Department of Chemistry Seminar Announcement

1. Department of Chemistry Seminar Announcement About the Speaker Professor Dai Hai-Lung, ICAS Fellow, is the Hirschmann-Makineni Chair Professor of Chemistry at the University of Pennsylvania. Prof Dai came to the US for graduate study in chemistry in 1976 at the University of California, Berkeley, after graduation from the National Taiwan University and military service. After a postdoctoral sting at MIT he arrived at Penn as an assistant professor in 1984. he was promoted to full professor in 1992 and was the Chairman of the Chemistry Department from 1996-2002. As an accomplished researcher, he has published more than 130 papers in the areas of molecular and surface sciences and received numerous honors include ing a Dreyfus Foundation Teacher-Scholar Award, a Sloan Fellowship, the 1990 Coblentz Prize in Molecular Spectroscopy, the 1992 Morino Lectureship (Japan), a Humboldt Fellowship (Germany), the 1995 American Chemical Society Philadelphia Section Award, and a Guggenheim Fellowship. While as the Chairman, Prof Dai, in collaboration with the Penn Graduate School of Education, established the MS in Chemistry Education program, which has trained more than 100 in-service high school teachers. Among many of his other responsibilities are a gubernatorial appointment in the Pennsylvania State Board on Drug, Device and Cosmetic. He is a fellow of the American Physical Society and has been elected by the membership to be the Chair of the Chemical Physics Division of the American Physical Society. Around the greater Philadelphia region, he has been the conductor of the Chinese Musical Voices Choir, a past President of the Taiwan University Alumni Association, a board member of the Mt Jade Science and Technology, and a member in the Arts and Science Committee of the Franklin Institute. Abstract The surface of nanometer and micron size particles, including nanoparticles and biological cells, in colloidal environments can be functionalized through molecular adsorption and chemical modification for specific technology applications. Knowing what is the chemical composition and structure at the surface of the particles buried deep in the colloid is critical to fundamental understanding of their properties and as well as their technology development. For molecular thin films, the electrical and mechanical properties often depend critically on the structure of the interfacial layer between the film and the substrate. Probing the small quantity of molecules at the interfacial layer in the background of the huge bulk, on the other hand, presents an experimental challenge. Nonlinear optical phenomena such as Second Harmonic Generation (SHG) has unique symmetry properties that can be used to discriminate one single layer of ordered molecules from the massive background of randomly oriented molecules, and subsequently can be used to detect the interfacial layer buried underneath the condensed media. The coverage, energy, and even structure of the molecules adsorbed at the surface of particles immersed in a colloid can be determined by SHG. This has been demonstrated for a variety of colloidal particles, including nanoparticles and biological cells. In thin films of organic semiconducting molecules and ionic liquids, it is found that the interfacial layer can be ordered due to surface corrugation or in response to external field. SHG can even be used to examine the membrane of living biological cells, monitoring molecular adsorption and transport in real time. All are Welcome