Multi-luminescent switching of metal-free organic phosphors for luminometric detection of organic solvents

Metal-free organic phosphors can be an attractive smart optical sensing materials since, in such compounds, intersystem crossing (ISC) and the phosphorescence process are placed in subtle competition with fluorescence, internal conversion (IC), and non-radiative decay pathways. Here, we report a unique environment-dependent multi-luminescence switching behavior of metal-free organic phosphorescent materials. Through combined photophysical measurements and computational electronic structure analysis, we systematically investigated how physicochemical properties of organic solvents affect the photophysical pathways of the metal-free organic phosphors. By rationally adapting the finding into phosphor-doped electrospun polymer fibers, we developed a new luminometric sensory platform and achieved selective detection of eight different common organic solvents. The presented finding provides new possibilities for metal-free organic phosphors to be a novel class of smart optical sensory materials.