The research objective of this award is to characterize novel routes to functionalize graphene, while preserving its planar lattice structure and high electron density, and to study the resultant electrical and structural properties and property-correlations. Graphene exhibits a wide range of superior quantum-mechanical properties. Its careful surface-engineering without corrupting its properties can enable its incorporation into several applications. This research will establish the following functionalization routes to minimally alter graphene's lattice and electronic properties: (1) metal-aromatic coordination bonding with metal carbonyls; and (2) pi-pi interfacing with polycyclic aromatics and their derivatives of biomolecules and other groups. The deliverables include: (a) detailed structural characterization: functionalization density, crystallography, and the effect of atomic mass (metal) and electronegativity of functional group; (b) detailed electrical characterization: carrier mobility, carrier density, scattering length scales, band-gap, and the carrier transport mechanism; (c) correlations, theories, and models defining the effect of functionalization on the electrical properties of graphene; and (d) incorporation of the results into engineering student education. Fundamental details about eta-6 and pi functionalized graphene will be uncovered; and their respective spectrometric signatures (Raman, XPS and UV-Vis) will be established. The results will be applied to develop strategies to further improve graphene-functionalization.
Surface-functionalization of metal and semiconducting nanomaterials has revolutionized science and technology. However, functionalization of graphene is still challenging. If successful, this research will provide novel, non-degrading routes for functionalization of graphene and for interfacing it with physical and biological components; thus, broadening its scope of applications. Results will directly facilitate sensor applications and gate-fabrication for FETs. The nanotechnology base at Kansas State University will be strengthened by development of curricula. The participation of women/underrepresented students in engineering will be positively influenced by collaboration with existing university outreach programs (EXCITE, GROW) for 7th to 12th grade girls. The perspective of graduate students will be broadened by providing exposure to multidisciplinary training in national labs and other research groups through synergistic collaborations.
The research objectives of this proposal were to characterize novel routes to functionalize graphene, and to study its electrical and structural properties and property-correlations. In this project, graphene has been functionalized via several routes: pi-pi interfacing, eta-6 functionalization, covalent functionalization and nanoparticle incorporation. Further, it has been established that graphene’s planar lattice is preserved after eta-6 functionalization. The electrical and structural properties have been characterized. Intellectual Merit: New routes (covalent, pi-pi, eta-6 and nano-incorporation) have been established to functionalize graphene or to interface it with other nanomaterials. The interplay between functionalization scheme, functional groups, nanoparticle, and the resultant electrical properties have been outlined. The influence of the molecular group’s structure and dipole moment on the carrier concentration of graphene has been studied. The detailed spectrometric and structural mapping of functionalization has been carried out via TEM, XPS and Raman. Further, functionalization of graphene has been employed to build sensors, molecular-machanics based devices and has been interfaced with bacterial cells for impermeable encasement. Functionalization schemes have been tested for atomic-layer-deposition. The following papers were published: Sreeprasad, T. S.; Berry, Vikas (2/11/13). How Do the Electrical Properties of Graphene Change with its Functionalization? SMALL. 9 (3), 341-350. Phong Nguyen; Berry, Vikas (4/19/12). Graphene Interfaced with Biological Cells: Opportunities and Challenges. JOURNAL OF PHYSICAL CHEMISTRY LETTERS. 3 (8), 1024-1029. Phong Nguyen, Junwen Li, T.S.Sreeprasad, Kabeer Jasuja, Nihar Mohanty, Myles Ikenberry, Keith Hohn, Vivek B. Shenoy* and Vikas Berry* (5/28/13). Covalent Functionalization of Dipole-Modulating Molecules on Trilayer Graphene: An Avenue for Graphene-Interfaced Molecular Machines. SMALL. 9 (3), 3823-3828, 2013. N. Mohanty, D. Moore, Z. Xu, T. S. Sreeprasad, A. Nagaraja, A. A. Rodriguez and V. Berry*, "Nanotomy Based Production of Transferrable and Dispersible Graphene-Nanostructures of Controlled Shape and Size", NATURE COMMUNICATIONS, 3, Article number: 844 Ahn, B. Kollbe; Sung, Jonggeun; Li, Yonghui; Kim, Namhoon; Ikenberry, Myles; Hohn, Keith; Mohanty, Nihar; Phong Nguyen; Sreeprasad, T. S.; Kraft, Stefan; Berry, Vikas; Sun, Xiuzhi Susan (4/24/12). Synthesis and Characterization of Amphiphilic Reduced Graphene Oxide with Epoxidized Methyl Oleate. ADVANCED MATERIALS. 24 (16), 2123-2129. Sreeprasad, T. S.; Rodriguez, Alfredo Alexander; Colston, Jonathan; Graham, Augustus; Shishkin, Evgeniy; Pallem, Vasanta; Berry, Vikas (4/1/13). Electron-Tunneling Modulation in Percolating Network of Graphene Quantum Dots: Fabrication, Phenomenological Understanding, and Humidity/Pressure Sensing Applications. NANO LETTERS. 13 (4), 1757-1763. S. Park, N. Mohanty, J. W. Suk, A. Nagaraja, J. An, R. D. Piner, W. Cai, V. Berry and R. S. Ruoff. Biocompatible, robust free-standing paper composed of TWEEN/graphene composite. ADVANCED MATERIALS. 22 (15), 1736-40, 2010. Broader Impacts: The educational activities conducted via this project are as follows. The PI organized two sessions for the Engineering Summer School Institute (ESSI) at KSU, where 10th and 11th grade students (21 students in total) were familiarized with nanotechnology concepts and encouraged to consider career in science, technology, engineering and mathematics (STEM). The PI also organized three tracks for the EXCITE programs (2010, 2011, and 2012) where ~30 high-school girls were encouraged to consider careers in engineering (5 enrolled into Chemical Engineering at KSU). In the above programs, the students prepared a nanoparticle based humidity sensor using a recipes developed by the PI. As a part of the proposal, the PI trained 3 PhD students (2 have graduated) and 5 undergraduate students. The research results have been published with graduate students and presentation have been delivered at several conferences and universities. The students received thorough training in graphene functionalization and one student decided to pursue academia and is currently an assistant professor of chemical engineering. On educational front, the PI incorporated nanotechnology concepts into chemical engineering curricula, brought students from classroom to laboratory space, and provided opportunities to receive mentoring from industrial collaborators.
