LAUSR

Fluoride ion detection in water focuses much attention due to the serious healthy impact in human pathologies. For the fluoride recognition, the chemical affinity between fluoride and silicon has been developed but based on the degradation mechanism. Thus, most fluorescent probes are "turn off" type due to the aggregation of the degradational products and performed in organic solvents. Herein, we first developed an "off-on" hydrophilic luminescent polymer composed of amino-functionalized polyhedral oligomeric silsesquioxane (AE-POSS) and perylene diimides (PDI) for fluoride ion in water. The AE-PDI polymer was "turn off" because of the photoinduced electron transfer (PET) between PDI and AE-POSS, and then after reaction with F-, the fluorescent emission could "turn on" obviously because the PET was blocked by the degradation of cage. The PET from amino-POSS to PDI was proved by FL spectrum and energies of HOMO and LUMO orbitals. With adding NaF, the induced FL enhancement of AE-PDI Polymer was increased by near 41 times and other common anions did not have any effect. 29Si, 19F NMR and 1H NMR titration, XRD, FTIR, size analysis and ion chromatograph were applied to demonstrate the degradation mechanism. These results indicated that the higher quantum yield could be obtained by introducing the amide group in the PDI and the products of AE-PDI Polymer might exist in the form of complex compounds with partially condensation of organosiloxane. With high selectivity and sensitivity (detection limit of 16.2 ppb), this probe was successfully applied for F-detection in actual water samples.