Toward chemical sensing: an electrochemical study of the selectivity trend of metal phthalocyanines

Metalated phthalocyanines (MPcs) are a special class of organic semiconductors having unique chemical structures and properties. The material’s conjugated 18-π electron structure enables a strong fusion with carbon nano tubes (CNTs) which have a highly delocalized π electron structure. This strong binding between MPc and CNT facilitates the study of the material in an electrochemical cell. Here in this account, we report a novel method of identifying the selectivity and sensitivity trend of several MPcs with different metal cores through an electrochemical approach. Sensor electrode was prepared by drop casting the MPc solution on paper strips coated with CNT ink, and then tested in electrochemical cell in a 2-electrode fashion. The nature of the redox reactions between MPc and the VOC analytes (i.e., acetone, ethanol, isopropanol, and methanol) were studied through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. Four different metalated phthalocyanines (CoPc, CuPc, MgPc, and ZnPc) are studied here. Experimental results suggest large shift in conductivity in the CoPc sensor upon exposure to ethanol, MgPc sensor upon exposure to isopropanol, and ZnPc sensor upon exposure to acetone.