Weiwei Gao

Department of Chemistry & Chemical Biology

Harvard University

Nearly all applications of oxides involve processes that take place on oxide surfaces. For example, in the chemical industry, it is on oxide surfaces that most hydrocarbon feedstocks are converted into more valuable oxygenates. In addition, oxides in photovoltaics absorb light and then transform it into electricity across the surface, which hold the promise for sustainable and clean energy production. Moreover, when oxide nanoparticle surfaces are functionalized with biomolecules, they can be delivered in a targeted manner for more efficient medical diagnosis, cancer magnetic hyperthermia and drug delivery.

Detailed knowledge of how local structure determines overall oxide functions and energetic processes is often the key for rational material design. Compared to what is known at the atomic and molecular levels of metal and semiconductor surfaces, little is known about metal oxides. This is mainly due to the difficulties to obtain large size oxide single crystal surfaces for modern surface and interface characterization. Challenges also exist in manipulating the composition and structure of oxides for systematic model studies. So far, research on oxides has largely been performed on powder samples. As a result, many fundamental issues such as the oxide photocatalytic mechanisms, the catalyst structure-reactivity relationship, and the oxide interaction with biomolecules have not been fully understood.

My past research was focused on developing oxide thin film deposition, creating model systems, and studying chemical reactions on oxides at the atomic level. During my Ph.D. studies at Yale University under the supervision of Professor Eric I. Altman, I constructed an oxygen-plasma assisted molecular beam epitaxy (OPA-MBE) system, which is ideally suited to create oxide thin films with surface and interfacial structures at the atomic level in a well-controlled manner. In addition to thin film growth, I also built up strong experimental skills in characterizing oxide thin films using scanning probe microscopy, photoelectron spectroscopy, transmission electron microscopy and electron diffraction techniques. To further study catalytic reaction mechanisms and kinetics on solid surfaces, I joined Professor Cynthia M. Friend's group at Harvard University for my post-doc training. During the past two years, I have been studying how the material local structure affects reaction pathways and energetics using oxidized gold and silver single crystals as model systems.

I plan to focus my future research on oxide surfaces and interfaces. With advanced oxide MBE technique in fabricating oxide substrates, I will create oxide model systems and further explore, probe and manipulate interactions and dynamics on oxide surfaces. My goal is to gain a better understanding of oxides and advance their applications in energy conversion, heterogeneous catalysis and biotechnology. I propose the following research plans:

(I) To develop oxides for efficient light conversion and artificial photosynthesis. Motivated by the oxide design in solar cell manufacture, which uses dye sensitizers and dopants, I would like to study how these approaches will collaborate with scavenging molecules and metal nanoparticles on oxide surfaces to achieve efficient chemical synthesis.

(II) To better understand the fundamental issues of catalyst structure-reactivity relationship. With the advantages of oxide MBE in growing doped oxides, I can separate electronic and structural effects of oxide substrates so that the oxide electronic impact on the structure and reactivity of the supported metal nanoparticles can be studied independently.

(III) To improve the interface between oxides and biomolecules. Using oxide MBE, I will manipulate oxide substrates by doping, coating, and patterning to study how the oxides can be better designed to template biomolecules including proteins, lipid bilayers and living cells.