The design of colloidal nanostructures as surface-enhanced Raman scattering (SERS) substrates requires control over both structural and optical characteristics. A widespread expectation is that the SERS efficiency depends crucially on whether the plasmonic excitation matches the exciting laser wavelength. However, also the balance between radiative (scattering) and nonradiative (absorbing) properties plays a major role, regarding both the efficiency of near-field enhancement and the experimentally observed signal intensity. We present a study of the influence of mode-excitation matching and extinction characteristics for core/satellite superstructures, comprising gold nanotriangles decorated with small gold nanospheres. The variation of the core size and aspect ratio allowed tuning the main coupled mode between 700 and 800 nm, from off-resonant through resonant at 785 nm, as well as tuning extinction contributions, from dominantly absorbing to dominantly scattering. We observed additional gains of 1–2 orders of magnitude in signal enhancement, which were correlated to core size and diffuse optical properties. Our findings indicate a competition between SERS enhancement and increased scattering losses in larger assemblies. Thus, a balance of optical parameters is required for efficient SERS and the development of assemblies as advanced sensing devices.

中文翻译：

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具有三角形核的胶体超结构：SERS效率的尺寸效应

胶体纳米结构作为表面增强拉曼散射（SERS）衬底的设计需要控制结构和光学特性。普遍的期望是，SERS效率主要取决于等离子体激发是否与激发激光波长匹配。但是，就近场增强效率和实验观察到的信号强度而言，辐射（散射）和非辐射（吸收）特性之间的平衡也起着重要作用。我们提出了一种模式激励匹配和消光特性对核心/卫星超结构的影响的研究，该结构包括用小金纳米球装饰的金纳米三角形。核心尺寸和长宽比的变化允许在700至800 nm之间调整主耦合模式，从非共振到在785 nm的共振，以及消光贡献的调整，从主要吸收到主要散射。我们观察到信号增强的额外增益为1-2个数量级，这与纤芯尺寸和漫射光学特性相关。我们的发现表明，在较大的组件中，SERS增强与散射损耗增加之间存在竞争。因此，光学参数的平衡对于有效的SERS和作为高级感测设备的组件的开发是必需的。我们的发现表明，在较大的组件中，SERS增强与散射损耗增加之间存在竞争。因此，光学参数的平衡对于有效的SERS和作为高级感测设备的组件的开发是必需的。我们的发现表明，在较大的组件中，SERS增强与散射损耗增加之间存在竞争。因此，光学参数的平衡对于有效的SERS和作为高级感测设备的组件的开发是必需的。