduced graphene oxide nanocomposite for detection of hydrazine and hydrogen peroxide at low potential in neutral medium

Electrocatalysis Using Cobalt Porphyrin Covalently Linked with Multi-Walled Carbon Nanotubes: Hydrazine Sensing and Hydrazine-Assisted Green Hydrogen Synthesis

Acid-treated multi-walled carbon nanotube (MWCNT) covalently functionalized with cobalt triphenothiazine porphyrin (CoTriPTZ-OH) A3B type porphyrin, containing three phenothiazine moieties (represented as MWCNT-CoTriPTZ) is synthesized and characterized by various spectroscopic and microscopic techniques. The nanoconjugate, MWCNT-CoTriPTZ, exhibits a pair of distinct redox peaks due to the Co2+/Co3+ redox process in 0.1 M pH 7.0 phosphate buffer. Further, it electrocatalytically oxidizes hydrazine at a low overpotential with a high current. This property is advantageously utilized for the sensitive determination of hydrazine. The developed electrochemical sensor exhibits high sensitivity (0.99 µAµM-1cm-2), a low limit of detection (4.5 ppb), and a broad linear calibration range (0.1 µM to 3.0 mM) for the determination of hydrazine. Further, MWCNT-CoTriPTZ is exploited for hydrazine-assisted green hydrogen synthesis. The high efficiency of hydrazine oxidation is confirmed by the low onset potential (0.45 V (vs RHE)) and 0.60 V (vs RHE) at the current density of 10 mA.cm-2. MWCNT-CoTriPTZ displays a high current density (77.29 mA.cm-2) at 1.45 V (vs RHE).

Electrodeposition of CoFeS nanoflakes on Cu2O nanospheres as an ultrasensitive sensing platform for measurement of the hydrazine and hydrogen peroxide in seawater sample

Nanoarchitectured design of the metal sulfides with highly available surface and abundant electroactive centers and using them as electrocatalyst for fabricate the electrochemical sensors for the detection of hydrazine (N2H4) and hydrogen peroxide (H2O2) is challenging and desirable. Herein, Cu2O nanospheres powder is firstly prepared using chemical reduction of copper chloride and then drop-casted on the glassy carbon electrode (GCE) surface. In the next step, CoFeS nanoflakes are electrodeposited on Cu2O nanospheres by cyclic voltammetry method to form CoFeS/Cu2O nanocomposite as a detection platform for measuring N2H4 and H2O2. Accordingly, Cu2O nanospheres are not only used as substrate, but also guided the CoFeS nanoflakes to adhere to the electrode surface without need to any binder or conductive additive, which enhances the electrical conductivity of the sensing active materials. As the hydrazine sensor, the CoFeS/Cu2O/GCE displayed wide linear ranges (0.0001-0.021 mM and 0.021-1.771 mM), low detection limit (0.12 μM), very high sensitivities (103.33 and 21.23 mA mM-1 cm-2), and excellent selectivity. The as-made nanocomposite also exhibited low detection limit of 1.26 μM for H2O2 sensing with very high sensitivities (12.31 and 3.96 mA mM-1 cm-2) for linear ranges of 0.001-0.03 mM and 0.03-2.03 mM, respectively, and negligible response against interfering substances. The superior analytical performance of the CoFeS/Cu2O for N2H4 electro-oxidation and H2O2 electro-reduction can be attributed to structure stability, high electroactive surface area, and good availability to analyte species and electrolyte diffusion. Moreover, to examine the potency of the prepared nanocomposite in real applications, the seawater sample was analyzed and results display that the CoFeS/Cu2O/GCE can be utilized as a reliable and applicable platform for measuring N2H4 and H2O2.

Structural Engineering of Hollow Microflower-like CuS@C Hybrids as Versatile Electrochemical Sensing Platform for Highly Sensitive Hydrogen Peroxide and Hydrazine Detection

Designing metal sulfides with unique configurations and exploring their electrochemical activities for hydrogen peroxide (H₂O₂) and hydrazine (N₂H₄) is challenging and desirable for various fields. Herein, hollow microflower-like CuS@C hybrids were successfully assembled and further exploited as a versatile electrochemical sensing platform for H₂O₂ reduction and N₂H₄ oxidation, of which the elaborate strategies make the perfect formation of hollow architecture, providing considerable electrocatalytic sites and fast charge transfer rate, while the appropriate introduction polydopamine-derived carbon skeleton facilitates the electronic conductivity and boosts structural robustness, thus generating wide linear range (0.05-14 and 0.01-10 mM), low detection limit (0.22 μM and 0.07 μM), and a rather low overpotential (-0.15 and -0.05 V) toward H₂O₂ and N₂H₄, as well as good selectivity, excellent reproducibility, and admirable long-term stability. It should be highlighted that the operating potentials can compare favorably with those of some reported H₂O₂ and N₂H₄ sensors based on noble metals. In addition, good recoveries and acceptable relative standard deviations (RSDs) attained in serum and water samples fully verify the accuracy and anti-interference capability of our proposed sensor systems. These results not only elucidate an effective structural nanoengineering strategy for electroanalytical science but also advance the rational utilization of H₂O₂ and N₂H₄ in practicability.

