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<p>This study presents a comprehensive theoretical investigation into the linear optical properties of CdS@Ag core–shell quantum dots (CSQDs) embedded in various dielectric matrices. Using a quasi-static approximation and a Lorentz–Drude model for the silver shell, we examine how structural parameters core radius, shell thickness and host matrix permittivity modulate the optical response, including plasmonic field enhancement, refractive index behavior, absorption/scattering cross-sections and extinction cross-sections. Key findings reveal that increasing shell thickness significantly boosts both the local field enhancement factor and the absorption cross-section (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\sigma _{\text {abs}}\)</EquationSource> </InlineEquation>), particularly in low-index hosts like PMMA. In contrast, increasing the core size results in a red-shift of the plasmon resonance while reducing field localization, highlighting a geometric trade-off between spectral tunability and optical intensity. Host permittivity also plays a crucial role: PMMA yields sharper and more intense plasmonic resonances, whereas <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\text {SiO}_2\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\text {Al}_{2} \text {O}_3\)</EquationSource> </InlineEquation> broaden and blue-shift the spectral response due to enhanced dielectric screening. These results offer valuable design guidelines for optimizing CSQDs in applications such as nanophotonic circuits, nonlinear optical switching, and plasmon-enhanced sensors.</p>

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Geometric and dielectric engineering of linear optical response in CdS@Ag core–shell quantum dots: a theoretical study of plasmonic enhancement and host effects

  • 期刊论文

  • 发表日期：

    2025年10月16日

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  • Shewa Getachew Mamo,
  • Asmamaw Tesega Abebe

摘要

This study presents a comprehensive theoretical investigation into the linear optical properties of CdS@Ag core–shell quantum dots (CSQDs) embedded in various dielectric matrices. Using a quasi-static approximation and a Lorentz–Drude model for the silver shell, we examine how structural parameters core radius, shell thickness and host matrix permittivity modulate the optical response, including plasmonic field enhancement, refractive index behavior, absorption/scattering cross-sections and extinction cross-sections. Key findings reveal that increasing shell thickness significantly boosts both the local field enhancement factor and the absorption cross-section ( \(\sigma _{\text {abs}}\) ), particularly in low-index hosts like PMMA. In contrast, increasing the core size results in a red-shift of the plasmon resonance while reducing field localization, highlighting a geometric trade-off between spectral tunability and optical intensity. Host permittivity also plays a crucial role: PMMA yields sharper and more intense plasmonic resonances, whereas \(\text {SiO}_2\) and \(\text {Al}_{2} \text {O}_3\) broaden and blue-shift the spectral response due to enhanced dielectric screening. These results offer valuable design guidelines for optimizing CSQDs in applications such as nanophotonic circuits, nonlinear optical switching, and plasmon-enhanced sensors.