In this study, surface-enhanced Raman scattering (SERS) spectra of different rare earth (RE) ion-citrate complexes were investigated for the first time for the qualitative classification of RE³⁺ ions. With the addition of RE³⁺ ions to citrate-capped silver nanoparticles in aqueous solutions, the Raman signals of RE-citrate complexes were enhanced, and characteristic peaks appeared near 1065 and 1315 cm^–1. The I₁₀₆₅/I₁₃₁₅ ratios of La-citrate and Gd-citrate were approximately 1 and 0.55, respectively. Thus, different RE³⁺ ions were classified based on the ratio of characteristic SERS peaks near 1065 and 1315 cm^–1. In addition, the effects of RE³⁺ ions in the RE-citrate complexes were analyzed based on density functional theory (DFT) calculations. Calculation results show that these characteristic peaks are attributed to the coordination of the C–O bond and COO^– groups of citrates with the RE³⁺ ions, suggesting that these are spin-related bands of the RE-citrate complexes.

中文翻译：

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使用表面增强拉曼散射对 La3+ 和 Gd3+ 稀土离子进行分类

在本研究中，首次研究了不同稀土（RE）离子-柠檬酸盐配合物的表面增强拉曼散射（SERS）光谱，以对RE ³⁺离子进行定性分类。当水溶液中的柠檬酸封端的银纳米粒子中添加RE ³⁺离子时，RE-柠檬酸配合物的拉曼信号增强，并且在1065和1315 cm ^–1附近出现特征峰。 La-柠檬酸盐和Gd-柠檬酸盐的I ₁₀₆₅ / I ₁₃₁₅比率分别约为1和0.55。因此，不同的RE ³⁺离子根据1065 和1315 cm ^–1附近的特征SERS 峰的比率进行分类。此外，基于密度泛函理论（DFT）计算分析了RE-柠檬酸盐复合物中RE ³⁺离子的影响。计算结果表明，这些特征峰归因于柠檬酸盐的C-O键和COO-基团与RE 3+ 离子的配位^，表明^这些特征峰是RE-柠檬酸盐配合物的自旋相关带。