Ben J. Lear

Ben J. Lear

Main Content

  • Associate Professor of Chemistry
Office:
126 Davey Lab

University Park, PA 16802
Email:
(814) 867-4625

Education:

  1. B.S. University of California, Davis, 2002
  2. M.S. University of California, San Diego, 2004
  3. Ph.D. University of California, San Diego, 2007

Selected Publications:

Chisholm, M.H.; Lear, B.J.; Moscatelli, A.; Peteanu, L.A.  Electroabsorption of dimers containing MM (M = Mo, W) quadruply bonded units: Insights into the electronic structure of neutral coupled redox centers and their relationship with mixed valence ions.  Inorg. Chem. (2010), 49, 3706-3713.

Lear, B. J.; Chisholm, M. H.  Oxalate bridged MM quadruply bonded complexes as test beds for current mixed valence theory: Looking beyond the IVCT transition.  Inorg. Chem. (2009), 48, 10954-10971.

Lear, B. J.; Glover, S. D.; Salsman, J. C.; Londergran, C. H.; Kubiak, C. P.  Solvent dynamical control of ultrafast ground state electron transfer: Implications for class II-III mixed valency.  J. Am. Chem. Soc., (2007) 129, 12772 – 12779.

Lear, B. J.; Kubiak C. P.  Origin of cooperative non-covalent host-guest chemistry in mixed valence complexes.  Phys. Chem. B, (2007), 111, 6766 -6771. 

Lear, B. J.; Kubiak C. P.  Charge gating and electronic delocalization over a dendrimeric assembly of trinuclear ruthenium clusters.  Inorg. Chem. (2006), 45, 7041-3.

Londergan, C. H.; Salsman, J. C.; Lear, B. J.; Kubiak, C. P.  Observation and dynamics of "mixed-valence isomers" and a thermodynamic estimate of electronic coupling parameters.  Chem. Phys.  (2006), 324, 57-62.

Information:

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.

Research Interests:

Inorganic

Interplay between electronic properties of materials and their chemical environment