A high-performance non-enzymatic electrochemical hydrazine sensor based on NiCo2S4 porous sphere

Fabrication of Curcumin-Based Electrochemical Nanosensors for the Detection of Environmental Pollutants: 1,4-Dioxane and Hydrazine

This work reports the development of novel curcuminoid-based electrochemical sensors for the detection of environmental pollutants from water. In this study, the first set of electrochemical experiments was carried out using curcumin-conjugated multi-walled carbon nanotubes (MWCNT-CM) for 1,4-dioxane detection. The MWCNT-CM/GCE showed good sensitivity (103.25 nA nM-1 cm-2 in the linear range 1 nM to 1 µM), with LOD of 35.71 pM and LOQ of 108.21 pM. The second set of electrochemical experiments was carried out with bisdemethoxy curcumin analog quantum dots (BDMCAQD) for hydrazine detection. The BDMCAQD/GCE exhibited good sensitivity (74.96 nA nM-1 cm-2 in the linear range 100 nM to 1 µM), with LOD of 10 nM and LOQ of 44.93 nM. Thus, this work will serve as a reference for the fabrication of metal-free electrochemical sensors using curcuminoids as the redox mediator for the enhanced detection of environmental pollutants.

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.

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.

Fabrication of nitrogen-carbon mediated γ-Mo2N nanocomposite based electrochemical sensor for rapid and sensitive determination of antioxidant 6-PPD in the environment

The rapid and sensitive determination of antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-henylenediamine (6-PPD) in the environment is crucial for early intervention to prevent its adverse effects. Here, a reliable electrochemical sensor based on a N-C mediated γ-Mo2N nanocomposite (γ-Mo2N@N-C) modified carbon paste electrode (CPE) was developed and applied for selective and sensitive determination of 6-PPD. Benefiting from the superior stability and faster electron diffusion coefficient, the peak current responded to 6-PPD on the sensor linearly over a concentration range from 5 × 10-8 mol L-1 to 1.0 × 10-5 mol L-1 with a detection limit of 1.67 × 10-8 mol L-1 (4.48 ng mL-1). Moreover, the sensor maintained good anti-interference ability in the determination of 6-PPD in soil samples from different regions in Zhengzhou City. Furthermore, the density functional theory (DFT) calculations combined with kinetics analysis proved that the enhanced basicity of the γ-Mo2N@N-C facilitated the deprotonation of 6-PPD, with the preferred orientation facet of (200) in γ-Mo2N playing a vital role in inducing the dissociation of 6-PPD, thereby improving the sensor's response. Such an electrochemical sensor, with its good stability and superior sensitivity, has the potential to be applied for real-time evaluation and monitoring of environmental pollutants.

Novel biosynthesis of gold nanoparticles for multifunctional applications: Electrochemical detection of hydrazine and treatment of gastric cancer

In this work, an environmentally friendly strategy was used to synthesize gold nanoparticles (Au NPs) using Olea europaea (olive) fruit. Transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) were used to characterize the physicochemical properties of the synthesized NPs. An Au NPs modified glassy carbon electrode was used to investigate the direct electrochemical oxidation of hydrazine. The suggested hydrazine sensor has good performance, such as a wide linear range (2.5-275 μM), low limit of detection (0.09 μM), notable selectivity and excellent reproducibility (RSD = 2.2%). The in-vitro cytotoxicity of three human cancer cell lines (KATOIII, NCI-N87, and SNU-16) was also explored with various concentrations of Au NPs prepared from olive fruit extract. Bio-synthesized Au NPs were found to have cytotoxic properties against gastric cancer in humans based on MTT assay protocol. The obtained results show that green synthesized Au NPs can be successfully employed in electrochemical sensing and cancer treatment applications.

Lignosulfonate-Assisted In Situ Deposition of Palladium Nanoparticles on Carbon Nanotubes for the Electrocatalytic Sensing of Hydrazine

This paper presents a novel modified electrode for an amperometric hydrazine sensor based on multi-walled carbon nanotubes (MWCNTs) modified with lignosulfonate (LS) and decorated with palladium nanoparticles (NPds). The MWCNT/LS/NPd hybrid was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The electrochemical properties of the electrode material were evaluated using cyclic voltammetry and chronoamperometry. The results showed that GC/MWCNT/LS/NPd possesses potent electrocatalytic properties towards the electro-oxidation of hydrazine. The electrode demonstrated exceptional electrocatalytic activity coupled with a considerable sensitivity of 0.166 μA μM-1 cm-2. The response was linear from 3.0 to 100 µM L-1 and 100 to 10,000 µM L-1, and the LOD was quantified to 0.80 µM L-1. The efficacy of the modified electrode as an electrochemical sensor was corroborated in a study of hydrazine determination in water samples.

