Zhang Weiwei, Tian Qingkun, Chen Zhanghua, Zhao Cuicui, Chai Haishuai, Wu Qiong, Li Wengang, Chen Xinhua, Deng Yida, Song Yujun
Centre for Modern Physics Technology, School of Mathematics and Physics, University of Science and Technology, Beijing Xueyuan Road 30, Haidian District Beijing 100083 China
Shunde Graduate School of University of Science and Technology Beijing Daliang Zhihui Road 2, Shunde Distinct Foshan 528399 China.
RSC Adv. 2020 Jun 23;10(40):23908-23915. doi: 10.1039/d0ra03803b. eCollection 2020 Jun 19.
Active substrates are crucial for surface-enhanced Raman scattering (SERS). Among these substrates, large uniform area arrayed nanoporous silver thin films have been developed as active substrates. Arrayed nanoporous silver thin films with unique anisotropic morphologies and nanoporous structures can be fabricated onto the nanoporous anodic aluminum oxide (AAO) of controlled pore size and interspacing by precisely tuning the sputtering parameters. These thin films preserve locally enhanced electromagnetic fields by exciting the surface plasmon resonance, which is beneficial for SERS. In this study, nanoporous silver thin films were transferred into polymethylmethacrylate (PMMA) and polydimethylsiloxane (PDMS) substrates using our recently invented template-assisted sol-gel phase inverse-imprinting process to form two different nanopore thin films. The as-formed Ag nanoporous thin films on PMMA and PDMS exhibited intensively enhanced SERS signals using Rhodamine 6G (R6G) as the model molecule. The two nanopore thin films exhibited opposite pore size-dependent SERS tendencies, which were elucidated by the different enhancement tendencies of the electric field around pores of different diameters. In particular, the Ag nanoporous thin film on PMMA exhibited an R6G detection limit of as low as 10 mol L, and the SERS enhancement factor (EF) was more than 10. The low detection limit and large EF demonstrated the high sensitivity of the as-prepared SERS substrates for label-free detection of biomolecules. Compared with conventional smooth films, this nanopore structure can facilitate future application in biomolecular sensors, which allows the detection of single molecules an electronic readout without requirement for amplification or labels.
活性基底对于表面增强拉曼散射（SERS）至关重要。在这些基底中，大面积均匀排列的纳米多孔银薄膜已被开发为活性基底。通过精确调整溅射参数，可以将具有独特各向异性形态和纳米多孔结构的排列纳米多孔银薄膜制备在孔径和间距可控的纳米多孔阳极氧化铝（AAO）上。这些薄膜通过激发表面等离子体共振来保持局部增强的电磁场，这对SERS是有益的。在本研究中，使用我们最近发明的模板辅助溶胶 - 凝胶相反转压印工艺将纳米多孔银薄膜转移到聚甲基丙烯酸甲酯（PMMA）和聚二甲基硅氧烷（PDMS）基底上，以形成两种不同的纳米孔薄膜。以罗丹明6G（R6G）为模型分子，在PMMA和PDMS上形成的银纳米多孔薄膜表现出强烈增强的SERS信号。这两种纳米孔薄膜表现出相反的孔径依赖性SERS趋势，这是由不同直径孔周围电场的不同增强趋势所阐明的。特别是，PMMA上的银纳米多孔薄膜表现出低至10⁻¹¹ mol L⁻¹的R6G检测限，并且SERS增强因子（EF）超过10⁶。低检测限和大的EF证明了所制备的SERS基底对生物分子无标记检测具有高灵敏度。与传统的光滑薄膜相比，这种纳米孔结构有助于未来在生物分子传感器中的应用，其允许在无需放大或标记的情况下通过电子读出检测单分子。
