Synthesis and electrochemical properties of a nickel(II) thiacalix[4]arene-based electrocatalyst for the hydrogen evolution reaction

Thiacalix[4]arene with four sulfur-bridging atoms and four hydroxy coordinating groups in the lower rim is a promising candidate for powerful electrocatalytic hydrogen production. However, there are only a few examples reported in the literature where conjugated thiacalix[4]arene is used as a pre-catalyst for the hydrogen evolution reaction. The present work evaluates the electrocatalytic performance of a nickel(II) coordination complex based on generic thiacalix[4]arene. The coordination complex is characterized by cyclic voltammetry, where two reduction peaks are observed at −0.57 and −1.33 V for the two redox couples Ni2+/Ni+ and Ni+/Ni, respectively. The proton reduction occurs at the second peak potential with a slight shift at about −1.0 V, with increasing peak currents directly related to the number of acetic acid equivalents. The maximum peak current was observed to be at about 67 µA for 20 equiv. of acetic acid.

Tryptophan-Stabilized Au-FexOy Nanocomposites as Electrocatalysts for Oxygen Evolution Reaction

Au-FexOy nanocomposites with a variable gold-to-iron ratio were stabilized with l-tryptophan. The synthetic methodology is based on the facile redox reaction between Au(III) and Fe(0) in the presence of gold nanoparticle as a seed at room temperature in an aqueous medium. The synthesis results in the deposition of Au nanoparticles on the surface of iron oxide layers. Composition variation in the nanocomposites was obtained by controlling the seed amount and reducing agent. These nanocomposites are used as electrocatalysts for the thermodynamically unfavorable oxygen evolution reaction (OER) from water. Among the nanocomposites, the most efficient OER activity was observed from the nanocomposite 12. The content of iron with respect to gold is at the maximum in the nanocomposite, which was obtained from the reaction with a minimum seed concentration and maximum reducing agent.

Electrochemical detection of dopamine by a calixarene-cellulose acetate mixed Langmuir-Blodgett monolayer

The sensing performance of a Langmuir-Blodgett monolayer was significantly improved by controlling the film organization at the air-water interface. Cellulose acetate (CA) and 4-tert-butylcalix [6]arene (calix) were co-spread and formed a Langmuir film, which was efficiently transferred onto a preoxidized gold electrode, Au_ox. The modified gold electrode was applied as a fast, highly sensitive electrochemical sensing platform for the quantitative determination of a model molecule, dopamine (DA). The modified gold electrode, CA-calix/Au_ox, demonstrated better recognition and sensing ability towards dopamine as compared with electrodes modified by a single component. Under the optimized conditions, the reduction peak currents at the CA-calix/Au_ox increased linearly within the concentration range of dopamine from 5 to 100 and 100-7500 nM, and exhibited a very low limit of detection (LOD) of 2.54 nM (S/N = 3). These results suggest a simple, superior and efficient approach for the controllable rearrangement of Langmuir-Blodgett monolayers on a molecular level. The electroanalytical performance was optimized from the perspective of the electrode-electrolyte interface.