Electrochemical behavior of phenol in alkaline media at hydrotalcite-like clay/anionic surfactants/glassy carbon modified electrode

High-Performance Voltammetric Aptasensing Platform for Ultrasensitive Detection of Bisphenol A as an Environmental Pollutant

Bisphenol A (BPA) as a pervasive endocrine-disrupting compound (EDC) has been shown to cause multiple detrimental effects including cardiovascular disorders, pregnancy complications, obesity, glucose metabolism disorders, and reproductive toxicity even at a concentration as low as tolerable daily intake (TDI) (4 μg/kg/day). In the present study, a novel ultra-sensitive, electrochemical aptasensor was designed using a screen-printed carbon electrode (SPCE) modified by gold nanoparticles (Au NPs) conjugated to thiolated aptamers for accurate determination of BPA in biological, industrial and environmental samples. To characterize the electrochemical properties of the aptasensor, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were implemented. Detection of BPA was also performed through differential pulse voltammetry (DPV) in [Fe(CN)₆]^3–/4– electrolyte solution. Under optimum condition, the present electrochemical aptasensor demonstrated an outstanding linear response in the concentration range of 1 pM to 10 nM with a remarkably low limit of detection of 0.113 pM. Due to the superb affinity between anti-BPA aptamers and BPA molecules, the designed aptasensor did not show any significant interaction with other analytes in real samples. Also, fabricated biosensor remained perfectly stable in long-term storage. The analytical results of the fabricated aptasensor are well compatible with those obtained by the ELISA method, indicating the trustworthiness and reasonable accuracy of the application of aptasensor in real samples. Overall, the proposed aptasensor would be a credible and economical method of precise, reproducible, and highly selective detection of minimum levels of BPA in food containers and clinical samples. This would be a promising strategy to enhance the safety of food products and reduce the risk of BPA daily exposure.

Electrocatalytic Oxidation of 4-Aminophenol Molecules at the Surface of an FeS2 /Carbon Nanotube Modified Glassy Carbon Electrode in Aqueous Medium

FeS₂ /carbon nanotube (CNT) nanocomposites were synthesized and immobilized on the surface of a glassy carbon electrode (GCE) in order to investigate the electrocatalytic conversion of 4-aminophenol (4-AP) into p-quinone in an aqueous medium. The reformed electronic properties (in terms of lowering of band-gap energy and charge-transfer resistance), as well as improved surface area, result in an enhanced redox reaction of 4-AP in the presence of FeS₂ -CNT NCs compared to that with FeS₂ alone. The 4-AP molecules undergo coupled two-proton and two-electron transfer quasi-reversible redox reactions with a symmetry factor of 0.55 and standard rate constant (k°) of 0.8 cm s^-1 . Here, quinone imine is generated as an intermediate which is later converted into quinone in an irreversible hydrolysis reaction. The best catalytic performance can be obtained at the pH value of 7.0.

Electrochemical determination of tetrabromobisphenol A in water samples based on a carbon nanotubes@zeolitic imidazole framework-67 modified electrode

Carbon nanotubes@zeolitic imidazole framework-67 (CNTs@ZIF-67), a conductive composite was prepared from carboxylic carbon nanotubes and a cobalt–imidazole framework. It possesses an excellent adsorption capacity (92.12 mg g⁻¹) for the flame retardant tetrabromobisphenol A (TBBPA). The composite was characterized by transmission and scanning electron microscopy, FTIR and X-ray diffractometry. It was then used to modify an acetylene black electrode. Electrochemical studies showed the current response of the modified electrode to be larger than that of electrodes modified with CNTs-COOH or ZIF-67 only. Electrochemical impedance spectroscopy showed this material combination to improve the conductivity of ZIF-67. The addition of perfluorodecanoic acid further improves the response. The sensor is stable, reproducible, and has a linear range of 0.01–1.5 μM TBBPA concentration, with a 4.2 nM detection limit (at S/N = 3). The sensor was successfully applied to the detection of TBBPA in spiked rain and pool water samples.

Carbon nanotubes@zeolitic imidazole framework-67 (CNTs@ZIF-67), a conductive composite was prepared from carboxylic carbon nanotubes and a cobalt–imidazole framework.

Heteropoly acid supported on sodium dodecyl benzene sulfonate modified layered double hydroxides as catalysts for oxidative desulfurization

The HPW/MgAl-LDH-DBS catalyst was synthesized, and the removal of DBT was almost 100% under the optimal conditions.

Highly stable and ultrasensitive chlorogenic acid sensor based on metal–organic frameworks/titanium dioxide nanocomposites

Metal–organic frameworks/titanium dioxide nanocomposites were utilized as novel electrode materials for ultrasensitive chlorogenic acid determination with improved stability.

Novel hydrothermal synthesis of MoS2nanocluster structure for sensitive electrochemical detection of human and environmental hazardous pollutant 4-aminophenol

A trace level electrochemical detection platform for the determination of environmentally hazardous pollutant 4-aminophenol at MoS₂nanoclusters is reported.

Preparation of platy Co/Al hydrotalcites using aluminum hydroxide and investigation of their tribological properties in base oil

In this study, the synthesis of Co/Al hydrotalcite (layered double hydroxides: LDHs) using insoluble Al(OH)3 by a hydrothermal method is described. The syntheses were conducted under various conditions. The as-prepared Co/Al-CO32–-LDH was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The tribological properties of the products were evaluated in base oil using four-ball and Plint friction testers. The LDH thus synthesized displays perfect hexagonal platelike morphology having a disk diameter in the range of 0.2–1.5 μm with a thickness of 40 nm. The addition of the product Co/Al-CO32–-LDH, as an additive to the base oil, significantly reduces the friction coefficient (22.3%) and wear (26.1%) compared to base oil alone. The morphology and chemistry of the worn surface were characterized by SEM, atomic force microscopy (AFM), and X-ray absorption near-edge structure (XANES) spectroscopy. The results show that the structural distortion of LDH induced by mechanochemical processes during friction consumes the friction force between the rubbed surfaces, and as a result, the friction and the wear is reduced. Thus, our results show that the LDH sheets absorbed on the worn surface can prevent direct contact between the friction pairs (surfaces) and decreases the roughness of the worn surface.

Introducing absorptive stripping voltammetry: wide concentration range voltammetric phenol detection

“Absorptive stripping voltammetry”, a new electroanalytical method, is validated by phenol detection.

Phenol determination on HDTMA-bentonite-based electrodes

The partial and complete substitution of cations in the interlayer region of clay with different amounts of hexadecyl trimethylammonium bromide (HDTMABr) was performed. The aim was to synthesize organo-bentonites to be used as constituents of porous electrodes for the electrooxidation of phenol. Domestic clay from Bogovina was subjected to a common procedure of the production of organo-bentonites. It included the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction (XRD) analysis, while the textural properties were evaluated by nitrogen physisorption. The multisweep cyclic voltammetry was applied to analyze the behavior of the clay modified glassy carbon electrode. The influences of the surfactant loading and pH of the support electrolyte were investigated. Rapid deactivation of electrodes occurred in an acidic environment, while good stability of the investigated electrodes was obtained in alkaline medium.