Covalent Organic Frameworks-TpPa-1 as an Emerging Platform for Electrochemical Sensing

Covalent organic frameworks (COFs) are a new type of metal-free porous architecture with a well-designed pore structure and high stability. Here an efficient electrochemical sensing platform was demonstrated based on COFs TpPa-1 constructed by 1,3,5-triformylphloroglucinol (Tp) with p-phenylenediamine (Pa-1), which possesses abundant nitrogen and oxo-functionalities. COFs TpPa-1 exhibited good water dispersibility and strong adsorption affinities for Pd²⁺ and thus was used as loading support to modify Pd²⁺. The Pd²⁺-modified COFs TpPa-1 electrode (Pd²⁺/COFs) showed high electrocatalytic activity for both hydrazine oxidation reaction and nitrophenol reduction reaction. In addition, TpPa-1-derived nitrogen-doped carbon presented high activity for the electro-oxidation of reduced glutathione (GSH), and sensitive electrochemical detection of GSH was achieved. The presented COFs TpPa-1 can be utilized as a precursor as well as support for anchoring electro-active molecules and nanoparticles, which will be useful for electrochemical sensing and electrocatalysis.

Fabrication and characterization of enhanced hydrazine electrochemical sensor based on gold nanoparticles decorated on the vanadium oxide, ruthenium oxide nanomaterials, and carbon nanotubes composites

This work describes the synthesis of mixed oxide film of vanadium and ruthenium by pulsed deposition technique on multiwall carbon nanotubes and the decoration of gold nanoparticles on the mixed film. A ternary electrocatalyst has been developed for the electrochemical oxidation of hydrazine by combining two metal oxide mixtures with Au nanoparticles. Surface morphology and chemical composition of the electrode have been examined with SEM, EDX, HRTEM, EIS, and XRD. The peak current of hydrazine increased 9 times at the AuNPs/(VOx-RuOx)/CNT/GCE compared to the bare GCE, and the peak potential shifted to negative 848 mV. Linear sweep voltammetry (LSV) and amperometric techniques revealed that the AuNPs/(VOx-RuOx)/CNT/GCE displays linear concentration range 2.5-10000 µM (LSV) and the concentration range 0.03-100 µM (amperometry). The limit of detection (LOD) is 0.5 μM and 0.1 μM at (S/N = 3) for LSV and amperometric technique, respectively. The results obtained show a good RSD% of 2.1%-3.2% and reasonable recovery of 97%-108% of hydrazine detection.

Aerosol-assisted nanostructuring of nickel/cobalt oxide thin films for viable electrochemical hydrazine sensing

Herein, we report the fabrication of NiO-CoO films for the electrochemical detection of hydrazine. An electrochemical sensor was devised where aerosol assisted chemical vapor deposition (AACVD) was employed as a nifty method for synthesizing NiO-CoO films over FTO electrodes. NiO-CoO-nanoparticle (NP) and NiO-CoO-nanowall (NW) films were fabricated over FTO substrates. The electrocatalytic analysis was performed in a standard three-electrode electrochemical setup. NiO-CoO-NW/FTO showed enhanced electro-oxidation for hydrazine at all concentrations tested. XRD, XPS, EDX, and FE-SEM techniques were used to characterize the structural, morphological, and elemental properties of NiO-CoO films. The results showed improved sensitivity, a large dynamic range, and good long-term stability of NiO-CoO-NW films. The amperometric response was used to measure the detection limit, and it was as low as 0.01 μM, and the sensitivity is ∼33 μA μM-1 cm-2. Besides, the NiO-CoO-NW/FTO electrodes showed significant selectivity towards hydrazine upon testing cross-sensitivity to other common interfering molecules. This strategy of using NiO-CoO-NW/FTO electrodes prepared via AACVD has great potential for the direct determination of hydrazine in environmental sensing applications.

