Oxygen concentration dependent studies reveal the Stern-Volmer constant KSV of ZnPc

The determination of the Stern-Volmer constant ( K SV ) for photosensitizers, a key parameter for characterizing energy transfer efficiency to oxygen, enables the understanding and optimization of photosensitizer functionality. In this study, a strategy was proposed for determining the K SV by replacing the analysis of the oxygen-dependent behavior of fluorescence intensity with a direct correlation between singlet oxygen quantum yield (Φ Δ ) and molecular oxygen. Zinc phthalocyanine (ZnPc) was selected for this work due to its promising photosensitizing properties. Through theoretical analysis using the rate equation model and experimental absorption measurements, the K SV of ZnPc was found to be 2.4(2) μM −1 . To verify the accuracy of the K SV , an oxygen-varying correlated fluorescence methodology was applied, reinforcing the reliability of the results. In addition, the determination of the K SV is achievable even in the absence of specific Φ Δ values and without the use of a standard reference.