A Polymer-Based Ultrasensitive Metal Ion Sensor

The fabrication of a dipyrido-[3,2-a: 2,3-c]phenazine (dppz)-based selective metal ion-sensing system with pico-molar sensitivity was reported. P1 was conveniently synthesized by the Suzuki couplings between 10,13-dibromodipyrido[3,2-a:2,3-c]phenazine and 1,4-bis(trimethylsilylethynyl)- 2,5-bis(butyloxy)benzene. Polymers P2, P3, and P4 were also synthesized in an analogous fashion. All polymers were purified by precipitation from methanol and obtained as slightly black solids. The purified polymers were characterized by H NMR, providing conclusive evidence for the well-controlled incorporation of both monomers within target structures. The molecular weights and polydispersity index (PDI) of these polymers were determined by size exclusion chromatography (SEC), with polystyrene as the reference. Absorption and emission spectra were collected for all polymer systems in THF at room temperature. An unprecedented picomolar sensitivity was achieved for the polymer with such a rigidly planar structure.