The Mallouk Group is interested in several problems in materials chemistry, including photoelectrochemistry, electrochemical energy conversion, low-dimensional physical phenomena, and motion on the nanoscale. Our approach involves the synthesis of materials that contain molecular and/or solid state components, and the study of their structure, assembly, and properties by a variety of physical techniques.
Overview of current research projects in the group
Solar and Electrochemical Energy Conversion. An important goal of this aspect of our research is to develop new kinds of nanomaterials that will lead to more efficient and less expensive solar energy conversion devices. Dye-sensitized solar cells, developed over two decades ago by Michael Gratzel and coworkers, generate electricity from sunlight through light absorption by molecular dyes. By incorporating nanoparticles that catalyze water oxidation into dye sensitized solar cells, it is possible to split water to hydrogen and oxygen using visible light. We use biomimetic principles to control electron and proton transfer reactions in these cells and transient electrochemical and spectroscopic techniques to measure their kinetics. These studies have recently led to a better understanding of system-level problems in the photoelectrolysis of water, and to the design of more efficient electrolyzers for converting CO2 to fuels and chemicals.
Template Synthesis of Nanowires and Metamaterials. Several projects in the group use porous membranes and colloidal crystals as templates for making nanomaterials. Multi-segment nanowires have interesting electronic properties, such as transistor and diode behavior and in some cases unusual low temperature transport properties. In collaboration with the Sen, Velegol, Cremer, and Crespi groups, we are studying the movement of asymmetric metallic and semiconducting nanoparticles that are powered by spontaneous catalytic reactions. These catalytic swimmers were the first examples, outside of biological systems, of autonomously powered nano- and micromotors. In many ways, they resemble living microbial motors and exhibit similar kinds of collective behavior. The principles of catalytically driven movement have now been used to design microscale pumps and rotors, and to study the powered motion of individual enzyme molecules. In collaboration with Mauricio Hoyos and Angelica Castro at ESPCI in Paris, we have recently discovered that micron-size metal “rockets” undergo a range of autonomous and cooperative motion when propelled by acoustic waves. These new motors are biocompatible and exhibit fast directional motion at ultrasonic power densities that are typically used in medical imaging. In collaboration with the Badding group in the Penn State MRSEC, we are using colloidal crystal templates to synthesize and study metalattices of semiconductors, ferromagnets, and other materials.
Layered Inorganic Solids. We are developing a set of soft chemical reactions that topochemically interconvert different structural families of layered and three-dimensionally bonded oxides. Layer perovskites, metal phosphates, clays, and other lamellar solids can be grown layer-by-layer and converted to other interesting nanoscale morphologies (such as nano-scrolls and tubes) by means of intercalation, exfoliation, and restacking reactions. In collaboration with the Crespi and Terrones groups, we are devising new ways to intercalate and exfoliate metal dichalcogenides, boron nitride, and graphite, without using redox cycles that damage the sheets. These unilamellar compounds are of particular interest as novel low-dimensional electronic conductors, as catalyst supports, as electrode materials for batteries, and as ionic conductors.
Positions Available. The Mallouk group includes high school students, undergraduates, graduate students, and postdoctoral fellows who work on a diverse set of intellectually stimulating research projects. Please see the links below for scholarships and fellowships that support student and postdoctoral research at Penn.
National Science Foundation GRFP
National Defense Science and Engineering Fellowship (NDSEF)
United Negro College Fund (UNCF)
National Organization for the Advancement of Black Chemists and Chemical Engineers (NOBCChE)
Penn’s Postdoctoral Fellowship for Academic Diversity program
VIEST Postdoctoral Fellowship
Mutual Respect and Cooperation. We are committed to following the code of mutual respect and cooperation. The 12 principles of the code are:
- Treat everyone equally and with respect
- Be courteous
- Be ready to communicate
- Encourage others and share your expertise with them
- Give and accept constructive criticism
- Be receptive to change
- Be a team player
- Get involved
- Have a positive attitude
- Be honest and accept responsibility
- Recognize other people’s priorities
- Strive to do your best