A sensitive electrochemical detection of hydrazine based on SnO2/CeO2 nanostructured oxide

Non-Enzymatic Glucose Sensors Composed of Polyaniline Nanofibers with High Electrochemical Performance

The measurement of glucose concentration is a fundamental daily care for diabetes patients, and therefore, its detection with accuracy is of prime importance in the field of health care. In this study, the fabrication of an electrochemical sensor for glucose sensing was successfully designed. The electrode material was fabricated using polyaniline and systematically characterized using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and UV-visible spectroscopy. The polyaniline nanofiber-modified electrode showed excellent detection ability for glucose with a linear range of 10 μM to 1 mM and a detection limit of 10.6 μM. The stability of the same electrode was tested for 7 days. The electrode shows high sensitivity for glucose detection in the presence of interferences. The polyaniline-modified electrode does not affect the presence of interferences and has a low detection limit. It is also cost-effective and does not require complex sample preparation steps. This makes it a potential tool for glucose detection in pharmacy and medical diagnostics.

Simultaneous removal of methylene blue and Cr(VI) in a dual-chamber photocatalytic microbial fuel cell with WO3/MoS2/FTO photocathode

Carbon felt was used as the anode and WO3/MoS2/FTO (fluorine-doped tin oxide) was used as the photocathode in a photocatalytic microbial fuel cell (PMFC). The photoelectric performance of the WO3/MoS2/FTO photocathode and the removal efficiency of methylene blue (MB) and Cr(VI) mixed pollutants were systematically investigated in the cathode chamber. The results showed that after 12 h of light irradiation in the PMFC with WO3/MoS2/FTO as the photocathode, the removal rates of MB and Cr(VI) were 84.56 and 68.11 %, respectively, which were much higher than those using WO3/FTO as a photocathode (55.57 % and 45.26 %, respectively). The corresponding maximum output power was 33.14 mW/m2, which was 1.85 times that of the WO3/FTO photocathode PMFC. These results can be attributed to the fact that WO3 is an n-type semiconductor and MoS2 is a p-type semiconductor. Analysis of trapping experiments showed that the composite of WO3 and MoS2 formed a Z-scheme heterojunction, which improved the separation efficiency of the photoelectric carriers and enhanced the pollutant removal efficiency of the photocathode. PMFCs are a new and environment-friendly technology for removing pollutants thereby providing an experimental basis for future engineering applications.

Parthenium hysterophorus derived nanostructures as an efficient carbocatalyst for the electrochemical sensing of mercury(II) ions

The sustainable utilization of resources motivate us to create eco-friendly processes for synthesizing novel carbon nanomaterials from waste biomass by minimizing chemical usage and reducing energy demands. By keeping sustainability as a prime focus in the present work, we have made the effective management of Parthenium weeds by converting them into carbon-based nanomaterial through hydrothermal treatment followed by heating in a tube furnace under the nitrogen atmosphere. The XPS studies confirm the natural presence of nitrogen and oxygen-containing functional groups in the biomass-derived carbon. The nanostructure has adopted a layered two-dimensional structure, clearly indicated through HRTEM images. Further, the nanomaterials are analyzed for their ability towards the electrochemical detection of mercury, with a detection limit of 6.17 μM, while the limit of quantification and sensitivity was found to be 18.7 μM and 0.4723 μM μA-1 cm-2, respectively. The obtained two-dimensional architecture has increased the surface area, while the nitrogen and oxygen functional groups act as an active site for sensing the mercury ions. This study will open a new door for developing metal-free catalysts through a green and sustainable approach by recycling and utilization of waste biomass.

Remarkably fast and reusable photocatalysis by UV annealed Cu2O-SnO2 p-n heterojunction

Powdered micro- or nano-particles photocatalyst has separation and recovery challenges, which may create a second pollution to environment and harmful to animals. To address those issues, SnO2, Cu2O and Cu2O-SnO2 p-n heterojunction thin films are formed on glass substrates using efficient co-sputtering method that is commonly employed for large-area high-definition display panel. Using first-order kinetics, 100 °C ultraviolet (UV) annealed Cu2O-SnO2 p-n heterojunction shows the superb fast degradation rate constant of 0.21 and 0.16 min-1 for methylene blue (MB) and methyl orange (MO) organic dyes, respectively, as photogenerated electron-hole pairs is increased. Record best degradation rate constants of 0.19 and 0.11 min-1 for respective MB and MO are still achieved even after four repeated cycles. The 100 °C UV annealed Cu2O-SnO2 film catalyst displays greater degradation efficiency in both dyes, reaching 100% degradation at room temperature after 30 and 35 min of illumination for MB and MO respectively. The scavenger experiments show that hydroxyl (·OH) and superoxide radicals (·O2-) are the major active species in the degradation of dye. The 100 °C UV annealed Cu2O-SnO2 film catalyst showed stability as well as reusability towards the dye degradation. As a result, the present work delivers an effective way to enhance the photocatalytic performance and also an easy recovery of the catalyst, which can be explored for various emerging pollutants.