A facile method for the fabrication of hierarchically structured Ni2CoS4 nanopetals on carbon nanofibers to enhance non-enzymatic glucose oxidation

Unique Ni₂CoS₄-carbon nanofiber (CNF) composite nanostructures were fabricated using a simple electrospinning-assisted hydrothermal route and used for the rapid and accurate electrochemical oxidation of glucose in real samples at the trace level. Electrochemical impedance spectroscopy and cyclic voltammetry of unmodified and modified electrodes revealed low charge-transfer resistance and the excellent electrocatalytic sensing of glucose when using the Ni₂CoS₄-CNF at a low potential due to the combined benefits of the highly conductive Ni₂Co₂S₄ anchored to the large surface area of the CNFs. Amperometric analysis of the fabricated sensor has shown an extremely low limit of detection (0.25 nM) and a large linear range (5-70 nM) for glucose at a working potential of 0.54 V (vs. Hg/HgO). The practicability of the Ni₂CoS₄-CNF for use in glucose determination was tested withl human saliva, blood plasma, and fruit juice samples. The Ni₂CoS₄-CNF/GCE showed acceptable recovery values for human saliva (99.1-100.8%), blood plasma (98.6-101.5%), and fruit juice (95.1-105.7%) samples. The proposed sensor also exhibited outstanding electroanalytical characteristics for glucose oxidation in these samples, including reusability, repeatability, and interference resistance, even in the presence of other biological substances and organic and inorganic metal ions.

Porous palladium-poly(3,4-ethylenedioxythiophene)-coated carbon microspheres/graphene nanoplatelet-modified electrode for flow-based-amperometric hydrazine sensor

A highly stable flow-injection amperometric hydrazine sensor was developed based on a glassy carbon electrode modified with palladium-poly(3,4-ethylene dioxythiophene) coated on carbon microspheres/graphene nanoplatelets (Pd-PEDOT@CM/GNP/GCE). The Pd-PEDOT@CM/GNP composite was characterized by scanning electron microscopy and energy-dispersive x-ray analysis (SEM/EDX). The modified GCE was electrochemically characterized using cyclic voltammetry and chronoamperometry. The electrocatalytic activity of the Pd-PEDOT@CM/GNP/GCE toward hydrazine oxidation was significantly better than the activity of a bare GCE, a CM/GCE, a GNP/GCE, a Pd-PEDOT/GCE, and a Pd-PEDOT@CM/GCE. The sensor operated best at a low working potential of + 0.10 V (vs. Ag/AgCl). Under optimal conditions, sensitivity toward hydrazine detection and operational stability (601 injections/one electrode preparation) were excellent. The response was linear from 1.0 to 100 μmol L^-1 and from 100 to 5000 μmol L^-1 with a detection limit of 0.28 ± 0.02 μmol L^-1 and high sensitivity of 0.200 μA μM^-1 cm^-2. The sensor showed good repeatability (relative standard deviation (RSD) < 1.4%, n = 15), reproducibility (RSD < 2.7%, n = 6), and anti-interference characteristics toward hydrazine detection. The feasibility of the electrochemical sensor was proved by the successful determination of hydrazine in water samples, and the results were in good agreement with those obtained from spectrophotometric analysis. Graphical abstract.

Recent developments in electrochemical sensors for detecting hydrazine with different modified electrodes

The detection of hydrazine (HZ) is an important application in analytical chemistry. There have been recent advancements in using electrochemical detection for HZ. Electrochemical detection for HZ offers many advantages, e.g., high sensitivity, selectivity, speed, low investment and running cost, and low laboriousness. In addition, these methods are robust, reproducible, user-friendly, and compatible with the concept of green analytical chemistry. This review is devoted to the critical comparison of electrochemical sensors and measuring protocols used for the voltammetric and amperometric detection of the most frequently used HZ in water resources with desirable recovery. Attention is focused on the working electrode and its possible modification which is crucial for further development.

