We present a solution to a longstanding challenge in nanoplasmonics and colloid chemistry: the anomalous optical absorption of noble metal nanoparticles in the ultrafine size range of 2.5–10 nm, characterized by a rapid long-wavelength shift in plasmon resonance as the particle size increases. Our investigation delves into the impact of alterations in electron density along the radial direction of nanoparticles and the resulting variations in dielectric constants on the spectral positioning of the plasmon resonance. We explore the interplay of the spill-out effect, volumetric compression, and their combined impact in different experimental conditions on electron density variation within the particle volume and its blurring at the particle boundary. The latter effectively forms a surface layer with altered dielectric constants and a size-independent extent. As particle size decreases, the influence of the surface layer becomes more pronounced, especially when its extent is comparable to the particle radius. These findings are specific to ultrafine plasmonic nanoparticles and highlight their unique properties.

中文翻译：

---

超细金属纳米颗粒等离子体吸收的独特特征：体积压缩和溢出效应的统一性和竞争性


我们提出了一种解决方案，解决了纳米等离子体和胶体化学中长期存在的挑战：2.5-10 nm 超细尺寸范围内贵金属纳米颗粒的异常光吸收，其特征是随着粒径的增加，等离子体共振的快速长波长偏移。我们的研究深入探讨了电子密度沿纳米粒子径向变化的影响以及由此产生的介电常数变化对等离激元共振光谱定位的影响。我们探讨了溢出效应、体积压缩及其在不同实验条件下对粒子体积内电子密度变化及其在粒子边界处模糊的综合影响的相互作用。后者有效地形成了一个表面层，其介电常数发生了变化，范围与大小无关。随着颗粒尺寸的减小，表面层的影响变得更加明显，尤其是当其范围与颗粒半径相当时。这些发现是超细等离子体纳米颗粒特有的，并突出了它们的独特特性。