A ratiometric fluorescence sensor for highly selective and sensitive detection of mercuric ion

Mercury is widely used in industry and easily leads to environmental pollution if discharged without proper waste control. On-site visual detection of mercuric ion is thus in demand and remains a great challenge. We herein demonstrate a detection method for rapid and on-site visualization of mercuric ion on the basis of integrating green-emissive imidazol fluorophore (PIPT) and red-emissive quantum dots (QDs) embedded in silica nanospheres. Such a nanohybrid fluorescent probe exhibits dual emissions at 500 nm and 657 nm under a single excitation wavelength. Due to the high chelating ability of PIPT toward mercuric ion, the fluorescence of PIPT could be selectively quenched while the fluorescence of the QDs is almost constant, leading to a distinct fluorescence color change from green to red, which can be applied for the rapid visualization of mercuric ion. This ratiometric fluorescent approach shows high sensitivity, high selectivity and anti-interference toward mercury against other metal ions. The detection limit of this method is determined to be 6.5 nM. The probe has also been successfully demonstrated for the determination of mercuric ion in real water samples. (C) 2014 Elsevier B.V. All rights reserved.