Abstract：
Plasmonic Au-Ag nanostars are excellent surface-enhanced Raman scattering (SERS) probes due to bimetallic coupling and the tip effect. However, the existing preparation methods of AuAg nanostars cannot achieve controlled growth of the Ag layer on the branches of nanostars and so cannot display their SERS to the maximum extent, thus limiting its sensitivity in biosensing. Herein, a novel strategy \"PEI (polyethylenimine)-guided Ag deposition method\" is proposed for synthesizing AuAg core-shell nanostars (AuAg@Ag NS) with a tunable distribution of the Ag layer from the core to the tip, which offers an avenue for investigating the correlation between SERS efficiency and the extent of spread of the Ag layer. It is found that AuAg@Ag NS with a Ag layer coated the whole branch has the strongest SERS performance because the coupling between the tips and Ag layer is maximized. Meanwhile, as a completely closed core-shell structure, AuAg@Ag NS can confine and anchor 4-ATP inside the Ag layer to avoid an unstable SERS signal. By connecting the aptamer, a reliable internal standard nanoprobe with a SERS enhancement factor (EF) up to 1.86 × 108 is prepared. Okada acid is detected through competitive adsorption of this SERS probes, and the detection limit is 36.6 pM. The results gain fundamental insights into tailoring the nanoparticle morphologies and preparation of internal standard nanoprobes and also provide a promising avenue for marine toxin detection in food safety.
摘要：
由于双金属耦合和尖端效应，等离子体Au-Ag纳米星是出色的表面增强拉曼散射（SERS）探针。然而,现有的AuAg纳米星的制备方法无法实现纳米星分支上Ag层的受控生长，因此无法最大程度地显示其SERS，从而限制了其在生物传感中的灵敏度。在这里，提出了一种新颖的策略“PEI（聚乙烯亚胺）引导的Ag沉积方法”，用于合成AuAg核壳纳米星（AuAg@AgNS），其Ag层从核到尖端的分布可调，这为研究SERS效率与Ag层扩散程度之间的相关性提供了途径。发现具有涂覆整个分支的Ag层的AuAg@AgNS具有最强的SERS性能,因为尖端和Ag层之间的耦合被最大化。同时,作为一个完全封闭的核-壳结构，AuAg@AgNS可以将4-ATP限制和锚定在Ag层内，以避免不稳定的SERS信号。通过连接适体，制备了SERS增强因子（EF）高达1.86×108的可靠内部标准纳米探针。通过这种SERS探针的竞争性吸附检测冈田酸，检测限为36.6pM。结果获得了对定制纳米颗粒形态和内标纳米探针制备的基本见解，也为食品安全中的海洋毒素检测提供了有希望的途径。
