Department of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, 64002, Taiwan.
Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung, 20224, Taiwan.
Sci Rep. 2017 Jul 14;7(1):5446. doi: 10.1038/s41598-017-05939-0.
It is desirable to extend the surface-enhanced Raman scattering (SERS) from the conventionally used visible range into the infrared region, because the fluorescence background is lower in the long-wavelength regime. To do this, it is important to have a SERS substrate suitable for infrared operation. In this work, we report the near infrared SERS operation based on the substrates employing star-shaped gold/silver nanoparticles and hyperbolic metamaterial (HMM) structure. We first fabricate the SERS substrate in which nanoparticles are separated from a silver film by a thin dielectric layer. Performance of the SERS substrate is investigated with a 1064-nm excitation source. Compared with similar silver film-based substrates employing respectively gold and silver spherical nanoparticles, it is found that, Raman intensity scattered by the substrate with star-shaped nanoparticles is 7.4 times stronger than that with gold nanoparticles, and 3.4 times stronger than that with silver nanoparticles. Following this, we fabricate the SERS substrate where the star-shaped nanoparticles are deposited over a HMM structure. The HMM structure comprises three pairs of germanium-silver multilayers. Further experimental result shows that, with the star-shaped nanoparticles, the HMM-based substrate yields 30% higher Raman intensity for near infrared SERS operation than the silver film-based substrate does.
将表面增强拉曼散射(SERS)从传统的可见光范围扩展到红外区域是可取的,因为在长波长范围内荧光背景更低。为此,拥有适合红外操作的 SERS 衬底非常重要。在这项工作中,我们报告了基于星形金/银纳米粒子和双曲超材料(HMM)结构的近红外 SERS 操作。我们首先制备了通过薄介电层将纳米粒子与银膜隔开的 SERS 衬底。使用 1064nm 激发源研究了 SERS 衬底的性能。与分别采用金和银球形纳米粒子的类似银膜基衬底相比,发现由星形纳米粒子组成的衬底散射的拉曼强度比金纳米粒子强 7.4 倍,比银纳米粒子强 3.4 倍。接下来,我们在 HMM 结构上制备了沉积有星形纳米粒子的 SERS 衬底。HMM 结构由三对锗-银多层组成。进一步的实验结果表明,对于近红外 SERS 操作,与银膜基衬底相比,具有星形纳米粒子的 HMM 基衬底的拉曼强度提高了 30%。