Highly selective fluorescence detection of Pt⁴⁺ over Pd²⁺ and Pt²⁺ using a polyethyleneimine-based nanosensor...

A novel polyethyleneimine (PEI)-based polymeric nanosensor (named PEIMP) was developed for specific fluorescence enhanced sensing of Pt⁴⁺ ion in aqueous media. The sensor was fabricated via "one-pot" three-component reaction using ortho-phthalaldehyde (OPA), PEI and mercaptopurine as raw materials, by which the formation of isoindole fluorophore and its chemical grafting onto PEI chain were achieved simultaneously. The morphology, size and structure of PEIMP have been characterized by various techniques. In buffered aqueous solution (pH 7.0), PEIMP had the ability to specifically bind with Pt⁴⁺ producing notable increase in fluorescence emission at 463 nm (excited at 395 nm). Based on investigations on the sensing mechanism, the fluorescence turn-on response towards Pt⁴⁺ was attributed to the binding of Pt⁴⁺ with purine group in PEIMP resulting in the inhibition of photoinduced electron transfer from purine to isoindole fluorophore. Under the optimal conditions (pH 7.0, incubated at 37 ℃ for 20 min) the detection of Pt⁴⁺ could be achieved with the linear range of 0.1-10 μM and the detection limit of 80 nM. The sensor had the advantages of low-cost raw materials, simple and environmental-friendly synthesis and analytical detection procedures. What's more, it could selectively and sensitively detect Pt⁴⁺ without the effects from common transition metal ions (Pb²⁺, Fe³⁺, Cr³⁺, Al³⁺, Ag⁺, Co²⁺, Hg²⁺, Cd²⁺, Cu²⁺, Mg²⁺, Ni²⁺, Mn²⁺, Zn²⁺), especially precious metalions of Pt²⁺ and Pd²⁺. The proposed method had been successfully applied to quantify Pt⁴⁺ in wastewater and urine samples, and also proved to be potential for monitoring Pt⁴⁺ in biological systems.