Functional polyterthiophene-appended uranyl-salophen complex: electropolymerization and ion-selective response for monohydrogen phosphate

We have synthesized a bis(terthiophene)-appended uranyl-salophen complex, comprising N,N′-bis4-(5,2′:5′,2″-terthiophen-3′-yl)salicylidene]-1,2-ethanediamine-uranyl complexes (TUS), and used it as a monomer for the electrochemical polymerizations (poly-TUS) on glassy carbon surfaces to prepare functionalized conducting polymer (CP) films. The poly-TUS films prepared from propylene carbonate/0.1 M tetrabutyl ammonium perchlorate (TBAP) on a glassy carbon electrode have both the functionality of ion-to-electron transducers (solid contact) and Lewis-acidic binding sites for a monohydrogen phosphate (MHP) ion-selective electrode (ISE). The CP/poly-TUS sensor showed a linear range between 1.0 × 10⁻¹ and 1.0 × 10^−4.5 M with a near-Nernstian behavior (−30.4 mV decade⁻¹) at a pH of 8.2. The detection limit of the electrode was 10^−5.0 M and the response time was improved (<10 s) compared to that of conventional ISEs (<20 s). For comparison, a conventional ISE (with an internal aqueous solution) based on a TUS monomer/o-nitrophenyl octylether (o-NPOE)/polyvinyl chloride (PVC) liquid membrane with or without tridodecylmethylammonium chloride (TDMACl) as an additive was also constructed and its performance as an MHP-ISE were studied. The superior selectivity and sensitivity of the CP/poly-TUS sensor enabled the direct measurement of MHP in a wide variety of applications.