CHARACTERIZATION OF THE SURFACE OF A CITRATE-REDUCED COLLOID OPTIMIZED FOR USE AS A SUBSTRATE FOR SURFACE-ENHANCED RESONANCE RAMAN-SCATTERING
CHARACTERIZATION OF THE SURFACE OF A CITRATE-REDUCED COLLOID OPTIMIZED FOR USE AS A SUBSTRATE FOR SURFACE-ENHANCED RESONANCE RAMAN-SCATTERING
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DOI：
10.1021/la00010a021
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发表时间：
1995-10-01
期刊：
影响因子：
3.9
通讯作者：
WHITE, PC
中科院分区：
文献类型：
--
作者：
MUNRO, CH;SMITH, WE;WHITE, PC
柠檬酸盐还原胶体可用于通过表面增强（共振）拉曼散射（SE（R）RS）进行可重现、灵敏和选择性分析。控制胶体表面的化学性质对于实现该方法的潜力至关重要。本研究旨在了解水溶液中的表面化学，表征最终表面的性质，并开发一种用于表面SE（R）RS分析的稳健方法。研究了柠檬酸三钠还原硝酸银的最佳条件。胶体形成的可见吸收光谱和光子相关光谱表明，Ag-I在柠檬酸盐加入后2 min内开始还原为Ag-0，形成的初始颗粒大（60-80 nm），多分散。随后的加热最初提供20-30和40-50 nm颗粒的较少多分散的混合物，并且最后提供较小颗粒（类似于27 nm）的近似单分散分布。胶体悬浮液的溶液NMR研究表明在整个胶体形成过程中溶液中存在柠檬酸盐及其分解产物、乙酰乙酸和甲酸盐。从聚集的等分试样的胶体的拉曼散射表明两种形式的柠檬酸盐取决于制备的阶段，但既不是乙酰乙酸也不是甲酸被检测到吸附在银表面。据信最终的大致单分散的颗粒通过柠檬酸银表面层稳定，并具有悬垂的负基团。胶体稳定性超过2个月。SE（R）RS效应需要胶体的受控聚集。聚集过程通常通过添加酸或活化离子（例如Cl-或I-）来诱导。聚集与酸（硝酸）和聚（L-赖氨酸）和抗坏血酸进行了比较。聚（L-赖氨酸）的方法是更有效的，提高单分散性的胶体聚集体。SERRS的重现性（相对标准偏差（RSD））
Citrate-reduced colloids can be used to give reproducible, sensitive, and selective analysis by surface-enhanced (resonance) Raman scattering (SE(R)RS). Control of the chemistry at the colloid surface is essential to realize the potential of this method. This study is aimed at understanding the surface chemistry in aqueous solutions, characterizing the nature of the final surface, and developing a robust method for SE(R)RS analysis at the surface. An optimized procedure for the reduction of silver nitrate with trisodium citrate is described. Visible absorption and photon correlation spectroscopies of colloid formation indicate that the initial reduction of Ag-I to Ag-0 occurs within 2 min of citrate addition, and the initial particles formed are large (60-80 nm) and polydisperse. Subsequent heating initially provides a less polydisperse mixture of 20-30 and 40-50 nm particles and finally an approximately monodisperse distribution of smaller particles (similar to 27 nm). Solution NMR studies of the colloidal suspension indicate the presence of citrate and its decomposition products, acetoacetic acid and formate in solution throughout colloid formation. Raman scattering from aggregated aliquots of colloid indicates two forms of citrate depending on the stage of preparation, but neither acetoacetic acid nor formate is detected as being adsorbed at the silver surface. The final, approximately monodisperse particles are believed to be stabilized by a surface layer of silver citrate, with pendant negative groups. The colloids are stable for over 2 months. The SE(R)RS effect requires controlled aggregation of the colloid. The aggregation process is generally induced by the addition of acid or activating ions, for example, Cl- or I-. Aggregation with acid (HNO3) and with poly(L-lysine) and ascorbic acid are compared. The poly(L-lysine) method is more effective, enhancing the monodispersity of colloidal aggregates. The reproducibility of SERRS (relative standard deviation (RSD)