A Luminescent Pt-NCN Complex Anchored onto a Polyethylene Film for Sequential Detection of Iodide and Mercury

Luminescent polymers have attracted attention as solid-state sensing platforms for selective analyte recognition; however, the use of [Pt-(NCN)-Cl]-based polymers for chemosensing remains largely unexplored. Herein, luminescent platforms (PE- g -MC-1-X) based on a [Pt-(NCN)-Cl] complex (NCN = 1,3-bis-(benzimidazol-2-yl)-benzene derivative bearing two tetraethylene glycol (TEG) chains) (1) anchored onto polyethylene grafted with methacryloyl chloride (PE- g -MC) by gamma irradiation at different doses (X = 2, 4, 6, and 8 kGy) were synthesized and characterized. Among luminescent platforms, PE- g -MC-1-8kGy film was studied as a chemosensor for anions, nucleotides, and oxyanions in ethanol/water (1:1, v/v). The luminescent polymer exhibited a selective quenching response toward iodide (I^-), with a quenching constant (K_q ) of 4.67(±0.49) × 10³ M^-1 and a limit of detection of 6.55(±0.26) ppm. Based on analyses by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), the binding mode of iodide was attributed to its accumulation within hydrophobic domains of TEG chains through an ion-specific effect, perturbing the electronic environment of the [Pt-(NCN)-Cl] unit. Sequential addition of mercury (Hg²⁺) in the presence of hydrochloric acid (HCl) restored the emission intensity, with a limit of detection of 2.40(±0.11) ppm. The luminescent material exhibited reversibility and reusability over multiple I^-/Hg²⁺ sensing cycles. These results confirm that immobilization of the Pt-NCN complex onto a polymer matrix functionalized by gamma irradiation provides a solid-state sensing platform for the sequential detection of I^- and Hg²⁺.