Highly selective chemosensor for repetitive detection of Fe3+ in pure water and bioimaging.

Combining octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) with amine-containing polyacrylamide (OV-POSS co-poly(acrylamide)) gives a new fluorescent polymeric chemo-sensor with complete water solubility. It shows better selectivity for Fe3+ in water over a wide detection range (pH = 4-10). The incorporation of Fe3+ into OV-POSS co-poly(acrylamide) results in a significant fluorescence enhancement in water over other metal ions. The bound ratio of OV-POSS co-poly(acrylamide)-Fe3+ complex was determined to be 1 : 2 according to the Job's plot. The association constant (Ka) of Fe3+ binding with the chemosensor was 7.416 × 107, and the detection limit was 0.9 × 10-9 M. Moreover, it was found that the system possessed low cytotoxicity, good permeability, high stability, and compatibility. Hence, it can be successfully applied in bio-imaging with bright blue fluorescence. In addition, a visible color change to the naked eye from colorless to bright yellow could be directly observed when Fe3+ was added into the chemosensor OV-POSS co-poly(acrylamide) compared with other metal ions.