Real-time, high-sensitivity, and label-free detection to single nanoparticles has been achieved via visualizing the interaction between surface plasmon polaritons (SPPs) and nanoparticles, which is widely applied to chemistry and biology. In this work, aiming to enhance the detection sensitivity to nanoparticles, we explore the interaction of SPP standing waves with single nanoparticles. Compared with SPPs, the inhomogeneous fields of SPP standing waves modulate charge distributions around the particle and excite different electric dipole modes that tailor localized enhancements. For nanoparticles situating at electric antinodes of SPP standing waves, a vertical electric dipole is excited and high-density charges are stimulated around nanoparticle-film nanocavities, leading to further increased localized enhancement. The localized enhancement experiences more increase with smaller particle size, lower particle refractive index, lower dielectric constant of surrounding medium, and lower real part of the metal dielectric constant. Via tailoring the localized enhancement by SPP standing waves, the sensitivity of SPP microscopy can be improved, which would broaden its applications on nanotechnology, biomedicine, and environmental monitoring.

通过可视化表面等离子体激元（SPP）和纳米粒子之间的相互作用，实现了对单个纳米粒子的实时、高灵敏度和无标记检测，广泛应用于化学和生物学。在这项工作中，为了提高对纳米粒子的检测灵敏度，我们探索了 SPP 驻波与单个纳米粒子的相互作用。与 SPP 相比，SPP 驻波的非均匀场调节粒子周围的电荷分布并激发不同的电偶极子模式，从而定制局部增强。对于位于 SPP 驻波电波腹处的纳米粒子，垂直电偶极子被激发并在纳米粒子薄膜纳米腔周围激发高密度电荷，导致进一步增加局部增强。局部增强随着粒径变小、粒子折射率降低、周围介质介电常数降低和金属介电常数实部降低而增加更多。通过调整 SPP 驻波的局部增强，可以提高 SPP 显微镜的灵敏度，这将扩大其在纳米技术、生物医学和环境监测方面的应用。