Accurate Determination of the Photosensitizer Stern-Volmer Constant by the Oxygen-Dependent Consumption of 1,3-Diphenylisobenzofuran

Because of the absence of phosphorescence, the Stern-Volmer constant (K_SV) of the photosensitizer is hard to determine accurately. Although the delayed fluorescence and correlated fluorescence methods have been proposed to determine K_SV, the weak signal detection and non-uniform excitation enlarged the measurement error. In this work, a method was proposed to accurately determine K_SV by oxygen-dependent consumption of 1,3-diphenylisobenzofuran. The consumption time (δ), as a measurable quantity, is introduced and could be obtained by the absorption spectrum with a high signal-to-noise ratio. Analytically, δ is linearly related to the inverse of oxygen content, and the ratio of the intercept to the slope equals K_SV. Experimentally, rose Bengal was selected to perform this determination; the K_SV is measured to be 43(1) kPa^-1, and the error is reduced by 1 order of magnitude. In addition, metalloporphyrin was used to verify this method.