“Hedgehog” particles (HPs) possess a micrometer-sized dielectric spherical core which is densely coated with nanoscale metal oxide spikes. This unique surface topography, resembling the appearance of a hedgehog, provides the particles with the exclusive physiochemical property to stably disperse in both polar and nonpolar solvents without the necessity of changing the surface chemistry. Optical extinction measurements of HP ensembles in aqueous solution indicate a broad spectral response in the visible range. However, there remains a dearth of fundamental knowledge about the cause of the broad optical resonance, as it can be a consequence of shape polydispersity in the many-particle system or intrinsic to each individual HP. In this paper, we present the first experimental study of the dark-field scattering of individual hydrophilic and hydrophobic HPs. Our measurements disclose that the expansive optical response in the visible spectral range is truly characteristic for the far-field scattering of a single HP. Our results also uncover how intrinsic particle features, such as spike length, as well as environmental changes affect the scattering of individual HPs. In particular, by changing the atmosphere around a hydrophilic HP from air to nitrogen and by completely immersing in water by employing a 3D optical trap, we discovered that the scattering from a hydrophilic HP is strongly modulated by excess water in its interstitial shell.

中文翻译：

---

单个刺猬粒子的散射特性

“刺猬”粒子（HP）具有微米级介电球形芯，该芯被纳米级金属氧化物尖钉密集地覆盖。这种独特的表面形貌类似于刺猬的外观，为颗粒提供了独特的物理化学特性，可以稳定地分散在极性和非极性溶剂中，而无需改变表面化学性质。水溶液中HP团簇的光学消光测量表明在可见光范围内有较宽的光谱响应。但是，由于广泛的光学共振的原因，尚缺乏基本的知识，因为这可能是多粒子系统中形状多分散性的结果，也可能是每个HP固有的。在本文中，我们提出了对单个亲水性和疏水性HP进行暗场散射的第一个实验研究。我们的测量结果表明，可见光范围内的广阔光学响应是单个HP远场散射的真正特征。我们的结果还揭示了固有的颗粒特征（例如峰长）以及环境变化如何影响单个HP的散射。尤其是，通过将亲水性HP周围的气氛从空气变为氮气，并通过使用3D光学阱将其完全浸入水中，我们发现，亲水性HP的散射受到其间隙壳中过量水的强烈调节。我们的测量结果表明，可见光范围内的广阔光学响应是单个HP远场散射的真正特征。我们的结果还揭示了固有的颗粒特征（例如峰长）以及环境变化如何影响单个HP的散射。尤其是，通过将亲水性HP周围的气氛从空气变为氮气，并通过使用3D光学阱将其完全浸入水中，我们发现，亲水性HP的散射受到其间隙壳中过量水的强烈调节。我们的测量结果表明，可见光范围内的广阔光学响应是单个HP远场散射的真正特征。我们的结果还揭示了固有的颗粒特征（例如峰长）以及环境变化如何影响单个HP的散射。尤其是，通过将亲水性HP周围的气氛从空气变为氮气，并通过使用3D光学阱将其完全浸入水中，我们发现，亲水性HP的散射受到其间隙壳中过量水的强烈调节。