Dr. Wei Gao, an Assistant Professor in the Textile Engineering, Chemistry & Science Department, worked as a Director’s Postdoctoral Fellow on fuel cells and batteries in the Los Alamos National Laboratory for the past three years. She obtained her Ph.D. in chemistry from Rice University in 2012, under the guidance of Professor Pulickel M. Ajayan. She also holds an M.S. in analytical chemistry and a B.S. in chemistry from the Nanjing University, China. Dr. Gao has several years of research experience in nanomaterials and nanotechnologies. Her Ph.D. thesis focused on a group of new materials named “graphene oxides” and their applications in fuel cells, supercapacitors, and batteries, as well as water purification systems. Her future research interests lie at the interfaces between nanotechnology development and textile engineering. Dr. Gao is also very enthusiastic about teaching. She received the Harry B. Weiser Teaching Award from Rice University when serving as a teaching assistant in the organic-chemistry lab. She also volunteered as a Judge in Science Fairs at several local high schools, a presenter on fuel cell topics to female students in the Expanding Your Horizons 2014 mini-conference in Santa Fe, and a teacher in Chinese for two semesters at a local Baptist church in Los Alamos.
Dr. Gao’s unique experience in carbon nanomaterial research, synthetic and analytical chemistry, as well as device design and fabrication inspires her plans for attaining better understanding and improved tailoring of nanomaterials for innovative energy-related systems. She wants to accomplish her research goals by engineering materials at the molecular level that promises to direct improvements in bulk properties such as the active surface area, chemical stability, and electronic/ionic conductivity, making them far superior to those of the current carbon-based materials.
Her research targets are to create and study new carbon-based nanomaterials crucial to
(1) thin-film supercapacitors and their incorporation with textiles
(2) next generation polymer electrolyte fuel cell membranes
(3) bioimaging and photothermal therapy
High Energy Density Graphene Oxide Micro-Supercapacitors
Although thin film supercapacitors offer superior power density and cycling ability over Li-based micro-batteries, a major bottleneck in their use is achieving both high energy and power densities, while maintaining a flexible fabrication process at a low cost. We would like to directly confront these issues by developing a GO-based thin-film supercapacitor first demonstrated by us that uses an innovative and industrially scalable laser pattering approach (Fig.1) In our device, GO acts as the electrolyte/ionic conductor that separates the laser exposed/electrically conducting reduced graphene oxide (rGO). Such devices can (theoretically) outperform existing state-of-the-art thin film micro-supercapacitors.
Figure 1. Schematic (left) of laser-patterning technique to make the GO thin film supercapacitors (right, black = RGO, grey=GO). http://www.nature.com/nnano/journal/v6/n8/abs/nnano.2011.110.html
Graphene Oxides for Better Protonic Conduction
During the past 20 years, there has been a tremendous acceleration in polymer-membrane research. In spite of the progress achieved, several challenges need to be addressed for ion-conducting membranes, including those made of state-of-the-art perfluorosulfonic-acid polymers, to become fully viable. The challenges involve low protonic conductivity under dry conditions, e.g., at 50% relative humidity and 120 °C (particularly suitable for automotive fuel cell systems), and insufficient longterm durability under extreme conditions, such as highly acidic and reducing/oxidizing environments. One way of addressing these key issues, which is proposed here, consists of the development of new types of materials (graphene oxides), free of the problems commonly encountered with current proton-conducting polymers (Fig.2).
Figure 2. Chemical oxidation process to convert (a) graphene to (b) graphene oxide (GO). (c) SEM image of the edge of a free-standing graphene-oxide membrane.http://onlinelibrary.wiley.com/doi/10.1002/anie.201310908/abstract
Quantum Dot Synthesis from Graphene and Other Two-Dimensional Nanomaterials One
One of the major drawbacks of graphene is its zero-bandgap electronic structure that limits its applications in semiconductor industries as well as optoelectronics. To extend its influence in these areas, material scientists have been synthesizing graphene samples with smaller sizes and different shapes, mainly graphene quantum dots (GQDs) and graphene nanoribbons (GNRs), which lead to bandgap opening in these nanocarbons due to quantum confinement and edge effects. Chemical oxidation and opening of carbon nanotubes or carbon nanofibers are the two major strategies to make GNRs, while electron-beam lithography and ruthenium-catalyzed C60 transformations, as well as hydrothermal or electrochemical treatment of graphene oxide, have been reported as GQD-synthesis recipes. All of these methods either require specific instrumentation or complicated and expensive chemicals, where tunability in size is quite limited. In 2012, we reported a facile synthesis of GQDs via acidic treatment of pitch carbon fibers, where we can tune the size of the product in between 1-10 nm. The thicknesses of the quantum dots are usually within three graphene layers (< 1nm), which give them a disk-like shape.
Figure 3. Left: AFM image of GQDs. Right: fluorescent images of human breast cancer cell T47D. The nucleolus were stained with blue DAPI and surrounded by our green GQDs (5-7 nm).http://pubs.acs.org/doi/abs/10.1021/nl2038979