Apparent quantum yield – Key role of spatial distribution of irradiation

Abstract

Based on the apparent quantum yield, photocatalytic activities are compared under various experimental conditions. However, their assessment from experimental data requires knowing the intensity of incident light, which generally differs from that emitted by a radiation source. Most reports provide apparent quantum yields derived from emission intensity, leading to inaccurate, and often strongly underestimated, figures. To correlate differences between emitted and incident light intensity, we measured local light intensity at discrete points of an incident surface, approximated its spatial distribution by linear interpolation and extrapolation, calculated total incident light energy by integration, and compared this value with that given by irradiation source manufacturer. The calculated incident light energy was lower than that provided by the manufacturers of all irradiation sources tested. Due to this refinement (lower energy), the obtained apparent quantum yields are actually higher, even 5 times higher in case of LED radiation, than those calculated using manufacturer data.