Quinoline-derived electron-donating/withdrawing fluorophores for hydrazine detection and applications in environment and bioimaging

Substitution can be employed to competently tune the photophysical properties of chemosensors. The effect of substituents on the absorption and emission properties of quinoline probes was investigated. Therefore, salicylaldehyde (S), N-diethylamino-salicylaldehyde (D), and nitro-salicylaldehyde (W)-based quinoline Schiff base derivatives were investigated with hydrazine and studied for their photophysical properties. The nucleophilic substitution reaction was used as a sensing mechanism between the probes and hydrazine and investigated with 1H NMR, HR-MS characterizations, and DFT calculations. The sensitivity of QW-R is greater than that of QS-R and QD-R because of the stronger intramolecular charge transfer (ICT) in QW-R. The calculated LOD values are 28 nM for QS-R, 30 nM for QD-R, and 9 nM for QW-R. The probes were employed to monitor gaseous hydrazine using a smartphone and analyze solution forms of hydrazine in soil, water, and food samples, and living cells. Moreover, the in situ hydrazine release was monitored with bioimaging by administering an isoniazid drug. Significantly, the electronic effect of substituents over fluorescence showing, ranging from electron-donating to electron-withdrawing was investigated. We anticipate that this approach may be a promising strategy for the rational design of fluorescent sensors.

AgBr nanoparticle surface modified SnO2 enhanced visible light catalytic performance: characterization, mechanism and kinetics study

In this study, a simple hydrothermal procedure and in situ precipitation method were used to prepare SnO2-AgBr composites, where the molar ratios of SnO2 and AgBr were 1 : 1, 1 : 2 and 2 : 1. Characterization results showed that the composites had excellent dispersion, crystallinity, and purity. A photocatalytic degradation experiment and first-order kinetic model indicate that SnO2-AgBr (1 : 1) had the best photocatalytic performance, and the degradation rates of 30 mg L-1 simulated MO and MG wastewater reached 96.71% and 93.36%, respectively, in 150 min, which were 3.5 times those of SnO2. The degradation rate of MO and MG increases with the dosage. Humic acid inhibited the degradation of MG, while a low concentration of humic acid promoted the degradation of MO, and the composite has good stability with pH. A free radical trapping experiment shows that ·OH and ·O2- were the main active substances, and h+ was the secondary one. According to the results of the characterization and photocatalysis experiments, a Z-scheme mechanism for the SnO2-AgBr composite was proposed, and the degradation pathway of target pollutants was speculated upon. This study has conceived novel methods for the development of a mature Z-scheme mechanism and in doing so has provided new approaches for the development of photocatalysis for water pollution control.

Investigation on the Structural and Photocatalytic Performance of Oxygen-Vacancy-Enriched SnO2-CeO2 Heterostructures

In this study, pure CeO2 and oxygen-vacancy-enriched SnO2-CeO2 composite materials were prepared using the sol-gel method, and their microstructures and photocatalytic properties were investigated. The results indicate that SnO2 coupling promotes the separation and transfer of photogenerated electrons and holes and suppresses their recombination. The 50% SnO2-CeO2 composite material exhibited a decreased specific surface area compared to pure CeO2 but significantly increased oxygen vacancy content, demonstrating the highest photogenerated charge separation efficiency and the best photocatalytic performance. After 120 min of illumination, the degradation degree of MB by the 50% SnO2-CeO2 composite material increased from 28.8% for pure CeO2 to 90.8%, and the first-order reaction rate constant increased from 0.002 min-1 to 0.019 min-1.

