This comprehensive numerical study systematically investigates the plasmonic behavior of \(TiO_2\) @Ag core–shell nanoparticles, with particular emphasis on the influence of geometric parameters and the surrounding dielectric environment on the local field enhancement factor (LFEF), as well as the absorption ( \(C_{\text {abs}}\) ), scattering ( \(C_{\text {sca}}\) ), and extinction ( \(C_{\text {ext}}\) ) cross-sections and their corresponding efficiencies ( \(Q_{\text {abs}}, Q_{\text {sca}}, Q_{\text {ext}}\) ). Utilizing a theoretical framework grounded in the quasi-static approximation and Mie theory, the analysis reveals that an intermediate Ag shell thickness yields an optimal trade-off between competing optical processes. Specifically, this configuration enhances absorption efficiency, which is advantageous for energy conversion applications, while simultaneously preserving sufficient scattering efficiency required for sensing and light management. The results further demonstrate that increasing the \(TiO_2\) core radius from 10 nm to 13 nm induces a significant localized surface plasmon resonance (LSPR) redshift of approximately 300 nm. In addition, variations in the host medium permittivity from \(SiO_2\) to ITO lead to a systematic and pronounced resonance redshift of up to 600 nm. These findings establish robust design guidelines for tailoring \(TiO_2\) @Ag nanostructures, enabling the identification of optimal geometric configurations and dielectric environments to maximize performance across a broad spectrum of applications, including photothermal therapy, photocatalysis, and biosensing.
