Research in the Hamers group lies at the intersection of chemistry, materials science, and nanotechnology. We are interested in developing and exploiting new types of surface chemistry to create and improve next-generation devices for renewable energy, and are interested in understanding the potential environmental and health effects associated with nanomaterials. Our work spans the range from very fundamental, experimental and computational studies of surfaces, all the way to using surface chemistry to control the formation and properties of devices such as next-generation solar cells, photocatalysts, batteries, and environmental safety of nanomaterials. The group is multidisciplinary and highly collaborative.
Our interest in surfaces is driven by the fact that the most important chemical and physical phenomena are often controlled by surfaces and/or interfaces between materials. This is particularly true with nanoscale materials, where a substantial fraction of the total atoms are located at their surfaces. Surfaces have their own, very unique chemistry because the atoms are typically in very unusually, highly asymmetric geometries. Most of our current work addresses surface chemistry issues relevant to renewable energy and/or nanotechnology and couples state-of-the-art surface chemistry with the electrochemical and/or photo-electrochemical properties of materials.
Interface Chemistry for Renewable Energy
This is the largest area of research in the group, with several complementary projects. Renewable energy technologies such as photovoltaic energy conversion, photocatalysis, and electrochemical energy storage all hinge on being able to control the transfer of electrons across interfaces between different materials. One major effort is to develop new "ultra-stable" surface chemistries to control chemical selectivity and electron-transfer properties at interfaces. Carbon-based materials (diamond, carbon nanofibers) and metal oxide semiconductors (TiO2, ZnO, SnO2) play especially important roles because of their intrinsically high stability and the fact that their semiconducting properties facilitate charge separation. By coupling these materials to molecules that can harvest light or catalyze reactions, we aim to develop "smart" materials with a high degree of functionality. In our own labs and through collaborations, we are investigating the dynamics of electron-transfer processes on time scales from seconds to femtoseconds. An expanding area of interest is the use of electrochemical and photochemical methods to produce energy-rich fuels from inexpensive and/or starting materials such as CO2. All of these projects hinge on a central theme of understanding how surface chemistry impacts charge-transfer processes at surfaces.
Electrochemical Energy Storage
Because solar and wind power are highly variable, renewable energy can only be truly effective if we can develop new and improved methods for storing energy. Increased interest in hybrid and all-electric vehicles as well as increasing reliance on portable electronics are driving a need for improved energy storage on all scales, from the iPod nano to the entire electrical power grid. We are engaged in research investigating the materials science and interface chemistry associated with next-generation lithium-ion batteries. Current-generation batteries are plagued by safety problems associated with the use of highly flammable organic electrolytes. One aspect of our research is to develop safer batteries using new organosilicon-based electrolytes. A second aspect involves research on new anode and cathode materials that have the potential to store nearly 10 times as much energy per unit weight as today's batteries. These projects involve a complex interplay of materials science, interface chemistry, and electrochemistry, and are largely performed in collaboration with industrial partners, including Silatronix, Inc. (co-founded by RJH in 2007) and Dow Chemical.
Environmental Impact of Nanomaterials
The explosion of interest in nanotechnology also raises questions about the possible environmental safety and health issues surrounding the potential release of engineered nanoparticles into the environment. Nanoparticles are often stabilized by surface ligands; these ligands strongly impact their stability and bioavailability in the environment. As part of a multidisciplinary collaboration with several groups we are investigating how the surface chemistry of nanoparticles affects bioavailability and toxicology. Even nominally non-toxic materials such as TiO2 can be highly toxic in nanoscale form through photocatalytic effects, such as generation of superoxide (O2-) ions and hydroxyl radicals from water in the presence of sunlight. In this collaboration, zebrafish are used as a model system because in the embryonic stage they are transparent, allowing one to directly view how nanoparticles influence embryonic organ development; transgenic fish and other state-of-the-art molecular biology methods are being used to achieve a molecular understanding of nanoparticle toxicity. Our group spans a range from very fundamental studies of surface chemical reactions and reaction mechanisms, to the practical applications of these materials to important problems in renewable energy and biomaterials. The work is interdisciplinary in scope, and students from all areas of chemistry, materials science and related fields are welcome.