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<p>Localized surface plasmon response (<i>LSPR</i>) excited in coated bimetallic alloy constructed from equiatomic Ag and Au is theoretically investigated in terms of core size (<i>r</i>), shell thickness (<i>t)</i>, and dielectric properties of the surrounding medium. In agreement with a previously published report, it has been found that the sensing competence of the Ag/Au-TiO<sub>2</sub> core–shell nanoparticles decays non-linearly with <i>t</i>. To sustain a high quality of plasmon-based nanosensor, the structural parameters <i>t</i>/<i>r</i> should be maintained at less than 2. This condition is independent on both metal type and core size. Within this limit, the resonance condition of the coated metallic nanoparticle is dominated by the effective dielectric medium expression. Increasing the shell thickness beyond that constraint results in a significant degradation in the detection performance of the core–shell nanoparticle. In this scenario, the coating material blocks the effect of the host matrix, and therefore, the dielectric function of the shell material entirely dominates the resonance condition of the metallic core. This universal scaling behavior is qualitatively explained in the frame of the dipole–dipole coupling model within the quasi-static approximation. The theoretical findings presented in the current study provide guidelines on the design of a bimetallic core-TiO<sub>2</sub> nanostructure to reach a desired photo-response for specific plasmon-based applications in photocatalysis and detecting devices.</p>

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Structural Tunability of the LSPR Excited in a Bimetallic Alloy-TiO2 Core–Shell System

  • 期刊论文

  • 发表日期：

    2025年5月21日

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  • Mohammed Alsawafta

摘要

Localized surface plasmon response (LSPR) excited in coated bimetallic alloy constructed from equiatomic Ag and Au is theoretically investigated in terms of core size (r), shell thickness (t), and dielectric properties of the surrounding medium. In agreement with a previously published report, it has been found that the sensing competence of the Ag/Au-TiO2 core–shell nanoparticles decays non-linearly with t. To sustain a high quality of plasmon-based nanosensor, the structural parameters t/r should be maintained at less than 2. This condition is independent on both metal type and core size. Within this limit, the resonance condition of the coated metallic nanoparticle is dominated by the effective dielectric medium expression. Increasing the shell thickness beyond that constraint results in a significant degradation in the detection performance of the core–shell nanoparticle. In this scenario, the coating material blocks the effect of the host matrix, and therefore, the dielectric function of the shell material entirely dominates the resonance condition of the metallic core. This universal scaling behavior is qualitatively explained in the frame of the dipole–dipole coupling model within the quasi-static approximation. The theoretical findings presented in the current study provide guidelines on the design of a bimetallic core-TiO2 nanostructure to reach a desired photo-response for specific plasmon-based applications in photocatalysis and detecting devices.