ELECTROCHEMICAL BEHAVIOR OF PILLAR[5]ARENE ON GLASSY CARBON ELECTRODE AND ITS INTERACTION WITH Cu2+ AND Ag+ IONS

The electrochemical behavior of pillar[5]arene (P[5]A) and of its reaction products with Ag+ and Cu2+ ions has been investigated using cyclic voltammetry, optical methods and transmission electron microscopy (TEM). Stepwise oxidation of hydroquinone units of P[5]A molecule is guided by self-assembling and acid-base interactions. From one to three hydroquinone units per P[5]A molecule are oxidized depending on the measurement conditions. The deposition of P[5]A on glassy carbon electrode (GCE) partially blocks the electron transduction. Interfering influence of dissolved oxygen can be partially eliminated by the use of carbon black as immobilization matrix. The reaction of P[5]A with silver ions results in formation of most stable form with three benzoquinone and two hydroquinone units stabilized by quinhydrone-like structure. The Ag nanoparticles formed in the reaction retain electron transduction with the electrode due to involvement of shielding P[5]A molecules. Similar reaction with Cu2+ ions does not lead to stable products because of the formation of Cu2+ particles detected by UV spectroscopy and TEM. Possible analytical applications of the materials obtained were proved by electrocatalytic reduction of hydrogen peroxide and mediated oxidation of thiocholine as model systems. In both cases, high sensitivity and wide range of the concentration determined were shown. (C) 2014 Elsevier Ltd. All rights reserved.