Ionofluorochromic Nanoparticles Derived from Octapyrene-Modified Polyhedral Oligomeric Silsesquioxane Organic Frameworks for Fluoride-Ion Detection

Three octapyrene-modified POSS molecules, POSS-(C 0 -Py) 8, POSS-(C 1 -Py) 8, and POSS-(C 3 -Py) 8, were successfully prepared by condensation reactions between pyrenecarboxylic acid and amino-substituted POSS in good yield, and they were structurally characterized by various spectroscopic methods. All three POSS molecules could form stable supramolecular hydrogen-bonded organic framework (HOF) structures via amide linkages. Among them, POSS-(C 1 -Py) 8 displayed the purest excimer emission because of the efficient stacking of pyrene residues in its HOF structure, which was further developed to a highly efficient green-emissive ionofluorochromic sensor for the F – ion. This ratiometric fluorescence sensor displayed unique selectivity to the F – ion with a detection limit of lower than 5 × 10 –5 M and rapid detection within 10 min, and it almost did not respond to anions such as Cl –, Br –, I –, AcO –, NO 3 –, ClO 4 –, and HPO 4 2– ions. A comparative experiment using the ion chromatography method to measure the concentration of the F – ion was conducted, revealing that our ionofluorochromic sensor had better selectivity and higher antiinterference ability than the traditional chromatography method particularly in the presence of interfering anions. In contrast to the common F – ion fluorescence sensors, which rely on the turn-on or turn-off of fluorescence, and other traditional chromatography techniques, this type of F – ionofluorochromic sensor would make fast and reliable detection of the F – ion attractive and convenient.