Ti3AlC2 MAX Phase Modified Screen-Printed Electrode for the Fabrication of Hydrazine Sensor.

Hydrazine is considered a powerful reducing agent and catalyst, showing diverse applications in agricultural industries, toxic degradation research, and wastewater management. Additionally, hydrazine can trigger some specific reactions when combined with suitable oxidants. Due to its highly polar nature, hydrazine can easily dissolve in alcohol, water, and various other polar solvents. Therefore, it can be extensively utilized in different areas of application and industries such as rocketry and various chemical applications. Despite its beneficial properties, hydrazine is unstable, posing significant risk due to its highly toxic nature. It is extremely hazardous to both human health and the environment. It can cause various illnesses and symptoms such as dizziness, temporary blindness, damage to the central nervous system, and even death when inhaled in sufficient quantities. Therefore, it is highly important to monitor the level of hydrazine to prevent its toxic and hazardous effects on human beings and the environment. In the present study, we discuss the simple fabrication of a disposable cost-effective and eco-friendly hydrazine sensor. We used a screen-printed carbon electrode, i.e., SPCE, as a base for the construction of a hydrazine sensor. The Ti3AlC2 MAX has been used as a suitable and efficient electrode material for the fabrication of disposable hydrazine sensors. We modified the active surface of the SPCE using a drop-casting approach. The resulting Ti3AlC2 MAX modified SPCE (Ti3AlC2@SPCE) has been utilized as an efficient and low-cost hydrazine sensor. Cyclic voltammetry, i.e., CV, and linear sweep voltammetry, viz., LSV, was employed as a sensing technique in this study. The optimization of pH and electrode material loading was conducted. The Ti3AlC2@SPCE exhibited excellent sensing performance toward hydrazine oxidation. A reasonable detection limit (0.01 µM) was achieved for hydrazine sensing. The fabricated sensor also demonstrated a reasonable linear range of 1-50 µM. This work provides the design and fabrication of simple disposable Ti3AlC2@SPCE as a suitable electrode for the determination of hydrazine using LSV technology.

Turn-on Coumarin Precursor: From Hydrazine Sensor to Covalent Inhibition and Fluorescence Detection of Rabbit Muscle Aldolase.

Hydrazine, a highly toxic compound, demands sensitive and selective detection methods. Building upon our previous studies with pre-coumarin OFF-ON sensors for fluoride anions, we extended our strategy to hydrazine sensing by adapting phenol protecting groups (propionate, levulinate, and γ-bromobutanoate) to our pre-coumarin scaffold. These probes reacted with hydrazine, yielding a fluorescent signal with low micromolar limits of detection. Mechanistic studies revealed that hydrazine deprotection may be outperformed by a retro-Knoevenagel reaction, where hydrazine acts as a nucleophile and a base yielding a fluorescent diimide compound (6,6'-((1E,1'E)-hydrazine-1,2diylidenebis(methaneylylidene))bis(3(diethylamino)phenol, 7). Additionally, our pre-coumarins unexpectedly reacted with primary amines, generating a fluorescent signal corresponding to phenol deprotection followed by cyclization and coumarin formation. The potential of compound 3 as a theranostic Turn-On coumarin precursor was also explored. We propose that its reaction with ALDOA produced a γ-lactam, blocking the catalytic nucleophilic amine in the enzyme's binding site. The cleavage of the ester group in compound 3 induced the formation of fluorescent coumarin 4. This fluorescent signal was proportional to ALDOA concentration, demonstrating the potential of compound 3 for future theranostic studies in vivo.

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.

First Dual Responsive "Turn-On" and "Ratiometric" AIEgen Probe for Selective Detection of Hydrazine Both in Solution and the Vapour Phase.

A new dual responsive "turn-on" and "ratiometric" aggregation-induced emission luminogen (AIEgen) 3-formyl-5-(piperidin-1-yl)biphenyl-4-carbonitrile 6 a (FPBC 6 a) for selective detection of hydrazine in solution as well as in vapour phase is described. At a low concentration of 2.5 µm, the probe FPBC 6 a is non-fluorescent (turn-off) but remarkably lights up (turn-on with blue emission) in the presence of hydrazine solution (0.25-25 µm). Interestingly, at higher concentrations, the nanoaggregates of FPBC 6 a (>25 µm, 99 % HEPES in DMSO) displayed ratiometric response in the presence of hydrazine with a remarkable hypsochromic shift from the green (500-550 nm) to blue regions (440-480 nm). Furthermore, a real application of FPBC 6 a was successfully demonstrated through the detection and visualization of hydrazine in live cervical cancer cells as well as using portable test strips.

Hydroxyapatite/chemically reduced graphene oxide composite: Environment-friendly synthesis and high-performance electrochemical sensing for hydrazine.

It is unexpectedly found that, the in-situ growth of hydroxyapatite (HAP) on graphene oxide (GO) under a moderate temperature (85°C) can effectively trigger the reduction of GO, which needs neither extra reducing agents nor high-temperature thermal treatment. The transmission electron microscope (TEM) experiment demonstrates that the rod-like HAP particles are well attached on the surface of reduced GO (rGO) to form the composite. Electrochemical sensing assays show that the synthesized HAP-rGO nanocomposite presents excellent electrocatalytic capacity for the oxidation of a toxic chemical of hydrazine. When the HAP-rGO modified electrode was utilized as an electrochemical sensor for hydrazine detection, outstanding performances in the indexes of low fabrication cost, short response time (~2s), wide linear range, low detection limit (0.43µM), and good selectivity were achieved. The developed sensor also shows satisfactory results for the detection of hydrazine in real industrial wastewater sample were achieved.