Enhanced electrocatalytic activity of fluorine doped tin oxide (FTO) by trimetallic spinel ZnMnFeO4/CoMnFeO4 nanoparticles as a hydrazine electrochemical sensor

In the present study, ZnMnFeO₄ and CoMnFeO₄ tri-metallic spinel oxide nanoparticles (NPs) were provided using hydrothermal methods. The nanoparticles have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and electrochemical techniques. A reliable and reproducible electrochemical sensor based on ZnMnFeO₄/CoMnFeO₄/FTO was fabricated for rapid detection and highly sensitive determination of hydrazine by the DPV technique. It is observed that the modified electrode causes a sharp growth in the oxidation peak current and a decrease in the potential for oxidation, contrary to the bare electrode. The cyclic voltammetry technique showed that there is high electrocatalytic activity and excellent sensitivity in the suggested sensor for hydrazine oxidation. Under optimal experimental conditions, the DPV method was used for constructing the calibration curve, and a linear range of 1.23 × 10^-6 M to 1.8 × 10^-4 M with a limit of detection of 0.82 ± 0.09 μM was obtained. The obtained results indicate that ZnMnFeO₄/CoMnFeO₄/FTO nano sensors exhibit pleasant stability, reproducibility, and repeatability in hydrazine measurements. In addition, the suggested sensor was efficiently employed to ascertain the hydrazine in diverse samples of cigarette tobacco.

A fluorescent probe based on triphenylamine with AIE and ICT characteristics for hydrazine detection

A fluorescent probe MAM based on triphenylamine scaffold was synthesized. The electron donating group 4-methoxyphenyl and the electron acceptor dicyanoethylene were introduced on the triphenylamine scaffold to form a D-π-A fluorescent probe. The probe MAM exhibited the typical aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) characteristics with the bright orange-red fluorescent emission in high water fraction (f_w ≥ 50%) and negligible emission in low water fraction. The probe MAM could detect hydrazine (N₂H₄) in DMSO-tris-HCl (10 mM, pH7.4, v/v, 3:1) with high selectivity and sensitivity. The specific reaction between MAM and hydrazine and the formation of the hydrazone blocked the ICT process, and the system emitted the cyan fluorescence which could be easily observed by naked eyes. The limit of detection (LOD) was 0.196 μM (6.25 ppb), which is lower than the US Environmental Protection Agency standard (10 ppb). The test strips prepared by the probe MAM could realize the convenient and rapid detection of N₂H₄ solution and vapor. The application of MAM in actual water samples and cells was investigated, and the results showed that MAM could sense N₂H₄ in environmental and biological aspects with potential application prospects.

Smartphone-assisted microfluidic and spectrophotometric recognition of hydrazine: a new platform towards rapid analysis of carcinogenic agents and environmental technology

Hydrazine (Hyd), a poisonous substance, is frequently employed in agriculture and industry as a scavenger to remove residues of oxygen from boiler feed water, electrical power plants, etc. Even at trace amounts, these chemicals are hazardous to humans. To limit the risks of exposure, there is a critical need for sensors for the monitoring of Hyd concentration to guarantee they are below harmful levels. In comparison to other approaches, the colorimetric method has garnered a great deal of interest due to its high sensitivity, speed, convenience, and simple optical color change detection. This study's primary purpose is to develop a portable tool for the colorimetric and spectrophotometric detection of Hyd using silver nanoparticles (silver nanoprism (AgNPr), silver nanowires (AgNW), and silver citrate (AgCit)). In addition, UV-visible spectroscopy was utilized for the quantitation evaluation of Hyd in real samples. The proposed approach demonstrated a linear range of 0.08 M to 6 M for Hyd by AgNW and 0.02 to 5 M by AgNPr as optical probes, whereas AgCit exhibited no color change (negative response). Using AgNPr and AgNW, the low limit of detection of Hyd was 200 μM and 800 μM, respectively. In addition, a novel method was employed for the first time to explore the effect of time on the determination of the candidate analyte. Consequently, the proposed method can be utilized to detect Hyd in real samples. Therefore, our method shows both qualitative and quantitative measurement of Hyd with high sensitivity, low cost, and fast analysis time and promisingly it can be industrialized for quick detection of Hyd in aquatic real samples.

Facile Fabrication of CuO Nanoparticles Embedded in N-Doped Carbon Nanostructure for Electrochemical Sensing of Dopamine

In the present study, a highly selective and sensitive electrochemical sensing platform for the detection of dopamine was developed with CuO nanoparticles embedded in N-doped carbon nanostructure (CuO@NDC). The successfully fabricated nanostructures were characterized by standard instrumentation techniques. The fabricated CuO@NDC nanostructures were used for the development of dopamine electrochemical sensor. The reaction mechanism of a dopamine on the electrode surface is a three-electron three-proton process. The proposed sensor's performance was shown to be superior to several recently reported investigations. Under optimized conditions, the linear equation for detecting dopamine by differential pulse voltammetry is I_pa (μA) = 0.07701 c (μM) − 0.1232 (R² = 0.996), and the linear range is 5-75 μM. The limit of detection (LOD) and sensitivity were calculated as 0.868 μM and 421.1 μA/μM, respectively. The sensor has simple preparation, low cost, high sensitivity, good stability, and good reproducibility.

