Knowledge Bank

The fluorescence of $Eu3+$ in organic solvents is subject to quenching by the solvent molecules both in the solvation sphere and outside the primary solvation sphere of the complex ion. Binary solvents were employed including $CH3COOH$ and one of the following derivatives of $CH3COOH$, i.e., $CCl3COCl,CF3COOH$, $CHCl2COCl$, $CH2ClCOCl$ $CH3COCl,CD3COOD$, etc. The rare earth salts, $EuCl3$ $\cdot$ $6H2O$, are insoluble in the latter solvents and therefore, the primary solvation sphere of the complex ion consists of $CH3COOH$ only. The primary fluorescence quenching, $kh$ is constant in all systems used whereas the secondary fluorescence quenching rate constant, $ksolvsec$, varies from solvent to solvent. It increases as the overlap between the normalized fluorescence of $Eu3+,IF(\nu ¯)$, and the near-infrared spectrum of the solvent $ϵsolv(\nu ¯)$, increases; i.e., $ksolvsec \alpha \int IF(\nu ¯) ϵsolv(\nu ¯)d\nu ¯$. This project was supported by Owens-Illinois, Corporate Research Laboratories.