Detection and discrimination of Zn2+ and Hg2+ using a single molecular fluorescent probe

Abstract

A new fluorescent probe (SAPH) has been introduced which shows specific sensing towards Zn²⁺ and Hg²⁺ at two different wavelength maxima at physiological pH. The probe shows a brilliant ratiometric red shift in emission spectra upon addition of Zn²⁺ at 678 nm while upon addition of Hg²⁺ it shows a turn-on ratiometric emission enhancement with a red shift at 647 nm. Job's plot confirms the 1 : 1 complexation for both Zn²⁺ and Hg²⁺. The binding constants have been calculated using the Benesi–Hildebrand equation and found to be 3.03 × 10⁵ M⁻¹ and 6.05 × 10⁴ M⁻¹ respectively for SAPH–Zn²⁺ and SAPH–Hg²⁺. DFT and TDDFT studies are conducted using the probe to establish a similarity between theoretical and experimental outcomes.