A near infrared fluorescent dye for trivalent ions sensing and working as a molecular keypad lock

Abstract

A near infrared fluorescent dye (DNSA-SQ) with internal charge transfer (ICT) properties is presented for selectively screening trivalent ions (Al³⁺/Fe³⁺/Cr³⁺) with a ratiometric fluorescence change over other metal ions. A 2 : 1 stoichiometric binding mode between the dye and the trivalent ions was confirmed. Moreover, DNSA-SQ prefers to interact with monovalent Ag⁺ ions in the presence of a protein, resulting in a fluorescence enhancement. Using a synergistic effect, DNSA-SQ also behaves as a molecular keypad lock with sequential chemical inputs of BSA and Ag⁺ ions.