Highly sensitive potentiometric sensors for thorium ions detection using morpholine derivative self-assembled on silver nanoparticles

Abstract

In this work, 1-dodecyl-4-(((3-morpholinopropyl)imino)methyl)pyridin-1-ium bromide (DMP-Br) [L1] was synthesized and self-assembled on silver nanoparticles (DMP-Br-SNPs) [L2]. The prepared compounds were used in the fabrication of screen-printed electrodes to quantitatively sense Th(IV) in real samples conditions. The optimized electrodes based on L1 and L2 exhibited Nernstian slopes of 14.30 ± 0.71 and 15.11 ± 0.47 mV per decade over Th(IV) concentration ranges of 4.0 × 10⁻⁷ to 1.0 × 10⁻¹ and 6.3 × 10⁻⁹ to 1.0 × 10⁻¹ mol L⁻¹ with detection limits of 4.0 × 10⁻⁷ and 6.3 × 10⁻⁹ mol L⁻¹; respectively. In addition, these electrodes showed independent response in the pH ranges 2.5–9.0 and 2.0–9.5, and fast response times of 11 and 5 seconds. Based on durability study results, the optimized electrodes containing L1 and L2 can be used for more than 6 and 7 months, respectively, without any divergence in the electrode potential. Selectivity studies showed that incorporation of SNPs led to enhanced selectivity toward Th(IV) over a wide variety of other metal ions. The effect of solution temperature on the electrode performance was investigated in the range 10–50 °C and the electrodes' isothermal temperature coefficients (dE°/dT) were calculated. The developed electrodes have been successfully applied for Th(IV) ion potentiometric determination in water samples with sensitivity comparable to the reference method and the ability of field measurement.