Effect of Intercalants inside Birnessite-Type Manganese Oxide Nanosheets for Sensor Applications

Hydrazine is a common reducing agent widely used in many industrial and chemical applications; however, its high toxicity causes severe human diseases even at low concentrations. To detect traces of hydrazine released into the environment, a robust sensor with high sensitivity and accuracy is required. An electrochemical sensor is favored for hydrazine detection owing to its ability to detect a small amount of hydrazine without derivatization. Here, we have investigated the electrocatalytic activity of layered birnessite manganese oxides (MnO₂) with different intercalants (Li⁺, Na⁺, and K⁺) as the sensor for hydrazine detection. The birnessite MnO₂ with Li⁺ as an intercalant (Li-Bir) displays a lower oxidation peak potential, indicating a catalytic activity higher than the activities of others. The standard heterogeneous electron transfer rate constant of hydrazine oxidation at the Li-Bir electrode is 1.09- and 1.17-fold faster than those at the Na-Bir and K-Bir electrodes, respectively. In addition, the number of electron transfers increases in the following order: K-Bir (0.11 mol) < Na-Bir (0.17 mol) < Li-Bir (0.55 mol). On the basis of the density functional theory calculation, the Li-Bir sensor can strongly stabilize the hydrazine molecule with a large adsorption energy (-0.92 eV), leading to high electrocatalytic activity. Li-Bir also shows the best hydrazine detection performance with the lowest limit of detection of 129 nM at a signal-to-noise ratio of ∼3 and a linear range of 0.007-10 mM at a finely tuned rotation speed of 2000 rpm. Additionally, the Li-Bir sensor exhibits excellent sensitivity, which can be used to detect traces of hydrazine without any effect of interference at high concentrations and in real aqueous-based samples, demonstrating its practical sensing applications.

Amperometric determination of hydrazine using a CuS-ordered mesoporous carbon electrode

An electrocatalytic sensor for hydrazine using copper sulfide-ordered mesoporous carbon (CuS-OMC) is described. A facile solvothermal synthetic strategy was adopted for CuS-OMC and the ordered mesoporous carbon was obtained through nanocasting method. The synthesized CuS-OMC was characterized using microscopic and spectrochemical techniques. CuS-OMC was immobilized on GCE and evaluated for its electrochemical sensing of hydrazine using cyclic voltammetry and amperometry. CuS-OMC modified GCE exhibited better hydrazine sensing at an optimized pH 7.4 in terms of oxidation potential and current compared with that of GCE, CuS, and OMC. The observed sensing performance of CuS-OMC was attributed to the presence of Cu (I/II) in CuS dispersed in OMC which acts as an electrocatalytic center for the sensing of hydrazine. Amperometry under optimized experimental condition with an applied potential of 270 mV was employed to obtain a linear calibration plot in the range 0.25 to 40 μM (R² = 0.9908) with a detection limit of 0.10 μM with a sensitivity of 0.915 (± 0.02) μA cm^-2 μM^-1. Real sample analyses were carried out by spiking of hydrazine in different water samples and the recoveries were in the range of 97 ± 2.1% (n = 3). Graphical abstract.

MOFs-Derived Nano-CuO Modified Electrode as a Sensor for Determination of Hydrazine Hydrate in Aqueous Medium

It very important to be able to efficiently detect hydrazine hydrate in an aqueous medium due to its high toxicity. Here, we have proposed a new idea: to construct a sensor for the rapid determination of hydrazine hydrate based on the nano-CuO derived by controlled pyrolysis of HKUST-1 [Cu3(BTC)2(H2O)3]. The as-prepared CuO at 400 °C possesses a uniform appearance with nano-structure via SEM images, and the nano-CuO-400 has exhibited excellent electrocatalytic activity towards hydrazine oxidation. Amperometric i-t curves shows the peak current as linearly proportional to the hydrazine concentration within 1.98-169.3 μmol L-1 and 232-2096 μmol L-1 with the detection limit of 2.55 × 10-8 mol L-1 and 7.01 × 10-8 mol L-1, respectively. Moreover, the sensor constructed in the experiment shows good selectivities, and it is feasible to determining actual water samples.

