Voltammetric Behavior of Copper(II) Phthalocyanine
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2025-07-11 |
| Journal | ECS Meeting Abstracts |
| Authors | Joseph Guillaume, Graham T. Cheek |
Abstract
Section titled āAbstractāIntroduction Metal substituted phthalocyanines have many applications including pigments (1) as well as sensors and electronic applications (2). The present paper explores the electrochemical behavior of copper(II) phthalocyanine (CuPC) in both aqueous and nonaqueous (acetonitrile) media at glassy carbon and boron-doped diamond (BDD) electrodes. It has been found in this laboratory that simply rubbing a glassy carbon (GC) or a boron-doped diamond (BDD) electrode on CuPC powder results in a surface deposit which allows electrochemical investigation. We report here the results of such investigations in aqueous 0.10 M KNO 3 and acetonitrile/0.0M tetraethylammonium tetrafluoroborate (TEA BF 4 ). The goal was to gain a general understanding of CuPC electrochemistry and to assess the possibility of producing electrochemical responses for ballpoint pen ink lines on paper. Experimental Water was purified using a Barnstead E-Pure system. Acetonitrile (anhydrous) and CuPC were obtained from Sigma/Aldrich. Potassium nitrate (KNO 3 ) was obtained from Fisher Scientific. Tetraethylammonium tetrafluoroborate (TEA BF 4 ) was purchased from Sachem. Voltammograms were acquired using a Gamry Interface 1010E potentiostat, and potentials were measured against a Ag/AgCl reference electrode (eDAQ ET073). Glassy carbon (GC, 3 mm diameter) electrodes were purchased from BASi, and the BDD (3 mm diameter) electrode was obtained from eDAQ. Results and Discussion Considering that CuPC has very limited solubility in most solvents (2), an alternative method of investigating CuPC electrochemistry was used. In a manner similar to that previously reported for PtPC (3), the glassy carbon or BDD electrode was rubbed in a circular fashion on several milligrams of CuPC in a weighing boat. This action produced sufficient CuPC deposit on the electrode surface to give easily measured currents for the CuPC electrochemical response. Figure 1 shows a typical cyclic voltammogram for a CuPC deposit on glassy carbon at 100 mV/s in acetonitrile/0.10M TEA BF 4 . The initial positive-going potential sweep from 0.00 V shows an initial multi-component oxidation process at +1.4 V vs Ag/AgCl, followed by another less complicated oxidation process at +1.7 V, probably due to ligand-centered oxidations (2). On the reverse sweep, several reduction processes are observed. Scan reversal at +1.50 V showed that the peak at +1.40 V is coupled to the reduction peak at +0.92 V. The reduction process at -1.27 V is independent of the oxidation processes noted above, having a similar appearance when an initial negative-going sweep was used. A second sweep resulted in very little current in the voltammograms, showing that the CuPC redox processes cause the CuPC film to be released from the electrode. A similar voltammogram in aqueous 0.10 M KNO 3 resulted in a series of poorly resolved oxidation processes in the +0.90 V to +1.50 V range, with virtually no reduction current on the return sweep. This observation is consistent with the lower potential range available in water compared to acetonitrile, and the possible interaction of water with the CuPC oxidation products. Experiments at BDD electrodes yielded mostly similar results. Finally, glassy carbon and BDD electrodes were rubbed on various blue ballpoint pen markings on copier paper, and voltammograms were obtained in aqueous 0.10 M KNO 3 . In some cases, broad oxidation processes were found in the +1.2 V to +1.4 V region. Such behavior shows the possibility of obtaining useful electrochemical signatures for ballpoint ink, which may prove useful for forensic investigations. Conclusions Useful cyclic voltammetric behavior for CuPC on glassy carbon and boron-doped diamond electrodes has been observed in both aqueous 0.1M KNO 3 and acetonitrile/0.1 M TEA BF 4 . Mechanical adhesion (ie, rubbing) of CuPC onto the electrode surfaces was employed due to the limited solubility of CuPC in these media. For some blue ballpoint pen inks on paper, voltammetric responses were obtained by the similar method of rubbing the electrodes on the paper samples. References Brunelle, R. L.; Crawford, K. R. Ink Chemistry. Advances in the Forensic Analysis and Dating of Writing Ink ; Charles C Thomas, 2003; pp. 13-46 LāHer, M and Pondaven, A., Electrochemistry of Phthalocyanines,in āThe Porphyrin Handbook,ā Kadish, K., Smith, K., and Guilard, R., Eds., Academic Press, New York, 2003, Volume 16, Chapter 104, pp 117-151. Jiang, J. and Kucernak, A., Electrochimica Acta , 2000, 45 , 2227-2239. Figure 1. Cyclic voltammogram of CuPC rubbed onto the surface of a glassy carbon (3 mm diameter) electrode in acetonitrile / 0.10 M TEA BF 4 . Scan rate: 100 mV/s. Figure 1