Suster Mihai C, Szymańska Aleksandra, Antosiewicz Tomasz J, Królikowska Agata, Wróbel Piotr
Faculty of Physics, University of Warsaw, Pasteura 5, Warsaw 02-093, Poland.
Faculty of Chemistry, University of Warsaw, Pasteura 1, Warsaw 02-093, Poland.
ACS Appl Mater Interfaces. 2025 Apr 16;17(15):23076-23093. doi: 10.1021/acsami.5c00716. Epub 2025 Apr 3.
Development of fabrication protocols for large-area plasmonic nanostructures with sub-10 nm gaps with a spatially controlled distribution is critical for their real-world applications. In this work, we develop a simple, cleanroom-free protocol for the fabrication of macroscopic-sized plasmonic substrates (>6 cm), featuring a tunable multiresonance optical response and light concentration in sub-10 nm gaps. Critically, these gaps are free to interact with the surrounding medium. This architecture consists of nonperiodically distributed dielectric nanospheres coated with a metal multilayer, forming semispherical core-shell-like nanostructures (CSLNs) surrounded by a planar film. The sub-10 nm gaps formed between metal caps and the planar film are easily tuned by adjusting fabrication parameters, such as multimetal layer thickness, composition, or nanosphere size and density. The excellent structural homogeneity, wide optical tunability, and extreme light confinement in the spatially controlled subwavelength nanogaps make CSLN-based substrates an ideal platform for comprehensive surface-enhanced Raman scattering (SERS) spectroscopy. This is proven through a combination of numerical modeling and iterative fabrication/characterization, leading to the optimized substrates showing cutting-edge spatial uniformity down to 1.9% determined as the relative standard deviation (RSD) of the SERS signal of -mercaptobenzoic acid for 225 spectra over the 3600 μm area. High sensitivity is evidenced by an enhancement factor of ∼10. The proposed substrates also meet all other demanding criteria, including sufficient signal temporal stability (RSD <4%), high substrate-to-substrate reproducibility (<15%), and SERS activity toward three various analytes. The unique geometry and wide spectral tunability of the CSLN substrates will also be of great value for other plasmon-driven applications.
开发具有空间可控分布、间隙小于10 nm的大面积等离子体纳米结构的制造协议对于其实际应用至关重要。在这项工作中，我们开发了一种简单的、无需洁净室的协议来制造宏观尺寸的等离子体基底（>6 cm），其具有可调谐的多共振光学响应以及在小于10 nm间隙中的光集中特性。关键的是，这些间隙可以自由地与周围介质相互作用。这种结构由涂覆有金属多层膜的非周期性分布的介电纳米球组成，形成被平面薄膜包围的半球形核壳状纳米结构（CSLN）。通过调整制造参数，如多金属层厚度、成分或纳米球尺寸和密度，可以轻松调节金属帽与平面薄膜之间形成的小于10 nm的间隙。基于CSLN的基底具有优异的结构均匀性、宽光学可调性以及在空间可控的亚波长纳米间隙中的极端光限制，使其成为综合表面增强拉曼散射（SERS）光谱的理想平台。这通过数值建模与迭代制造/表征相结合得到了证明，优化后的基底在3600μm区域内225个光谱的对巯基苯甲酸SERS信号的相对标准偏差（RSD）确定为1.9%，显示出前沿的空间均匀性。增强因子约为10证明了其高灵敏度。所提出的基底还满足所有其他苛刻标准，包括足够的信号时间稳定性（RSD<4%）、高基底间重现性（<15%）以及对三种不同分析物的SERS活性。CSLN基底独特的几何形状和宽光谱可调性对于其他等离子体驱动的应用也将具有重要价值。
