In this work, we report a quick and controllable method for fabricating Ag nanoparticles (NPs) and nano-assemblies (NAs) on silicon (Si) surface via a galvanic reaction assisted by surfactant hexadecyltrimethylammonium bromide (CTAB). Obtained Si substrates with high density Ag NAs serve as surface-enhanced Raman scattering (SERS) substrates for unlabelled molecular sensing. The addition of CTAB enables not only the electromagnetic enhancement by controllable producing Ag NAs “hotspots”, but also the signal enhancement by enriching probe molecules via hydrophobic interaction. Two concentration regimes of 1.0 × 10^-8-1.0 × 10^-11 M and 1.0 × 10^-12-1.0 × 10^-16 M have been obtained for quantitative and qualitative detection of Rhodamine 6 G (R6 G) in aqueous solution, respectively. As a result, for determination of R6 G, the quantitative and qualitative detection limits of 1.0 × 10^-11 and 1.0 × 10^-16 M have been obtained, respectively, with high reproducibility showing the relative standard deviation (RSD) of ∼7.3%. Simulation has been carried out using finite-difference time-domain (FDTD) to evaluate the dependence of electric field on the size and inter-gap of Ag NPs, showing good agreement with experimental results. The high sensitivity also enables SERS characterization of non-resonant and low Raman cross-section biomolecules, for example, amino acids. Such a fabrication process is simple, fast, cheap and reproducible; and therefore, it would be helpful to produce high sensitive SERS substrates to broaden their applications in chemical and biological fields for molecular diagnostics to single-/multiple-molecule detection.

在这项工作中，我们报告了一种通过表面活性剂十六烷基三甲基溴化铵（CTAB）辅助的电反应在硅（Si）表面上制备Ag纳米颗粒（NPs）和纳米组件（NAs）的快速且可控的方法。获得的具有高密度Ag NAs的Si衬底可用作表面增强拉曼散射（SERS）衬底，用于未标记的分子传感。添加CTAB不仅可以通过可控制的产生的Ag NAs“热点”实现电磁增强，而且还可以通过疏水相互作用富集探针分子来增强信号。两种浓度范围1.0×10 ^-8 -1.0×10 ^-11 M和1.0×10 ^-12 -1.0×10 ^-16已获得M分别用于定量和定性检测水溶液中的罗丹明6 G（R6 G）。结果，对于R6 G的测定，定量和定性的检出限为1.0×10 ^-11和1.0×10 ^-16分别获得了具有高重现性的M，相对标准偏差（RSD）约为7.3％。已经使用有限差分时域（FDTD）进行了仿真，以评估电场对Ag NP尺寸和间隙的依赖性，与实验结果吻合良好。高灵敏度还使得能够对非共振和低拉曼截面生物分子（例如氨基酸）进行SERS表征。这样的制造过程是简单，快速，便宜和可重复的。因此，生产高敏感度的SERS底物对于拓宽其在化学和生物学领域的应用将很有帮助，可用于单分子/多分子检测的分子诊断。