Lithium phthalocyanine (γ-structure) as a molecular oxygen sensor

Synthesis and characterization of lithium phthalocyanine radicals were performed, which were followed by an investigation on its ability to detect oxygen levels in biologically relevant concentrations. EPR studies confirmed the presence of at least two phases, one sensitive to oxygenation (γ-phase) and the second one insensitive to oxygenation (α-phase). Contrary to the findings reported in the literature, it was observed that the γ-phase was not stable at and above 95 °C and slowly transformed into the α-phase crystallographic structure. Above 150 °C, only a broad signal of α-phase existed. Additional characterizations were performed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry, dynamic light scattering (DLS), and Raman spectroscopy on pristine crystals Li₂Pc and LiPc sensors.