Spectral assignments to the light emissions of fluorescent organic small molecules in aqueous medium

Spectrofluorometric identifications of artificial organic dyes have important environmental significance, but both scattered light signals and the fluorescence signals were twins in fluorospectroscopy, and the light scattering signals are always the interference sources of spectrofluorometry. In order to investigate the relationship between the light scattering and fluorescence in the spectrofluorometric measurements, herein we discuss the scattered light and fluorescence emission properties of organic small molecules (OSMs) using Lignin Pink (LP) in neutral medium as an example. With the help of UV–vis measurements, and starting from three-dimensional light emission measurements, scattered light and fluorescence emissions could be assigned. Investigations by increasing LP concentration showed that the light emission at 282.0 and 344.0 nm could be attributed to the resonance light scattering (RLS) signals and that at 420.0 and 570.0 nm are composed of both RLS and fluorescence emissions, respectively. UV–vis measurements showed that LP does not have the tendency of aggregation, and the strong RLS signals should be ascribed to the large hydrodynamic diameter of LP itself in aqueous medium, supported by dynamic light scattering (DLS) measurements.