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<p>This study develops a high-sensitivity surface plasmon resonance (SPR) refractive index sensor by integrating Fe<sub>3</sub>O<sub>4</sub> nanospheres onto a gold film. Fe<sub>3</sub>O<sub>4</sub> nanospheres (~ 80&#xa0;nm diameter) were synthesized hydrothermally and deposited on a 50&#xa0;nm Au-coated BK-7 prism via drop-casting. Finite element simulations revealed that a 10&#xa0;nm Fe<sub>3</sub>O<sub>4</sub> layer enhances sensitivity by 45.13% and extends penetration depth to 228.0&#xa0;nm compared to bare Au. Experimentally, sensors with two drop-casting cycles achieved a refractive index sensitivity of 3638.68&#xa0;nm/RIU—a 72.8% improvement over bare Au (2105.51&#xa0;nm/RIU)—while maintaining a 90.08% resonance depth and a figure of merit (FOM) of 21.99 RIU<sup>−1</sup>. This performance attributed to Fe<sub>3</sub>O<sub>4</sub>’s high refractive index, hierarchical stacking structure, large specific surface area (24.104 m<sup>2</sup>/g), and mesoporous distribution (7–25&#xa0;nm), which amplify light-matter interactions. The sensor demonstrated excellent repeatability (resonance wavelength SD &lt; 0.86&#xa0;nm) and long-term stability. This work establishes a quantitative model for Fe<sub>3</sub>O<sub>4</sub> coating optimization and highlights the potential of magnetic nanomaterials for advanced SPR sensing.</p>

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High-sensitivity SPR refractive index sensor modified with Fe3O4 nanospheres

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Yanpei Xu,
  • Haixing Hao,
  • Qi Wang

摘要

This study develops a high-sensitivity surface plasmon resonance (SPR) refractive index sensor by integrating Fe3O4 nanospheres onto a gold film. Fe3O4 nanospheres (~ 80 nm diameter) were synthesized hydrothermally and deposited on a 50 nm Au-coated BK-7 prism via drop-casting. Finite element simulations revealed that a 10 nm Fe3O4 layer enhances sensitivity by 45.13% and extends penetration depth to 228.0 nm compared to bare Au. Experimentally, sensors with two drop-casting cycles achieved a refractive index sensitivity of 3638.68 nm/RIU—a 72.8% improvement over bare Au (2105.51 nm/RIU)—while maintaining a 90.08% resonance depth and a figure of merit (FOM) of 21.99 RIU−1. This performance attributed to Fe3O4’s high refractive index, hierarchical stacking structure, large specific surface area (24.104 m2/g), and mesoporous distribution (7–25 nm), which amplify light-matter interactions. The sensor demonstrated excellent repeatability (resonance wavelength SD < 0.86 nm) and long-term stability. This work establishes a quantitative model for Fe3O4 coating optimization and highlights the potential of magnetic nanomaterials for advanced SPR sensing.