Xia Lixin, Kim Nam Hoon, Kim Kwan
Laboratory of Intelligent Interfaces, Department of Chemistry, Seoul National University, Seoul 151-742, Republic of Korea.
J Colloid Interface Sci. 2007 Feb 1;306(1):50-5. doi: 10.1016/j.jcis.2006.10.012. Epub 2006 Nov 7.
Micrometer-sized Ag (microAg) powders are very efficient substrates for both the infrared and Raman spectroscopic characterization of molecular adsorbates assembled on silver. In particular, the Raman spectrum of organic monolayers on microAg powders is a surface-enhanced Raman scattering (SERS) spectrum. To use microAg powders as a core material for constructing molecular sensing/recognition units operating via SERS, it is first necessary to stabilize the SERS-marker molecules that are directly in contact with the microAg powders. One promising strategy is the fabrication of silica shells onto SERS-marker molecules, and herein we demonstrate its feasibility by choosing 4-mercaptophenol (4-MPH) as a model SERS-marker molecule. Due to the presence of the hydroxyl group of 4-MPH, silica was readily deposited onto microAg particles by the base-catalyzed hydrolysis of tetraethyl orthosilicate, and its subsequent condensation, to form a cagelike structure. The formation of silica shells was confirmed with infrared, Raman, and X-ray photoelectron spectroscopy, coupled with field emission scanning electron microscopy. We were able to tune the thickness of silica shells simply by varying the silanization reaction time.
微米级银粉（microAg）是用于对组装在银上的分子吸附物进行红外和拉曼光谱表征的非常有效的基底。特别是，microAg粉末上有机单层的拉曼光谱是表面增强拉曼散射（SERS）光谱。要将microAg粉末用作构建通过SERS运行的分子传感/识别单元的核心材料，首先需要稳定与microAg粉末直接接触的SERS标记分子。一种有前景的策略是在SERS标记分子上制备二氧化硅壳，在此我们通过选择4-巯基苯酚（4-MPH）作为模型SERS标记分子来证明其可行性。由于4-MPH中存在羟基，通过原硅酸四乙酯的碱催化水解及其随后的缩合反应，二氧化硅很容易沉积在microAg颗粒上，形成笼状结构。通过红外光谱、拉曼光谱、X射线光电子能谱以及场发射扫描电子显微镜证实了二氧化硅壳的形成。我们能够通过改变硅烷化反应时间简单地调节二氧化硅壳的厚度。
