Abstract Surface-enhanced Raman scattering (SERS) has been applied utilizing colloidal suspensions of silver nanoparticles (AgNPs), for the detection of brilliant green (BG) at very low concentrations. Proper stimulated surface-enhanced resonance Raman scattering (SERRS) spectra collected from BG aqueous solutions at different low concentration ranges revealed a variation of the relative intensity ratio of certain BG bands attributed to a respective alteration of the molecular orientation of the analyte with respect to the AgNPs. This behavior is closely related to a different packing of the BG molecules on the nanoparticle surface when the concentration increases and the available space decreases. Additionally, the addition of suitable amounts of cetyl thrimethyl ammonium bromide (CTAB) to the BG aqueous solutions enhanced the detection limit of the analyte. This enlightens the role of the cationic surfactant in tuning the interparticle distances of AgNPs in the colloidal suspension; this presumably allows an optimization of the SERS enhancement factor. The concentration of CTAB that maximizes the SERS of BG is the same with the critical micelle concentration (CMC) of the surfactant. Most probably, CTAB at the CMC acts as a spacer keeping the AgNPs at a certain distance suitable for the generation of SE(R)RS hotspots.

中文翻译：

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亮绿的表面增强拉曼散射：阳离子表面活性剂 CTAB 对“热点”间距的堆积密度和稳定作用

摘要 表面增强拉曼散射 (SERS) 已利用银纳米粒子 (AgNP) 的胶体悬浮液应用于检测极低浓度的亮绿色 (BG)。从不同低浓度范围的 BG 水溶液中收集的适当的受激表面增强共振拉曼散射 (SERRS) 光谱揭示了某些 BG 谱带的相对强度比的变化，这归因于分析物的分子取向相对于AgNPs。当浓度增加和可用空间减少时，这种行为与纳米颗粒表面上 BG 分子的不同堆积密切相关。此外，向 BG 水溶液中加入适量的十六烷基三甲基溴化铵 (CTAB) 提高了分析物的检测限。这揭示了阳离子表面活性剂在调节胶体悬浮液中 AgNPs 颗粒间距离方面的作用；这大概允许优化 SERS 增强因子。使 BG 的 SERS 最大化的 CTAB 浓度与表面活性剂的临界胶束浓度 (CMC) 相同。最有可能的是，CMC 处的 CTAB 充当间隔物，将 AgNP 保持在适合生成 SE(R)RS 热点的特定距离处。使 BG 的 SERS 最大化的 CTAB 浓度与表面活性剂的临界胶束浓度 (CMC) 相同。最有可能的是，CMC 处的 CTAB 充当间隔物，将 AgNP 保持在适合生成 SE(R)RS 热点的特定距离处。使 BG 的 SERS 最大化的 CTAB 浓度与表面活性剂的临界胶束浓度 (CMC) 相同。最有可能的是，CMC 处的 CTAB 充当间隔物，将 AgNP 保持在适合生成 SE(R)RS 热点的特定距离处。