Detection of silver(I) ions based on the controlled self-assembly of a perylene fluorescence probe

In the current work, we report a label-free fluorescence turn-on approach for the sensitive and selective sensing of Ag+. A cationic perylene derivative, compound A, was used as the fluorescence probe. Compound A monomer is strongly fluorescent, and the fluorescence can be efficiently quenched through self-aggregation (self-assembly). A cytosine (C)-rich oligonucleotide, oligo-C, was employed. In the absence of Ag+, oligo-C induced strong compound A aggregation due to electrostatic interactions in aqueous media, and very weak fluorescence signal was detected. However, in the presence of Ag+, the specific interactions between oligo-C and Ag+ induced hairpin structure formation of oligo-C through C–Ag+–C bonding interactions. Oligo-C binding to compound A aggregates was weakened; therefore, compound A monomer could be released and detected. The intensity of the fluorescence signal was directly related to the amount of Ag+ added to the assay solution. Our method is highly sensitive—a limit of detection of 5 nM was obtained—and also very selective. Ag+ detection in complex sample mixtures was also demonstrated.