Spectroscopic investigation of inner filter effect by magnolol solutions

Spectroscopy is useful tool for aggregation studies on fluorephores. One of the major problems with this technique is that the inner filter effect becomes unavoidable since the samples are used at high concentration. In this work, our investigation on magnolol spectroscopic properties shows that the inner filter effect (IFE) of fluorescence plays a critical role in the spectra of magnolol. The strong dependence of the fluorescence parameters on the concentration accounts for the apparent experimental evidence of magnolol aggregation at high concentrations. There are some questions despite the aggregation model based on fluorescent aggregates seems to describe the behavior of the system. The mathematical correction on the emission intensities shows the linear fluorescence–concentration relationship. Furthermore, we propose a mathematic model of excitation spectrum based on the primary IFE (absorption of light of excitation wavelength), which provide a correct explanation of the unusual spectral shift and spectral narrowing in the excitation spectra of magnolol at high concentrations. The shapes of spectra are completely independent on magnolol aggregation and are due only to experimental artifacts, i.e. IFE.