Concentric-Electrode Organic Electrochemical Transistors: Case Study for Selective Hydrazine Sensing.

We report on hydrazine-sensing organic electrochemical transistors (OECTs) with a design consisting of concentric annular electrodes. The design engineering of these OECTs was motivated by the great potential of using OECT sensing arrays in fields such as bioelectronics. In this work, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based OECTs have been studied as aqueous sensors that are specifically sensitive to the lethal hydrazine molecule. These amperometric sensors have many relevant features for the development of hydrazine sensors, such as a sensitivity down to 10-5 M of hydrazine in water, an order of magnitude higher selectivity for hydrazine than for nine other water-soluble common analytes, the capability to entirely recover its base signal after water flushing, and a very low operation voltage. The specificity for hydrazine to be sensed by our OECTs is caused by its catalytic oxidation at the gate electrode, and enables an increase in the output current modulation of the devices. This has permitted the device-geometry study of the whole series of 80 micrometric OECT devices with sub-20-nm PEDOT:PSS layers, channel lengths down to 1 µm, and a specific device geometry of coplanar and concentric electrodes. The numerous geometries unravel new aspects of the OECT mechanisms governing the electrochemical sensing behaviours of the device-more particularly the effect of the contacts which are inherent at the micro-scale. By lowering the device cross-talk, micrometric gate-integrated radial OECTs shall contribute to the diminishing of the readout invasiveness and therefore further promote the development of OECT biosensors.

Preparation and characterization of AuNPs/CNTs-ErGO electrochemical sensors for highly sensitive detection of hydrazine.

A highly sensitive electrochemical sensor of hydrazine has been fabricated by Au nanoparticles (AuNPs) coating of carbon nanotubes-electrochemical reduced graphene oxide composite film (CNTs-ErGO) on glassy carbon electrode (GCE). Cyclic voltammetry and potential amperometry have been used to investigate the electrochemical properties of the fabricated sensors for hydrazine detection. The performances of the sensors were optimized by varying the CNTs to ErGO ratio and the quantity of Au nanoparticles. The results show that under optimal conditions, a sensitivity of 9.73µAµM(-1)cm(-2), a short response time of 3s, and a low detection limit of 0.065µM could be achieved with a linear concentration response range from 0.3µM to 319µM. The enhanced electrochemical performances could be attributed to the synergistic effect between AuNPs and CNTs-ErGO film and the outstanding catalytic effect of the Au nanoparticles. Finally, the sensor was successfully used to analyse the tap water, showing high potential for practical applications.

High performance of electrocatalytic oxidation and determination of hydrazine based on Pt nanoparticles/TiO2 nanosheets.

In this work, highly dispersed Pt nanoparticles (PtNPs) were deposited on the surface of the TiO2 nanosheets (TiO2NSs) by the photodeposition method in the presence of methanol as holes scavengers. The results indicated that PtNPs were distributed on TiO2NSs successfully with the diameter of ca. 5-9 nm. The electrochemical experiments such as electrochemical impedance spectroscopy and cyclic voltammetry were used to study the electrochemical properties of the PtNPs/TiO2NSs modified glassy carbon electrode (GCE). The as-prepared PtNPs/TiO2NSs/GCE presents excellent electrocatalytic activity for hydrazine. The sensor can be used to determine hydrazine at low potential with a wide linear range, high sensitivity, and fast response time. Moreover, the sensor exhibits good selectivity and reproducibility. In addition, the recoveries were 100.1-105.3% for hydrazine in the tap water, indicating the PtNPs/TiO2NSs/GCE should be a promising sensor for the determination of hydrazine in real samples.

Ag-doped ZnO nanoellipsoids: potential scaffold for photocatalytic and sensing applications.

Well-crystalline Ag-doped ZnO nanoellipsoids (NEs) were synthesized in large quantity and used as effective photocatalyst for the photocatalytic degradation of methyl orange (MO) and efficient electron mediator for the fabrication of highly sensitive, reliable and robust hydrazine chemical sensor. The Ag-doped NEs were synthesized by facile low-temperature (~60°C) solution process and characterized in detail using various characterization techniques. The characterizations revealed that the synthesized nanostructures are well-crystalline, possessing ellipsoidal shapes and were grown in very high density. The photocatalytic activities of these Ag-doped NEs were evaluated by measuring the rate of photodegradation reaction of hazardous methyl orange (MO) dye under UV light irradiation. By comparing the photocatalytic performance of Ag-doped ZnO NEs with those of ZnO nanoflowers, the former was found to be a much superior photocatalyst than the later. Further, Ag-doped ZnO NEs based hydrazine sensor exhibited a high sensitivity of ~9.46 µA/cm(2)µM and detection limit of 0.07 µM in a response time of <10s. Thus we find that Ag-doped ZnO nanomaterials synthesized by simple solution process holds potential as efficient photocatalysts and efficient electron mediators for the fabrication of robust and highly sensitive chemical sensors.