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

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Sensing

Background:

• Lithium phthalocyanine (LiPc) radicals are investigated for oxygen sensing applications.
• Understanding phase stability and oxygen sensitivity is crucial for sensor development.

Purpose of the Study:

• To synthesize and characterize lithium phthalocyanine radicals.
• To investigate their oxygen detection capabilities at biologically relevant concentrations.
• To determine the thermal stability of different LiPc phases.

Main Methods:

• Electron paramagnetic resonance (EPR) spectroscopy to identify and quantify phases.
• Electrochemical impedance spectroscopy (EIS) for electrical properties.
• Cyclic voltammetry (CV) for electrochemical behavior.
• Dynamic light scattering (DLS) for particle size analysis.
• Raman spectroscopy for structural characterization.

Main Results:

• Two distinct phases of LiPc were identified: an oxygen-sensitive γ-phase and an oxygen-insensitive α-phase.
• The γ-phase was found to be unstable above 95 °C, transforming into the α-phase.
• Above 150 °C, only the α-phase signal was observable.
• Characterization of pristine Li2Pc and LiPc sensors was performed.

Conclusions:

• Lithium phthalocyanine radicals exhibit potential for oxygen sensing.
• Thermal instability of the oxygen-sensitive γ-phase limits its application at elevated temperatures.
• Further research may focus on stabilizing the γ-phase or utilizing the α-phase for different sensing mechanisms.