Abstract
Metal phthalocyanines are well-known sensing phases with applications in different scientific fields due to their interesting properties. Detailed characterization by Raman spectroscopy was performed in order to study the shifting of the vibrational bands related to the coordination sphere of each metal phthalocyanine. In this work, a study involving the use of screen-printed electrodes (SPEs) with various metal phthalocyanines to electrochemically detect and quantify chlorine (Cl2) gas is presented. The Cl2 gas was generated in-situ via oxidation of the chloride present in form of aqueous salt solutions. The developed method offers not only the possibility to quantify chlorine, but also to discriminate among several chlorinated species due to the changes observed in the voltammetric profiles associated with the interaction between the specie assayed and the phthalocyanine metallic center. Optimization of detecting parameters was also performed to apply this procedure for the quantification of chlorine generated from commercial chlorine tablets. The development of this proof of concept shows interesting possibilities and easy-to-use applications with novel on metal phthalocyanines based SPE sensors.
Highlights
Phthalocyanines are planar aromatic systems analogous to porphyrins but with an important feature, the central cavity of the ring can be replaced with a metal ion bonded to the four pyrrole nitrogen atoms
Four commercial phthalocyanine based screen-printed electrodes (SPEs) have been characterized by the Raman spectroscopic technique
The Raman spectra show that their vibrational bands are located at the same position, the characteristic band between 1510 and 1540 cm−1 allows us to quickly identify them because they are metal dependent: 1533 cm−1 for CoPH, 1524 cm−1 for CuPH, 1512 cm−1 for MnPH
Summary
Phthalocyanines are planar aromatic systems analogous to porphyrins but with an important feature, the central cavity of the ring can be replaced with a metal ion bonded to the four pyrrole nitrogen atoms. About 70 different metals [1] can be used as the central ion, opening new gates in the generation of phthalocyanines with tunable properties. As it is well known, Raman spectroscopy is one of the most interesting techniques for characterizing different materials, compounds and electrochemical processes [11,12,13,14,15,16]. It is a potential approach for characterizing metal phthalocyanines because it provides structural information related to their molecular vibrational modes [17]. The resonance Raman effect of metal phthalocyanines allows obtaining well-defined bands in Raman spectra, being interesting for their ability of identification in pigments, solutions and biological matrices [18] and the study of their structural
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