Microscopic Probing of Silica Surfaces

在这个项目中，特拉华大学的玛丽·J·沃斯得到了分析和表面化学项目续期拨款的支持。她将研究有机阳离子在硅胶基色谱表面的吸附，以了解层析分离中区带拖尾的物理现象，这是阻碍蛋白质和药物等大量重要化合物分离的长期存在的问题。原子力显微镜将被用来在很大的pH范围内测量表面电荷密度。有机阳离子罗丹明123的单分子检测将被用来探测侧向扩散和解吸速率作为表面电荷密度的函数，表面电荷密度由pH控制。将合成具有不同硅醇浓度、单层覆盖率和单层疏水性的固定相，以及水平聚合的单层以降低表面电荷密度。吸附等温线将从罗丹明123在无孔硅胶上洗脱获得的数据生成，并通过对相同材料进行单分子和原子力显微镜实验进行测试。在这项工作中，将调查导致目前药物和蛋白质等重要化合物的层析效率低下的物理和化学因素。将要进行的实验本质上是多学科的，汇集了光学光谱学、自组装单层研究、扫描探针显微镜和化学分离的想法。这项工作的实际影响将导致更快、更完整的分离，用于分析和准备目的。

In this project, Mary J. Wirth of the University of Delaware is supported by a renewal grant in the Analytical and Surface Chemistry Program. She will study the adsorption of organic cations to silica-based chromatographic surfaces in order to understand the physical phenomena responsible for zone tailing in chromatographic separations which is a long-standing problem hindering separation of a large number of important compounds such as proteins and pharmaceuticals. Atomic force microscopy will be used to measure surface charge density over a wide pH range. Single-molecule detection of an organic cation, rhodamine 123, will be used to probe lateral diffusion and desorption rates as a function of surface charge density, which is controlled by pH. Stationary phases will be synthesized with varying silanol concentration, monolayer coverage and monolayer hydrophobicity, along with horizontally polymerized monlayers to reduce surface charge density. Adsoption isotherms will be generated from data obtained by elution of rhodamine 123 on nonporous silica gel and tested by performing the single-molecule and atomic force microscopy experiments on the same material. In this work, physical and chemical factors responsible for the currently inefficient chromatography of important classes of compounds such as pharmaceuticals and proteins will be investigated. The experiments to be done are multidisciplinary in nature, bringing together ideas from optical spectroscopy, self-assembled monolayer research, scanning probe microscopy and chemical separations. The practical impact of the work will result in faster more complete separations for analysis and preparative purposes.