Solid-State and Nanotechnology
Chemically Enhanced Carbon Nanomaterials for Electronics, Energy, and Medicine
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Carbon nanomaterials have attracted significant attention due to their potential to improve applications such as transistors, transparent conductors, solar cells, batteries, and biosensors. This talk will highlight our latest efforts to develop strategies for purifying, functionalizing, and assembling carbon nanomaterials into functional devices. For example, we have recently developed and commercialized a scalable technique for sorting surfactant-encapsulated single-walled carbon nanotubes (SWCNTs) by their physical and electronic structure using density gradient ultracentrifugation (DGU). The resulting monodisperse SWCNTs enhance the performance of thin film transistors, infrared optoelectronic devices, photovoltaics, catalysts, and transparent conductors. The DGU technique also enables multi-walled carbon nanotubes to be sorted by the number of walls and solution phase graphene to be sorted by thickness, thus expanding the suite of monodisperse carbon nanomaterials. By extending our DGU efforts to carbon nanotubes and graphene dispersed in biocompatible polymers (e.g., DNA, Pluronics, Tetronics, etc.), new opportunities have emerged for monodisperse carbon nanomaterials in biomedical applications.
Beyond solution-phase approaches, this talk will also discuss vacuum compatible methods for functionalizing the surfaces of carbon nanomaterials. For example, a suite of perylene-based molecules form highly ordered self-assembled monolayers (SAMs) on graphene via gas-phase deposition. Due to their noncovalent bonding, these SAMs preserve the superlative electronic properties of the underlying graphene while providing uniform and tailorable chemical functionality. In this manner, disparate materials (e.g., high-k gate dielectrics) can be seamlessly integrated with graphene, thus enabling the fabrication of capacitors, transistors, and related electronic/excitonic devices. Alternatively, via aryl diazaonium chemistry, functional polymers can be covalently grafted to graphene, while exposure to atomic oxygen in UHV enables chemically homogeneous and thermally reversible epoxidation of graphene. In addition to presenting opportunities for graphene-based chemical and biological sensing, covalent grafting allows local tuning of the electronic properties of the underlying graphene.
Mark C. Hersam is a Professor in the Materials Science & Engineering, Chemistry, and Medicine at Northwestern University in Evanston, Illinois. He received the BS in Electrical Engineering at the University of Illinois at Urbana-Champaign, the M. Phil. in Microelectronic Engineering and Semiconductor Physics, University of Cambridge, and Ph.D. in Electrical Engineering, University of Illinois at Urbana-Champaign. He previously worked at the Argonne National Laboratory, and the IBM T. J. Watson Research Center. Currently at Northwestern University, his Hersam Research Group studies, develops, and manipulates hybrid hard and soft nanoscale materials for applications in information technology, biotechnology, nanotechnology, and alternative energy. His recent honors include AVS Prairie Chapter Award for Outstanding Research, Materials Research Society Outstanding Young Investigator Award, and SES Research Young Investigator Award-Electrochemical Society, and five years of Teacher of the Year Awards in his department at NU; while his professional memberships include SPIE, IEEE, MRS, AVS, AIP, APS, ACS, TMS, ASEE, and AAAS. More information about his work can be found from his webpage at Northwestern http://www.hersam-group.northwestern.edu/index.html