Novel urchin-like FeCo oxide nanostructures supported carbon spheres as a highly sensitive sensor for hydrazine sensing application

Herein, we successfully fabricated a novel nanostructure based on hierarchical urchin-like FeCo oxide supported carbon spheres (FeCo Oxide/CSs) via a two-step hydrothermal method followed by a simple annealing step at 300 °C under air. It was found that such urchin-like FeCo Oxide/CSs structure exhibited superior catalytic activity towards hydrazine oxidation to CSs, Fe Oxide/CSs, Co Oxide/CSs, and FeCo Hydroxide/CSs material. In this regard, the FeCo Oxide/CSs displayed a wide linear detection range of 0.1-516.6 μM, low detection limit of 0.1 μM, and long-term stability. The material also showed good selectivity towards hydrazine detection in the presence of various interferences, such as uric acid, ascorbic acid, urea, dopamine, Na⁺, SO₄^2-, K⁺, and Cl-. The excellent sensing performance of the FeCo Oxide/CSs was assumed to the unique hierarchical urchin structure with the high density and uniformity of nano-sized FeCo Oxide nanoneedles, which produced massive electroactive sites and enhanced charge transfer ability. The achieved results implied that the FeCo Oxide/CSs may be a great candidate for sensitive hydrazine detection.

Selective hydrazine sensor fabrication with facile low-dimensional Fe2O3/CeO2 nanocubes

Here, the binary-doped metal oxides of Fe₂O₃/CeO₂ nanocubes were prepared using reliable hydrothermal process, which is applied to fabricate an efficient and selective hydrazine chemical sensor shows good analytical sensing performances as well as validated the sensor prove with the environmental and extracted real samples.

A bifunctional NiCo2S4/reduced graphene oxide@polyaniline nanocomposite as a highly-efficient electrode for glucose and rutin detection

A novel NiCo₂S₄/reduced graphene oxide@polyaniline (NiCo₂S₄/rGO@PANI) composite was synthesized by a facile two-step hydrothermal treatment and calcination, which was coupled with an in situ polymerization process.

An ultrasensitive electrochemical immunosensor based on the synergistic effect of quaternary Cu2SnZnS4 NCs and cyclodextrin-functionalized graphene

Cu₂ZnSnS₄ nanocrystals were first used as electrocatalysts for H₂O₂ reduction for the ultrasensitive detection of alpha-fetoprotein.

2-Dimensional graphene as a route for emergence of additional dimension nanomaterials

Dimension has a different and impactful significance in the field of innovation, research and technologies. Starting from one-dimension, now, we all are moving towards 3-D visuals and try to do the things in this dimension. However, we still have some very innovative and widely applicable nanomaterials, which have tremendous potential in the form of 2-D only i.e. graphene. In this review, we have tried to incorporate the reported pathways used so far for modification of 2-D graphene sheets to make is three-dimensional. The modified graphene been applied in many fields like supercapacitors, sensors, catalysis, energy storage devices and many more. In addition, we have also incorporated the conversion of 2-D graphene to their various other dimensions like zero-, one- or three-dimensional nanostructures.

A highly sensitive non-enzymatic hydrogen peroxide and hydrazine electrochemical sensor based on 3D micro-snowflake architectures of α-Fe2O3

In the present work, well crystalline 3D micro-snowflake structured α-Fe₂O₃ has been successfully synthesized on a large scale via a simple hydrothermal reaction by hydrolysis of a K₃Fe(CN)₆ precursor.

Reduced graphene oxide/gold tetraphenyl porphyrin (RGO/Au–TPP) nanocomposite as an ultrasensitive amperometric sensor for environmentally toxic hydrazine

A gold tetra phenyl porphyrin/reduced graphene oxide (RGO/Au–TPP) nanocomposite film modified glassy carbon electrode (GCE) was prepared for the trace level detection of hydrazine.

Manganese dioxide–vulcan carbon@silver nanocomposites for the application of highly sensitive and selective hydrazine sensors

Active carbon supported MnO₂@Ag nanocomposites were developed for the highly sensitive and selective electrochemical detection of hydrazine.

Electropolymerization of cobalt tetraamino-phthalocyanine at reduced graphene oxide for electrochemical determination of cysteine and hydrazine

A simple electrodeposition route to prepare tetraamino phthalocyanine polymers on reduced graphene oxide for electrochemical determination of cysteine and hydrazine.

An electrochemical synthesis strategy for composite based ZnO microspheres–Au nanoparticles on reduced graphene oxide for the sensitive detection of hydrazine in water samples

RGO/ZnO–Au nanocomposite towards the toxic hydrazine sensor.

Synthesis of Ag–HNTs–MnO2 nanocomposites and their application for nonenzymatic hydrogen peroxide electrochemical sensing

Flower-like Ag–HNTs–MnO₂ nanocomposites have been synthesized successfully and they were used for fabricating a non-enzymatic hydrogen peroxide (H₂O₂) sensor.