Sun Aileen Y, Lee Yang-Chun, Chang Sih-Wei, Chen Shau-Liang, Wang Hsueh-Cheng, Wan Dehui, Chen Hsuen-Li
Institute of Biomedical Engineering and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Road, Hsinchu 300044, Taiwan.
Department of Materials Science and Engineering and Center of Atomic Initiative for New Materials (AI-MAT), National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106319, Taiwan.
Anal Chem. 2021 Mar 9;93(9):4299-4307. doi: 10.1021/acs.analchem.0c05307. Epub 2021 Feb 26.
The localized surface plasmon resonance of plasmonic nanoparticles (NPs) can be coupled with a noble metal substrate (S) to induce a localized augmented electric field (E-field) concentrated at the NP-S gap. Herein, we analyzed the fundamental near-field properties of metal NPs on diverse substrates numerically (using the 3D finite-difference time-domain method) and experimentally [using surface-enhanced Raman scattering (SERS)]. We systematically examined the effects of plasmonic NPs on noble metals (Ag and Au), non-noble metals (Al, Ti, Cu, Fe, and Ni), semiconductors (Si and Ge), and dielectrics (TiO, ZnO, and SiO) as substrates. For the AgNPs, the Al (11,664 times) and Si (3969 times) substrates produced considerable E-field enhancements, with Al in particular generating a tremendous E-field enhancement comparable in intensity to that induced by a Ag (28,224 times) substrate. Notably, we found that a superior metallic character of the substrate gave rise to easier induction of image charges within the metal substrate, resulting in a greater E-field at the NP-S gap; on the other hand, the larger the permittivity of the nonmetal substrate, the greater the ability of the substrate to store an image charge distribution, resulting in stronger coupling to the charges of localized surface plasmon resonance oscillation on the metal NP. Furthermore, we measured the SERS spectra of rhodamine 6G (a commonly used Raman spectral probe), histamine (a biogenic amine used as a food freshness indicator), creatinine (a kidney health indicator), and -butylbenzene [an extreme ultraviolet (EUV) lithography contaminant] on AgNP-immobilized Al and Si substrates to demonstrate the wide range of potential applications. Finally, the NP-S gap hotspots appear to be widely applicable as an ultrasensitive SERS platform (∼single-molecule level), especially when used as a powerful analytical tool for the detection of residual contaminants on versatile substrates.
等离子体纳米颗粒（NPs）的局域表面等离子体共振可以与贵金属基底（S）耦合，以诱导集中在NP-S间隙处的局域增强电场（电场）。在此，我们通过数值方法（使用三维时域有限差分法）和实验方法[使用表面增强拉曼散射（SERS）]分析了不同基底上金属NP的基本近场特性。我们系统地研究了作为基底的等离子体NP对贵金属（Ag和Au）、非贵金属（Al、Ti、Cu、Fe和Ni）、半导体（Si和Ge）以及电介质（TiO、ZnO和SiO）的影响。对于AgNP，Al基底（增强11,664倍）和Si基底（增强3969倍）产生了相当可观的电场增强，特别是Al产生的巨大电场增强，其强度与Ag基底（增强28,224倍）所诱导的相当。值得注意的是，我们发现基底的优良金属特性使得在金属基底内更容易感应镜像电荷，从而在NP-S间隙处产生更大的电场；另一方面，非金属基底介电常数越大，其存储镜像电荷分布的能力越强，导致与金属NP上局域表面等离子体共振振荡电荷的耦合越强。此外，我们测量了固定在AgNP-Al和AgNP-Si基底上的罗丹明6G（一种常用的拉曼光谱探针）、组胺（一种用作食品新鲜度指标的生物胺）、肌酐（一种肾脏健康指标）以及叔丁基苯[一种极紫外（EUV）光刻污染物]的SERS光谱，以证明其广泛的潜在应用。最后，NP-S间隙热点似乎作为一种超灵敏的SERS平台（~单分子水平）具有广泛的适用性，特别是当用作检测通用基底上残留污染物的强大分析工具时。
