Seed-mediated growth has been employed as a simple and powerful means to the shape-controlled synthesis of metal nanocrystals. In this work, we apply the principle of seed-mediated growth in analytical chemistry, and achieve improved sensitivity due to the low energy barrier in the target-induced formation of bimetallic nanoparticles with core-shell structure. As a result, a simple, reliable, highly sensitive and selective method for the detection of ellagic acid (EA), a naturally occurring polyphenolic antioxidant, has been developed. With the aid of EA in alkaline solution, Ag+ ions can be transformed to Ag atoms and deposit on the surfaces of Au nanorods (AuNRs, act as seeds here) to generate Au@Ag core-shell nanorods, accompanied by blue shift of the longitudinal localized surface plasmon resonance (LSPR) band of AuNRs from near-infrared region to shorter wavelengths. Based on the linear relationship between the wavelength change of longitudinal LSPR band and the concentration of EA, our method achieves a detectable range of 0.2-20 μM and a limit of detection as low as 40 nM toward EA. This approach is highlighted by its high sensitivity for EA assay, which benefits from the viewpoint of thermodynamics in the nucleation/growth mode of metal nanoparticles. Moreover, this method shows high selectivity for EA detection when potential species coexist, and thus has been successfully applied in the detection of EA in skin-whitening cosmetics. The proposed strategy of seed-mediated growth herein can also be extended to other systems for sensing.

中文翻译：

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Au@Ag核壳纳米棒的种子介导生长用于检测美白化妆品中的鞣花酸

种子介导的生长已被用作一种简单而有效的金属纳米晶体形状控制合成方法。在这项工作中，我们将种子介导的生长原理应用于分析化学，由于靶诱导形成具有核壳结构的双金属纳米粒子的低能垒，实现了更高的灵敏度。因此，开发了一种简单、可靠、高灵敏度和选择性的检测鞣花酸 (EA)（一种天然存在的多酚类抗氧化剂）的方法。在碱性溶液中的 EA 的帮助下，Ag+ 离子可以转化为 Ag 原子并沉积在 Au 纳米棒（AuNRs，这里充当种子）的表面上以生成 Au@Ag 核壳纳米棒，伴随着 AuNRs 的纵向局域表面等离子体共振 (LSPR) 带从近红外区域到较短波长的蓝移。基于纵向 LSPR 波段的波长变化与 EA 浓度之间的线性关系，我们的方法实现了 0.2-20 μM 的可检测范围和对 EA 低至 40 nM 的检测限。这种方法的突出特点是其对 EA 分析的高灵敏度，这得益于金属纳米粒子成核/生长模式的热力学观点。此外，该方法在潜在物种共存时对EA检测表现出较高的选择性，因此已成功应用于美白化妆品中EA的检测。本文提出的种子介导生长策略也可以扩展到其他传感系统。