Influence of temperature variation on spinel-structure MgFe2O4 anchored on reduced graphene oxide for electrochemical detection of 4-cyanophenol

4-Cyanophenol herbicide sensor using multi-walled carbon nanotube embedded dual-microporous polypyrrole nanoparticles as metal-free and environmentally friendly hybrid electrode

A highly sensitive 4-cyanophenol (4-CP) sensor was fabricated using multi-walled carbon nanotube (MWCNT)-embedded dual-microporous polypyrrole nanoparticle-modified screen-printed carbon electrodes (SPCE/DMPPy/MWCNT). The well-defined dual pores of DMPPy and MWCNT (~ 0.53 and ~ 0.65 nm) acted as good analyte absorption agents (shortening the ion diffusion path) and conducting agents (reducing the internal electron-transfer resistance). This enhanced electrical conductivity resulted in the improved electro-oxidation of 4-CP. A higher sensitivity (19.0 μA μM^-1 cm^-2) and lower limit of detection (0.8 nM) were achieved with a wide detection range of 0.001-400 µM (R² = 0.9988). The proposed sensor exhibited excellent recovery of 4-CP in real-world samples. Therefore, the SPCE/DMPPy/MWCNT sensor is regarded highly suitable for rapidly detecting 4-CP.

Carbon Nanomaterials-Based Screen-Printed Electrodes for Sensing Applications

Electrochemical sensors consisting of screen-printed electrodes (SPEs) are recurrent devices in the recent literature for applications in different fields of interest and contribute to the expanding electroanalytical chemistry field. This is due to inherent characteristics that can be better (or only) achieved with the use of SPEs, including miniaturization, cost reduction, lower sample consumption, compatibility with portable equipment, and disposability. SPEs are also quite versatile; they can be manufactured using different formulations of conductive inks and substrates, and are of varied designs. Naturally, the analytical performance of SPEs is directly affected by the quality of the material used for printing and modifying the electrodes. In this sense, the most varied carbon nanomaterials have been explored for the preparation and modification of SPEs, providing devices with an enhanced electrochemical response and greater sensitivity, in addition to functionalized surfaces that can immobilize biological agents for the manufacture of biosensors. Considering the relevance and timeliness of the topic, this review aimed to provide an overview of the current scenario of the use of carbonaceous nanomaterials in the context of making electrochemical SPE sensors, from which different approaches will be presented, exploring materials traditionally investigated in electrochemistry, such as graphene, carbon nanotubes, carbon black, and those more recently investigated for this (carbon quantum dots, graphitic carbon nitride, and biochar). Perspectives on the use and expansion of these devices are also considered.

Integration of iron-manganese layered double hydroxide/tungsten carbide composite: An electrochemical tool for diphenylamine H•+ analysis in environmental samples

Incompetent governance of post-harvest horticultural crops especially apples and pears lead to numerous physiological storage disorders. In order to manage this issue, diphenylamine (DPA) is widely used as an antioxidant and anti-scald agent to preserve fruits from superficial scalds and degradation during storage. As a result, this research focuses on utilizing disposable electrodes constructed with sphere-shaped iron-manganese layered double hydroxide (FeMn-LDH) entrapped tungsten carbide (WC) nanocomposite on its electrochemical performances towards emergent food contaminant, DPA. The importance of the current work is the selection and design of hierarchically structured functional materials especially layered double hydroxides, in virtue of their outstanding properties. These multi-dimensional structures when introduced to form a composite with the highly beneficial tungsten carbide offer excellent characteristics such as exceptional accessibility to active sites, enhanced surface area, and high mass transport and diffusion which serves as advantageous for the electrochemical quantification of DPA. Furthermore, the synergy between FeMn-LDH and WC nanomaterials contributes to the higher active surface area, increased electrical conductivity, fast electron transportation, and ion diffusion, resulting in static properties including a wide linear range (0.01-183.34 μM), low detection limit (1.1 nM), greater sensitivity, selectivity, and reproducibility thus confirming the potential capability of the WC@FeMn-LDH sensor towards the interference-free determination of DPA which validates its practicality and feasibility in real-time. Hence, this work aims to stimulate the fabrication of various advanced hierarchical structures by a simple hydrothermal approach that can have veracity of potential applications.

