报告题目：Understanding the Stöber Silica
报告人： Hongyu Chen
Dr. Hongyu Chen obtained his B. Sc. from University of Science and Technology of China (USTC) in 1998. He then moved to Yale University and studied Mn complexes and water oxidation chemistry. After obtaining his Ph.D. degree in 2004, he worked as a post-doctoral fellow in Cornell University on the topic of protein-nanoparticle hybrids. In 2006, he joined the Division of Chemistry and Biological Chemistry in Nanyang Technological University in Singapore, where he is currently an Associate Professor and Associate Dean (College of Science). His main research interest is in the development of new synthetic methodologies for nanostructures and the underlying mechanisms.
In nanoscience, the word “silica” is used to broadly refer to a variety of different materials that are derived from the hydrolysis of siloxanes. It is well known that the silica materials contain many dangling bonds, not to mention impurities such as H2O, NH3, ions, dyes, and surfactants. Generally speaking, the paradigm is to view the materials as silica-centered hybrids: the silica is the dominate framework to which various types of impurities are simply adsorbed. As such, the impurities are expected to play minor roles in the formation and stability of the framework. In this talk, I show that the spontaneous incorporation of NH4+ ions plays a critical role in both the formation and dissolution of silica nanoparticles. Through a series of specifically designed control experiments, the dissolution of Stöber silica in water is shown to be mainly due to its solubility, as opposed to Ostwald ripening. These results explain well why the inner portion of silica nanoparticles is selectively removed during etching, i.e., the origin of the selective etching. With this knowledge, we show that a variety of ions could be readily incorporated in silica domains and the pore size of silica can be easily controlled.
 Yi Jian Wong, Liangfang Zhu, Wei Shan Teo, Yan Wen Tan, Yanhui Yang, Chuan Wang,* and Hongyu Chen*, Journal of the American Chemical Society, 2011, 133 (30), 11422-11425.
 Xiaohui Song, Tao Ding, Lin Yao, Cuicui Liu, Tan Lee Siew Rachel, and Hongyu Chen*, manuscript in preparation, 2014.