Thermal and electrochemical studies of Cu(II) 8-hydroxyquinoline organophilic montmorillonite

Abstract

The thermal and electrochemical behavior of montmorillonite clay-8-hydroxyquinoline (8-HQ) film was studied in the absence and presence of aqueous Cu(II) ions. The suggested formation of the ternary complex type: {Pt/[> Si–O]n[Cu(II)(OH2)n(8-HQ)k]}3−n−k, with thermal stability up to 350 °C, was studied, based on UV-spectroscopy, thermal (DTG-DSC, molecular fluorescence and XRD. The Pt/binary composite film (SWy-1:8-HQ) interphase composed of montmorillonite (SWy-1) with 8-hydroxyquinoline (8-HQ) was investigated by electrochemical techniques analyzing the cyclic voltammograms (CVs) obtained at different scan rates (v) and copper(II) ion concentrations. The mechanical stability of the thin films was demonstrated by performing 80 successive voltammetric cycles. Two pairs of redox peaks, indicated by peaks A/D and C/B were observed. For Cu(II) ions in solution, the log i p × log v relationships showed processes controlled by adsorption, peaks A/D, and by diffusion, peaks C/B. The analysis of i p/v 1/2 and i pa/i pc versus v suggested two homogeneous coupled reactions, being both reversible and fast kinetic chemical reactions, associated to the mechanisms chemical-electrochemical (CE) and electrochemical-chemical (EC), respectively. The modified electrode showed a good sensitivity to low concentrations of Cu(II) ions, which opens the possibility of being used in chemical analysis.