Laser induced fluorescence spectroscopy of aqueous eosin Y solution

Abstract

Eosin Yellow (EY) is commonly used for staining in medicine, biology, food industry, textiles, painting and cosmetics. The spectroscopic and photochemical properties of this synthetic dye have also attracted attention, making it an excellent tool for chemical identification and biosensor applications. Since EY is prone to photo-degradation upon illumination by photons at wavelengths near to the main absorption bands, special considerations should be taken into account regarding its optical characterization. In the present report, laser induced fluorescence (LIF) features of aqueous EY solution due to excitation at 405 nm and 532 nm wavelengths, under conditions with the least likelihood of photo-degradation, have been assessed by emphasizing the effect of LIF internal filters. The quantum distribution of LIF emission is demonstrated to be dependent on both the excitation wavelength and EY concentration, as well as the detection line of sight. Since the fluorescence spectrum of EY is a convolution of the monomer and dimer emissions, and those contributions change unevenly under the influence of internal filters, the corresponding spectral changeovers were investigated based on the assessment of spectral asymmetry and the use of difference spectra analysis. The inner filter effects, dimerization, and resonance energy transfer between monomers and dimers were the basis for the discussion of the results.