Synthesis of new rhodanine derivative molecules, their biological properties and sensor applications in environmental samples

In this study, two new rhodanine derivative molecules (3 and 4) were synthesized, and the potentiometric sensor properties and certain biological functions of these novel molecules were investigated, following their characterization. The potentiometric performance characteristics of sensor 2 prepared using the molecule 3, and of sensor 10 prepared using the molecule 4 were further investigated under laboratory conditions. The sensors in which new rhodanine derivative molecules were used as ionophores were found to exhibit selectivity against Ba²⁺ ions among 19 different cations (Na⁺, Li⁺, K⁺, Ca²⁺, Mg²⁺, Pb²⁺, Cu²⁺, Zn²⁺, Co²⁺, Sr²⁺, Mn²⁺, Ni²⁺, Cd²⁺, Cr³⁺, Al³⁺, Gd³⁺, Nd³⁺ and In³⁺). In the potential measurements performed using Ba²⁺ ion solutions, sensor 2 had a near-Nernstian response of 25.0 ± 2.5 mV/decade, and a detection limit of 7.66 × 10^-7 M in the concentration range of 1.0 × 10^-6 - 1.0 × 10^-1 M, while sensor 10 had a near-Nernstian response of 27.0 ± 2.3 mV/decade, and a detection limit of 9.77 × 10^-8 M in the concentration range of 1.0 × 10^-1 - 1.0 × 10^-7 M. Both sensors had a quick response time of 6 and 5 s, respectively; and sensor 10 was shown to be able work in a wider pH range (5.0-9.0) without being influenced by the changes in pH. Furthermore, both sensors exhibited a repeatable and stable behavior. The surface morphologies of the prepared potentiometric sensors were also examined by scanning electron microscope (SEM). Ba²⁺ ion analysis was performed in different environmental water samples using sensor 10, and the newly fabricated sensor was found to be able to determine Ba²⁺ ions with very high recoveries. These novel rhodanine derivative molecules were also observed to have a slight growth inhibitory potential against particular bacterial species in vitro.