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

Three
octapyrene-modified POSS molecules, POSS-(C0-Py)8, POSS-(C1-Py)8, and POSS-(C3-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-(C1-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–, NO3–, ClO4–, and HPO42– 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.