A highly selective ratiometric fluorescent chemosensor for Ag+ based on a rhodanineacetic acid–pyrene derivative

A highly selective ratiometric fluorescent Ag+ chemosensor RAAP which featured Ag+-induced enhancement of fluorescence emission and blue-shift of the UV-vis spectrum (64 nm) was developed. Both of the changes are due to the Ag+-induced conformational changes from a pyrene monomer to a pyrene excimer and the formation of a crossing configuration. The fluorescence detection limit of Ag+ can reach 1.0 × 10−7 M, which complies with the standards of US EPA and World Health Organization (WHO) for drinking water (5.0 × 10−7 M). RAAP is organic solvent-stable and pH-stable and its spectral response toward Ag+ is found to be reversible.