Economical, green and rapid synthesis of CDs-Cu2O/CuO nanotube from the biomass waste reed as sensitive sensing platform for the electrochemical detection of hydrazine

Reeds live widely in swamp and wetland and have an important ecological balance functions in environmental protection. However, the use of reeds is not effectively. The carbon dots (CDs) have been developed as the family of 0D nanocarbon materials and have all the advantages of the carbon family. In this work, we prepared CDs via hydrothermal method using reed. It is surprising that the reed-derived CDs are an effective reducing agent. A highly catalytically active composite material CDs-Cu₂O/CuO was synthesized using economical, green, one-step ultrasonic method and used for the detection of hydrazine. The electrochemical detection of hydrazine was investigated by cyclic voltammetry. The result shows that the CDs-Cu₂O/CuO exhibited good electrocatalytic activity for the oxidation of hydrazine. The fabricated sensor presented a wide linear range from 0.99 μM to 5903 μM and a detection limit of 0.024 μM. In addition, the CDs-Cu₂O/CuO exhibited good sensitivity, stability and repeatability. Therefore, the CDs-Cu₂O/CuO provides a new idea for the utilization of reed and low-cost electrocatalytic nanocomposite.

Ultrasonic synthesis of CeO2@organic dye nanohybrid: Environmentally benign rabid electrochemical sensing platform for carcinogenic pollutant in water samples

A novel organic-inorganic nile-blue - CeO₂ (CeO₂/NB) nanohybrid has been synthesized by environmentally benign ultrasonic irradiation method for the selective determination of the environmental pollutant, carcinogenic hydrazine (HZ) in environmental water samples. Hydrophobic dyes have generally been as redox mediators in electrochemical sensors fabrication due to strong electron transfer capacity and they would allow the oxidation and reduction of the analytes at lower potentials. The CeO₂ nanoparticles were initially synthesized by the ultrasonic irradiation of Ce(NO₃)₂, NH₄OH and ethylene glycol mixture for 6 h using probe sonicator (20 kHz, 100 W) followed by calcination. The organic-dye NB was then added and ultrasonicated further 30 min for the formation of CeO₂/NB nanohybrid material. Various spectroscopic and microscopic tools such as UV-vis and FT-IR spectroscopy, XRD, SEM and high-solution TEM and surface analysis tool Brunauer-Emmett-Teller (BET) confirm the formation of the nanohybrid. HR-TEM images showed the well-covered CeO₂ on NB molecules and the average size of the nanohybrid is ~35 nm. For the fabrication of environmental pollutant electrochemical sensor, the prepared CeO₂/NB nanohybrid was drop-casted on the electrode surface and utilized for the determination of HZ. The nanohybrid modified electrode exhibits higher electrocatalytic activity by showing enhanced oxidation current and less positive potential shift towards HZ oxidation than the bare and individual CeO₂ and NB modified electrodes. The fabricated sensor with excellent reproducibility, repeatability, long-term storage stability and cyclic stability exhibited the sensational sensitivity (484.86 µA mM^-1 cm^-2) and specificity in the presence of 50-fold possible interfering agents with the lowest limit of detection of 57 nM (S/N = 3) against HZ. Utilization of the present sensor in environmental samples with excellent recovery proves it practicability in the determination of HZ in real-time application.

Iron-Doped Titanium Dioxide Nanoparticles As Potential Scaffold for Hydrazine Chemical Sensor Applications

Herein, we report the fabrication of a modified glassy carbon electrode (GCE) with high-performance hydrazine sensor based on Fe-doped TiO2 nanoparticles prepared via a facile and low-cost hydrothermal method. The structural morphology, crystalline, crystallite size, vibrational and scattering properties were examined through different characterization techniques, including FESEM, XRD, FTIR, UV–Vis, Raman and photoluminescence spectroscopy. FESEM analysis revealed the high-density synthesis of Fe-doped TiO2 nanoparticles with the average diameter of 25 ± 5 nm. The average crystallite size of the synthesized nanoparticles was found to be around 14 nm. As-fabricated hydrazine chemical sensors exhibited 1.44 μA µM−1 cm−2 and 0.236 µM sensitivity and limit of detection (LOD), respectively. Linear dynamic ranged from 0.2 to 30 µM concentrations. Furthermore, the Fe-doped TiO2 modified GCE showed a negligible inference behavior towards ascorbic acid, uric acid, glucose, SO42−, NO3−, Pb2+ and Ca2+ ions on the hydrazine sensing performance. Thus, Fe-doped TiO2 modified GCE can be efficiently used as an economical, easy to fabricate and selective sensing of hydrazine and its derivatives.