The
Lear Laboratory
Learn about our current interests
Molecular scale heat for molecular scale transformations
A mismatch in time and space
The vast majority of chemical reactions are driven using bulk-scale heat. A flask boiling away in a heating mantle for hours is a familiar site to most chemists. The transformations targeted under such conditions usually involve bond-breaking, bond making, or bond isomerization. These transformations occur at a scale roughly a billion times smaller than the scale at which heat is applied, and approximately a trillion times faster.
Precision in applying heat
We wish to understand the benefits that may arise from applying heat on a time and length scale more closely matched to the elementary steps of chemistry. To this end, we use the photothermal effect of nanoscale materials as a means to apply heat with nanometer and nanosecond precision.
Remarkable chemical behaviors
Using this more precise form of heat, we have demonstrated that we can drive chemical reactions at extreme temperatures, while preserving control over the reaction. Indeed, we have observed the ability to drive reactions at temperatures well above 700 K, while realizing the same products as obtained at 300 K. The only difference is that we attain these products roughly one billion times faster.
Scope and scale
To date, we have demonstrated the effectiveness of molecular scale heat for driving the decomposition and the formation of polymeric materials and for small molecule transformations. We have driven chemistry in the solid state and in solution. We have driven reactions at scales of a few microliters to tens of milliliters and over areas of tens of square centimeters. Future work will focus on increasing this scale and understanding the fundamental aspects of molecular scale heat
Ligand control over nanoscale metals
A coveted framework
In molecular inorganic chemistry, the dominant paradigm is ligand control. If one wishes to influence the electronic properties and behaviors of a metal center---a catalyst, perhaps---then one naturally turns to ligands to do so. As a result, there is more than a century of accumulated knowledge that one can draw from, and one has an excellent chance to rationally control the metal center behavior.
New tools for a new perspective
Part of this effort requires the development of new tools that provide a sensitive and selective probe for the electronic properties and behavior of the metallic core. Our lab focuses on developing both EPR and NMR methods for probing the metallic core. These are tools that are readily available to many researchers, and which report on ground state properties.
Metal nanoparticles as metal centers
By comparison, the focus on ligand chemistry in metallic nanoparticles is not as well-developed and so there is not so rich a framework from which to draw, when one wishes to control the behavior of nanoscale metals. Indeed, for much of their history, the dominant means to control the behavior of metal nanoparticles is through the size and shape of their core. Ligands, however, offer a much broader set of possible changes. For this reason, we choose to view the metallic core as a large metal cluster, and seek ways to use ligands to rationally control the electronic properties and behavior of the core.
The nature of ligand control
To date, we have focused on thiolate-metal interfaces, which are one of the most widely employed interfaces in nanoscience. We have found that the ligands at these interfaces allow for strong tuning effects of the metallic core, and that the primary mode of action is adjusting the position of the Fermi Energy.