Investigation of T site variation in spinel aluminates TAl2O4 (T= Mg, Zn & Cu), and formation of electrocatalyst CuAl2O4/carbon for efficient sensing application

Spinel structured aluminates TAl₂O₄ (T = Mg, Zn, and Cu) were synthesized by a facile hydrothermal method. The resultant enhancement in the electrochemical behavior was achieved due to the covalent synergism among the elements coexisting together. Structural and morphological characterizations were performed by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy. MgAl₂O₄, ZnAl₂O₄ and CuAl₂O₄ has displayed same space group Fd3m of Laue class lattice type of the cubic structure as they were synthesized at same temperature (600 °C). CuAl₂O₄ spinel structure displayed a nanoneedle like structure along with the small sized cylindrical particles alongside to which CuAl₂O₄ spinel is combined with activated carbon (CuAl/C) and was applied to develop a facile sensor for the electrochemical detection of Acetaminophen (ACAP) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which exhibited maximum conductivity, and a substantial electroactive surface area. Finally, the defect-rich composite, CuAl/C, showed excellent sensor performance towards DPV with 21.5 nM limit of detection (LOD) in a wide linear working range of 0.199 μM-165.88 μM ACAP concentration, with a high sensitivity of 19.1221 μA μM^-1cm². Additionally, the sensor showed excellent recovery results in real-time analysis for environmental aquatic samples like industrial wastewater and Tuna Fish.

Vanadium selenide decorated reduced graphene oxide nanocomposite: A co-active catalyst for the detection of 2,4,6 - Trichlorophenol

Transition metal chalcogenides (TMCs) have great potential in diverse electrochemical technologies owing to their unique characteristics. In the present work, we portray the design and synthesis of Vanadium selenide (V₂Se₉)/reduced graphene oxide (rGO) forming a two-dimensional (2D) hybrid nanocomposite via a simple hydrothermal method. The successfully synthesized nanocomposite underwent in-depth surface and morphological characterizations by XRD, Raman spectroscopy, XPS, TEM, STEM and its potential as an electro catalyst was investigated by using glassy carbon electrode (GCE) for the detection of 2,4,6-trichlorophenol (TCP). The structural features favored a high charge transfer ratio, high surface area as well as excellent conductivity and catalytic activity. The V₂Se₉/rGO/GCE modified electrode showed a low charge transfer resistance (R_ct) of 54.057 Ω cm², a decent detection limit (LOD) of 35.07 nM and a very high sensitivity of 22 μA μM^-1 cm^-2 in a working range of 0.001 μM-1150 μM. This is due to the active proton interaction, surface enhancement, and positive synergistic effect between rGO and V₂Se₉. The proposed sensor has good detection potential in agricultural soil, river water, fish, and beverage samples like wine and apple juice. The obtained results from our investigation would elucidate the application of the catalyst in electrochemical sensors.

Fabrication of Novel and Potential Selective 4-Cyanophenol Chemical Sensor Probe Based on Cu-Doped Gd2O3 Nanofiber Materials Modified PEDOT:PSS Polymer Mixtures with Au/µ-Chip for Effective Monitoring of Environmental Contaminants from Various Water Samples

Herein, a novel copper-doped gadolinium oxide (Cu-doped Gd2O3; CGO) nanofiber was synthesized by a simple solution method in the basic phase and successfully characterized. We have used Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Energy-Dispersive Spectroscopy (EDS) techniques for characterization of the CGO nanofiber. The CGO nanofiber was used later to modify Au-coated μ-Chips with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer mixtures (coating binder) to selectively detect 4-cyanophenol (4-CP) in an aqueous medium. Notable sensing performance was achieved with excellent sensitivity (2.4214 µAµM-1 cm-2), fast response time (~12 s), wide linear dynamic range (LDR = 1.0 nM-1.0 mM: R2 = 0.9992), ultra-low detection limit (LoD; 1.3 ± 0.1 pM at S/N = 3), limit of quantification (LoQ; 4.33 pM), and excellent reproducibility and repeatability for CGO/Au/μ-Chip sensor. This CGO modified Au/μ-chip was further applied with appropriate quantification and determination results in real environmental sample analyses.

