College of Physics and Optoelectronics Engineering , Dalian University of Technology , Dalian 116024 , China.
Département de chimie and Centre Québécois sur les Matériaux Fonctionnels (CQMF) , Université de Montréal , CP. 6128 Succ. Centre-Ville , Montreal , QC H3C 3J7 , Canada.
Anal Chem. 2018 Jun 5;90(11):6683-6692. doi: 10.1021/acs.analchem.8b00496. Epub 2018 May 21.
2D nanoplasmonic substrates excited in transmission spectroscopy are ideal for several biosensing, metamaterial, and optical applications. We show that their excellent properties can be further improved with plasmonic coupling of Au nanoparticles (AuNPs) on gold-coated nanodisk arrays excited at large incidence angles of up to 50°. The Bragg modes (BM) thereby strongly couple to AuNP immobilized on the plasmonic substrate due to shorter decay length of the plasmon at higher incidence angles, leading to a further enhanced field between the AuNP and the plasmonic substrate. The field was highest and two hotspots were created at orthogonal positions for AuNP located close to the corner of the Au film and Au nanodisk, which was also observed for AuNP dimers. Hybridization between single-stranded DNA (ssDNA) immobilized on the surface of the AuNPs and the capture ssDNA on the gold-coated nanodisk arrays led to at least a 5-fold signal improvement and a 7-fold lower limit of detection at 7 pM for ssDNA-functionalized AuNPs at large incident angles. Thus, we demonstrate that higher field strength can be accessed and the significant advantages of working with high incidence angles with AuNP on a 2D plasmonic crystal in plasmonic sensing.
在传输光谱中激发的 2D 纳米等离子体衬底非常适合于几种生物传感、超材料和光学应用。我们表明，通过在高达 50°的大入射角下激发金覆盖的纳米盘阵列上的金纳米粒子 (AuNP) 的等离子体耦合，可以进一步改善其优异的性能。由于在较高入射角下等离子体的衰减长度较短，因此布拉格模式 (BM) 与等离子体衬底上固定的 AuNP 强烈耦合，导致 AuNP 和等离子体衬底之间的场进一步增强。对于靠近 Au 膜和 Au 纳米盘角的 AuNP，场最强，并在正交位置产生了两个热点，这也在 AuNP 二聚体中观察到。固定在 AuNP 表面上的单链 DNA (ssDNA)与金覆盖的纳米盘阵列上的捕获 ssDNA 之间的杂交导致信号增强至少 5 倍，在大入射角下，ssDNA 功能化的 AuNP 的检测下限降低了 7 倍，达到 7 pM。因此，我们证明了在等离子体传感中，可以获得更高的场强，并利用金纳米粒子在二维等离子体晶体上的大入射角获得显著的优势。
