Platinized agarose microspheres as a new modifier in graphite paste electrodes for the electrochemical determination of 4-aminophenol

Optimization of voltammetric parameters for sensitive and simultaneous determination of ferulic acid and vanillin using a glassy carbon electrode based on 2-aminonicotinic acid in the presence of surfactant media

The electrochemical sensor for simultaneous determination of ferulic acid (FA) and vanillin (VA) was prepared by electrochemical deposition of 2-aminonicotinic acid (2-ANA) on the glassy carbon (GC) electrode. The voltammetric determination of FA and VA was performed in the BR buffer solution in the presence of sodium dodecyl sulfate as a surfactant with SWV. The parameters of the SWV technique were optimized by response surface methodology experimental design. Under optimized conditions, the 2-ANA/GC modified electrode presented a linear working range of 2.8 × 10-8 M to 7.50 × 10-6 M and 7.50 × 10-6 M to 2.45 × 10-5 M for FA, 3.06 × 10-8 M to 1.27 × 10-5M for VA. The detection limit (LOD) values for FA and VA were 6.87 nM and 9.23 nM, respectively. Using the 2-ANA/GC sensor, concentrations of FA and VA in instant coffee and milk samples were determined with %recovery values between 103.40 and 97.07 and %RSD values between 0.76 and 4.40.

Chlorocobaloxime containing N-(4-pyridylmethyl)-1,8-naphthalamide peripheral ligands: synthesis, characterization and enhanced electrochemical hydrogen evolution in alkaline medium

Two new discrete cobaloxime based complexes with the general formula [ClCo(dioxime)₂L] (1 and 2), L1 = N-(4-pyridylmethyl)-1,8-naphthalamide, L2 = 4-bromo-N-(4-pyridylmethyl)-1,8-naphthalamide have been synthesized and characterized by various spectroscopic techniques such as FT-IR, ¹H, ¹³C{¹H} NMR and PXRD. The molecular structures of both complexes have also been determined using single crystal X-ray crystallography. The solid state molecular structures revealed distorted octahedral geometry around the Co(III) central metal ion with two dioximes in the equatorial plane and axial positions are occupied by chloro and pyridine nitrogen of N-(4-pyridylmethyl)-1,8-naphthalamide ligands. Both complexes exhibit weaker non-covalent interactions (C-H⋯O, C-H⋯Cl and C-H⋯π(Centroid) in complex 1 whereas C-H⋯O and C-H⋯Br in complex 2) resulting in the formation of dimeric and 1D supramolecular structures. Furthermore, these complexes are immobilized onto the surface of activated carbon cloth (CC) and their electrocatalytic performance for the hydrogen evolution reaction (HER) has been investigated in alkaline and acidic media as well as buffer solution. In alkaline medium, we found that complex 2 exhibited impressive electrocatalytic HER activity and produced a current density of -10 mA cm^-2 at an overpotential of 260 mV, whereas complex 1 produced the same current density at an overpotential of 334 mV. An electrochemical impedance spectroscopy (EIS) spectral study revealed the faster charge transfer kinetics of complex 2 than that of complex 1. Similarly, the low Tafel slope (100 mV dec^-1) for the HER with complex 2 indicates faster HER kinetics compared to complex 1. The chronoamperometric study showed that complex 2 is stable under electrocatalytic HER conditions for 5 h without losing the initial current density and it has also been established that the complex structure is retained after electrocatalysis.

Screen-printed graphite electrode modified with Co3O4nanoparticles and 2D graphitic carbon nitride as an effective electrochemical sensor for 4-aminophenol detection

We fabricated a new electrochemical 4-aminophenol sensor based on a nanocomposite of Co₃O₄nanoparticles and graphite carbon nitride (Co₃O₄@g-C₃N₄), used for the modification of a screen-printed electrode (Co₃O₄@g-C₃N₄/SPE). The synthesized nanocomposite was characterized using field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and Fourier transform-infrared (FT-IR) techniques. The electro-oxidation of 4-aminophenol in phosphate buffer solution (pH = 7.0) was investigated via cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The peak current of oxidation in the optimized conditions had a linear relationship with various 4-aminophenol contents (0.05-780.0μM) with a correlation coefficient of 0.9996 and the limit of detection (S/N = 3) of 1.5 × 10^-8M. The developed method was successful to determine 4-aminophenol in real specimens, with acceptable outcomes.