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<p>This study presents a systematic investigation of dielectric core engineering in Au nanoshells, establishing a unified framework linking core dielectric properties to plasmonic response, near-field behavior, and refractive-index sensing. Using finite-difference time-domain (FDTD) simulations, nanoshells with cores spanning a broad refractive index range (air, SiO₂, ZnO, and TiO₂) are analyzed with controlled variations in core radius and shell thickness to capture coupled material–geometry effects. The results show that nanoshell optical behavior is governed by a dielectric–geometric coupling mechanism arising from plasmon hybridization between cavity and sphere modes. Core permittivity (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:{\epsilon\:}_{c}={n}_{c}^{2}\)</EquationSource> </InlineEquation>) modulates interfacial polarization, which governs hybridization strength and electromagnetic energy distribution within the structure. As a result, resonance position, near-field enhancement, and refractive-index sensitivity exhibit consistent nonlinear scaling with core refractive index. The resonance undergoes a nonlinear redshift, while near-field intensity and sensing response decrease due to redistribution of electromagnetic energy from the outer interface toward the nanoshell interior, reducing environmental overlap. A key outcome is a fundamental trade-off between electromagnetic confinement and sensing performance: low-index cores maximize external field overlap and sensitivity, whereas high-index cores enhance internal confinement and spectral tunability but reduce environmental accessibility. Overall, this work provides a unified mechanistic framework for predicting and tuning plasmonic responses in Au nanoshells, with implications for sensing, spectroscopy, and photocatalytic applications.</p>

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Dielectric core engineering in spherical gold nanoshells: tuning spectral response and refractive index sensitivity

  • 期刊论文

  • 发表日期：

    2026年5月11日

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  • Mohammed Alsawafta

摘要

This study presents a systematic investigation of dielectric core engineering in Au nanoshells, establishing a unified framework linking core dielectric properties to plasmonic response, near-field behavior, and refractive-index sensing. Using finite-difference time-domain (FDTD) simulations, nanoshells with cores spanning a broad refractive index range (air, SiO₂, ZnO, and TiO₂) are analyzed with controlled variations in core radius and shell thickness to capture coupled material–geometry effects. The results show that nanoshell optical behavior is governed by a dielectric–geometric coupling mechanism arising from plasmon hybridization between cavity and sphere modes. Core permittivity ( \(\:{\epsilon\:}_{c}={n}_{c}^{2}\) ) modulates interfacial polarization, which governs hybridization strength and electromagnetic energy distribution within the structure. As a result, resonance position, near-field enhancement, and refractive-index sensitivity exhibit consistent nonlinear scaling with core refractive index. The resonance undergoes a nonlinear redshift, while near-field intensity and sensing response decrease due to redistribution of electromagnetic energy from the outer interface toward the nanoshell interior, reducing environmental overlap. A key outcome is a fundamental trade-off between electromagnetic confinement and sensing performance: low-index cores maximize external field overlap and sensitivity, whereas high-index cores enhance internal confinement and spectral tunability but reduce environmental accessibility. Overall, this work provides a unified mechanistic framework for predicting and tuning plasmonic responses in Au nanoshells, with implications for sensing, spectroscopy, and photocatalytic applications.