Alina Catrinel Ion

Electrochemical recognition of metal cations by poly(crown ether ferrocene) films investigated by cyclic voltammetry and electrochemical impedance spectroscopy

Abstract The electrochemical behavior of the pyrrole-substituted crown ether ferrocene 1 was investigated in detail in 0.1 M TBAP+CH 3 CN by cyclic voltammetry (CV) and chronoamperometry. In the potential range 0–0.7 V, a reversible diffusion-controlled process was observed with a formal potential of 0.53 V corresponding to the ferrocene/ferricinium redox couple. Electro-oxidative polymerization of 1 was accomplished either by repeated CV scans, or by controlled potential electrolysis. The resulting polymer films were tested in acetonitrile electrolyte for the amperometric recognition of alkali and alkaline earth metal cations. Their remarkable recognition properties towards Ca 2+ and Ba 2+ cations have been confirmed by electrochemical impedance spectroscopy (EIS). EIS allowed construction of a calibration curve based on the variation of the low frequency capacity of the film as a function of the guest cation concentration, reflecting the variation of the formal potential between the free and the complexed immobilized redox couple. Capacity measurements using EIS appear to be an attractive method for cation sensing with films based on molecular redox receptors.

A Thermodynamics Study on the Tetrahydrofuran Effect in Exfoliated Graphite Nanoplatelets and Activated Carbon Mixtures at Temperatures between 293.15 and 308.15 K

A thermodynamics study on exfoliated graphite nanoplatelets dispersed in tetrahydrofuran in comparison with activated carbon dispersed in same solvent was realised. The refractive index, speed of sound, and density of diluted mixed binary solutions of exfoliated graphite nanoplatelets and activated carbon in tetrahydrofuran were measured between 0 and 100 kg·m−3 with composition step of 20 kg·m−3 and at temperatures from 293.15 to 308.15 K and at normal pressure. The isentropic compressibility, acoustic impedance, specific refraction, relaxation strength, and space-filling factor have been evaluated for six concentrations, at four different temperatures for each system. The identified possible molecular interactions between the edges and the surface of exfoliated graphite nanoplatelets and tetrahydrofuran molecules, which include modifications in the structure of exfoliated nanostructured materials in tetrahydrofuran solvent and the influence of the temperature, and of the solute concentration have been calculated based on the obtained experimental values.