According to recent research, amphiphilic surfactants can stabilize metal nanoparticles because of their excellent dispersibility. Therefore, herein, amphiphilic polyethylenimine (PEI) dendritic polymer nanocapsules were synthesized by using PEI and poly(urea/malonamide) dendrons of different generations. Then, silver nanoparticles (AgNPs) were immobilized on PEI dendritic polymer nanocapsules for surface-enhanced Raman scattering (SERS) detection. Well-designed amphiphilic PEI dendrons possessed abundant nucleation sites for AgNP reduction, which could directly reduce silver ions to AgNPs without additional reducing agents at room temperature, showing the stronger reducing capability than pristine PEI. The size and interparticle gap of AgNPs were manipulated by varying the size of the PEI dendritic polymer and the ratio of PEI dendritic nanocapsules/AgNO₃. As a result, the Ag-PEI-dendritic polymer was able to perform Raman enhancing capability. Especially, a sample, namely, Ag-PEI-G0.5, exhibited the strongest Raman enhancement effect, due to the optimal size and interparticle gap of AgNPs. The Ag-PEI dendritic SERS nanocapsules could rapidly and reproducibly detect many kinds of biomolecules (adenine, methylene blue, and beta-carotene) with a linear calibration curve. The limit of detection (LOD) of adenine was lower than 10^–7 M. Therefore, this facile method to in situ prepare Ag-PEI dendritic SERS nanocapsules (reducing agent free) possesses high potential to be applied in rapid SERS detection for the quantitative analysis of biomolecules.

中文翻译：

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用于表面增强拉曼散射检测的两亲性银-聚乙烯亚胺树枝状聚合物纳米胶囊的制备

根据最近的研究，两亲性表面活性剂由于其优异的分散性可以稳定金属纳米颗粒。因此，本文利用PEI和不同代的聚(脲/丙二酰胺)树枝状分子合成了两亲性聚乙烯亚胺(PEI)树枝状聚合物纳米胶囊。然后，将银纳米颗粒（AgNPs）固定在PEI树枝状聚合物纳米胶囊上，用于表面增强拉曼散射（SERS）检测。精心设计的两亲性PEI树枝状结构具有丰富的AgNP还原成核位点，可以在室温下直接将银离子还原为AgNPs，无需额外的还原剂，表现出比原始PEI更强的还原能力。通过改变PEI树枝状聚合物的尺寸和PEI树枝状纳米胶囊/AgNO ₃的比例来控制AgNP的尺寸和颗粒间间隙。结果，Ag-PEI-树枝状聚合物能够发挥拉曼增强能力。特别是，由于 AgNP 的最佳尺寸和颗粒间间隙，Ag-PEI-G0.5 样品表现出最强的拉曼增强效果。 Ag-PEI树枝状SERS纳米胶囊可以快速、可重复地检测多种生物分子（腺嘌呤、亚甲蓝和β-胡萝卜素），并具有线性校准曲线。腺嘌呤的检测限 (LOD) 低于 10 ^–7 M。因此，这种原位制备 Ag-PEI 树枝状 SERS 纳米胶囊（不含还原剂）的简便方法在快速 SERS 检测中具有很高的应用潜力，可用于定量分析。生物分子分析。