Influence of Biodiesel Content on Fluorescence Anisotropy of Undiluted Diesel-Biodiesel Blends Using Anisotropy-Resolved Multidimensional Emission Spectroscopy (ARMES)

The production of diesel-biodiesel blends (DBB) aims to mitigate the environmental impacts of diesel combustion. However, gaps remain in understanding their molecular properties, particularly fluorescence anisotropy (FA), which reflects molecular rotation and environmental constraints (e.g., viscosity, polarity). This property depends on the viscosity and polarity of the medium and understanding it can provide valuable insights for the development of robust analytical methods to evaluate the biodiesel content in undiluted DBB. In this study, anisotropy-resolved multidimensional emission spectroscopy (ARMES) was applied to investigate the FA, providing new insights into the molecular behavior of these mixtures under undiluted conditions. The biodiesel samples were produced through the transesterification of soybean oil, and the DBB mixtures were prepared with varying biodiesel contents (0 to 100% w/w). ARMES was applied to the samples, enabling the acquisition of anisotropy maps (AM) for each mixture. It was observed that anisotropy varied significantly with the biodiesel content and was more pronounced in intermediate blends (B10 to B50) due to the increased viscosity of the samples. Additionally, the polarity of the mixtures influenced molecular rotation, affecting the observed anisotropy values. The ARMES technique proved to be effective in analyzing complex systems such as DBB, providing new insights into the molecular behavior of these mixtures in undiluted environments.