Synthesis of branched alkoxy side chains containing phthalocyanine derivates and their application in mass sensitive QCM sensors

Abstract

2,3,9,10,16,17,23,24-Octakis-(7,11-dioxaheptadecane-9-oxo) phthalocyanine (Pc) and its Ni and Co derivatives were synthesized, characterized, and systematically investigated in their gas sorption and sensing properties using four different volatile organic compounds. The sorption mechanism and the interaction processes during sorption are followed using multi reflection Attenuated Total Reflection FTIR spectroscopy and the quartz crystal microbalance to determine the active species on the Pc surface and clarify the interaction mechanism. Besides the influence of the Pc centre, substituents effects are discussed and compared to previous investigations of Pcs with electronegative substituents of different strength. The results show that while Pcs with electronegative substituents are more sensitive to polar molecules due to 'rr-'rr and Tr -H interactions, branched alkoxy substituted Pcs as presented here have an unexpected sensitivity to non -polar hydrocarbons due to dominant Van der Waals interactions between the long alkyl moiety of the substituent and the analyte. These are important results for the design of new sensitive molecules in order to improve sensor performance, e.g., in terms of selectivity and sensitivity. However, to complete the understanding of all processes related to the interaction with analyte molecules and responsible for sensor sensitivity and selectivity, parameters such as layer morphology have to be considered, as well. (C) 2016 Elsevier B.V. All rights reserved.