Highly selective fluorescence detection of Pt4+ over Pd2+ and Pt2+ using a polyethyleneimine-based nanosensor prepared via facile three-component reaction

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 celcius for 20 min) the detection of Pt4+ could be achieved with the linear range of 0.1-10 mu M 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 Pt(4+ )without the effects from common transition metal ions (Pb2+, Fe3+, Cr3+, Al3+, Ag+, Co2+, Hg2+, Cd2+, Cu2+, Mg2+, Ni2+, Mn2+, Zn2+), especially precious metal ions 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.