Fan Meikun, Brolo Alexandre G
Department of Chemistry, University of Victoria, Victoria, Canada.
Phys Chem Chem Phys. 2009 Sep 14;11(34):7381-9. doi: 10.1039/b904744a. Epub 2009 Jul 15.
Highly sensitive SERS substrates with a limit of detection in the zeptomole (for Nile blue A and oxazine 720) range were fabricated through a bottom-up strategy. Ag nanoparticles (Ag NPs) were self-assembled onto glass slides by using 3-mercaptopropyltrimethoxysilane (MPTMS) sol-gel as linker. The substrates were characterized by UV-Vis and AFM after each deposition of Ag NPs. It was found that the glass slide presented just a few Ag NPs aggregates scattered throughout the surface after just one deposition. The glass surface was gradually covered by a homogeneous distribution of Ag NPs aggregates as the deposition number increased. Surface-enhanced Raman scattering (SERS) of the substrates was examined at different numbers of Ag NPs deposition using nile blue A and oxazine 720 as probe molecules and two laser excitations (632.8 nm and 785 nm). Optimum SERS was observed after six depositions of Ag NPs. SERS mapping indicated that at lower deposition numbers (less than 3 Ag NPs depositions) the substrates presented a few SERS "hot-spots" randomly distributed at the surface. After 7 Ag NPs depositions, spatial distribution of the SERS signal followed a Gaussian statistics, with a percent relative standard deviation (RSD%) of approximately 19%. In addition, the sample-to-sample reproducibility of the SERS intensities under both laser excitations was lower than 20%. It was also found that these substrates can provide giant Raman signal enhancement. At optimum conditions and with a 632.8 nm laser, the signal from an estimated of only approximately 44 probe molecules (100x objective) can still be detected.
通过自下而上的策略制备了检测限在zeptomole（针对尼罗蓝A和恶嗪720）范围内的高灵敏度表面增强拉曼散射（SERS）基底。使用3-巯基丙基三甲氧基硅烷（MPTMS）溶胶-凝胶作为连接剂，将银纳米颗粒（Ag NPs）自组装到载玻片上。每次沉积Ag NPs后，通过紫外可见光谱（UV-Vis）和原子力显微镜（AFM）对基底进行表征。发现仅一次沉积后，载玻片表面仅出现少量分散的Ag NPs聚集体。随着沉积次数增加，玻璃表面逐渐被均匀分布的Ag NPs聚集体覆盖。以尼罗蓝A和恶嗪720作为探针分子，并使用两种激光激发（632.8 nm和785 nm），在不同沉积次数的Ag NPs下检测基底的表面增强拉曼散射（SERS）。在Ag NPs沉积六次后观察到最佳SERS。SERS映射表明，在较低沉积次数（少于3次Ag NPs沉积）时，基底表面随机分布有一些SERS“热点”。在7次Ag NPs沉积后，SERS信号的空间分布遵循高斯统计，相对标准偏差百分比（RSD%）约为19%。此外，在两种激光激发下，SERS强度的样品间重现性低于20%。还发现这些基底可提供巨大的拉曼信号增强。在最佳条件下，使用632.8 nm激光时，估计仅约44个探针分子（100倍物镜）发出的信号仍可被检测到。
