Correia-Ledo Debby, Gibson Kirsty F, Dhawan Anuj, Couture Maxime, Vo-Dinh Tuan, Graham Duncan, Masson Jean-Francois
Department of Chemistry, Universite de Montreal, C.P. 6128 Succ. Centre-Ville, Montreal, Quebec (Canada), H3C 3J7.
J Phys Chem C Nanomater Interfaces. 2012 Mar 29;116(12):6884-6892. doi: 10.1021/jp3009018.
The increasing popularity of surface plasmon resonance (SPR) and surface enhanced Raman scattering (SERS) sensor design based on nanotriangle or nanohole arrays, and the possibility to manufacture substrates at the transition between these plasmonic substrates, makes them ideal candidates for the establishment of structure-property relationships. This work features near diffraction-limited Raman images and FDTD simulations of nanotriangle and nanohole arrays substrates, which clearly demonstrate that the localization of the hot spot on these SERS substrates is significantly influenced by the ratio of diameter/periodicity (D/P). The experimental and simulation data reveal that the hot spots are located around nanotriangles (D/P = 1), characteristic of localized SPR. Decreasing the D/P ratio to 0.75-0.7 led to the creation of nanohole arrays, which promoted the excitation of a propagating surface plasmon (SP) delocalized over the metal network. The optimal SERS intensity was consistently achieved at this transition from nanotriangles to nanoholes, for every periodicity (650 nm to 1.5 μm) and excitation wavelength (633 and 785 nm) investigated, despite the presence or absence of a plasmonic band near the laser excitation. Further decreasing the D/P ratio led to excitation of a localized SP located around the rim of nanohole arrays for D/P of 0.5-0.6, in agreement with previous reports. In addition, this manuscript provides the first evidence that the hot spots are positioned inside the hole for D/P of 0.4, with the center being the region of highest electric field and Raman intensity. The compelling experimental evidence and FDTD simulations offer an overall understanding of the plasmonic properties of nanohole arrays as SERS and SPR sensors, which is of significant value in advancing the diversity of applications from such surfaces.
基于纳米三角形或纳米孔阵列的表面等离子体共振（SPR）和表面增强拉曼散射（SERS）传感器设计越来越受欢迎，并且有可能在这些等离子体基底之间的过渡区域制造基底，这使得它们成为建立结构-性能关系的理想候选者。这项工作展示了纳米三角形和纳米孔阵列基底的近衍射极限拉曼图像以及时域有限差分（FDTD）模拟，清楚地表明这些SERS基底上热点的定位受直径/周期比（D/P）的显著影响。实验和模拟数据表明，热点位于纳米三角形周围（D/P = 1），这是局域SPR的特征。将D/P比降低到0.75 - 0.7会导致纳米孔阵列的形成，这促进了在金属网络上离域的传播表面等离子体（SP）的激发。对于所研究的每个周期（650 nm至1.5 μm）和激发波长（633和785 nm），在从纳米三角形到纳米孔的这种转变过程中始终能实现最佳的SERS强度，无论激光激发附近是否存在等离子体带。进一步降低D/P比会导致在D/P为0.5 - 0.6时，在纳米孔阵列边缘周围激发局域SP，这与之前的报道一致。此外，该论文首次提供证据表明，当D/P为0.4时，热点位于孔内，中心是电场和拉曼强度最高的区域。令人信服的实验证据和FDTD模拟提供了对纳米孔阵列作为SERS和SPR传感器的等离子体特性的全面理解，这对于推进此类表面应用的多样性具有重要价值。
