Electrochemical sensor amplified with cellulose nanofibers/Fe3O4 composite to the monitoring of hydrazine as a pollutant in water and wastewater samples

A quite swift and sensitive analytical instrument was designed in this work to detect and monitor hydrazine in various water and wastewater samples. The glassy carbon electrode (GCE) was amplified using cellulose nanofibers/Fe₃O₄ composite (CNF-Fe₃O₄/NC) for monitoring hydrazine in the concentration range of 0.001 - 140 M with a superior detection limit of 0.5 nM. Results showed a diffusion control process for the oxidation of hydrazine at the surface of CNF-Fe₃O₄/NC/GCE. Under the optimum condition (pH=8.0), the oxidation current of hydrazine was improved by about 2.3 times and the oxidation potential was reduced by about 60 mV at the surface of CNF-Fe₃O₄/NC/GCE compare to unmodified GCE. A standard addition method was employed to assess CNF-Fe₃O₄/NC/GCE's capability for the detection of hydrazine in water and wastewater samples, and a recovery range of 97.6 % to 104.9 % was noted.

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.

Flow injection amperometric sensing of hydroxylamine at a Cu(ii)–neocuproine-functionalized multiwalled carbon nanotube/screen printed carbon electrode

In the electrocatalytic oxidation mechanism of NH₂OH at modified electrode, firstly NH₂OH reacted with [Cu(Ncp)₂]²⁺ and oxidized to N₂O. The formed [Cu(Ncp)₂]⁺ was reoxidized by giving electrons to electrode resulting in enhancement of anodic current.

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.

Integrating brucine with carbon nanotubes toward electrochemical sensing of hydroxylamine

Based on the intrinsic electrochemical features of brucine integrated with carbon nanotubes (brucine/SWNTs), dimeric quinoid brucine was electrochemically generated by electroactivation of a brucine/SWNTs-modified GC electrode and used as a novel electrocatalyst for efficient electro-oxidation of hydroxylamine (HA). The electrocatalytic activity was investigated with cyclic voltammetry in the range pH 2.0 to pH 11.0, and the best electrocatalytic performance of the electrocatalyst was obtained at pH 10.0. By taking advantage of the electrocatalytic activity of the dimeric quinoid brucine toward HA, we have developed an electrochemical sensor for HA measurements based on a brucine/SWNTS-modified GC electrode using amperometry with the applied potential of + 0.1 V (vs. Ag/AgCl). Under the optimized conditions, the current response toward HA concentration shows a linear relationship in the dynamic ranges of 0.1-10 μM and 10-1000 μM with a detection limit of 0.021 μM based on the 3σ criterion. The sensor was used to assay HA in pharmaceuticals including hydroxyurea tablets and pralidoxime iodide injections with satisfactory results. The spike-and-recovery for samples of tap water (n = 9) and lake water (n = 9) was within 97.17-100.16%. Graphical abstract Schematic illustration of electrochemical sensing of hydroxylamine (HA) enabled by integrating brucine with single-walled carbon nanotube (brucine/SWNTs) based on electro-activation of brucine/SWNTs-modified GC electrode.

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.

Electrosynthesis of carbon aerogel-modified AuNPs@quercetin via an environmentally benign method for hydrazine (HZ) and hydroxylamine (HA) detection

An ultrasensitive electrochemical sensor fabricated using a hydrothermal and environmentally benign methods for the detection of environmental pollutions, namely, hydrazine (HZ) and hydroxylamine (HA) has been described.

Heterostructural CuO-ZnO Nanocomposites: A Highly Selective Chemical and Electrochemical NO2 Sensor

A simple one-step chemical method is employed for the successful synthesis of CuO(50%)-ZnO(50%) nanocomposites (NCs) and investigation of their gas sensing properties. The X-ray diffraction studies revealed that these CuO-ZnO NCs display a hexagonal wurtzite-type crystal structure. The average width of 50-100 nm and length of 200-600 nm of the NCs were confirmed by transmission electron microscopic images, and the 1:1 proportion of Cu and Zn composition was confirmed by energy-dispersive spectra, i.e., CuO(50%)-ZnO(50%) NC studies. The CuO(50%)-ZnO(50%) NCs exhibit superior gas sensing performance with outstanding selectivity toward NO2 gas at a working temperature of 200 °C. Moreover, these NCs were used for the indirect evaluation of NO2 via electrochemical detection of NO2 - (as NO2 converts into NO2 - once it reacts with moisture, resulting into acid rain, i.e., indirect evaluation of NO2). As compared with other known modified electrodes, CuO(50%)-ZnO(50%) NCs show an apparent oxidation of NO2 - with a larger peak current for a wider linear range of nitrite concentration from 20 to 100 mM. We thus demonstrate that the as-synthesized CuO(50%)-ZnO(50%) NCs act as a promising low-cost NO2 sensor and further confirm their potential toward tunable gas sensors (electrochemical and solid state) (Scheme 1).

Quantum chemical and electrochemical studies of lysine modified carbon paste electrode surfaces for sensing dopamine

We have improved the sensitivity of a carbon paste electrode from lysine for the sensitive detection of dopamine.