Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, China.
Nano Lett. 2013 Nov 13;13(11):5039-45. doi: 10.1021/nl401920u. Epub 2013 Oct 4.
Surface-enhanced Raman scattering (SERS) systems utilizing the interparticle nanogaps as hot spots have demonstrated ultrasensitive single-molecule detection with excellent selectivity yet the electric fields are too confined in the small nanogaps to enable reproducible biomolecule detections. Here, guided by finite-difference-time-domain simulation, we report hexagonal-packed silver-coated silicon nanowire (Ag/SiNW) arrays as a nanogap-free SERS system with wide-range electric fields and controlled interwire separation. Significantly, the system achieves a SERS detection of long double-strand DNA of 25-50 nm in length with a relative standard deviation (RSD) of 14% for measurements of above 4000 spots over an area of 200 × 200 μm(2). The high reproducibility in the SERS detection is attributed to (1) the large interwire spacing of 150 nm that allows access and excitation of large biomolecules; and (2) 600 nm wide-range electric field generated by propagating surface plasmons along the surface of continuous Ag coating on a SiNW. Moreover, a reproducible multiplex SERS measurement is also demonstrated with RSDs of 7-16% with an enhancement factor of ~10(6). The above results show that the ordered Ag/SiNW array system may serve as an excellent SERS platform for practical chemical and biological detection.
表面增强拉曼散射（SERS）系统利用粒子间纳米间隙作为热点，具有超灵敏的单分子检测能力和优异的选择性，但纳米间隙中的电场过于局限，无法实现可重复的生物分子检测。在这里，我们通过有限差分时域模拟指导，报告了六边形排列的银包裹硅纳米线（Ag/SiNW）阵列作为一种无纳米间隙的 SERS 系统，具有宽范围的电场和可控的线间分离。值得注意的是，该系统实现了对长 25-50nm 的双链 DNA 的 SERS 检测，在 200×200μm^2 的面积上测量超过 4000 个点时，相对标准偏差（RSD）为 14%。SERS 检测的高重现性归因于：（1）150nm 的大线间间距允许大生物分子的进入和激发；以及（2）由沿 SiNW 表面传播的表面等离激元产生的 600nm 宽范围的电场。此外，还证明了具有 7-16%RSD 和~10^6 增强因子的可重复的多路 SERS 测量。上述结果表明，有序的 Ag/SiNW 阵列系统可以作为一种用于实际化学和生物检测的优秀 SERS 平台。
