The discrimination between phospholipids of diverse structure and phosphacoumarins of various hydrophobicity through fluorescent response of Tb-doped silica nanoparticles decorated by cationic surfactant.

The work represents colloids of silica nanoparticles displaying fluorescent response on biorelevant compounds exemplified by phosphacoumarins and phospholipids. The luminescent properties of the colloids arise from Tb(III) complexes doped into silica nanoparticles (SNs). The noncovalent decoration of SNs by dicationic surfactant with further interfacial binding of dye anions enables to develop colloids programmed to display a substrate induced fluorescent response. The latter results from the quenching of Tb(III) centered luminescence by dye anions through dynamic mechanism and subsequent displacement of quenching anions by the non-quenching substrates from the interface of SNs. Both negative charge and hydrophobicity of substrates are the key factors affecting the selectivity of the substrate induced fluorescent response. The peculiar effects of zwitter-ionic and anionic phospholipids on the fluorescent response have been revealed. The applicability of the fluorescent procedure in the sensing of impurities in commercial phosphatidylcholine is also introduced.