Sandy Asher

Analytical Chemistry, Biophysical Chemistry, Materials Science and Physical Chemistry

Professor Asher's research program is interdisciplinary and brings together scientists in analytical chemistry, biophysical chemistry, materials science and physical chemistry to solve important scientific and technological problems. The research has bothfundamental and applied aspects. The most fundamental research involves calculations of the interactions between light and matter, and the examination of excited states of molecules. Applied work includes the spectroscopic investigation of protein structure and function, and development of a chemical understanding of the gas phase and solid phase reactions occurring during synthesis of diamond in CVD diamond reactors. Another example is the fabrication of new "smart" materials for use in novel optical devices, sensors, and for use in optical computers.

Examples of research projects underway include:

Amide Excited States and Proteins Folding

The Asher group has pioneered the development of UV Raman spectroscopy to study molecular structure. UV excitation with novel laser sources, allows us to study interactions between the molecular electron cloud and nuclear vibrations. This gives us incisive glimpses into molecular structure.

We have developed a new methodology for structure characterization of proteins using UV resonance Raman spectroscopy. For the first time, we have applied nanosecond time-resolved UVRR spectroscopy for kinetic studies of protein folding. Rapid laser-induced temperature jumps are used to initiate the folding process; transient vibrational spectra are recorded using time-delayed probe pulses to characterize of the intermediate states involved (Fig. 1).

Diamond Growth Chemistry

We have constructed a UV Raman instrument on a CVD diamond reactor at Westinghouse Corp. and are developing an in situ spectroscopic method to monitor the diamond growth and the gas phase chemistry, in order to optimize the growth conditions. This project represents a unique partnership between academia and industry.

Materials Science and Non Linear Optics

We have developed novel materials based on crystalline colloidal (CCA) self assembly. CCA are ordered arrays of colloidal particles formed in a liquid. The colloidal particles repel each other and form a cubic array which Bragg diffracts light from the UV through the visible and the IR spectral region. These arrays serve as diffracting optical devices. We have developed methods to polymerize these arrays in solid films that change dimension in response to chemical, electrical, and thermal environmental changes (Fig. 2). We have utilized these materials to develop a new chemical sensing motif which creates a new generation of optical switches for use in optical computing, for chemical separations and for thin film display devices.