Chemical and Structural Engineering of Nanomaterials for Energy Applications

ChEMS Seminar

Prof. Richard Robinson

Materials Science and Engineering Department

Cornell University

Our research is centered on chemical and structural engineering of nanomaterials for energy devices.  By applying novel nanosynthetic design concepts to tailor the properties of nanomaterials and by understanding the fundamental physics of nanomaterials we seek to develop new materials and methods for electrochemical storage, electrocatalysis, and thermoelectrics. 

In this talk I will discuss our recent results through each stage in the process: synthesis, chemical transformations, surface engineering, and devices. First I’ll discuss our work on new methods for nanoparticles synthesis and scale-up reactions.  In this work we developed a rational method for the synthesis of monodisperse metal sulfide nanocrystals in organic solutions by using (NH₄)₂S as a sulfide precursor.  The method enables low temperature (< 100 ^oC) syntheses, open-air reactions, high conversion yields, and large-scale production of monodisperse nanocrystals can be synthesized in a single reaction (more than 100x that of conventional “hot-injection” methods).  Next, I’ll show how we have learned how to post-synthetically manipulate these nanoparticles to control their composition through chemical transformation reactions. Our group is using x-ray absorption spectroscopy (XAS) to study the structural evolution and the diffusion processes which occur during the phase transformation of nanoparticles (e.g., ɛ-Co to Co₂P to CoP).  Results from experimental characterization and density functional theory calculations (collaboration with R. Hennig group) reveal that nanoscale Kirkendall hollowing is more complex than previously believed.  To modify the organic ligand shell we have developed a novel surface modification method to link nanoparticles together through inorganic bridges.  We show a method to completely remove bulky surfactant ligands from both II-VI and IV-VI semiconducting nanocrystal films, leaving the post-treated nanoparticle surfaces metal-sulfur rich but free of organics.  Finally, I’ll discuss our new structural characterization tool, where we have developed a microfabricated phonon spectrometer.  Non-thermal distributions of phonons are locally excited and detected in silicon nanostructures by decay of quasiparticles injected into an adjacent superconducting tunnel junction. In our phonon spectrometer we have demonstrated a frequency resolution of ~20 GHz, and a frequency range from ~80 to ~800 GHz.  Our results on Si nanosheets indicate that the Casimir limit is reached at much lower frequencies than previously believed.



Bio:

Richard received his BS and MS in Mechanical Engineering from Tufts University and his PhD in Applied Physics from Columbia University. During his doctoral studies, he worked on phase transitions in metal oxide nanoparticles. Richard won a postdoctoral fellowship at University of California, Berkeley/LBNL in the research group of Paul Alivisatos working on nanoparticle synthesis, chemical transformations, and advanced property characterizations.  In 2008 he joined the Materials Science Department in Cornell University where his group focuses on understanding the fundamental physics of nanomaterials and applying novel nanosynthetic design concepts to tailor their properties.  He has won a number of awards including the 3M Non-tenured Faculty Award (2012-2014), the NSF CAREER award, and the R&D 100 Award. His research has been featured in Physics Today, was selected by the New Journal of Physics in the exclusive ‘Highlights of 2013’ collection, and he has been named an “Emerging Investigator” by the Journal of Materials Chemistry A (2014).