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

Abstract

The popular textbook and literature model I(λ x ,λ m ) = λ λ − − K( , )(1 10 ) A x m 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 ) = λ λ − + K A ( , ) 10 A d A d x m x,f ( ) x,s x m,s 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.

Effects of Cascading Optical Processes: Part I: Impacts on Quantification of Sample Scattering Extinction, Intensity, and Depolarization

“…One example is the inner filter effect (IFE) imposed by the sample light absorption. The absorption IFE introduces nonlinearity to light scattering, Raman scattering, surface-enhanced Raman scattering, and fluorescence emission intensities as a function of the analyte concentration and causes spectral distortion. − …”

“…There is extensive literature on the effects of light absorption on optical spectroscopic measurements, including the mathematical models for correcting the absorption IFE on the sample scattering and fluorescence intensities. − However, the literature studying the impact of light scattering on spectroscopic measurements is sporadic. For example, questions like the general applicability of Beer’s law for experimental scattering extinction have, to our knowledge, not been critically examined.…”

Total Luminescence Spectroscopy for Quantification of Temperature Effects on Photophysical Properties of Photoluminescent Materials

“…This approach can lead to questionable conclusions because the fluorophore emission intensity is related to both its fluorescence QY and its light absorption in a rather complex manner, as shown in a recently developed firstprinciple model. 39 Third, the existing literature has been predominantly focused on the temperature effects at the fluorophore Stokes-shifted fluorescence (SSF). A few recent works have been devoted to the temperature effects on anti-Stokes-shifted fluorescence (ASSF).…”

“…51 The use of the TPL method for studying the temperature effects on the optical properties of PL materials is inspired by our recent work performed with anthracene (ANT). 39 This earlier work showed that the temperature effect on ANT fluorescence depends on the employed excitation and emission wavelengths. However, the general applicability of the conclusion is unknown because ANT is the only fluorophore used, and only four excitation wavelengths were employed for fluorescence excitation.…”

“…Second, many studies explicitly or implicitly attribute the temperature-induced emission intensity change to the variation in the fluorophore fluorescence quantum yield (QY). − The possible temperature effects on the sample light absorption are not considered. This approach can lead to questionable conclusions because the fluorophore emission intensity is related to both its fluorescence QY and its light absorption in a rather complex manner, as shown in a recently developed first-principle model . Third, the existing literature has been predominantly focused on the temperature effects at the fluorophore Stokes-shifted fluorescence (SSF).…”