Sensitive analytical detection of nitrite using an electrochemical sensor with STAB-functionalized Nb2C@MWCNTs for signal amplification

An electrochemical sensor based on stearyl trimethyl ammonium bromide - functionalized niobium carbide@multi-walled carbon nanotubes (Nb₂C@MWCNTs-STAB) for signal amplification was successfully constructed for sensitive detection of nitrite (NO₂^-). Niobium carbide@multi-walled carbon nanotubes (Nb₂C@MWCNTs) with high electrical conductivity and water dispersibility were first prepared in a one-pot hydrothermal synthesis, after which cationic STAB was added to overcome the negative surface charge on the Nb₂C@MWCNTs. The electrostatic attraction between Nb₂C@MWCNTs-STAB and NO₂^- was improved by the STAB, which enhanced the sensitivity of the constructed sensor for NO₂^-. Under optimized conditions, Nb₂C@MWCNTs-STAB/GCE exhibited excellent analytical performance for detection NO₂^- with two wide liner ranges (0.1-100 μmol L^-1 and 100-2000 μmol L^-1) and a limit of detection of 0.022 μmol L^-1. Nitrite recovery tests in milk and spinach samples showed recoveries in the range of 89.82-104.52%. The NO₂^- residues in ham and pickled vegetable (cedrela sinensis) samples were analysed using the presented sensor and a spectrophotometric method, with no significant difference found between the results of the two methods.

Role of Working Temperature and Humidity in Acetone Detection by SnO2 Covered ZnO Nanowire Network Based Sensors

A randomly oriented nanowire network, also called nanonet (NN), is a nano-microstructure that is easily integrated into devices while retaining the advantages of using nanowires. This combination presents a highly developed surface, which is promising for sensing applications while drastically reducing integration costs compared to single nanowire integration. It now remains to demonstrate its effective sensing in real conditions, its selectivity and its real advantages. With this work, we studied the feasibility of gaseous acetone detection in breath by considering the effect of external parameters, such as humidity and temperature, on the device’s sensitivity. Here the devices were made of ZnO NNs covered by SnO₂ and integrated on top of microhotplates for the fine and quick control of sensing temperature with low energy consumption. The prime result is that, after a maturation period of about 15 h, the devices are sensitive to acetone concentration as low as 2 ppm of acetone at 370 °C in an alternating dry and wet (50% of relative humidity) atmosphere, even after 90 h of experiments. While still away from breath humidity conditions, which is around 90% RH, the sensor response observed at 50% RH to 2 ppm of acetone shows promising results, especially since a temperature scan allows for ethanol’s distinguishment.

Palladium-Nickel Electrocatalysts on Nitrogen-Doped Reduced Graphene Oxide Nanosheets for Direct Hydrazine/Hydrogen Peroxide Fuel Cells

In the present work, nitrogen-doped reduced graphene oxide-supported (NrGO) bimetallic Pd–Ni nanoparticles (NPs), fabricated by means of the electrochemical reduction method, are investigated as an anode electrocatalyst in direct hydrazine–hydrogen peroxide fuel cells (DHzHPFCs). The surface and structural characterization of the synthesized catalyst affirm the uniform deposition of NPs on the distorted NrGO. The electrochemical studies indicate that the hydrazine oxidation current density on Pd–Ni/NrGO is 1.81 times higher than that of Pd/NrGO. The onset potential of hydrazine oxidation on the bimetallic catalyst is also slightly more negative, i.e., the catalyst activity and stability are improved by Ni incorporation into the Pd network. Moreover, the Pd–Ni/NrGO catalyst has a large electrochemical surface area, a low activation energy value and a low resistance of charge transfer. Finally, a systematic investigation of DHzHPFC with Pd–Ni/NrGO as an anode and Pt/C as a cathode is performed; the open circuit voltage of 1.80 V and a supreme power density of 216.71 mW cm−2 is obtained for the synthesized catalyst at 60 °C. These results show that the Pd–Ni/NrGO nanocatalyst has great potential to serve as an effective and stable catalyst with low Pd content for application in DHzHPFCs.