Using Electrochemical Data to Obtain Energy Diagrams for Layer-By-Layer Films from Metallic Phthalocyanines

Abstract

Energy diagrams have been obtained for iron tetrasulfonated phthalocyanine (FeTsPc) and nickel tetrasulfonated phthalocyanine (NiTsPc) from electrochemical and electronic absorption measurements in layer-by-Layer (LbL) films with chitosan in the cationic layers. This was made possible because the chitosan/FeTsPc and chitosan/NiTsPc modified electrodes exhibited a reversible, highly stable electrochemical response, with the voltammetric signal being preserved after several cycles in the range between 0 and 1.0V vs Ag/AgCl. The ionization potential (IP), electroaffinity (EA) and energy gap (Eg) were similar for both systems, suggesting that the coordinating metal atom does not play an important role in the elelctronic properties of the immobilized phthalocyanines. Chitosan was found suitable for the cationic layers as it did not affect the electrochemical current appreciably. The anodic peak current varied linearly with the scan rate for chitosan/NiTsPc and chitosan/FeTsPc films, denoting charge transport via electron hopping within the film, typical of a polymer-modified electrode.

Keywords

• layer-by-layer
• energy diagrams
• ionization potential
• energy gap
• phthalocyanine
• chitosan