A phthalimide-based ESIPT fluorescent probe for sensitive detection of Cu2+ in complete aqueous solution

Abstract

A novel fluorescence-enhanced probe 2-butyl-1,3-dioxoisoindolin-4-yl picolinate (BDIP) has been developed for the detection of Cu²⁺ based on the excited-state intramolecular proton transfer (ESIPT) process. BDIP utilized a phthalimide derivative as the fluorophore and selected picolinate ester as the recognition site for Cu²⁺. The probe displayed high selectivity, strong anti-interference ability, and a significant fluorescence enhancement effect for Cu²⁺ in phosphate buffer saline (PBS, 10 mM, pH 7.4) with the detection limit of 31 nM. BDIP also possesses the advantages of simple synthesis steps, large Stokes shift, and good water solubility. Moreover, BDIP was used for Cu²⁺ detection in real water samples, with the result being satisfactory.

Keywords: 3-hydroxyphthalimide; Copper ion (II); Excited-state intramolecular proton transfer; Fluorescent probe.