<p>This work presents an analysis of long-range surface plasmon resonance (LRSPR) sensor with a high-figure of merit (FoM) and imaging sensitivity (S_imag) for the detection of Cu²⁺ and Mg²⁺ ions in aqueous medium that is based on a Cytop-Cu (Copper)–ZrN (Zirconium Nitride) structure. Optimizing of resonance properties and improving sensing performance was obtained by analyzing the impact of Cytop and Cu layer thicknesses on the reflectance curve. To investigate the distribution of electric fields, plasmonic confinement, and resonance behavior at various thicknesses, numerical simulations utilizing Maxwell’s equations and fine mesh analysis were performed. The findings show that, in noble materials, the addition of ZrN as a plasmonic layer significantly enhances field confinement at the metal–dielectric interface while lowering optical losses. The maximum FoM of 1818.41/RIU and S_imag of 5844.3/RIU at Cytop 900&#xa0;nm and Cu 20&#xa0;nm thicknesses. The maximum detection accuracy (DA) 100/° is achieved for the detection of both ions Cu²⁺ and Mg²⁺. The synergy between Cu and the ultrathin ZrN interfacial layer, along with the inherent stability advantages of ZrN over conventional plasmonic metals like Ag and Al, are liable for the performance improvement seen in the suggested sensor. While the addition of an ultrathin ZrN layer successfully alters the interfacial optical properties, resulting in better mode confinement, decreased optical damping, and increased symmetry of the LRSPR mode, Cu offers a strong plasmonic response in the visible region. Additionally, the penetration depth (PD) of 496.05&#xa0;nm is obtained at 0&#xa0;mol/kg concentration of Cu²⁺ and Mg²⁺ions. Overall, the proposed Cytop-Cu–ZrN-based LRSPR structure shows enhanced stability, DA and FoM, and field enhancement, making it a promising platform for chemical sensing and ion detection applications.</p> Graphical Abstract <p></p>