Toward the Development of Disposable Electrodes Based on Holmium Orthovanadate/f-Boron Nitride: Impacts and Electrochemical Performances of Emerging Inorganic Contaminants

Rare-earth metal orthovanadates have great technological relevance in the family of rare-earth compounds owing to their excellent physical and chemical properties. A significant number of studies have been carried out on this class of compounds to exploit their electrochemical properties in virtue of variable oxidation states. But holmium vanadate (HoV) and its morphology selective synthesis have not been considered, which can have potential applications similar to the rest of the family. In this work, we propose the synthesis of superior architectures of HoV with a functionalized boron nitride (f-BN) nanocomposite. The synergistic effect between HoV and f-BN can have a positive effect on the physical characteristics of the nanocomposite, which can be explored for its electrochemical capacity. Here, HoV incorporated with f-BN is explored for the electrochemical detection of Hg²⁺ ions, which is known for its toxicity-induced environmental health hazards. The structural and compositional revelation reveals higher conductivity and faster electron transfer in the composite, which facilitates a wide working range (0.02-53.8 and 64.73-295.4 μM), low limit of detection (5 nM), higher sensitivity (66.6 μA μM^-1 cm^-2), good selectivity over 10-fold higher concentration of other interfering compounds compared to Hg²⁺ ion concentration, and good cycles stability (30 segments) toward Hg²⁺ ion detection. This also envisages the morphology selective synthesis and utilization of other rare-earth metals, whose electrochemical capacities are unexplored.

Integration of samarium vanadate/carbon nanofiber through synergy: An electrochemical tool for sulfadiazine analysis

Antibiotic pollution causes worldwide concern due to its more apparent consequences, namely antibiotic resistance and destruction of the environment. Extensive use of antibiotics in human and veterinary drugs releases a significant amount of toxins into the sphere of living matter, causing adverse ecological impacts. This requires the design of new analytical protocols for the effective mitigation and monitoring of hazardous pharmaceutical products to reduce the environmental burden. Therefore, we present here the hydrothermal synthesis of samarium vanadate/carbon nanofiber (SmV/CNF) composite for the determination of sulfadiazine (SFZ). The synergistic effect arising from the combination of SmV and CNF accelerates charge transfer kinetics along with the creation of more surface-active sites that benefit effective detection. The structural and compositional disclosure indicates the high purity and superior attributes of the composite material that possesses the ability to improve catalytic performance. The proposed SmV/CNF sensor exhibits important static characteristics such as wide linear response ranges, low detection limit, high sensitivity and selectivity, and increased stability. To the best of our knowledge, this is the first report on the electrochemical performance of SmV/CNF, establishing its potential application in real-time analysis of environmentally hazardous contaminants.

An electrochemical sensing of phenolic derivative 4-Cyanophenol in environmental water using a facile-constructed Aurivillius-structured Bi2MoO6

Harmful chemicals are always found in the environment and it is necessary to construct a viable sensor to detect those chemicals. In order to construct an electrochemical sensing platform, designing an electrode using bismuth mixed oxides are more important and which grabbed more attention due to its high electrocatalytic ability and conductivity. In this literature, we report a facile synthesis of thorn apple like structured pure bismuth molybdate (Bi₂MoO₆) using a simple hydrothermal assisted one-step calcination method and we report a facile method to sense 4-cyanophenol by electrochemical technique. Bi₂MoO₆ modified (Glassy Carbon electrode) GCE possess two linear ranges 0.1-39.1 µM and 46.6-110.1 µM with excellent detection limit 0.008297 µM and 0.01097 µM. Also, this novel sensor is steady with good stability, repeatability, and reproducibility. Successfully, the environmental water sample is analyzed as a real sample with a feasible and quantification results which were compared with HPLC analysis.

Sustainable synthesis of AFe2O4 (A = Mg, Zn, Mn) catalysts: comparing the photooxidative and electrochemical properties towards organic dyes detection and degradation

By serving as alternatives to toxic and hazardous solvents, green solvents assist in implementing the idea of sustainability.