School of Pharmaceutical Sciences, Central South University , Changsha, Hunan 410013, People's Republic of China.
Anal Chem. 2016 May 3;88(9):5009-15. doi: 10.1021/acs.analchem.6b01194. Epub 2016 Apr 14.
The potentiality of surface-enhanced Raman scattering (SERS) to detect ultralow concentrations of analyte has attracted much attention in detection of trace components in both medicinal and environmental samples. However, detection at trace concentration usually requires sophisticated systems. Here, we present an ultrasensitive and facile SERS approach, a two-step centrifugation method, which achieved a detection limit of 500 fM with phenformin hydrochloride and risperidone as acidic and alkaline analyte, respectively. This method consists of two steps: (1) centrifuging colloidal silver to increase nanoparticles' concentration and to remove small-size nanoparticles, thus increasing the chance of analyte adsorption on large nanoparticles that have strong SERS activity; (2) centrifuging samples after the analytes were mixed with nanoparticles. After the first centrifugation and mixing with aqueous analyte, the colloidal silver is either flocculated (for high-concentration samples) or forms a nanoparticle-analyte complex (for low-concentration samples). Until the second centrifugation, the concentration of analyte and hot-spot formation is significantly increased, and thus a high SERS enhancement factor is obtained. In short, the two-step centrifugation method overcomes drawbacks of the traditional method, which demands not only sophisticated operation but also expensive instruments, to fully exploit the potential of SERS detection.
表面增强拉曼散射（SERS）具有探测超低浓度分析物的潜力，因此在医学和环境样品中痕量成分的检测方面引起了广泛关注。然而，在痕量浓度下进行检测通常需要复杂的系统。在这里，我们提出了一种超灵敏且简单的 SERS 方法，即两步离心法，该方法以盐酸苯乙双胍和利培酮分别作为酸性和碱性分析物，实现了 500 fM 的检测限。该方法包括两步：（1）离心胶体银以增加纳米粒子的浓度并去除小尺寸的纳米粒子，从而增加分析物吸附在具有强 SERS 活性的大纳米粒子上的机会；（2）在与纳米粒子混合后离心样品。在第一次离心和与水溶液分析物混合后，胶体银要么絮凝（用于高浓度样品），要么形成纳米粒子-分析物复合物（用于低浓度样品）。直到第二次离心，分析物的浓度和热点形成显著增加，从而获得了高 SERS 增强因子。简而言之，两步离心法克服了传统方法的缺点，该方法不仅需要复杂的操作，还需要昂贵的仪器，以充分发挥 SERS 检测的潜力。
