We are interested in the interaction between nanoparticles
and their nearby chemical environment.
Chemical control over electronic properties of metal nanoparticles
In classical inorganic chemistry, ligands are used to
control the electronic properties of the metal centers to which they are
attached, in turn effecting a myriad of important properties, such catalytic
activity. As a result, ligand control
has emerged as the dominant paradigm in inorganic complex design and the large
body of work in this area has produced a predictive framework that allows for
efficient design of new inorganic complexes.
We are interested in understanding the extent to
which the insights gained in traditional inorganic chemistry can be extended to
control the properties of nanoscale materials.
Specifically, we wish to understand the extent to which changes in the
ligands bound to metallic nanoparticles can be used to effect changes in the
electronic structure of these nanoparticles.
For this, we synthesize new surfactants/nanoparticle composites and then
study their electronic behavior using UV-visible and EPR spectroscopies. Together, this approach yields detailed
insight into the dependence of the electronic properties of nanoparticles upon
their ligand chemistry.
Photothermally driven chemical transformations
Heat is one of the oldest and most useful tools for promoting
chemical transformations. It is prized for its generality, as any thermally
activated transformation can be effectively driven simply by setting an
appropriate temperature – without need to consider the specifics of the
chemical reaction. This generality, of course, also leads to known-known problems,
such as the promotion of unwanted chemical reactions.
We believe that much of the disadvantage of heat stems from
the scale at which it is applied: typically longer than centimeters and for
many minutes. If one compares these scales with those of the elementary steps of
reactions (shorter than nanometers and picoseconds), it is easy to see that
there is a large mismatch in time and space between the scale off the desired
transformation and the application of heat. This lack of matching in terms of scale leads
to imprecise usage of heat.
In my lab, we attempt to overcome this poor scale matching
by using the photothermal effect of nanoparticles to produce elevated
temperatures on scales close to those for elementary steps of reaction. For instance, a 30 nm gold nanoparticle that
absorbs a nanosecond pulse of light is capable of producing temperatures on the
order of 2000 K, but only over a few nanometers and for a few nanoseconds. We
have been able to demonstrate that these localized and transient temperatures
are able to drive conventional organic chemical reactions (such as
polymerization of urethane) cleanly – even at such extreme temperatures. Further
work in our lab focuses on understanding the breadth of this approach as well
as how to best tune the effect for promoting desired chemical transformations.