Back to the Drawing Board: A Unifying First-Principle Model for Correlating Sample UV-Vis Absorption and Fluorescence...

The popular textbook and literature model I(λ_x,λ_m) = $K({\lambda }_x,{\lambda }_m)(1-{10}^{-A_x})$ or its variants for correlating the sample absorption and fluorescence often fails even for the simplest samples where the fluorophore is the only light absorber. Reported is a first-principle model I(λ_x,λ_m) = $K({\lambda }_x,{\lambda }_m)A_{x,f}{10}^{-(A_{x,s}{d}_x+A_{m,s}{d}_m)}$ for correlating the sample fluorescence measured with a conventional spectrofluorometer and its UV-vis absorbance quantified with a conventional UV-vis spectrophotometer. This model can be simplified or expanded for a variety of fluorescence analyses. First, it enables curve-fitting fluorescence intensity as a function of the fluorophore or sample absorbance over a sample concentration range impossible with existing models. Second, it provides the theoretical foundation for an inner-filter-effect (IFE)-correction method developed earlier and explains mathematically the linearity between the IFE-corrected fluorescence and the fluorophore concentration or absorbance. Third, this model can be expanded for quantitative mechanistic studies of fluorescence intensity variations triggered by stimuli treatments. One demonstrated example is to quantify temperature effects on the emission-wavelength-specific and total fluorescence quantum yield of anthracene. We expect that this first-principle model will be broadly adopted for both student education that promotes evidence-based learning and a variety of fluorescence applications where disentangling sample absorption and emission are critical for reliable data analysis.