Label-free selective sensing of mercury(ii)via reduced aggregation of the perylenefluorescent probe

Abstract

In the present work, we report a fluorescence turn-on approach for the sensitive and selective detection of Hg²⁺. A cationic perylene derivative (compound 1) was used as the fluorescence probe, and a thymine-rich oligonucleotide (oligo-M) was employed for the specific interaction with Hg²⁺. Compound 1 shows strong tendency to self-aggregate into linear chain structures in aqueous media because of the π–π stacking interactions of its planar aromatic ring structure. The compound 1 free monomer is strongly fluorescent, whereas its aggregates are not fluorescent. When oligo-M and compound 1 were mixed, oligo-M induced strong compound 1 aggregation and resulted in significant fluorescence quenching. In the presence of Hg²⁺, the specific interactions between oligo-M and Hg²⁺ induced hairpin structure formation of oligo-M and thus weakened its binding to compound 1 aggregates. As a result, free probe monomers were released, and increased fluorescence was observed. The fluorescence intensity increase was in direct proportion to the concentration of Hg²⁺ added. Our method provides a simple, fast, and efficient means for Hg²⁺ quantification, it is highly sensitive with a limit of detection of 1 nM, and is also highly selective against other common metal ions.